o? ■&"->>. NATURAL HISTORY AND DISEASES OF THE HUMAN TEETH. THE NATURAL HISTORY DISEASES THE HUMAN TEETH, JOSEPH FOX, M. R. C. S. L., MEMBER OF THE SOCIETY OF MEDICINE, PARIS ; LECTURER ON THE STRUCTURE AND DISEASES OF THE TEETH, AT GUY'S HOSPITAL; AND SURGEON DENTIST TO THEIR ROYAL HIGHNESSES THE DUKES OF KENT AND SUSSEX. FIRST AMERICAN FROM THE THIRD LONDON EDITION. REMODELED, WITH AN INTRODUCTION AND NUMEROUS ADDITIONS, BY CHAPIN A. HARRIS, M.D., D.D.S., PROFESSOR OF PRACTICAL DENTISTRY AND DENTAL PATHOLOGY IN THE BALTIMORE COLLEGE OF DENTAL SURGERY; FELLOW OF THE AMERICAN SOCIETY OF DENTAL SURGEONS J MEMBER OF THE MEDICO-CHIRURG1CAL FACULTY OF MARYLAND ; AUTHOR OF PRINCIPLES AND PRACTICE OF DENTAL SURGERY, ETC. ETC. ILLUSTRATED WITH THIRTY PLATES. PHILADELPHIA: ED. BARRING TON AND GEO. D. HAS WELL, 1846. PEiKFAi.TTBRARY X V> CrV Entered according to act of Congress, in the year one thousand eight hundred and forty-six, By Ed. Barrington and Geo. D. Haswell, In the Clerk's Office of tlie District Court of tlie Eastern District of Pennsylvania. WO 0 .'S44> JOHN D. TOT, PUINTKK 9 * • «** i r • • * i v. '.• -♦• TO HENRY CLINE, Esq. lecturer on anatomy, and surgeon op st. thomas' hospital. Dear Sir: 4 The numerous and continued marks of friendship and attention which I have received from you, demand my most grateful acknowledgments. When at a very early age I was deprived of my father, you kindly stepped forward with your advice, and, by your countenance, and the sanction of your name, trans- ferred to me the confidence of his friends, and secured the continuance of a respectable practice. To the knowledge I obtained from you when your pupil, and the opportunities of information I have since derived from the easy access with which you have always favoured me, I attribute, in a very considerable degree, the success which has attended my practice in that particular branch of the profession to which I haye applied. •2 VI DEDICATION. Your having been pleased to speak favourably respect- ing the utility of the present Work, is a great encourage- ment to me in submitting it to the Public; and, in permitting me to inscribe it to you, I feel another flattering mark of attention conferred on, Dear Sir, Your faithful and obedient servant, Joseph Fox. No. 54 Lombard Street, April 20, 1803. PEE EAC E TO THE AMERICAN EDITION. The first complete edition of this Work was published in 1806; and, notwithstanding the rapid progress which Dental Surgery has made subsequently to that period, it still occupies a high place in the literature of this depart- ment of medicine. It has been more extensively quoted than any other Treatise upon the same subject, and has passed through three editions in England. The last of which was published in 1833. There is still, both in Europe and America, a steady demand for it. The Author, during his professional career, enjoyed a high reputation as a practitioner of Dental Surgery; and for many years previously to his death was a lecturer on this branch of medicine in Guy's Hospital. Although he has passed from among the living, he has left behind him a memorial which will perpetuate his name to the latest period of time. Wherever, and so long, as this branch of Surgery shall be practiced by educated men, will the name of Fox be held in grateful remembrance. In preparing the work for republication in this country, the editor has found it necessary to make numerous and yiii PREFACE TO THE AMERICAN EDITION. extensive additions, in order to adapt it to the present state of dental practice. These are designated [by brack- ets,] and are about equal to three-fourths of the original text. He has also added seven plates, remodeled the arrangement of the subjects, and placed over each an appropriate caption. The English editions are divided into two parts. This has three. The last is devoted to artificial teeth, obtura- tors and palates, and with the exception of four or five pages, consists of additions furnished by the editor. Although it has been deemed necessary to change the arrangement of some of the subjects of the Treatise, the whole of the original text, with the exception of some ten or twelve pages, will be found in the present edition of the work. These were left out, because they related to treatment of affections of the teeth which at present is never adopted. It will be found that the scope of the work has not been materially enlarged—the chief aim of the editor having been, to supply such details of subsequent im- provements in practice, as the present state of the science and art seemed to demand. If the manner in which he has done this shall prove satisfactory to his professional brethren, his object will have been accomplished, and he will not regret having consented to assume the task. CHAPIN A. HARRIS. Baltimore, Md. Jan. 1, 1846. P 11 E E A C E TO THE THIRD LONDON EDITION. Since the appearance of the Second Edition of this work, the profession have lost the personal services of its respected Author; but, notwithstanding twenty years have clasped since he gave his last attention to the sub- ject, it is the opinion of good authorities that neither alterations nor additions are required. The importance of duly attending to the diseases of the teeth, and the motives which induced the Author to publish, cannot be better explained than by making the following reprint of his own preface. " The operations of the living functions of all animal bodies having a constant tendency to consume the sub- stance of which the general frame consists, a certain and regular provision is required for the repairs of those in- juries which the body commits upon itself. "Abundant supplies for the production of new cor- poreal matter exist, as articles of food, in the animal and vegetable kingdoms; and, by a bountiful Providence, are adapted to the taste and instincts of all his creatures. x PREFACE TO THE But before these articles of food can become nutriment for the body, they must undergo certain processes. The first is, that whereby it is broken down into small par- ticles, and, being mingled with the fluids of the mouth, is comminuted into a fine mass, and prepared for the action of the stomach, in the process of digestion. "The teeth are the organs provided by nature for the mastication of food, which is an operation so essen- tial to health, that without a due preparation of the aliments, the digestion must always be more or less deranged. "The teeth which appear in the early part of life are adapted to the state of childhood; and at a certain period are succeeded by a second set, which are designed to continue during the remainder of life. "The first, or temporary set of teeth, are very liable to become diseased; and in the majority of cases they do not naturally fall out in sufficient time to permit the second, or permanent, set of teeth to arrange themselves in their proper order. "A knowledge of the changes which the teeth un- dergo, is a very interesting part of natural history, and is absolutely requisite to enable a practitioner in surgery to render such assistance during the progress of the second dentition, as may preserve the permanent teeth from being injured by the diseases of the temporary teeth; or, from acquiring that irregularity which always occasions so much deformity, and often destroys correct pronun- ciation. THIRD LONDON EDITION. XI "An attention to the appearance of the teeth;—a de- sire to preserve them in a healthy state;—and the neces- sity which exists of procuring relief when affected by disease, are sources of considerable occupation. In the metropolis and large towns, professional men, as dentists, are enabled to confine their practice to this department alone; but in those situations where surgeons are obliged to undertake medicine and surgery in all their branches, it is very necessary that they should be as well acquainted with the structure and diseases of the teeth, as of any other part of practice whatsoever. " Mr. Hunter's publication on the teeth was the first scientific book ever published upon this subject; and, as an anatomical work, must ever enjoy great celebrity; but not having practically devoted much of his attention to the operations upon the teeth, there can be no re- flection upon Mr. Hunter's merit in stating, that in many essential points he was wholly, but unavoidably, deficient; particularly in regard to the right management of the teeth during the second dentition." Further it appears that during the time the Author was engaged as a dresser with Mr. Cline, he found amongst the pupils of St. Thomas' and Guy's Hospitals a great desire to obtain particular information concerning the diseases of the teeth. Frequent conversation on these subjects, and descriptions of the modes of per- forming some operations, led to the delivery of a Course of Lectures on the Structure and Diseases of the Teeth. In this undertaking, much assistance was rendered by \ Xii PREFACE TO THE THIRD LONDON EDITION. Mr. (now Sir Astley) Cooper. The first Course was given in the Spring of 1799, after which they were con- tinued as one of the Spring Courses of Lectures delivered at Guy's Hospital, and finally gave origin to the present work. London, Oct. 15, 1833. CONTENTS. Introduction, ...... 21 PART FIRST. The Natural History of the Formation and Structure of the Teeth, &c &c,.......27 CHAPTER FIRST. Of the Formation of the Temporary Teeth, . . .29 CHAPTER SECOND. Of the Formation of the Permanent Teeth, . . 35 CHAPTER THIRD. Of the Manner in which the Teeth are Formed, . . 44 Manner of the formation of the Enamel, .... 52 Arteries of the Teeth, ........59 Nerves of the Teeth,.......60 Absorbents of the Teeth, .......61 Articulation of the Teeth, ......62 Structure of the Teeth, .... . ib. CHAPTER FOURTH. Of the Shedding of the Teeth,.....66 xiv CONTENTS. CHAPTER FIFTH Of the Irregularity of the Teeth, Accretion of the Jaws, CHAPTER SIXTH. Of the Treatment to Prevent Irregularity of the Teeth, 83 CHAPTER SEVENTH. Of the Treatment to Remedy Irregularity of the Teeth, 87 CHAPTER EIGHTH. Of Supernumerary Teeth, ....... 103 CHAPTER NINTH. Of the Decay of the Temporary Teeth, . . . 105 CHAPTER TENTH. Of the Diseases which attend Dentition, . . . 108 CHAPTER ELEVENTH. The Analysis of the Human Teeth, .... 123 Analysis of the Enamel, ....... 125 EXPLANATION OF PLATES TO PART FIRST. Plate One, Plate Two, Plate Three, Plate Four, Plate Five, Plate Six, Plate Seven, Plate Eight, Plate Nine, 76 78 132 134 135 136 136 137 140 CONTENTS. XV Plate Ten,..........143 Plate Eleven,.........145 Plate Twelve,..........147 Plate Thirteen,.........148 Plate Fourteen,.........149 Plate Fifteen,.........150 PART SECOND. The History and Treatment of the Diseases of the Teeth, Gums, &c. Sec,.......151 Introduction, . . . . ... . . . 153 CHAPTER FIRST Of Caries, ...... Proximate Cause of Caries, Predisposing Cause of Caries, Prevention of Caries, Treatment of Caries, .... CHAPTER SECOND. Of Filing the Teeth,.......179 CHAPTER THIRD. Of Stopping the Teeth, ....... 185 CHAPTER FOURTH TOOTH-ACHE,..... Treatment of Tooth-Ache, CHAPTER FIFTH. Of the Extraction of the Teeth, .... 209 Instruments Employed in the Operation, .... 210 The Key Instrument,......ib. 157 160 166 172 176 197 198 Xvi CONTENTS The Paces,........212 The Perpendicular Extractor, . . . . . 213 Of the Forceps,........ib. Forceps for the Extraction of the Superior Incisores and Cuspidati,........215 Forceps for the Extraction of the Superior Molares, . .216 Forceps for the Extraction of the Superior Dentes Sapientiae, 217 Forceps for the Extraction of the Bicuspides of both Jaws and the Inferior Cuspidati and Dentes Sapientiae, . . ib. Forceps for the Extraction of the Inferior Incisores, . .218 Forceps for the Extraction of the Inferior Molares, . . ib. Manner of Extracting Teeth,......219 Directions for the Extraction of the Incisores and Cuspidati, 220 Directions for the Extraction of the Bicuspides and Molares, 222 Directions for the Extraction of Roots of Teeth, . . 229 Particular Directions for the use of the Key Instrument, . 233 Hemorrhage after Extraction, .*.... 237 CHAPTER SIXTH. Of Exostosis of the Fangs of the Teeth, . . . 238 CHAPTER SEVENTH. Of Necrosis affecting the Fangs of the Teeth, . . 245 CHAPTER EIGHTH. Of the Disease resembling Spina-Ventosa, . . . 247 CHAPTER NINTH. Of the Removal of the Enamel by the Denuding Process, 249 CHAPTER TENTH. Of the Wearing of the Teeth by Mastication, . 252 CHAPTER ELEVENTH. Of Fractures of the Teeth,..... 254 CONTENTS. xvii CHAPTER TWELFTH. Of the Diseases of the Gums,......260 Of the Scurvy in the Gums,......261 Of Preternatural Growth of the Gums, .... 265 CHAPTER THIRTEENTH. Of Gum-Boil and Abscess,......275 CHAPTER FOURTEENTH. Of the Diseases of the Alveolar Processes, . . . 286 CHAPTER FIFTEENTH. Of Tartar (Salivary Calculus) of the Teeth, . . 296 Analysis of the Tartar,.......302 Analysis,.........303 CHAPTER SIXTEENTH. Of Scaling (Removing the Tartar) of the Teeth, . 306 CHAPTER SEVENTEENTH. Of the Effects of Mercury upon the Teeth, . . 309 CHAPTER EIGHTEENTH. Of the Diseases of the Antrum Maxillare, . . . 317 CHAPTER NINETEENTH. Of Luxation of the Lower Jaw,.....325 EXPLANATION OF PLATES TO PART SECOND. Plate Sixteen,..........353 Plate Seventeen,.........337 Plate Eighteen,..........338 Plate Nineteen, . ......339 xviii CONTENTS. Plate Twenty, . Plate Twenty-one, . Plate Twenty-two, Plate Twenty-three, Plate Twenty-four, Plate Twenty-five, . Plate Twenty-six, Plate Twenty-seven, Dissection of Tumour, PART THIRD. Artificial Teeth, Obturators and Palates, . . . 351 CHAPTER FIRST. Artificial Teeth, ........ 353 CHAPTER SECOND. Of the Manner of Inserting a Pivot Tooth, . . . 370 Manner of Preparing the Root,.....371 Of the Manner of Fitting and Attaching a Tooth to the Root, 376 CHAPTER THIRD. Of the Manner of Fitting and Adapting a Plate, and At- taching Clasps and Artificial Teeth to it, . . 380 Of the Manner of taking a Wax Impression, .... 381 Of the Manner of obtaining a Plaster and Metallic Model and Counter Model,.......382 Of the manner of Fitting and Stamping a Plate and attaching Clasps to it,........384 Of the manner of Fitting and Antagonizing the Teeth, at- taching them to the Plate, and finishing the work, . 387 340 341 342 343 344 345 346 347 349 CONTENTS. XIX CHAPTER FOURTH. Of the Teeth to which it is most proper to apply Clasps, and the manner of counteracting the injury liable to result from such application, ..... 395 CHAPTER FIFTH. Of the Construction of a double set of Artificial Teeth mounted on plates with spiral springs, . . . 399 CHAPTER SIXTH. Of the Construction of Plates for Artificial Teeth in particular cases, . .......404 CHAPTER SEVENTH. Of Artificial Obturators and Palates, .... 408 Absence of a Portion of the Palatine Organs, . . . ib. Of the Construction of Obturators,.....412 Of Obturators and Palates complicated with Artificial Teeth, 417 Of the Construction of a complete Palate with a Set of Artificial Teeth,.........419 Artificial Palate and Nose, ......421 EXPLANATION OF PLATES TO PART THIRD. Plate Twenty-eight,........429 Plate Twenty-nine,.........430 Plate Thirty,.........431 INTRODUCTION BY THE EEITOE. The teeth are not only among the most useful and important organs of the human body, but they are also among the most ornamental. They play an important part in the animal economy, and form an essential por- tion of the organism of man—contributing, when sound, to the health of the whole body, and when diseased, to the impairment of many, and often of all its functional operations. Planted deeply in the alveolar border of each jaw, they are important both in an anatomical and in a physiological point of view. They sustain, through the medium of the fifth pair of nerves, an intimate re- lation with the brain and whole nervous system, as well as with all the parts dependent on them. They are the prime organs of mastication—an operation which consti- tutes the first stage of digestion, and which, if impro- perly performed, necessarily vitiates the whole process of assimilation. They contribute too, in an eminent degree, to distinct enunciation, and by preventing the jaws from coming together, they give rotundity and symmetry to the face. Therefore, in whatever light they may be viewed, they are of priceless importance to the well-being and comfort of every individual. 4 22 INTRODUCTION. But notwithstanding the value and importance of the teeth, they, like other parts of the body, are liable to disease, and are often destroyed by it at a very early period of life. Unlike other parts of the body, how- ever, these organs are not endowed with recuperative powers. When attacked by disease, art only can stop its progress, and repair the injury which it has inflicted; and happily her resources, when applied in time, have been found amply sufficient, both for the one and the other. Skilful, however, must be the hand, and perfect the knowledge of the operator, who deals with organs, the diseases of which can only be arrested by mechani- cal means; and, it is greatly to be regretted, that so few of the practitioners of dental surgery, possess these in- dispensable qualifications. The numerous unsuccessful operations on the teeth, daily performed, and the last- ing, and often irreparable injury resulting therefrom, are all attributable to the want of a sufficiently thorough, theoretical and practical knowledge of this branch of the curative art. But the treatment of the diseases of the teeth and the replacement of their loss with artificial substitutes, do not comprise all the duties of the surgeon dentist. The treatment of the various affections of the gums, alveolar processes, and their contiguous parts, as well as the man- agement of second dentition, when effected in a faulty or improper manner, and the correction of irregularity in the arrangement of these organs, all come legitimately within his province. He therefore who would be a suc- cessful practitioner of the dental branch of medicine, should not only be thoroughly skilled in the various mechanical manipulations which belong to it but he should also have a knowledge of anatomy, physiology, pathology, and the therapeutical indications of disease INTRODUCTION. 23 generally. Without this knowledge, no one should take upon himself the responsibility of practising the profes- sion, and to obtain it, requires much time and close and persevering application. Neither mechanical ability nor the highest medical attainments, nor both combined, without a thorough knowledge of the diseases of the dental apparatus and their treatment, can make a skilful practitioner of this branch of the healing art. That any one, therefore, should be guilty of the egre- gious folly of committing the treatment of the diseases of organs so valuable as the teeth, to an individual totally destitute of all qualifications, and having no other claim to skill in their management, than the mere assumption of the name of dentist, is almost incredible; and yet it is done every day, and by persons who would not think of putting a watch, or any common jewelry for repair into the hands of a man not known to be well skilled in such matters. Such inconsistency, might seem paradox- ical, if it were not constantly observed in individuals moving in the most learned and polished walks of so- ciety, and manifesting in most matters great prudence, shrewdness and judgment. But this is not so culpable in others, when medical men, eminent for erudition and skill in their profession, have been known to employ and recommend practitioners of this description. Thus en- couraged they have multiplied with most astonishing rapidity, and if it were not that some men of education, talent and ingenuity are engaged in this field of practice, they would, long before now, have destroyed all confi- dence in the alleviatory resources of the profession. But thanks to the efforts and unwearied labour of such men, notwithstanding the multiplication of empirics, the pro- gress of the science and art of dental surgery has been rapid; it has outstripped the most ardent flights of imagi- 21 INTRODUCTION. nation, and has already attained a degree of excellence, which a few years ago was supposed impossible. The importance of a higher standard of qualification for practitioners in this department is beginning to be felt every where, and it is gratifying to perceive that efforts are now making for the accomplishment of this important object. That it has not been previously done, is not at all surprising, for until recently, the practice had not assumed the importance it now possesses, nor had any public or ample private facilities been furnished for the acquisition of a thorough and comprehensive know- ledge of the art. Therefore, it was only by the appli- cation of rare abilities and the most untiring efforts, that those who have attained to eminence and skill in it, wrere enabled to do so. But the dawn of a brighter day has begun. Ample facilities are now furnished by the Baltimore and Cin- cinnati Colleges of Dental Surgery, for obtaining a tho- rough medico-dental education. The former was char- tered by the Legislature of Maryland in 1840, and has been in successful operation five years; the latter was chartered about twelve months since, by the Legislature of Ohio, and commenced operation in November last. The advantages of collegiate over private instruction are as great in dental surgery as they are in medicine and general surgery. Few private teachers are provided with the means and necessary facilities for imparting a thorough knowledge of the various branches that should enter into the professional education of an accomplished dentist, and most of those who commenced practice with no other information upon the subject, than that which they obtained from private instructors, did so with ex- ceedingly limited qualifications, and soon found that they had still much to learn. INTRODUCTION. 25 The study of dental surgery is now invested with peculiar interest. A revolution has commenced in the ranks of the profession, which must before long result in an entire change in the character of the pursuit and its relation to the liberal sciences. The number of edu- cated men engaged in it is rapidly increasing, and they are uniting their energies to accomplish this change. They have already done much toward effecting it, and the result of their past labours encourages, nay warrants, the belief that the day is not distant, when none but men capable of practising the art upon scientific principles, and of enriching it by the result of enlightened observa- tion and critical research, shall be permitted to exercise its duties. Then, and not till then, will the malign influ- ence of dental empiricism cease, and the sanatary and restorative resources of this branch of medicine be pro- perly appreciated and acknowledged. PART I. THE HISTORY OF THE FORMATION AND STRUCTURE OF THE TEETH. THE SYMPTOMATIC DISEASES INCIDENTAL TO THE FIRST DENTITION. THE CHANGES WHICH TAKE PLACE DURING THE SECOND DENTITION; AND THE TREATMENT TO PREVENT AND REMEDY IRREGULARITIES IN THE ARRANGEMENT OF THE TEETH. PAET FIRST. CHAPTER FIRST. OF THE FORMATION OF THE TEMPORARY SET OF TEETH. When the foetus has advanced so far in the organiza- tion of its different parts, as to take some determinate form or figure, we may perceive a considerable progress in the preparatory steps for the formation of the teeth. As soon as the ossific deposit commences in the cartil- aginous parts of the embryo, both jaws are filled with small membranous sacs; and, in the anterior parts, we may perceive the rudiments of alveolar processes. In a foetus of about four months, the jaw bones are distinctly formed; but at this time they only consist of thin grooved bones, having a cavity extending through their whole length.* In the under jaw, anteriorly, this cavity is narrower and deeper; but, posteriorly, it becomes wider and more shallow. At this time, if the mem- branous parts be removed, small processes of bone may be perceived shooting across from each side; which as * The description of what takes place in one jaw, will completely exhibit what con- cerns the formation of the teeth in both; therefore, in order to avoid confusion, I shall refer to the under jaw only. 5 30 OF THE FORMATION OF THE the foetus increases in growth, gradually acquire more distinctness, and at length form separate sockets for the teeth.* During the foetal state, and also for some months after birth, the blood vessels and nerves belonging to the teeth, run along at the bottom of this cavity, immediately below the pulps of the teeth; but afterwards a distinct canal is formed, through which the principal vessels and nerves pass; separate filaments being sent off to the several teeth. When the gum which covers the alveolar groove of a foetus of the age above-mentioned, is stript off from the bone, small processes or elongations from the inner surface of the gums may be distinctly perceived; these are the first appearances of the pulps from which the teeth are formed.f The alveolar processes soon become perfectly distinct; for, the bony partitions wThich divide the longitudinal cavity in the jaw, rise to the upper margin; and thus those membranous processes, now enlarged and become more evolved, begin to be contained in separate cells. J In a foetus of about four months old, the rudiments of the teeth may be very distinctly seen; upon examining those substances found in the jaws, they are seen to be soft, or pulpy bodies, bearing a resemblance to the figure of the body of the tooth to be formed, and each of them is contained in a membrane proper to itself. || For some time during the formation of the teeth, the alveoli grow much faster than the teeth themselves, which are consequently but loosely contained within them. At the time of birth, the alveolar processes have increased so much, that they almost enclose or cover the teeth; thus a firm support is given to the gums, and the infant is enabled to make considerable pressure in sucking, &c. * Plate I. Fig. 1. tPlateI.Fig.2. } Plate I. Fig. 3, 5. || Plate I. Fig. 4. TEMPORARY SET OF TEETH. 31 without injury to the progress which is going on under- neath. The ossification of the teeth begins to take place very early; it is first visible upon the tips of the incisores. In a foetus of about five or six months, ossification has com- menced upon the pulps of the incisores and cuspidati, and on the points of the molares; this gradually advances and extends itself, over the pulp, down to the neck of the tooth, from the cutting edges or highest points, where it had first commenced. At the time of birth, the bodies of ten teeth are distinct- ly formed in each jaw; these are the teeth designed to serve during the years of childhood, and are commonly called the temporary, shedding, or milk teeth.* These temporary teeth, which constitute the first set, are twenty in number, and are divided into three classes, incisores, cuspidati and molares. In each jaw there are four incisores, two cuspidati, and four molares, and the teeth on one side of the mouth correspond in figure with those of the other, so that they are situated in pairs. Besides these twenty teeth, there are in a very early stage of their formation, the rudiments of some other teeth, which are to form part of the permanent or adult set.f [At birth, the jaws contain the rudiments of fifty-two teeth—twenty temporary and thirty-two permanent.] After birth, as the ossification goes on, the teeth be- come too long to be contained within the alveolar cavity, they therefore begin to make pressure upon those parts which cover them; this produces the process of absorp- tion, which proceeds with the enlargement of the tooth, first removing the membranes which enveloped the teeth, and afterwards the thick gum which covered them, this * Plate II. Fig. 1. t Plate II. Fig. 1. a. b. 32 OF THE FORMATION OF THE gradually becoming thinner and thinner, till at length the teeth are suffered to pass through. There is considerable variety as to the precise time when the teeth begin to make their appearance. This frequently seems to depend upon the health and vigour of the child: for sometimes the first tooth comes as early as four or five months, while on the contrary, in those of more delicate and weakly constitutions, no tooth makes its appearance until the child is ten or twelve months old; and it is not very uncommon for a child to be turned of fourteen months before any tooth appears. It may be expected that the formation of the teeth will go on more rapidly in the healthy, and proceed more slowly in the weak and delicate: Yet there are excep- tions to this, for often the teeth seem not to be influenced by any state of health. Those of a weakly child will sometimes arise in rapid succession, while those of one more robust will often come forwrard but slowly. In general, children begin to have their teeth about the sixth, seventh, or eighth month after birth;* those which correspond with each other generally appearing about the same time, first in the under jaw, and then in the upper. The following is the order in which the teeth of a child * Sometimes a child is born having one or two teeth; these are generally the cen- tral incisores of the under jaw: In such cases the socket for the forming tooth has not been sufficiently deep, and therefore the tooth has passed through the gum premature- ly. These early productions are only the upper parts or crowns of teeth, no fangs having yet been formed. And as they have only a weak attachment to the gums, they soon get loose, producing a considerable inflammation in the mouth of the child, as well as occasioning inconvenience to the mother. It is therefore advisable to ex- tract them immediately, for they can never come to perfection. [If teeth, which appear through the gums at birth, had as the author asserts, always a weak attachment, and soon get loose, it would be proper to adopt the practice which he recommends. But having met with cases where they were firmly articulated, and were productive of no unpleasant effects, I cannot join with him in recommending their immediate removal; this operation should only be resorted to when they give rise to irritation of the gums.] TEMPORARY SET OF TEETH. 33 generally appear.—The first teeth are the central incisores of the under jaw, one generally coming a few days before the other; then, in the course of a month, the two central incisores of the upper jaw. These are succeeded in a few weeks by the lateral incisores of the under jaw, and then soon after by the lateral incisores of the upper jaw. The cuspidati are generally slower in completing their growth than the molares, they are placed deeper in the jaw, and therefore are preceded by the first molares. The small molares of the under jaw usually come before those of the upper; they commonly appear about the fourteenth or sixteenth month, and are soon met by those of the upper jaw. After these, the cuspidati come through, first in the lower jaw, and then in the upper. At some time between two years and two years and half, the second molares make their appearance, and thus complete the temporary set of teeth.* The obtaining of the temporary teeth usually occupies a child from about the sixth or eighth month until be- tween two or three years of age. The teeth most com- monly follow the order above-mentioned; but this is not always to be expected: there are often great irregulari- ties; sometimes the upper teeth appear before the under; now and then the lateral incisores precede the central. I once saw an instance of the first molares of the under jaw appearing before the lateral incisores; and sometimes more teeth come about the same time than ought natural- ly to be expected. These cases of irregular succession of the teeth are often attended with considerable derange- ment of health, and alarming symptoms of irritation. [The periods for the eruption of the temporary teeth are stated by Mr. Thomas Bell, to be, for the four central incisores, from the fifth to the eighth month; for the four ♦Plate II. Fig. 2, 3, 4. 34 FORMATION OF TEMPORARY TEETH. lateral, from the seventh to the tenth; for the four anterior molares, from the twelfth to the sixteenth; for the cus- pidati, from the fourteenth to the twentieth; and for the posterior molares, from the eighteenth to the twentieth. I am however of the opinion, that he is somewhat in error with regard to that of the last. The second temporary molares seldom appear before the twenty- fourth month.] CHAPTER SECOND. OF THE FORMATION OF THE PERMANENT SET OF TEETH. In the management of the teeth of children, it is highly necessary that the surgeon should have a perfect knowledge of the order in which the teeth of the perma- nent set are formed, and of the time when each tooth is expected to pass through the gums. The formation and perfection of this set of teeth, occupy a very important portion of our limited exist- ence; no less than twenty years, and often more, being- necessary for their complete evolution. Nature begins to attend to the production of these permanent instru- ments of mastication, even before birth, and in many instances, they are not wholly completed before the twenty-fifth, or thirtieth year. The permanent set of teeth vary much from the tem- porary set, some of the teeth being much larger, and others differing much in figure; they are in number thirty-two, and therefore consist of twelve teeth more than the temporary set. This set of teeth may be divided into two distinct classes; those which are to succeed the temporary, and those which are superadded; the formation of both these divisions begins nearly about the same time, and the. progress furnishes one of the most curious changes the animal frame can exhibit.—The incisores and cuspidati of 36 OF THE FORMATION OF THE the child are succeeded by teeth similar in form, but larger in size, and they have the same appellation; but the teeth, which take the places of the temporary mo- lares, are much smaller, and being divided at their grind- ing surfaces into two points, are called bicuspides. The molares of the adult are the teeth which are superadded, and these succeed one another as the jaws advance in growth.* The teeth of the adult are divided into four classes: incisores, cuspidati, bicuspides, and molares. The teeth differ very much in the figure of their bodies, and in the number and shape of their fangs. The cuspidati are of a middle nature between the inci- sores and the bicuspides; as are the latter between the cuspidati and the molares. The incisores, or cutting teeth, are situated in the ante- rior part of the jaw, and form the front of the mouth. In each jaw they are four in number, and are so placed, that the two central stand somewhat more advanced than the lateral. The bodies of the incisores are broad, and rather flat. The anterior surface is convex, the posterior concave; they both go off from the neck of the tooth somewhat sloping: the two surfaces terminate in a cutting edge, which is placed in a direct line with the apex of the fang. When viewed in front, the cutting edge is seen to be the broadest part of the tooth, but gradually becomes smaller as we approach to the neck. When viewed laterally, the cutting edge is the thinnest, and the tooth, to the neck of it, increases in thickness. This gives to the body of the tooth the form of a wredge, which is its true office, it being used to cut or divide soft substances. The enamel is continued farther, and is thicker on the * Plate VII. PERMANENT SET OF TEETH. 37 anterior and posterior surfaces than on the sides; it is even thicker on the fore part than on the back part of the tooth. The fangs are conical, and are shorter than those of the cuspidati. In the upper jaw, the central incisores are much broader and larger than the lateral; in the lower jaw they are all nearly of the same size, but much smaller than those of the upper jaw. The cuspidati are four in number, one of them being placed on the outer side of each of the lateral incisores. The shape of the crown of a cuspidatus is like that of an incisor, with its corners rubbed off, so as to end in a point, instead of a broad edge. The fang is thicker and larger, and is more depressed at the sides, which causes it to appear considerably broader, when viewed laterally, than when seen in front. The fang, which is the largest of any of the teeth, may be felt with the finger, running up a considerable length, and projecting beyond those of the other teeth. The cuspidati of the lower jaw very much resemble those of the upper, both in figure and in length. The enamel covers more of the lateral parts of these teeth than of the incisores: When they are first formed they are pointed, but by the friction of each upon the other in mastication, they become rounded, and sometimes ac- quire a flat edge. The use of the cuspidati is not like that of the inci- sores, to cut and divide substances, nor like the molares for mastication; but they are similar to the canine teeth of carnivorous animals, and seem to be designed for the laying hold of and tearing of substances. The bicuspides are situated immediately behind the cuspidati. They were formerly called the first and sec- ond grinders, but as they do not possess the true figure 6 38 OF THE FOR ft] ATI ON OF THE of grinders, and only have an intermediate resemblance between those teeth and the cuspidati, Mr. Hunter con- sidered them as a particular class. These teeth are very much like each other, and when viewed as they are situated in the mouth, are not unlike the cuspidati. They are eight in number; those belong- ing to the upper jaw have the body divided into two points, one external, the other internal. Their fangs ap- pear as if compressed at the sides, and resemble two fangs united, with a depression running between them: commonly the first bicuspis has two small fangs, the sec- ond has seldom more than one; but in this they are sub- ject to variety. [The editor has several superior bicuspides in his ana- tomical cabinet, each of which has three fangs.] The bicuspides of the under jaw are smaller than those of the upper; the points upon their surfaces are not so distinct, and they have only one fang. The enamel is distributed nearly equally around the crown, and they stand in the jaw almost perpendicularly, but have a slight inclination inwards. The molares, or grinders, are placed behind the bicus- pides; there are three on each side of the jaw, making twelve in the whole. The first and second molares are so much alike in every particular, that the description of one will convey a perfect idea of the other. The third grinder has several peculiarities, and therefore must be described separately. The molares are the largest teeth; they have a broad base, furnished with several points, which fits them for their office in grinding of food, and they have several fangs. The molares of the under jaw have an inclination in- wards, while those of the upper jaw are placed nearly perpendicularly with respect to the jaw. PERMANENT SET OF TEETH. 39 The upper grinders have commonly three fangs, two situated on the outer part of the tooth, and one on the in- ner; the inner fang is very oblique in its direction, and is larger and rounder than the others. Those of the under jaw have two fangs, one placed forwards, the other back- wards; they are rather flat, and continue broad all down their length. Sometimes molares of the upper jaw are met with hav- ing four distinct fangs.* I have one with five fangs, which is the only one I ever saw.f The molares of the under jaw now and then have three fangs. J The third molaris is called dens sapientiae; it is smaller than the others, its body is rather rounder, and the fangs are not so regular and distinct: they often appear as if squeezed together, and sometimes there is but one fang. The dentes sapientiae of the lower jaw often have their fangs curved, and sometimes they are so much inclined inwards, as scarcely to rise above the ridge of the coro- noid process. The incisores of the upper jaw being much broader than the same teeth in the under jaw, cause the other teeth to be placed farther back in the circle than the cor- responding teeth of the lower jaw; hence in a well-formed mouth, when the teeth are shut close, the central inci- sores of the upper jaw come over the central and half of the lateral incisores of the lower jaw: The lateral incisor of the upper jaw covers the half of the lateral incisor, and more than half of the cuspidatus of the under jaw. The cuspidatus of the upper jaw falls between and projects a little over the cuspidatus and first bicuspis of the under jaw. The first bicuspis of the upper jaw falls partly upon the two bicuspides in the lower jaw: The second bicus- pis shuts upon the second bicuspis and the first molaris: ♦Plate IX. Fig 11. t Fig. 13. J Fig. 6. 40 OF THE FORMATION OF THE The first upper molaris covers two-thirds of the first and part of the second molaris of the under jaw: The second upper molaris shuts upon the remainder of the second and part of the third; and the third molaris of the upper jaw, being smaller than that in the under jaw, shuts even upon it.* From this mechanism of the teeth their power in mas- tication is increased, and if one tooth be extracted, the antagonist tooth does not become useless, since it can in part act upon another. [When this is not the case, as often happens, it be- comes elongated, or is gradually forced from its socket by a deposition of bony matter at the bottom of the alveo- lus; and from this it would seem, that when a tooth has lost its antagonist, it becomes, in some degree, obnoxious to the system, and an effort is made by the economy to expel it from the jaw. In accordance with this indica- tion of nature, Dr. Koecker recommends the removal of such teeth. But as this tendency can in many cases, by constant attention to the cleanliness of the tooth, be mea- surably counteracted, the operation should be resorted to only in those cases where it is absolutely required.] The permanent incisores and cuspidati are formed behind the temporary incisores and cuspidati; the bicus- pides underneath the temporary molares, and they are contained in sockets of their own. The molares are, one after the other, formed in par- ticular parts of the jaws: In the upper jaw, that posterior part called the tubercle, is the place for the formation of the upper molares; and the molares of the under jaw are formed in that part situated beneath the coronoid process, one succeeding the other, as the jaws in their growth carry the teeth forwards. * Plate VIII. Fig. 1. PERMANENT SET OF TEETH. 41 Those teeth of the permanent set which first begin to be formed are the anterior molares, the pulps of which may be found in a foetus a short time previous to birth, when they are situated quite at the posterior parts of the jaws. At the time of birth ossification has commenced upon their highest points; at this time also, on examining the membranes of the temporary incisores, small mem- branous sacs, containing a jelly-like substance, will be found attached to them at the posterior and upper part. These are the early rudiments of the permanent molares; ossification commences upon their tips soon after birth, but always first in the lower jaw. When an infant has cut the central incisores of the upper jaw, and the four incisores of the under jaw, a con- siderable progress has been made in the ossification of the permanent incisores and first molares; in the under jaw it has begun on the points of the cuspidati, and in the upper jaw, pulps for cuspidati have become distinct, the ossification of which usually commences when a child is aged about sixteen months.* Between two and three years, when all the temporary teeth have appeared through the gums, the size of those permanent teeth already mentioned is much increased, and ossification has commenced upon the points of the bicuspides of the under jaw.f After this time the teeth very much alter their position: At first the permanent teeth are contained in the same sockets as the temporary; but as the formation of both sets advances, the permanent teeth, by the growth of the alveolar processes, become placed in a kind of niche; there is also a small bony process, shooting across the bottom of the common socket, which gradually increases, till at length nearly a complete separation is produced, * Plate II. Fig. 2 and 3. t Plate II. Fig. 4. 42 OFTHEFORMATIONOFTHE and the permanent teeth are contained in sockets of their own. This may be very well observed in the head of a child of about four years of age; at this time the jaws have become deeper, in consequence of the complete for- mation of the temporary teeth and their alveolar proces- ses, and the permanent set may be presented to view, upon removing the external plate of the jaws.* About this age the ossification of the incisores, cuspi- dati, first bicuspides, and first molares, is much advanced, some progress has been made in the formation of the second molares, and soon after, the ossification of the second bicuspides commences. At about six years of age those teeth designed to suc- ceed the temporary ones, and the first and second molares, are in considerable forwardness, and if none of the tem- porary teeth have yet heen removed, there are at this time in the head, forty-eight teeth, twenty in situ, and within the jaws beneath the gums, in the progress of for- mation, twenty-eight.f In the eighth or ninth year the formation of the third molares, or dentes sapientiae begins, by this time some of the front teeth have been shed, and all the others are much advanced in growth.J [The rudiments of the dentes sapientiae have been dis- covered at birth, but at this period they exist only as mucus papillae.] The permanent incisores and cuspidati, during their formation, are all situated on the inner side of the tempo- rary teeth, consequently they are contained within the segment of a circle, smaller than that which holds the temporary teeth; they are also much larger, and therefore very much crowded and forced into irregular order. The lateral incisores are placed sometimes crossways, and * Plate III. f Plate IV. J Plate V. PERMANENT SET OF TEETH. 43 always behind, in the space between the central incisores and cuspidati. In the upper jaw the cuspidati are placed so high as only to be just underneath the suborbitar process, and in the lower jaw they are placed almost as deep as the under margin. This description which has been given of the progres- sive steps taken by nature in the formation of the teeth, may not exactly agree writh that given by some respecta- ble writers. Into Mr. Hunter's treatise, for w7ant of closer attention, many inaccuracies have been suffered to creep. Besides, descriptions of this kind are liable to disagree, because the formation of teeth in children of the same age may be in a more or less advanced state. But from various preparations and observations I have made, the above is the order in which the formation generally takes place. CHAPTER THIRD. OF THE MANNER IN WHICH THE TEETH ARE FORMED. The teeth are formed in a manner peculiar to them- selves, differing from the mode observed in the formation of bones in general; instead of having for their basis car- tilage or membranous substance, as the cylindrical and flat bones have, they are formed from a soft pulpy sub- stance, which possesses the shape of the body of the tooth to be produced. [The pulp of a tooth, according to Mr. Nasmyth, is of a cellular structure, having the aspect when examined under a microscope, of small vesicles—varying in size from the smallest perceptible microscopic appearance, to an eighth of an inch in diameter. These are arranged in layers "throughout the body of the pulp." When macerated, these layers, says Mr. N. "present an irregu- lar reticular appearance," and are "interspersed with granules."] Each pulp is covered by a membrane strongly attached to the gum, and to the pulp at its base, so that the pulp at its edge is loosely contained within the membrane, which is only reflected over it; at the base the pulp is weakly connected with the alveolar cavity in the jaw. When a jaw has been minutely injected, we find that the pulps are vascular, and also the membranes by which they are enveloped These membranes may with care MANNER IN WHICH TEETH ARE FORMED. 45 be separated into two lamellae, the external of which is rather of a loose and spongy texture, and possessed of vascularity; the internal lamella is more smooth, and is also vascular: the membranes derive their vessels from their gums, and the pulps receive theirs from the artery which passes through the jaw. Some preparations, in the injection of which I have very happily succeeded, fully warrant the above state- ment in all its variations from those of Mr. Hunter or Dr. Blake the author of an inaugural dissertation, published in Edinburg in 1798, containing many excellent physio- logical remarks on the formation of the teeth. Mr. Hun- ter observes, that the external membrane is soft and spongy, without vessels, the other much firmer, and extremely vascular. Dr. Blake says, "they (the mem- branes) can easily be separated into two lamellae, the external of which is spongy and full of vessels; the inter- nal one is more tender and delicate, and seems to contain no vessels capable of conveying red blood." In several preparations which are minutely injected, taken from the human subject, and also from the foetal calf, I have found both the lamellae to be very vascular.* The manner in which the permanent teeth derive their origin, was never properly understood until described by Dr. Blake, and is a discovery which shews very accurate observation. [The supposed discovery of Dr. Blake with regard to the manner of the formation of the permanent teeth, is said to have been made twenty years before, by a French dentist by the name of Herbert.] When the rudiments of the temporary teeth are some- what advanced, a new sac is given off at the upper and posterior part of their membranes. These sacs are at * Plate X. Fig. 1, 2, 3, 4. 7 46 OF THE MANNER IN WHICH first contained in the same socket, and are so intimately connected with the membranes of the temporary teeth, that they cannot be separated without tearing one or both.* As the sacs of the permanent teeth advance, the sockets of the temporary ones become enlarged, and little niches are formed in the internal plate of the alveolar processes; these increase in proportion with the size of the permanent sacs, and gradually form a distinct socket round each of them. There is however an opening left immediately under the gum, through which the membranes of both sets of teeth continue to be connected.! When the temporary teeth have risen in the socket, the membranes are much elongated, and remain attached to the gum at the neck of the tooth, small foramina being left in the jaw for them to pass through; thus they continue to derive their vessels from the gums. J The second and third permanent molares are in like manner formed from the first: a small processor sac is sent off posteriorly, which is at first contained in the same socket as the pulp of the first molaris; by degrees a new socket is formed in which the pulp of the second molaris becomes perfect: this then sends off another pro- cess, which forms the third molaris. || [The recent researches of Arnold and Goodsir have thrown much new and valuable light on the manner of the formation of the teeth. Their progress, almost from the moment of their appearance, as simple mucous papil- lae, until the completion of both sets, has been minutely and accurately traced, by the last named gentleman, and his observations go to prove many of the views of Dr. Blake upon this subject to be incorrect. § * Plate X. Fig. 5. t Fig- 10. J Fig. 6. || Fig. 9. § Vide Edinburg Medical and Surgical Journal for January, 1839. THE TEETH ARE FORMED. 47 Without entering into a minute or detailed description of the result of the researches of Mr. Goodsir, it will be sufficient to state, that the formation of the temporary teeth, commences as early as the seventh week after con- ception. At this period, the germ of the first temporary molaris of the upper jaw, may be seen rising up from the mucous membrane lining the floor, of what he denomi- nates the primitive dental groove, in the form of a "simple free granular papilla," of an "ovoidal" shape—"the long diameter of wrhich is anterio-posterior." Another papilla, of a rounded and granular form, between the " middle and anterior " curve of the jaw, on the floor of the same groove, is observable about the eighth week. This is the rudiment of the temporary cuspidatus. The germs of the incisores—the central first and then the lateral, make their appearance in the form of mucous pa- pillae, during the ninth week. During the tenth week, the sides of the groove before and behind the first molar papilla, gradually approach each other, sending off pro- cesses from each side, which meet, and enclose it in a follicle. A similar follicle, in the mean time, is gradually forming around the germ of the cuspidatus. The papilla of the second temporary molaris, makes its appearance during the latter part of the tenth week. The incisor follicles are formed during the eleventh and twelfth weeks, and during the thirteenth week, a follicle is formed for the papilla of the second temporary molaris. Each papilla now begins to assume a particular shape, the incisores that of the 'future teeth/ the cuspi- dati that of 'simple cones,' the molares 'become flattened transversely.' About this time, the papillae begin to grow faster than the follicles, and soon protrude from their mouths. The depth of the follicles varies to correspond with the length of the fangs of the future teeth; and their 48 OF THE MANNER IN WHICH mouths as they become more developed, are formed into opercula, which, in some measure, correspond with the crowns of the future teeth. The incisor follicles have two opercula—one anterior and one posterior—the first larger than the latter; the follicles which contain the cus- pidati papillae, have three—one external and two inter- nal, and the molar follicles, as many as there are tubercles on the masticating surfaces of these teeth. During the fourteenth week, the lips of the primitive dental groove meet in a valvular manner, giving to the papillae the appearance of having receded back into the follicles, in which they are nearly hid by the closing of the opercula. The germs and follicles of the lower teeth do not ap- pear quite so soon as those of the upper, but in every other respect the manner of their formation and their progress are almost precisely similar. At about the last mentioned period, provision is made for the production of the teeth of replacement, consisting in the formation of a crescent-shaped depression, imme- diately behind the inner opercula of each follicle—first of the central incisores, next of the lateral, then of the cus- pidati, and lastly of the first and second molares. These cresent-shaped depressions, are soon formed into what Mr. Goodsir calls " cavities of reserve," and from which the sacs and pulps of the ten anterior permanent teeth are produced. The primitive dental groove has by this time attained a higher level, and is now very properly denominated, by Mr. Goodsir, the secondary dental groove. It has now extended itself back of the second temporary mola- ris, and from the floor of which, about the sixteenth or seventeenth week, the papilla and follicle of the first per- manent molaris begins to be developed. THE TEETH ARE FORMED. 49 As the papillae of the temporary teeth increase in size, they gradually assume the shape of the teeth they are respectively destined to form. The pulps of the upper molares are perforated by three canals, which penetrate to their centres, and the lower by two. The primary base is divided into an equal number of secondary bases. From these, the roots of the future teeth are formed. The sacs of the teeth now grow more rapidly than the pulps, so that a space is formed between them. There is deposited in this, a gelatinous granular substance. This, at first, is small in quantity, and adheres only to the proximal surfaces of the sacs, but about the fifth month, it becomes closely and intimately attached to the whole of the interior of these organs, except for a small space of equal breadth, all around the base of the pulps, and as these become perforated by the canals just men- tioned, the granular matter sends processes into them, which adhering, reserve the narrow space described above, between themselves and the secondary bases. These processes of granular matter disappear near the point of junction of the canals which enter the pulp. The granular matter does not adhere to the pulps, but is accurately moulded to all their depressions and prominences. The cavities of reserve gradually recede and assume a position behind the temporary teeth, and about the fifth month the distal extremities of the anterior ones begin to distend, and give rise to the germs of the replacing teeth, which soon acquire the appearance of dental pulps. About a month later, bony septa are thrown across the alveolar groove, and niches formed in the posterior walls of the alveoli for the sacs of the permanent teeth. Up to the eighth, and sometimes even up to the ninth month, the sacs of the permanent molares are embedded in the 50 OF THE MANNER IN WHICH maxillary tuberosity. In the formation of the roots of the temporary incisores, " three cotemporaneous actions," says Mr. Goodsir, "are employed, viz: the lengthening of the pulp; the deposition of tooth substance upon it; and the adhesion to the latter of that portion of the inner sac which is opposite to it." The sacs of the permanent teeth continue to recede during the advance of the tem- porary teeth and "their sockets to their perfect state," and to "insinuate themselves" "between the sacs of the former" until "they are only connected by their proximal extremities" through the alveolo-dental canals or itinera dentium, as they are termed by M. Delabarre. From the foregoing brief summary of the result of the researches of Mr. Goodsir, as given at length by himself, it will be perceived, that the germs of the permanent teeth, although like those of the temporary, originating from mucus membrane, are nevertheless of distinct origin, and have no connection with them. Their origin and progress, however, as well as those of the temporary, will be more readily and better understood by an exami- nation of plate VII. copied from the diagram given by the author of the paper in question.] A tooth is composed, of two substances, one of which, called the enamel, is spread over that part which is not covered by the gums. The other substance is bone; it consists of the fang and all the body of the tooth situated within the enamel. [To these may be added the pulp and crusta petrosa, or cementum.] [The pulp is soft, gelatinous, and has a semi-transpa- rent appearance; its surface is covered by an extremely thin and vascular membrane, designated by Raschkow, the praeformative membrane. This membrane constitutes the bond of union between the enamel and the bone of the tooth.] THE TEETH ARE FORMED. 51 The bone of the tooth is formed from the pulp, and the enamel from the investing membrane. The bony part of the tooth is begun to be formed before the enam- el. 'When the ossification of a tooth is commencing, bone is deposited from the vessels of the pulp upon its extreme points. In the incisores it begins upon their edges, and in the molares, upon the points of their grind- ing surfaces. The ossification usually begins in the in- cisores in three spots; these increase, soon unite and pro- duce the cutting edge of the tooth: In the molares it be- gins in as many spots as there are grinding points, which in the lower jaw are commonly four, and in the upper, five: These soon unite and form one thin layer of bone of the upper surface of the pulp. The ossification soon extends to the sides of the pulp, and a thin shell of bone is spread over its whole surface.' If this shell be removed, the pulp, when uncovered, will be found very vascular. This is extremely well seen in the teeth of large animals, when in a state of formation. Some time ago I had the opportunity of examining the pulps of the teeth of a young elephant, which was dis- sected by Mr. Astley Cooper. Upon removing the ossi- fication which had taken place upon the pulps, I found the vessels to be exceedingly full of blood: There was also a considerable degree of force required to separate the bone from the pulp, and this strength of union be- tween the pulp and the ossified part, I have always found to be in proportion to the size of the tooth. In the formation of the bone of a tooth the ossific mat- ter is deposited in strata, one within the other; thus a tooth is formed from the outer part to the inner, and this deposition of bone continues until the tooth becomes complete. When the body of the tooth is formed, the pulp elongates, and takes that form of the fang proper to 52 MANNER OF THE each particular tooth, and bone is deposited upon it: It then becomes gradually smaller, until it terminates in a point. If a tooth have two or more fangs, the pulp divides, and the ossification proceeds accordingly. The cavity within a tooth, as it is forming, is at first very considerable; it becomes less as the formation advances, until it arrives at a certain point, when a cavity is left in it extending nearly through the whole length, and re- taining the shape of the tooth.* In the crown of the tooth, the cavity is of the same figure, and it divides into as many canals as there are fangs to the teeth, a canal extends through each fang connected with the cavity in the body of the tooth: Into this cavity the nerves and blood-vessels enter and ramify upon the membrane of the pulp, which remains to line the cavity after the formation of the teeth. In this man- ner the nerves give sensation to the teeth, and the inter- nal parts of them are nourished. [MANNER OF THE FORMATION OF THE ENAMEL.] The enamel is situated upon all that part of a tooth which in the healthy state of the gums is not covered by them. This portion of the tooth is called the body, or crown. It is formed by the membrane which invests the pulp: When a shell of bone has been formed upon the pulp, this membrane secretes a fluid, from which a very white soft substance is deposited upon the bone; this at first is of a consistence not harder than chalk, for it may be scratched or scraped off by the nail; it how- ever soon grows hard, and seems to undergo a process similar to that of crystalization, for it takes a regular and peculiar form. * Plate IX. Fig. 4. FORMATION OF THE ENAMEL. 53 The deposition of the enamel continues nearly as long as a tooth is contained within the membrane; it is always most in quantity upon those parts where its formation first began; it is thicker upon the edges and grinding sur- faces of the teeth than upon the sides, and it gradually becomes thinner as it approaches the necks of the teeth. A tooth, when sawn through, shews the arrangement of the enamel; and as it requires more heat to blacken and burn this hardest part of the animal frame than the bony part of the tooth, we can, by exposing it to the effects of fire, obtain a still more distinct exhibition of it.* By the time the enamel is completely formed, the tooth has risen so much in the socket, that by its pressure it occasions an absorption of the membrane, which completely prevents any further addition of enamel. When perfect, the enamel of the teeth is so hard, that a file in cutting it is soon worn smooth; and when struck with it, sparks of fire will be elicited; an effect I have several times produced with human teeth, and which may be very readily seen by striking the teeth of large animals with steel, particularly those of the Hippopo- tamus. The enamel, when broken, appears to be composed of a great number of small fibres, all of which are so ar- ranged as to pass in a direction from the centre to the circumference of the tooth, or to form a sort of radii round the body of the tooth. This is the crystalized form it acquires some time after its deposit; by this dis- position of its fibres, the enamel acquires a great degree of strength, and thus it is not so readily worn down in mastication, nor so easily fractured by violent action of the teeth.f * Plate IX. Fig. 1. t Plate IX. Fig. 2, 3. 8 54 MANNER OF THE [The foregoing explanation of the manner of the for- mation of the enamel, has, until recently, been regarded by anatomists and most writers on odontology, as correct, but the recent researches of Raschkow and others, have very conclusively proven it to be erroneous. In fact a different theory was promulgated as early as 1819, by M. Delabarre, in his treatise on Second Dentition. This writer contends that the enamel is an integral part of the tooth, that it proceeds from the dental embryo, and is produced by an immense number of small exhalent vessels, which form a sort of imperceptible velvet. Into these, he supposes the calcareous ingredients are de- posited, and in such a way as not to destroy their organic sensibility. According to Raschkow, the gelatinous granular sub- stance, spoken of by Goodsir, and situated between the follicle and germ of the tooth, is the organ destined for the formation of the enamel. Raschkow calls it the ada- mantine organ, and says it forms a 'globular nucleus' be- tween the follicle and dental germ, at a very early period of the growth of the latter, with a bulging externally, and presenting internally a parenchymatious appearance, gradually exhibiting angular granulations, which are con- nected with each other, by 'filaments of cellular tissue,' resembling 'a kind of actinenchyma, such as may be seen in plants.' The editor has frequently had opportunities, in dissecting the jaws of young animals, of demonstrating the existence of this granular substance, and it was the discovery of this, that induced him to believe the gene- rally received opinion of the manner of the formation of the enamel, to be erroneous. This granular substance is surrounded by a limpid fluid resembling the liquor amnii, and as ossification commences on the pulp of the tooth, it is gradually transformed into a membrane, attaches FORMATION OF THE ENAMEL. 55 itself to it, and to which it adheres with considerable tenacity. Raschkow says, 'the dental germ, in advancing further and further into the dental follicle, makes first only a slight impression on the globular mass of the enamel organ, but this impress is rendered gradually deeper as the growth of the germ proceeds. When the germ has penetrated further into the hollow thus made, it appears narrower towards the base, and thicker under the apex, and is enclosed around on every side by the parenchyma of the enamel organ, which thus assumes the appearance of a hood, covering the dental germ when advanced in its development.' It is disconnected from the dental capsule, except at the coronal part, where it is apparently united by some loose vessels, which supplies the paren- chyma of the enamel organ with the numerous capilla- ries that pervade it; and from this, our author assumes, that while the tooth germ originates from the extremity of the sac next the fang, the enamel organ has its origin from the opposite extremity, and thus, 'arising at opposite points' they 'approach each other, are adapted together, and both contribute' to the production of the tooth. He also describes a peculiar organ on the inner surface of this granular substance, 'consisting of short uniform fibres, placed perpendicularly' 'to the cavity, and forming as it were, a silky lining to it, which may readily be distin- guished in a transverse section of the enamel organ, from the stellated parenchyma' of this substance, which he calls the pulp. This stratum of fibres, he represents, as originating in the transformation of the enamel pulp, with which it is for a time connected, but from which it afterwards sepa- rates, so as only to adhere by a 'few filaments of cellular tissue, and becomes a genuine membrane,' wThich he 56 MANNER OF THE styles, 'the enamel membrane.' The inner surface of this membrane, he says, 'consists of hexangular, nearly uniform corpuscules, visible only through a magnifying glass, towards the centre of each of which, is a round eminence. These corpuscules are nothing more than the ends of short fibres, of which the whole membrane is composed, and which being pressed together, assume freely the hexangular form.' They are disposed in regu- lar series, and correspond with the arrangement of the fibres of the enamel. These corpuscules, he regards as secretory ducts, whose peculiar office is to secrete the enamel fibres which correspond to them. This process begins immediately after the commencement of the ossification of the pulp of the tooth, and while it is going on, Raschkow thinks an organic lymph is secreted from the parenchyma of the enamel membrane, which diffuses itself between the fibres, rendering the whole substance soft, but which afterwards, by means of a kind of chemico-organic process, combines with the earthy substances, and forms the animal base of the enamel. The membrane covering the pulp of the tooth, he calls the praeformative, and this, no doubt, as has been before intimated, constitutes the bond of union between the enamel and bone of the tooth. Little is known with regard to the manner of the for- mation of the cementum, or fourth substance entering into the composition of the tooth. Raschkow thinks that it may be produced by the remains of the enamel pulp. I am of the opinion, however, that it is secreted by the dental periosteum, and the more so, as it cannot be de- tected on the crowns of the human teeth.] While some eminent physiologists have contended, that the teeth, when they have attained their full growth, FORMATION OF THE ENAMEL. 57 are to be considered as extraneous bodies, and that they no longer receive nutriment, like the other bones of the body; others have supposed, that even the enamel is kept up in future life by continued deposit: but that this cannot be the case will be obvious, when it is considered, that the membrane which invested the pulp and entirely produced the enamel is destroyed before the tooth can appear. When a tooth first appears, the enamel is thick- er than at any other period of life, and from that time it begins to decrease; this may be remarked in some of the permanent teeth. The incisores, when they first pass through the gum, have their edges notched; the cuspidati are sharp at their points, and the grinding sur- face of the molares is always irregular. This sharpness of the points of the teeth is occasioned by a larger de- posit upon those parts where ossification had first com- menced. By the friction of the teeth against each other, and against the food in mastication, the teeth are worn smooth, the notches upon the incisores disappear, the points of the cuspidati are rounded, or in many cases en- tirely removed, and the surfaces of the molares become much smoother. The case is quite the reverse with the bony part, for when a tooth is first seen through the gum, scarcely more than two-thirds of the fangs are formed, but the ossifica- tion continues for a considerable time afterwards. The enamel upon some teeth has a very defective for- mation; instead of being a hard white substance, having a smooth polished surface, it is frequently met with of a yellow colour, and having a great number of indentations upon its surfaces. This occasions the teeth to resemble the exterior of sponge, and gives them what has been termed a honey-combed appearance. Sometimes this appearance of the enamel is only met 58 MANNER OF FORMATION OF ENAMEL. with on the front teeth, near the cutting edge; at others it extends nearly over half of the tooth, the remaining parts being perfect. When the roughness is near the edge, it often wears out in a few years, or at the age of maturity it may be filed out. In some, one, two, or three indented lines pass across the front of the teeth.* [The affection under consideration may result from the destruction of a portion of the praeformative membrane or some one or more of the enamel fibres, caused by disease of the general system, and some writers are of the opinion that it is wholly referable to the occurrence of eruptive diseases during the formation of the enamel. M. Duval has given to the disease the name of atrophy.] This defective formation of the enamel is usually confined to the incisores, cuspidati, and first permanent molares: it is rarely met with on the bicuspides, or second and third molares.—No certain reason can be assigned why the membrane secreting the enamel should so often deviate from its natural action. It can only be referred to some peculiarity of constitution, occasioning an irregu- lar action in the membranes of the pulps, during the first months; for this appearance is only met with on those teeth, the formation of which commences about the time of birth: and even upon them, in those parts only which are first formed. In a few months after, the membranes acquire a healthy action, and the teeth which are formed later, rarely have defective enamel. It is very remarkable that this circumstance often occurs in several children of the same family; indeed there is scarcely any part in which they resemble each other more, than in the appearance and arrangement of the teeth. I have however constantly observed that these kind of teeth are not so liable to decay, as those which * Plate IX. Fig. 14. ARTERIES OF THE TEETH. 59 have the enamel very beautiful and transparent. We here find nature, as she does in many other particulars common to humanity, making up for defects in one part of her work, by bestowing greater perfection upon an- other. [The editor's observations upon this subject do not exactly accord with the opinion of Mr. Fox. He has seldom known more than one or two of the same family to have their teeth thus affected, and he has found that atrophied teeth were just as liable to decay as any other, but the parts marked by the disease are the portions least liable to be attacked by caries.] Sometimes in the formation of the teeth two pulps unite, .and upon their surfaces, appear as two distinct teeth, but upon attempting to remove one, it is discovered to be united to the next. In Plate IX. are figures of several teeth of this kind, which must be regarded as lusus naturae.* Very often the fangs of the teeth become crooked, from some obstruction to their growth; and teeth having two or three fangs, are now and then met with, so much bent at their points as to occasion them to be very firmly placed in the jaw. When these circumstances occur, the ex- traction of the teeth is unavoidably an operation of the utmost difficulty. [ARTERIES OF THE TEETH.] The arteries which supply the teeth with blood, are called the dental; they are branches of the internal max- illary artery, which arises from the external carotid, at that part where it is covered by the parotid gland, and lies behind the middle of the upright plate of the lower *Plate IX. Fig. 8, 9, 10. 60 NERVES OF THE TEETH. jaw, where it divides into the condyloid and coronoid processes. It passes first between the jaw and the ex- ternal pterygoid muscle, and afterwards runs in a very winding direction towards the back part of the antrum maxillare; it here sends numerous branches to the parts belonging to both jaws, and to the teeth of the upper jaw. It then gives off one branch to the lower jaw, called by some, the inferior maxillary, and by others, the dental. This enters the jaw-bone at the posterior maxillary fora- men, passes through the maxillary canal, and gives off branches to the fangs of each tooth, and also supplies the substance of the bone: This vessel having sent a branch to the incisores, passes out at the anterior maxillary fora- men; it is distributed to the gums, and communicates upon the chin with branches of the facial artery. [NERVES OF THE TEETH.] The nerves, which are distributed to the teeth, arise from the fifth pair, the trigemini. This pair of nerves divides into three branches; the opthalmic, the superior maxillary, and the inferior maxillary. The opthalmic branch passes through the foramen lacerum of the orbit, and is distributed to the parts in the neighbourhood of the eye; the superior maxillary nerve goes out at the foramen rotundum of the sphenoid bone, and divides into several branches, being continued to the posterior part of the nose, the palate, velum palati, and contiguous parts. At the posterior part, small filaments of nerves, accom- panying branches of arteries, enter the superior maxillary bone by foramina which lead to the molares, and also to the membrane lining the antrum maxillare: The nerve then goes into the canal under the orbit, and forms the infra orbitar nerve. Whilst in the canal, it sends off ABSORBENTS OF THE TEETH. 61 branches to the bicuspides, cuspidati, and incisores; it afterwards passes out at the foramen infra orbitarium, and is distributed upon the cheek, under eyelid, upper lip, and side of the nose. The inferior maxillary nerve passes through the fora- men ovale of the sphenoid bone, and is distributed to the muscles of the lower jaw: it sends off a large branch, the lingual, which goes to the tongue, which is the true gustatory nerve; it then enters the maxillary canal of the lower jaw, passes through the bone under the alveoli, and gives off branches, which entering the fangs, ramify upon the membrane within the cavities of the teeth; it passes out at the anterior maxillary foramen, and is spent about the chin and lip.* [ABSORBENTS OF THE TEETH.] There is another set of vessels, called absorbents, of the existence of which, in the structure of common bone, I believe there is no doubt; and on account of certain effects produced upon the teeth, wre must conclude that they are not destitute of them. During the progress of the second dentition, the fangs of the temporary teeth are absorbed; and even the per- manent teeth, when diseased, often lose a considerable portion of the fangs. It may be argued, that in these cases the absorbent vessels are situated in the socket, and act upon the tooth as if it were an extraneous body. But in some cases, we find the teeth undergo the ulcera- tive process, and a considerable quantity of the inner part is removed, a circumstance which could not happen un- less there wTere absorbents entering into the cavities of the teeth, and properly belonging to them. * Plate IX. Fig. 5. 9 62 STRUCTURE OF THE TEETH. Besides these instances, the effects of absorption in the tusks of elephants are often seen; sometimes in sawing these bodies, iron balls, spear heads, &.c. are met with, which have been forced into them in attempting to kill these animals. These extraneous substances are always found loose, having a space in which they can be moved. This could never happen, unless there were some action going on, by which part of the bone could be removed, and there is no other mode in which it can be effected, but through the medium of the absorbent vessels. [As the editor will have occasion in the chapter treat- ing of the destruction of the roots of the temporary teeth, to make some remarks concerning the phenomenon here alluded to, it will not be necessary, in this place, to enter upon its further explanation.] [ARTICULATION OF THE TEETH.] The teeth are fixed in their sockets by that species of articulation called gomphosis. They are attached to the alveolar cavity by a strong periosteum, which is extended over the fangs, and which also lines the socket; it is connected to the gums at the neck of the tooth, and it is vascular, like the periosteum in other parts of the body. [STRUCTURE OF THE TEETH.] It is very extraordinary that Mr. Hunter should have considered the teeth as devoid of internal circulation, and destitute of the living principle. The structure of the teeth is similar to that of any other bone, and differs only in having a covering which is called enamel, for the exposed surface, and in the bony part being more dense. There are several parts of the body in which we cannot STRUCTURE OF THE TEETH. 63 by injections demonstrate the existence of blood-vessels, of the vascularity of which no one can entertain a doubt; and as bones in general are continually receiving nourish- ment from the vessels which enter into their substance, it may be justly inferred that the blood sent to the teeth affords a similar supply, especially as a considerable portion of animal matter enters into their composition. A large quantity of blood is distributed to the teeth; this may frequently be seen in performing some opera- tions. In cutting off the crown of a tooth, in which the caries had not spread to the fang, for the purpose of en- grafting a new tooth, I have several times seen a dis- charge of blood from the internal cavity. This blood came from the vessels of the membrane in the cavity, which I have also several times seen injected. Blood carries with it the basis of nutrition, and is sent to those parts only where renovation is necessary. For what other reason then, but to impart some principle of nutri- tion, can so much blood flow into the teeth? If the teeth, after their first formation, received no supply from vessels, or did not require any nourishment, it would have been better if they had been destitute of an internal cavity, and of regular organization. [The vascularity of the teeth is now too well estab- lished to leave any room for doubt. The editor has, in his anatomical cabinet, sections of two human teeth, in which, by the aid of a microscope, vessels injected with red blood can be distinctly traced. A microscopic view of one of these is given in the second volume of the American Journal of Dental Science. The existence of vessels in tooth bone has also been subsequently demon- strated by Dr. Maynard of Washington City, and Mr. Norton of New York.] It is always observed, that as persons advance in life, 64 STRUCTURE OF THE TEETH. their teeth lose that whiteness which they possessed in the time of youth. This change in the appearance of the teeth seems to depend upon one which takes place in their cavities, by which the vessels entering them are gradually destroyed, and the supply of blood is propor- tionably diminished. In the teeth of persons advanced in years, the cavity is very frequently obliterated, in con- sequence of a deposit of bony matter, which entirely de- stroys the internal organization. When this happens, the teeth always lose their colour, and become very yellow, their texture also becomes more brittle, and they acquire a horny transparency. When a tooth has been loosened by a blow, and has afterwards fastened in its socket, a great alteration in its colour is the consequence; it gradually loses its white- ness, and acquires a darker hue; this proceeds from the vessels which enter the teeth, being destroyed, and the teeth consequently losing their supply of blood. The teeth being constructed like common bones, are governed by the same laws, and are liable to be affected by similar diseases; like them, they are affected by the various causes of inflammation, and have the same dis- eased appearances produced upon them. [That all of the diseases of the teeth are identical with those which attack other bones, is obviously erroneous. With the exception of exostosis and necrosis, they do not bear the slightest resemblance to them. Neither are they produced by the same causes nor can they be cured by the same remedies.] In bones, the power of resisting the effects of disease is in an inverse proportion to their density. The living principle is always less in the close textured cylindrical bones, and greater in those which are flat and spongy. The teeth being the most dense bones in the body, have STRUCTURE OF THE TEETH. 65 the least power of resisting disease, and, in them, the general termination of inflammation is in mortification. The teeth do not possess the power of exfoliation, it is not necessary they should, for the system suffers no in- jury by the loss of a tooth: and no person would have sufficient patience to bear the pain attending upon, or wrait the progress of so slow a process. Like other bones, the teeth are subject to that species of inflammation called the ossific, by which the fangs become increased in size, acquire an additional quantity of bone, and exhibit all the appearances of exostosis. They are also liable to inflam- mation of the membrane lining the cavity, and to its sup- puration, during the progress of which the inner part of the tooth is removed by the absorbents, and an appear- ance is produced like that disease of bones called spina ventosa. CHAPTER FOURTH. OF THE SHEDDING OF THE TEETH. The falling out of the temporary teeth, to make way for those which are to be permanent, is commonly called the shedding of the teeth. It is the consequence of one of the most curious actions of nature, and is of great im- portance to our comfort, since the beauty of the face, and the proper articulation of speech in a considerable degree depend upon the regularity with which this part of her work is accomplished. The necessity of teeth for the mastication of food com- mences as soon as the time of support from the mother ceases, and therefore a set is provided at a very early period, which occupies but a few months in formation, and only continues a few years without falling into a state of decay. These teeth are only proportioned to the size of the mouth during childhood, and would consequently be too small and too few in number, for the extended state of the jaws in the adult; hence the formation of new teeth becomes indispensable, and according to the man- ner already described, a set of teeth is formed, of a mag- nitude and number proportioned to the mature state of the body, and intended, from their compact structure to continue through life.* * The same circumstances take place in all animals: They, like the human sub- ject, shed their teeth, and obtain a new set. But in some animals there is a variety in the mode, arising from the peculiar structure of their teeth and jaws. This is OF THE SHEDDING OF THE TEETH. 67 It is during the growth of the permanent teeth that the very curious process of absorption is going on in the tem- porary ones, which facilitates their removal from the socket, and affords a free passage to the permanent teeth. It has been observed, that the pulps of the new teeth are placed behind the temporary ones, and in that situa- tion they are very much crowded, and occupy but a small space. Now it is evident that as they advance in growth, they will require an increase of room, to obtain which they must come forward, so as to form a larger circle. This effort first produces a considerable pressure against the bony partition, placed between the temporary and permanent teeth, and then upon the posterior part of the fangs of the shedding teeth. The pressure in this instance acts precisely in the same manner as it generally does in other cases where it is applied. It induces an absorption of the parts pressed against; and as the new teeth augment, the fore part of the socket which was formed around the pulp, and separated it from the tempo- rary tooth, is removed by the process of absorption.* The second teeth still continuing to protrude, press against the fangs of the temporary teeth, at which place their substance begins to be taken up: The absorption goes on until the greater part, or the whole, of the fangs are removed; at the same time the new teeth come for- ward, underneath the temporary ones, which soon drop out, when the edges of the new teeth may generally be distinctly felt. particularly and very curiously the case in the elephant, which animal, instead of having its new teeth formed under the temporary ones, they are formed in sockets beyond those to be shed, which in due time advance from the back to the front part of the jaw. This is very accurately described by Mr. Corse, in his paper in the Phil- osophical Transactions. A similar mode is observed to take place in one grinder of the Sus Ethiopicus, as described by Mr. Home, whose paper, with that of Mr. Corse, are in the Transactions for 1799. * Plate II. Fig. 1,2,3, 4. 68 OF THE SHEDDING OF THE TEETH. The absorption gives to the fangs of the teeth an ap- pearance of being broken, but this, when compared with a fracture, will be found to differ from it very materially. While the absorption of the fangs of the temporary teeth seems to depend so much on the pressure of the rising permanent ones, it is often found to go on without such pressure; for in some children the temporary teeth will loosen and drop out many months before new teeth ap- pear, and in many cases the same effect takes place where a new tooth does not rise to replace the one which has been shed. These circumstances seem to prove that the absorption of the fangs of the temporary teeth is an action of nature, sometimes independent of pressure: and it is a very singular circumstance, that at a time of life when so great a quantity of ossific matter is poured forth from all the arteries concerned in the formation of bone, in one par- ticular part, there should thus be an absorption of this substance taking place. In many instances, however, absorption of the fangs of the temporary teeth never takes place; and it is by no means uncommon to find one, two, or sometimes more of them, remain in their sockets for a great number of years. When this happens to be the case with several teeth, it is found that no permanent teeth had been formed: which shews that the absorption of temporary teeth, although a regular action in the animal oeconomy, is very considera- bly influenced by the pressure of forming teeth. This defect always produces an unseemly appearance, from the small size of the old teeth, when compared with the new. Cases of deficiency of the permanent teeth are by no means unfrequent. I have seen a young lady of about twenty years of age, who had never shed the two central OF THE SHEDDING OF THE TEETH. 69 incisores of the under jaw; and in the upper jaw, all the temporary incisores remained, except one of the lateral, which had been shed. [The editor cannot believe, that this curious and sin- gular operation of the animal economy is the result, wholly, of the action of the absorbents. Bourdet, ob- serving a carneous substance behind the root of the temporary tooth, ascribed to it the agency of its destruc- tion, which he believed to be effected by means of a sol- vent fluid which it exhales. Laforgue gives to this substance the name of absorbing apparel, believing its function to be the removal of the root of the temporary tooth, and in this opinion M. Delabarre concurs. Having given a brief exposition of the last named au- thor's views upon this subject, in his Principles and Practice of Dental Surgery, accompanied by his own, he wall here repeat what he there stated. 'While the crown of the tooth of replacement,' says Delabarre, 'is only in formation, the exterior membrane of the matrix is simply crossed by some blood vessels; but as soon as it is completed, the capillaries are then developed in a very peculiar manner, and form a tissue as fine as cob-web; from this tissue the internal membrane, instead of con- tinuing to be very delicate, and of a pale-red colour, increases in thickness and assumes a redder hue. As was before said, it is at the instant in which commences the reaction of the coats of the matrix, that are conveyed from the gum to the neck of the tooth, that the plaiting of the vessels, that enter into their tissue, compose a body of a carneous appearance, whose absorbents extend their empire over all the surrounding parts; it is, there- fore, the dental matrix itself, that, after being dilated to serve as a protecting envelope to the tooth, is contracted to form not only this bud-like body which we find imme- 10 70 OF THE SHEDDING OF THE TEETH. diately below the milk tooth, at the instant in which it naturally falls out, and whose volume is necessarily aug- mented as odontocia gradually goes on; but also a car- neous mass by which the whole is surrounded and whose thickness is the more remarkable as the organ that it envelopes is nearer its orifice.' After giving this description he asks, 'is there a dis- solving fluid that acts chemically on the surrounding parts, or do the absorbents, without any intermedial, destroy every thing that would obstruct the shooting up of the tooth ?' In reply to this, he says, 'Not possessing positive proof, suitable to guide me in the decision of this question, and finding those of others of little import- ance, I shall not attempt to answer them.' In pursuing the subject further, he states that the ves- sels of the temporary tooth often remain entire in the midst of this carneous substance, and continue to convey their fluids to the central part of the tooth, wThilst the cal- careous ingredients and the gelatine have been removed, and that at other times they too are destroyed. And the conclusion to which he arrives, after a careful examina- tion of the whole subject, is, that whether the earthy and animal parts of the root are removed by the absorb- ents of the carneous tubercle in question, without any previous change, or whether they are decomposed by the chemical action of a fluid exhaled from it, they are ultimately carried back into the general circulating system. In proof of the agency of the fleshy tubercle in the destruction of the roots of the temporary teeth, he men- tions one fact that goes very far to establish it, and if his views be correct, will account for those cases which are occasionally met with, where one or more of the perma- nent teeth fail to appear. It is this: if this substance fails to be developed, or is destroyed by an injurious OF THE SHEDDING OF THE TEETH. 71 operation, the tooth often remains in its socket, and never makes its appearance. Cases of this kind have fallen under the notice of almost every practitioner. In as few words as possible, I have given the views of this ingenious writer, on the subject under consideration, and although they do not seem to have attracted much attention from English writers, and are rejected by Mr. Bell, on the ground, as he says, but which I have never known to be the case, that the destruction of the root of the temporary frequently commences on a part 'the most remote from the sac of the permanent tooth,' I am dis- posed to believe them, for the most part, correct. As to the existence of the fleshy tubercle, there can be no question, and that it is through the agency of these that the roots of the temporary teeth are destroyed, seems more than probable. But whether it is through the agency of their absorbent vessels or a chemical fluid ex- haled for the purpose, may not, as Delabarre says, be so easy to determine. The change that takes place in the external membrane of the dental sac, as noticed by Delabarre, is observable first on the peduncle or chord leading from it to the gum behind the temporary tooth. It here becomes thickened about the time the root of the new tooth begins to form, and assumes a fleshy appearance, and it is here that the destruction of the surrounding bone commences, enlarg- ing the alveolo-dental canal, and gradually removing the intervening long partition, and finally the root of the temporary tooth. The agency of this thickened and fleshy condition of the exterior membrane of the dental capsules, in the removal of the roots of the temporary teeth, is rendered more conclusive by the fact, that, in those cases where the roots of the permanent teeth have become partially destroyed, the alveolo-dental periosteum 72 OF THE SHEDDING OF THE TEETH. had assumed a similar appearance. In the formation too of alveolar abscess, the tubercle at the extremity of the root presents a like aspect. It oftentimes happens, that the root of a temporary tooth fails to be destroyed, and that the crown of the replacing organ comes through the gum in a wrong place. Whenever this happens, the carneous body is developed only beneath the parts through the opening of which the new has appeared, and is not brought in con- tact with the bony partition between it and the root of the temporary. The manner of the destruction of the roots of the temporary teeth has been a subject of close and critical enquiry with me for several years, and the more I have examined it, the more fully have I become convinced, that it is the result of the action of this fleshy tubercle upon them, and while its formation seems to be the result of the contraction of the dental sac and its appen- dage, for the purpose of effecting the eruption of the tooth, it is especially charged with the removal of every thing that would obstruct its passage. In conclusion, it is only necessary to observe, that the temporary teeth are shed in the same order in which they at first appear. After one pair has been shed, a sufficient time usually elapses before the shedding of another, for those of the same class of the permanent set to come forward and take their place. Thus, the jaws are never deprived, unless from some other cause than the destruction of the roots of the temporary teeth, of more than two teeth in each jaw at any one time.] It frequently happens in the upper jaw, that the per- manent central incisores only are formed, the lateral ones never appearing. Many persons are deficient in one or more of the bicuspides. I know a gentleman who re- OF THE SHEDDING OF THE TEETH. 73 sides at Bath, who has never had the incisores of the under jaw; and it is remarkable, that two other persons of his family are in the same situation. I have seen a lady who had only four teeth of the permanent set in each jaw. Mr. Taunton, Surgeon of the City Dispen- sary, has the preparation of a child's head, in the upper jaw of which only one incisor was forming.* These de- viations often occur in the human subject; but so far as I have observed, they are very rare in animals, yet I once saw a horse rising between eight and nine years, which still retained one of the milk incisores. The appearance of the fangs of the teeth, when ab- sorbed, has given rise to a popular but erroneous opinion, that the first teeth have no fangs, and this was even taught by some of the old anatomists. It has also been erroneously conceived that the temporary teeth are pushed out by the permanent: Now that this cannot take place, will be seen by observing the state of the two sets of teeth. The temporary ones are firmly placed in sock- ets, whilst the new teeth, during their formation, are con- tained in cavities larger than themselves, and can only make such pressure as their gradual growth will permit. On this account, if the absorption of the old tooth be re- tarded, or the formation of the new tooth proceed too quickly, the latter will take an improper direction when they come through the gums, and form a second row of teeth, from the temporary teeth still remaining. More- over, if the old teeth were pushed out by the new, we should always find those teeth about to be displaced, forced out the line of the others, a circumstance which never occurs. The period at which children begin to shed their teeth varies considerably. In some, the teeth become loose as * Plate XI. Fig. 6. 74 OF THE SHEDDING OF THE TEETH. early as five or six years of age; in others, this process does not begin until the eighth year: about six or seven years of age may be taken as the standard time. The teeth of the permanent set, which usually appear first, are the anterior molares, which being somewhat more early in their formation, generally precede the in- cisores; and we must always expect, soon after the cut- ting of one or other of these teeth, that the shedding of the temporary teeth will begin. Soon after the first permanent molares have appeared, the two central incisores of the under jaw become loose, and when they are but slightly attached to the gum, easily come away; the permanent central incisores soon after appear, one coming a little time before the other; in about two or three months the central permanent inci- sores of the upper jaw become loose, and having dropt out, the permanent central incisores succeed them. In about three or four months more, the under lateral incisores, having lost their fangs, come away, and the permanent lateral incisores succeed them. The lateral incisores of the upper jaw are the next which drop out, and the permanent ones appear shortly afterwards. In about six or twelve months more, the temporary molares begin to loosen; they generally come out before the cus- pidati, the long fangs of which take a much longer time in being absorbed. The first bicuspides take the place of the first molares, and about the time they appear, the second temporary molares, and the temporary cuspidati, become loose, and having been shed, are succeeded by the permanent cus- pidati, and the second bicuspides. The shedding of the teeth, commencing at six or seven years of age, is commonly completed in about five or six years, when all the temporary have come out, and those OF THE SHEDDING OF THE TEETH. 75 of the permanent set as far as the second molares, have taken their stations. There yet remain, to complete the set, the third molares, or dentes sapientiae., and these usu- ally appear between eighteen and twenty-one years of age, but sometimes they do not come till much later; not before twenty-seven or thirty years; and I once was con- sulted by a gentleman, fifty years of age, who had great pain cutting one of these teeth. [The periods for the eruption of the permanent teeth are, like those of the temporary, exceedingly variable. The following, however, may be regarded as very nearly correct. The first molares usually come through the gums between the fifth and sixth year; the central inci- sores, between the sixth and eighth; the lateral incisores, between the seventh and ninth; the first bicuspides, be- tween the ninth and tenth; the second, between the tenth and eleventh, or eleventh and a half; the cuspidati, be- tween the eleventh and twelfth; the second molares, be- tween the twelfth and fourteenth; and the dentes sapi- entiae, between the eighteenth and twentieth.] CHAPTER FIFTH. OF THE IRREGULARITY OF THE TEETH. During the shedding of the teeth there are several circumstances which prevent the permanent teeth from acquiring a regular position, and often give rise to very great irregularity in 'their arrangement. The most frequent cause is a want of simultaneous action between the increase of the permanent teeth, and the decrease of the temporary ones, by the absorption of their fangs. It rarely happens that so much of the fang of a temporary tooth is absorbed as to permit its removal by the efforts of the child, before the permanent tooth is ready to pass through: on which account the new tooth takes an improper direction, and generally comes through on the inside. Cases are very frequent in which scarcely any absorp- tion of the fangs of the temporary teeth had taken place previous to the appearance of several of the permanent teeth; and it often happens, that upon the removal of the shedding teeth to give room for the permanent ones, that no absorption of the fangs of the temporary teeth has taken place. Irregularity of the permanent teeth is most commonly occasioned by the resistance made by the nearest tempo- rary teeth; this"is always the case if the temporary teeth are small and close set, for as the permanent incisores are OF THE IRREGULARITY OF THE TEETH. 77 much larger than the temporary, they require more room; but as the space left by the shedding of the temporary teeth is too.small for the regular position of the permanent, they are exposed to the pressure of the next tooth, and hence are frequently turned out of their right direction. Another cause of the irregularity of the teeth arises from the permanent teeth being too large for the space occupied by the temporary ones; those parts of the jaws not being sufficiently extended to permit a regular posi- tion of the new teeth—in this case the irregularity is con- siderable, and occasions great deformity in the appearance of the mouth. The incisores and cuspidati being much larger than those of the child, require more room, for want of which they are turned out of their proper positions. The central incisores overlap each other—the lateral in- cisores are either placed obliquely with their edges turned forwards, or. they are pushed back, and stand between and behind the central incisores and the cuspidati; the cuspidati are projected, occasioning the lip to stand out with considerable prominence, and the bicuspides are placed very irregularly. [Malconformation of the jaws may be mentioned as another cause of irregularity. The superior alveolar arch is sometimes too narrow—having a compressed ap- pearance, and projecting so as to prevent the upper lip from covering the front teeth. The arch at other times is too broad, giving to the roof of the mouth a flattened ap- pearance, and causing the teeth to be separated from each other. The effect upon the appearance of the individual in either of these cases, is bad, but worse in the first than the last. The lower jaw is liable to similar faulty configurations. The disposition to defects such as these, is observable in early childhood, and is regarded by most of those who 11 78 ACCRETION OF THE JAWS. have treated of it, as hereditary, and more peculiar to the people of some countries than others. Some at- tribute it to a rickety diathesis of the general system, but this opinion is gratuitous, as is shown by the fact, that most persons labouring under this affection, have good palates and well developed jaws. It cannot, therefore, with any degree of propriety be regarded as having any agency in the production of a faulty configuration of the jaws. There is also another species of deformity sometimes met with in the upper jaw, equally difficult of explana- tion. It is characterized by one or more divisions of the upper lip, alveolar border, and palatine arch, always giv- ing rise to irregularity in the arrangement of the teeth. This description of malconfiguration is congenital. Supernumerary teeth too, may be reckoned among the causes of irregularity. But examples of this are of com- paratively rare occurrence.] It will be proper, in this place, to observe the manner in which the jaw bones grow, (the under one being taken as the example) and to point out the difference between the temporary and permanent teeth. [ACCRETION OF THE JAWS.] After a child has obtained all the temporary teeth, the jaw in general grows very little, in the part which they occupy. In those children who are an exception to this rule, the temporary teeth become a good deal separated from each other, and these are the cases in which the shedding of the teeth is effected without any assistance of art. When the jaw of a child is compared with that of an adult, very striking difference is observed; that of a child ACCRETION OF THE JAWS. 79 forms nearly the half of a circle, while that of an adult is the half of a long ellipsis. This comparison clearly points out the part in which the jaw receives its greatest increase, to be between the second temporary molaris and the coronoid process; and this lengthened part of the jaw is destined to be the situation of the permanent molares. By the elongation of the jaw a great change in the form of the face is produced; that of a child is round, the cheeks are plump and the chin flat; in an adult the face is more prominent, with a flatness of cheek and a considerable length of chin. The temporary incisores and cuspidati are much smaller than the permanent, while the molares of the temporary set are larger than the bicuspides which succeed them. Hence it is, that the incisores and cuspidati are so fre- quently irregular, and they never could be otherwise were it not that some space were gained from the mo- lares, in consequence of the bicuspides being much smaller. This circumstance is rendered intelligible, by exam- ining jaws at various ages, and observing in what particu- lars they differ from each other. Until about twelve months after birth, the jaw grows uniformly in all its parts, and at that time as far as the teeth extend, it approaches nearly to a semicircle; at about three years of age, when all the temporary teeth have appeared, it begins to lose its semicircular form, and become somewhat elongated; an extension takes place between the last temporary molaris and the coronoid pro- cess; and in that part, in an advanced state of formation, the first permanent molaris will be found. At about seven or eight years of age, the jaw is more extended, the first permanent molaris has grown up, and 80 ACCRETION OF THE JAWS. the second is advancing in formation. At about eleven or twelve years of age it will be found still longer; the second molaris is ready to come through the gum, and the third molaris has begun to form. The jaw acquires its full proportion, at about eighteen or twenty years of age, when the third molaris makes its appearance, and the teeth are seen in the figure of their arrangement to form part of an ellipsis. The growth of the jaw being nearly confined to the part situated behind the temporary teeth, where the per- manent molares are placed, the anterior part of the jaw undergoes little more than an alteration in form; it adapts itself to the permanent teeth there situated, and scarcely receives any increase of size. The same comparison of jaws exhibits the cause of ir- regularity in the permanent incisores and cuspidati. When a child is about to shed its teeth, the first perma- nent molares come through the gums behind the tempo- rary molares, and therefore the teeth which are situated anteriorly to the permanent molares, can obtain no ad- ditional space. The permanent incisores occupy the space of the tem- porary incisores, and half of that of the cuspidati. It commonly happens that the bicuspides are earlier in their appearance than the cuspidati; therefore, when the first temporary molares are shed, a little room is gained, as the teeth which succeed them are smaller. When the second molares are shed, still more room is gained; the two bicuspides go back against the first permanent molares, and thereby give sufficient room for the cuspi- dati. Thus, by the change of the molares of the child, which are large, for the bicuspides of the adult, which are small, room is obtained for the increased size of the permanent incisores and cuspidati. ACCRETION OF .THE JAWS. 81 [There exists considerable diversity of opinion with regard to the increase of that portion of the jaw occu- pied by the temporary teeth. Some writers contend that it continues to grow until these teeth are replaced by the permanent ones, while others assert that the in- crease, after the completion of first dentition, is wholly confined to the back part of the jaw, between the second molares and the coronoid processes, and that the ante- rior portion undergoes no increase whatever. Among the former is M. Delabarre. This writer endeavours to prove that a very considerable increase takes place in this part of the jaw, but Mr. Fox entertains a different opin- ion, as may be perceived from what he has said upon the subject, and he endeavours to establish the correctness of his views by the measurement of several jawrs, as may be seen by reference to Plate XL Fig. 5. But the only way to arrive at the truth of the matter is, to measure the same jaw at different ages, as proposed by Mr. Thomas Bell. For example, let that portion of the jaw of a child, containing the temporary teeth, be measured im- mediately after the completion of this dentition, or say the third year, and then after they are replaced with the permanent teeth. If this be done, the portion of the jaw occupied by these teeth will be found to have in- creased a little, but not as much as Delabarre supposes. I allude to the change which takes place in the span or extent of the circle of the arch, not to the trans- verse or perpendicular dimensions of the bone. These continue to augment until the sixteenth or twentieth year. The premature loss of a temporary tooth, may, by the approximation of the adjoining teeth, cause a diminution of the span of the anterior portion of the jaw. For this reason the temporary teeth should never be extracted, except when called for by urgent necessity. 82 ACCRETION OF THE JAWS. The popular opinion, that inasmuch as the temporary teeth are soon to be replaced, it is of little consequence whether they be retained in the jaw until they are re- moved by the operations of the economy, or are lost a few years earlier, is erroneous, and has been productive of a vast amount of injury.] This change of small teeth for larger, and of larger for smaller, points out the necessity of giving some assistance to nature in one of her processes, viz: that of throwing out the temporary teeth before the permanent teeth ap- pear: if this be done at a proper time, the teeth will always take a regular position, and every deformity arising from irregularity be prevented. During the progress of the second dentition, an oppor- tunity presents itself for effecting this desirable object; but every thing depends upon a correct knowledge of the time when a tooth requires to be extracted, and also of the particular tooth; for often more injury is occasioned by the removal of a tooth too early, than if it be left a little too long; because a new tooth, which has too much room long before it is required, will sometimes take a di- rection more difficult to alter, than a slight irregularity occasioned by an obstruction of short duration. If an im- proper tooth be extracted irreparable mischief will ensue; as in the case where young permanent teeth have been removed, instead of the obstructing temporary ones, which I have several times known to have been done. CHAPTER SIXTH. OF THE TREATMENT TO PREVENT IRREGULARITY OF THE TEETH. The advantage which attends the removing the teeth of children, depends upon its being done at the precise time when nature is tardy in effecting the absorption of the fangs of the temporary teeth. The performance of any improper operation will be prevented by a knowledge of the progress of the formation of the teeth, combined with observations upon the appearance of the gums, which become full when a tooth is about to pass through them. To assist the permanent teeth in acquiring their proper arrangement, the mouth should be examined from time to time, that the operation be performed at the time re- quired; for it is not sufficient to remove an obstructing tooth, when the new one is perceived to be coming irreg- ularly, because it always requires a considerable time to bring the latter into its proper place, and often the ir- regularity remains unaltered. The shedding of the teeth commonly begins at about seven years of age: sometimes it may be earlier, and at others rather later; however, it is about this time that a child's mouth begins to require frequent inspection. There are two circumstances, the presence of either of which always denotes that the shedding of the teeth is about to commence. The first permanent molares of the under jaw make their appearance; or one or both of the central incisores in the under jaw begin to loosen. 84 OF THE TREATMENT TO PREVENT Sometimes the absorption of the fangs of the temporary teeth goes on so slowly, that they do not get loose pre- vious to the passing of the new tooth through the gums behind them. If then the permanent molares have been cut for some time, and there be a fulness of the gums be- hind the under permanent incisores, it will be expedient that the two central incisores be extracted immediately ? although not yet loose. It most commonly happens that the under central incisores, by the early absorption of their fangs, becomes loose, and are taken out by the child some time previous to the appearance of the new teeth; but it often occurs, that although they have got somewhat loose, they are not sufficiently so, to come out of them- selves before the new teeth are ready to pass through. When in this state, the temporary central incisores should be removed, and this will permit the permanent central incisores to take their proper place. It will soon be seen, as the new teeth arise, whether they have sufficient room; if not, it will be necessary to remove the temporary lateral incisores. In two or three months afterwards, or sometimes later, attention must be paid to the central incisores of the up- per jaw. If they have got loose they should be taken out, or if not, and there be the least fulness of the gums behind them, they must be extracted, or else one or both of the permanent incisores will come through, and pro- duce one of the most unseemly cases of irregularity, as well as one of the most difficult to treat. When the permanent central incisores are passing through the gum, there is seldom sufficient room for them, and it will be proper to extract the temporary lateral incisores. [The author seems to have overlooked the fact, that, by the time the upper permanent central incisores are IRREGULARITY OF THE TEETH. 85 ready to come through the gums, the temporary lateral incisores have become so much loosened by the wasting of their roots, as to yield sufficiently to the pressure of the former to permit these teeth to take their proper place in the arch. But when this is not the case, the temporary lateral incisores should be extracted.] The attention is next to be turned to the under jaw, for in three, or six months time, the lateral permanent incisores may be expected to appear, and if there be any fulness of the gum, wThere those teeth are to pass, the temporary cuspidati must be taken out. In two or three months more the same observations should be made upon the upper jaw, and as soon as the permanent lateral in- cisores exhibit signs of approach, by a fulness of the gums, the temporary cuspidati should be extracted. When the teeth are in this state, they may often re- main without farther attention for near a twelve-month, during which time the incisores will be acquiring their complete growth; and the cuspidati and the bicuspides be ready to come through. Care must now be taken that the permanent cuspidati do not take an improper direction; the gums should be examined, and if any prominence be felt, the first temporary molares must be extracted. It frequently happens that the first tempo- rary molares get loose previous to any appearance of the cuspidati, and that when they are removed, the bicus- pides soon appear. [The shedding of the first, and often the second tempo- rary molares, takes place previous to that of the temporary cuspidati, so that when it becomes necessary to procure room for the permanent cuspidati, it has to be obtained by the removal of the first or second bicuspides, or when the first permanent molares are decayed, by the extrac- tion of these teeth, instead of the first temporary molares 12 86 TREATMENT TO PREVENT IRREGULARITY. as recommended by Mr. Fox. But it is only in the fewer number of cases that the resources of art are re- quired in the dentition of the secondary teeth. Nature in most instances, is amply sufficient to manage her own work. Irregularity of the teeth more frequently results from the premature removal of the temporary teeth, than from their retention too long in the jaws.] After this, the treatment must be guided by circum- stances. If either of the cuspidati exhibit signs of early approach, and there be scarcely room between the latter incisor and the bicuspis already in its place, it will be proper to take out the second temporary molaris, the first bicuspis will then go somewhat back and the cuspidatus will get more room. When the second temporary molares have been re- moved, there remain no other obstacles in the way of the completion of the second dentition. The second bicus- pides will come properly into their places, and the mo- lares having no obstruction, will progressively occupy their proper stations. Though the shedding of the teeth generally requires a period of four or five years, it sometimes occupies nearly six years. In some children the changes take place quickly, and in others slowly. I have seen a child of only seven years of age more advanced in the process of dentition, than another of the same family when near eleven. CHAPTER SEVENTH. THE TREATMENT TO REMEDY IRREGULARITIES OF THE TEETH. [There is no truth in surgery, more fully established, than is that of the practicability of altering the position of a tooth in the mouth, after the completion of its growth; and yet there is no branch of practice in den- tistry more neglected than the treatment of irregularity in the arrangement of these organs. Notwithstanding the acknowledged importance of regularity in the ar- rangement of the teeth, not only to an agreeable expres- sion of the countenance, but also to the health and durability of the whole dental apparatus—hardly one practitioner in twenty ever gives the subject a thought. Their manipulations are almost wholly confined to filing and plugging the natural teeth and the substitution of ar- tificial ones for their loss. The attention of a few of the more scientific and skilful practitioners, however, have been directed to the treatment of irregularity, and the results of their labour in this department of physical alle- viation, have been as gratifying to their own feelings as they have been beneficial to their patients. The cases of irregularity of the teeth are so various and sometimes complicated in their nature, that the skill, patience and ingenuity of the operator are often put to the severest test. Different cases require to be treated differently. To construct the appliance best calculated 88 VARIETIES OF IRREGULARITIES to overcome the difficulty in every case, requires no small amount of tact and inventive ingenuity. It often too, becomes necessary to vary the means employed in the same case, or to use different fixtures in different parts of the operation; and the length of time required for its accomplishment, is sometimes such as to call for a greater amount of patience and perseverance on the part of both practitioner and patient, than every one can be prevailed upon to exercise. A deviating tooth cannot always be moved to the place which it should occupy in a day or a week. Months are oftentimes required to do it, and during the whole progress of the operation, the most constant attention is necessary.] The mode of treatment described in the preceding chapter, is not always had recourse to, at a time when every irregularity might be easily obviated. Parents most commonly wait, until, by an irregular growth of their children's teeth, a manifest deformity is produced, ere they perceive the necessity of advice. In all cases of irregularity during the shedding of the teeth, the treatment to be observed is to remove the ob- structing temporary teeth, and then to apply pressure in the most convenient manner upon the irregular tooth, in order to direct it into its proper situation. [VARIETIES OF IRREGULARITIES OF THE TEETH.] I will now describe the different states of irregularity, and to avoid confusion, take each jaw separately. In the under jaw, when the growth of the permanent central incisores has exceeded the absorption of the tem- porary ones, they growT up immediately behind them, in a direction towards the tongue. These two new teeth are generally so broad as nearly to cover the inner sur- OF THE TEETH. 89 face of the four temporary incisores. It will therefore be necessary, in order to obtain room for these teeth, that the four temporary incisores be extracted. The new teeth will then gradually come forward, in which they will naturally be assisted by the pressure of the tongue of the child, and may be occasionally helped by the finger of the parent or nurse.* If the temporary central incisores have loosened, and come out previous to the appearance of the permanent teeth, the space is seldom sufficiently wide, and the new teeth will either grow up with their sides turned forward, or one will be placed before the other. In this case the two lateral incisores must be taken out.f When the permanent central incisores have completely grown up, they occupy full two-thirds of the space, which contained the four temporary incisores; therefore, when the permanent lateral incisores appear, they are placed partly behind the centrals and the temporary cus- pidati ; or they grow up with one corner turned forwards and the other pointing backwards. In either of these cases the temporary cuspidati must be removed to give room.| [This arrangement, is often, though not always, forced upon the lateral incisores by want of room between the centrals and cuspidati. The space between the last men- tioned teeth is often amply sufficient for the four inci- sores.] The four permanent incisores take up nearly the whole of the space of the temporary incisores and cuspidati. The permanent cuspidati are large teeth, and wrhen they have not sufficient room, they occasion very great irregu- larity. Sometimes they come through on the inside, but most commonly they cut the gum on the outside, and * Plate XII. Fig. 1. t Pig- 2. X Fig- 3, 4. 90 VARIETIES OF IRREGULARITIES project very much out of the circular line from the tem- porary incisores to the temporary molares. In this case the necessity of the removal of the first temporary molares is obvious.* [The author here has evidently mistaken the order of the eruption of the permanent teeth. The first tempo- rary molares and oftentimes the second are replaced with bicuspides before the cuspidati appear, so that if the re- moval of any teeth becomes necessary to make room for the last mentioned organs, it will be the first or second bicuspides, but as these are much smaller than their pre- decessors, it is comparatively seldom that the sacrifice of any is called for.] It is not very common that the bicuspides of the lower jaw are irregular, because the temporary molares are gen- erally removed before they appear; but when this is not the casej they always come through the gums on the in- side, pointing towards the tongue, in which case the tem- porary molares must be removed, that the bicuspides may rise into their proper situations.! In the upper jaw the permanent central incisores some- times pass through the gums behind the temporary ones; when this happens, the four temporary incisores must be extracted, [if the wrong direction taken by the former has resulted from wrant of room between the latter,] and frequent pressure by the thumb should be applied to the new teeth, in order to bring them forward as soon as possible, and prevent one of the cases of irregularity most difficult to be remedied. When the temporary central incisores have come out, the space is generally too narrow for the permanent ones, and hence they are pressed into some shape of distortion. Their edges do not assume the regular curve, but stand ♦Plate XII. Fig. 5. tFig. 6. OF THE TEETH. 91 obliquely, or even sometimes one before the other. Ca- ses of this kind require the removal of the temporary lateral incisores.* [The practice recommended in the last paragraph, is based upon the erroneous belief that the anterior part of the jaw acquires no increase of dimensions after the den- tition of the temporary teeth. But by the slight increase which takes place in this part of the alveolar border and the yielding of the temporary lateral incisores, to the pressure of the permanent centrals, the latter, in the ma- jority of cases, acquire their proper position between the former. Therefore, it is only when they are forced to take a wrong direction in their growth, by want of room between the temporary lateral incisores, that these last should be extracted.] The permanent central incisores are very broad; they occupy the greater part of the space of the four temporary ones, and leave scarcely any room for the permanent late- ral incisores; on which account these latter teeth must grow very irregularly; they generally pass through be- hind, being forced considerably backwards by the resist- ance of the central incisores and the temporary cuspidati. Some times they pass through edgeways, and now and then they project forwards. In any of these cases the re- moval of the temporary cuspidati is absolutely necessary, and unless the operation be timely performed, the irregu- larity is with difficulty remedied-! [As has been intimated in a preceding place, a tempo- rary tooth should not be extracted, except to make room for a permanent one, or when called for by some other special necessity. The practice in the preceding para- graph, as that in the one noticed before it, is based upon a false theory.] * Plate XII. Fig. 7. t Fig. 8, 9. 92 VARIETIES OF IRREGULARITIES The greatest deformity is generally occasioned by the want of room for the lateral incisores and the cuspidati, and when too long neglected usually becomes permanent. When the permanent cuspidati make their appearance, [in an improper place] they generally project very much forwards, and not only disfigure the mouth, but are very dangerous. I have known several instances, where, from the accident of a blow, the upper lip has been cut through. Whenever the cuspidati are growing thus, the first tem- porary molares ought to be extracted.* When the bicuspides appear before the temporary molares have been [removed by the destruction of their roots or] extracted, they pierce the gums above the shed- ding teeth, and may be seen by raising the cheek and upper lip. The removal of the temporary molares im- mediately permits them to come down into their right situation.! [Irregularity in the arrangement of these teeth is, however, of comparatively rare occurrence.] In almost all the cases of irregularity which occur in the under jaw, nothing more is necessary after the re- moval of the obstructing tooth, than to apply the frequent pressure of the finger, in such a manner as to direct the irregular tooth into its proper place. It will assist the natural tendency of the teeth to form a regular circle, and to take up as large a space as possible. But in the upper jaw, when the irregularity has been suffered to remain for any length of time, it cannot be obviated without having recourse to other assistance. Irregularity is often occasioned by the teeth being much too large for the space allotted them, and then it will be necessary to remove one or more of the perma- nent teeth. When the incisores are perfectly regular, and the * Plate XII. Fig. 10. t Fig. 11. OF THE TEETH. 93 bicuspides have appeared before the cuspidati, there is so little space left, that the cuspidati are thrust forward.* It has been the common practice to admit the cuspidati to grow down to a certain length, and then to extract them. This operation certainly removes the deformity of projecting teeth, but it destroys the symmetry of the mouth, and takes away two teeth of great importance. The cuspidati are exceedingly strong; they form the support of the front of the mouth, and in the advanced periods of life, to those persons who have the misfortune to lose the incisores, they furnish an excellent means of fixing artificial teeth. [The practice, formerly so com- mon, of attaching artificial teeth to the cuspidati, is, at the present time, seldom adopted, when there are other teeth in the mouth further back, to which a support for artificial ones can be attached.] On these accounts [or more properly for the reason first stated,] they should be preserved, and therefore it will be right to extract the first bicuspis on each side. The cuspidati will then fall into the circle, and if there should be any vacant space, it will be so far back, that no defect will be perceived. This is often the case in the under jaw, as well as in the upper, and the same practice ought to be adopted. [The better practice, in cases of this sort, is, to extract the second, instead of the first bicuspis, as recommended above, except when the space between the first and the lateral incisor, is very narrow, say not more than equal to one-third the width of the cuspidatus, and in which case the first should be removed instead of the second, for although after the extraction of the other, it might be made to take its place, and the deviating tooth brought within the circle, yet still there would be such an over- 13 *PlateXII.Fig. 12. 94 VARIETIES OF IRREGULARITIES laping of the roots of the two within their sockets, as would occasion a considerable prominence on the anterior part of the alveolar border, which would be likely to give rise to an unhealthy action in the investing soft tissues.] The first permanent molares often become carious soon after they appear; when this is the case, and the other teeth have not sufficient room, considerable advantage always attends their extraction. Their removal permits the bicuspides to fall back, and gives way for the regular position of the cuspidati. The removal of these teeth when decayed ought always to be recommended, although they may not occasion pain, or there be no irregularity in the front teeth; diseased teeth always affect others, and therefore ought never to remain in the mouths of children. If they be extracted before the second permanent molares appear, in a short time they will not be missed, because the bicuspides will go back, and the second and third molares will come forward, so that no space will be left. [When there is irregularity in the front teeth, or good reason for believing there will be, or that they will be crowded unless some of the permanent teeth are removed, the extraction of the first permanent molares when de- cayed, is unquestionably advisable, but under any other circumstances, the decision of the practitioner, should be determined by the situation and extent of the disease. If the decay has commenced on the grinding surface of the tooth, and has not invaded a very considerable portion of the organ, the better practice would be to remove the diseased part, and fill the cavity with gold.] The front teeth may even derive much benefit from this gain of room, as there will probably be left a small space between them, which will tend to their preserva- OF THE TEETH. 95 tion; for it is observed, when teeth are situated so close as to press hard upon each other, they almost always fall into a state of decay. Sometimes the upper jaw is too narrow from side to side, the teeth in the fore part are thrown forwards, and project very much over the teeth of the lower jaw: they also push out the upper lip. In this case the first bicuspis on each side should be extracted, which will permit the teeth to fall into a more regular curve. [But should they fail to do so, they should be brought back by means of ligatures attached to one or more of the molares, and so applied to them, that a constant and regular pressure shall be kept upon them in the direction they require to be moved, only one tooth, however, on each side should be moved at a time.] When the permanent incisores of the upper jaw have cut the gum behind the temporary teeth, and have been suffered to remain until considerably advanced in growth, they always stand so much inwards, that when the mouth is shut, the incisores of the under jaw stand before them, which is always an obstacle to their acquiring regularity, and occasions a great deformity. There are four states of this kind of irregularity. The first, when one central incisor is turned in, and the under teeth come before it, whilst the other central incisor keeps its proper place, standing before the under teeth.* The second is, when both the central incisores are turned in, and go behind the under teeth; but the lateral incisores stand out before the under teeth.! The third variety is, when the central incisores are placed properly, but the lateral incisores stand very much in; and when the mouth is shut, the under teeth project before them and keep them back ward. J * Plate XIII. Fig. 1. t Fig. 2. X Fig. 3. 96 VARIETIES OF IRREGULARITIES The fourth is, when all the incisores of the upper jaw are turned in, and those of the under jaw shut before them. This is sometimes occasioned by too great a length of the under jaw, in consequence of which it projects considerably more forward than the upper jaw.* But the majority of such cases originate entirely from neglect, and may be completely remedied by early as- sistance. [It is also proper to sta^e that the cuspidati as well as the incisores sometimes come out behind the dental arch, so as at each occlusion of the jaws, to strike behind the lower teeth. But this variety of irregularity with these teeth is less frequent than with the incisores. The editor has, however, treated several cases within the last four years, and he has one case at this time under treatment. Plate XIV. Fig. 8, represents an inclined plane which he employed for the purpose of bringing a deviating cuspidatus forward to its proper place in the dental circle.] The time to affect any material alteration in the posi- tion of the teeth, is before thirteen or fourteen years of age, and as much earlier as possible; for after that time the sockets of the teeth acquire a great degree of strength, and the teeth are so fixed that they cannot be moved without much difficulty. If the irregularity be left to a much later period, it becomes a great deal more dif- ficult to produce any alteration, and frequently all attempts are fruitless. [Not only is the difficulty increased by delaying to a later period, and especially after the twentieth or twenty- first year, but an increased susceptibility to morbid im- pressions will be induced in the sockets of the teeth whose position has been changed, which will ever after * Plate XIII. Fig. 4. OF THE TEETH. 97 remain, and render them more liable to the attacks of disease.] To remove the kind of irregularity above mentioned, two objects must be accomplished; one, to apply a force which shall act constantly upon the irregular tooth, and bring it forward; the other, to remove that obstruction which the under teeth, by coming before the upper, always occasion. The first of these objects may be attained by the appli- cation of an instrument adapted to the arch of the mouth, which, being attached to some strong teeth on each side, will furnish a fixed point in front, to which a ligature previously fastened on the irregular tooth may be applied, and thus, by occasionally renewing it, a constant pressure is preserved, and the tooth may be drawn forward. The second object, that of removing the resistance of the under teeth, must be attained by placing some inter- vening substance between the teeth of the upper and under jaws, so as to prevent them from completely closing, and be an obstruction to the coming forwards of the irregular tooth. The instrument may be made of gold or silver; it should be so strong as not easily to bend; if about the sixteenth of an inch in breadth, and of a proportionate thickness, it wrill be sufficiently firm. This bar of gold must be bent to the form of the mouth, and should be long enough to reach to the temporary [or first perma- nent] molares, which are the teeth to which it is to be tied. Holes are to be drilled in it at those places where ligatures are required, which will be on the parts op- posed to the teeth designed to be the fixed points, and also at the parts opposite to the place where the irreg- ular tooth or teeth are situated. Then to the bar a small square piece of ivory is to be connected, by means 98 VARIETIES OF IRREGULARITIES of a little piece of gold, which may be fastened to the ivory and the bar by two rivets. This piece of ivory passes under the grinding surfaces of the upper teeth, is kept there fixed, and prevents the teeth from closing, and consequently takes off all obstruction in front.* [Gold caps are now pretty generally employed instead of blocks of ivory. These, when well adapted to the teeth over which they are placed, are far preferable, as they are less annoying to the patient, and can conse- quently be worn with less inconvenience. The first per- manent molares are the most suitable teeth to be em- ployed for the purpose. The second temporary molares, may, however, be used, or if they have been molted and replaced with bicuspides, these will answer, though less suitable than either of the others. When caps are used, it is not necessary to attach them to the gold bar passing round the front teeth.] The bar is to be attached by a strong silk ligature to the teeth at the sides, so that if possible, it may remain tight as long as it is required; a ligature is then to be tied around the irregular tooth, and the ends, being brought through the holes in the bar, are to be tied in a firm knot. In two or three days this ligature must be removed and a new one applied; the tooth will soon be perceived to move. A fresh ligature must be used every three or four days, in order to keep up a constant pres- sure, sufficiently powerful to bring the tooth into a line with the others.! The same mode of treatment is to be observed whether there be one, two, or three teeth growing in a similar manner. The teeth are usually brought forwards in about a month or five weeks, and as soon as they are so * Plate XIII. Fig. 5. t Fig. 6, 7. OF THE TEETH. 99 much advanced as to allow the under teeth to pass on the inside, the piece of ivory may be removed, and the bar only be retained for a few days, until the teeth are per- fectly firm, which will prevent the accident of the teeth again receding. [The gold bar and caps should be removed, and the teeth thoroughly cleansed, every time the ligatures are removed. This is necessary to prevent the teeth from being injured by the chemical action of the corrosive matter that forms between them and the gold bar, caps and ligatures.] In cases where the irregularity has been suffered to continue too long, no success can be expected to follow attempts to remove it; we must content ourselves in the treatment of these cases in adults, with taking away the most irregular teeth, and thus, as much as possible, lessen the deformity. [Various other methods have been proposed and adopted for the purpose of remedying irregularity of the teeth. M. Delabarre recommends the employment of ligatures, so applied, as to keep up a constant action upon the deviating teeth. Instead of using blocks of ivory or gold to prevent the teeth from coming together and forming a permanent obstacle to the adjustment of a tooth which has come out so far back of the dental circle, as to fall behind the lower teeth every time the mouth is closed, he employs wire caps or grates placed upon two of the lower molares. (See Plate XIV. Fig. 5.) This treatment, if it were the most efficient, would for several reasons be objectionable. In the first place, the ligatures, when applied so as to act upon a deviating tooth, acts with equal force upon the adjoining teeth, and moves them just as far from their place, as it does the other toward the place it should occupy. In the second 100 VARIETIES OF IRREGULARITIES place, it is difficult to apply it so as to prevent it from coming in contact with and irritating the gums. Thirdly, it cannot be made to act with as much force when thus applied as when used in connection with the gold bar. The fourth and last objection, applies to the wire grates. These cannot be fixed to the teeth as readily as either the ivory blocks or gold caps, and such as could be conveniently employed for the purpose, would not inter- pose a barrier sufficiently thick in all cases to prevent the front teeth from coming together. For remedying the description of irregularity under consideration, M. Catalan proposes the employment of an inclined plane, which may be made either of gold or silver, but the former is preferable, as the latter is liable to corrode in the mouth, fixed upon the lower teeth, in such a way that it shall strike behind the deviating tooth, at each occlusion of the jaws, and press it forward toward the place it should occupy. When several of the upper front teeth had come out behind the arch so as to fall behind the lower incisores, Catalan employed as many inclined planes as there were deviating teeth. See Plate XIV. Figs. 1, 2, for a copy of the engraving of his instrument, taken from the Journal Giniral de Midecine, de Chirurgie et de Pharmacie, for January, 1814, and the representation here given will supercede the neces- sity of any other description. When only one tooth strikes behind the circle of the lower teeth, a single in- clined plane will be all that is necessary, as in the case represented in Plate XIV. Figs. 6, 7, 8. The gold frame or case applied to the lower teeth, and to which the inclined plane is attached, should be fitted with the nicest accuracy, and made to enclose one or both of the bicuspides on each side. The cutting edges of the incisores and points of the cuspidati need not be OF THE TEETH. 101 covered with it. Its adaptation, when applied, should be such as to hold it firmly and securely in its place, and prevent the action of the deviating tooth upon the in- clined plane from jostling or moving it in the least. It will be necessary too in adjusting the inclined planes to this frame, so that they shall act upon the right points on the deviating teeth, to have a plaster antagonizing model. The manner of obtaining this will be described in another part of this wrork. When this instrument is employed, it of course is not necessary to interpose any substance between the back teeth, and it is unquestionably the most efficient and pow- erful agent that has ever been used for remedying this description of irregularity. But before it is applied, it should be ascertained whether there be a sufficient aper- ture in the dental circle for the reception of the deviating tooth, or teeth, if there be more than one, and if there is not, more room should be obtained by the removal of one of the bicuspides on each side, or the first molaris, if that be decayed. The tooth too, which is to be brought for- ward, should always be opposite the aperture it is in- tended it should occupy, before it is submitted to the action of the inclined plane. Therefore, when it is situ- ated at either side, as is often the case, it should be moved with ligatures, to a point directly behind the va- cuity, in which it is intended it should be forced, by the inclined plane, before that is applied. It often happens, that one or more of the teeth, though situated in the circle, stands obliquely or transversely across it, so that its anterior and posterior surfaces, pre- sent laterally. All that is necessary in cases of this sort, is simply to turn the tooth or teeth, if there be more than one, partially round, in their sockets. To do this, M. Delabarre applies a gold cap to the twisted tooth, with 14 102 IRREGULARITIES OF THE TEETH. ligatures attached to each side, which he passes round the adjoining teeth and secures to the temporary molares or bicuspides on either side, in such a manner as to make them act constantly in the direction the tooth is to be turned, upon it.* I have found a gold ring, properly fitted to the tooth, to answer better than a cap, for the reason that it is less annoying to the patient. The object may sometimes be accomplished with ligatures alone.] ♦Plate XIV. Fig. 3, 4. CHAPTER EIGHTH. OF SUPERNUMERARY TEETH. The growth of more teeth than the natural number frequently occurs, and is always the cause of great irregu- larity of the teeth. It most commonly happens that supernumerary teeth are met with in the upper jaw, and they are chiefly placed in some part about the incisores and cuspidati. They are only rarely met at the posterior part of the mouth, and then they resemble small dentes sapientiae, being placed on one side or other of those teeth. The form of supernumerary is very different from that of any of the other classes of teeth; they are generally small round teeth, resembling the point of a quill,* and sometimes they are not much unlike a broad bicuspis of the under jaw.! When these teeth appear, they always create a con- siderable deformity; commonly there is only one of them, and that is placed either between the central incisores, or projecting over them, or between the central and the lateral incisores, or behind, turning towards the roof of the mouth.| When there are two supernumerary teeth, the fore part of the mouth is so filled as to occasion the incisores and cuspidati to be placed in a double row. I have seen * Plate XIII. Fig. 1. t Fig. 2. J Fig. 4, 5. 104 OF SUPERNUMERARY TEETH. three remarkable instances of this kind: in one, there were two supernumerary teeth, of the conical kind, which were placed together, and had come behind and between the central incisores, which they had thrust forwards. The lateral incisores grew in a line even with the super- numerary teeth, behind the central incisores and cuspidati, and so formed a second row. This was the most con- spicuous deformity of the teeth I ever saw, for the mouth could not be opened to speak, without completely pre- senting them to view.* In the other two cases the supernumerary teeth re- sembled bicuspides of the lower jaw; they had large crowns, with depressions at their bases, and, by thrusting the other teeth into very improper situations, produced an appearance of a double row.! [Supernumerary teeth are sometimes met with which bear so close a resemblance to the others, that it is impossi- ble to distinguish the one from the other. I have met with several examples of this sort, both in the upper and lower jaws.] These supernumerary teeth should always be extracted as soon as they are perceived; and if they have occasioned the other teeth to turn out of their right direction, the application of a ligature will soon bring them again into their regular situation. * Plate XV. Fig. 6. f Fig. 7. CHAPTER NINTH. OF THE DECAY OF THE TEMPORARY TEETH. The temporary teeth are very liable to become carious, and generally cause a great deal of pain. Sometimes this disposition to decay shews itself very early, and in two or three cases I have seen every tooth in a diseased state at so early a period as three years. The little pa- tients are generally dreadfully afflicted, and by their rest being disturbed, and their being unable to masticate food with comfort, the health is often much impaired. These circumstances render the extraction of these decayed teeth highly necessary. Sometimes abscesses of considerable extent form about the sockets and gums of these carious teeth, and produce considerable mischief. I have seen the gums acquire a sloughy appearance, discharging a quantity of fetid mat- ter; and sometimes so much injury is done as to occasion the death and exfoliation of portions of the jaw bones; when this happens it usually extends so far as to include the sockets containing the forming permanent teeth, which I have seen come away with the diseased tempo- rary ones.* On these accounts it should always be recommended, when a child's teeth have become carious, and occasion pain, gum-boils, or abscesses, to extract them, as they not * Plate XVI. Fig. 12. 106 OF THE DECAY OF THE TEMPORARY TEETH. only very materially injure the health, but also are liable to prevent the formation of the permanent teeth. [The preservation of the temporary, as has been stated in a preceding place, until they are removed by the ope- rations of the economy, to give place to the secondary or permanent ones, or until the latter are about to appear, is of the utmost importance, and this, in the majority of cases, might be effected by timely and proper attention. The temporary teeth should be cleansed with a brush and waxed floss silk, three or four times every day, and if this were done from the time they make their appear- ance, there would not be one decayed deciduous tooth where there are now twenty. But when from neglect or any other cause, they do decay, such treatment should be instituted, as may be best calculated to arrest the pro- gress of the disease. This, however, should be had re- course to, before the teeth have become much loosened from the wasting of their roots, for then, the use of the file upon them, and plugging, which are the proper reme- dies for caries, might, by shaking them in their sockets, cause injury to the new teeth beneath. But previously to this time, the treatment may be applied with impunity and it will be found as successful in the preservation of these as the permanent teeth. For arresting the pro- gress of caries on the approximal surfaces of the tempo- rary teeth, and especially the incisores, filing is preferable to plugging, but wThen the decay is in the grinding sur- face of the molares, the last operation is the proper remedy. Sound teeth are as desirable and just as necessary to the comfort and health of a child as they are to an adult, and therefore they should not be permitted, from neglect of the means of their preservation, to decay, and the temporary teeth require as much care as do the perma- OF THE DECAY OF THE TEMPORARY TEETH. 107 nent ones, and they should never be extracted except for the relief of pain, that cannot be removed by any other means, or the cure of an alveolar abscess, or, as has been before stated, to make room for a permanent tooth. The popular opinion, that inasmuch as these teeth are to be replaced with others, it is of little importance whether they remain in the mouth until they are removed by na- ture to make room for their successors, or are lost a year or two earlier, is erroneous, and has been productive of much injury.] CHAPTER TENTH. OF THE DISEASES WHICH ATTEND DENTITION. The period of dentition in children is generally con- sidered as one of the most critical in life. In infancy the animal frame is so delicate, that the least local irritation produces a sudden and universal sympathy throughout the whole body. Hence the excitement occasioned by the passage of the teeth through the gums often gives rise to the most alarming constitutional symptoms, which are always with difficulty alleviated, and not unfrequently terminate in death. The mode in which the teeth pass through the gums is very much misunderstood; the prevailing opinion is, that as the teeth advance in growth, they find their way through the gums by their own mechanical pressure. The idea has given rise to the common expression of cutting the teeth, and the pain during dentition has been considered as being produced by a laceration of the membrane and gum covering the tooth. That this is an erroneous opinion will be perceived, when the state of the teeth and gums at that time is con- sidered. During its formation a tooth is loosely con- tained in the socket, and can exert no force sufficient to perforate so firm a substance as the gums. The gums also possess a certain degree of elasticity, and could by the gradual pressure of the rising teeth, be stretched so DISEASES WHICH ATTEND DENTITION. 109 as to become elongated with the progress of the teeth, and would continue to cover them. A passage for the teeth is opened by the process of ulceration. By the pressure of any extraneous substance upon a sound part, or by a diseased enlargement of some part within the body, an absorption of the parts subjected to the pressure will take place. This, in a very remark- able degree, is seen in cases of aneurism, in which, by the pressure of a soft tumour, bones of the most compact structure are removed by the process of absorption, and that unattended with any secretion of pus. [The foregoing explanation of the mechanism of den- tition is too general to be very clearly or well understood. The most ingenious, and at the same time most plausible theory that has been advanced upon this subject, is given by M. Delabarre. This writer is of the opinion that the escape of a tooth from its matrix or sac, and passage through the gum is analogous, if not identical with that of the birth of a child. He regards the sac in connec- tion with its neck or chord which passes from it to the surface of the gum, as the prime agent in this operation of the economy. It is by the retraction of this upon the neck of the tooth to which it is attached, that the tooth is raised from its socket towards the mouth or orifice of the matrix, and ultimately brought to a level with the gums. The peduncle or chord leading from the sac to the surface of the gum, is said by Goodsir to be solid, but Delabarre has demonstrated conclusively, that it is hollow, and there is reason for believing that as the tooth advances, it dilates so as to give egress to the tooth, and ultimately becomes the margin or free edge of the gum around its neck. This is the only theory that explains upon any thing like sound philosophical principles, this most curious and 15 110 OF THE DISEASES singular operation of nature. As the Editor has stated in another place, he repeats, it is difficult to imagine how the elongation of the pulp, or the moulding of the alveolar walls to it, can have any agency in raising or depressing a tooth through the gums. If the elongation of the pulp commenced before the crown of the tooth had made any progress toward the gums, it would at once come in con- tact with the floor of the alveolus, and in its soft and yielding condition, be caused to'assume a configuration different from that presented by the root of a naturally developed tooth. The crown of the tooth must there- fore make some progress toward the gums, before the elongation of its pulp can commence, and it is difficult to conceive how this can be effected, if it is not, as Dela- barre supposes, by the contraction of the fibres of its sac] When the teeth have advanced so much in their for- mation as to be too long to be contained in the socket, under the gum, they press upon the membranes which enclose them; these become absorbed, and then the pres- sure being applied against the gum, that also is removed, and the teeth make their appearance. When the absorp- tion of the membrane and gum takes place early, the child suffers no inconvenience during the progress of dentition. The teeth advance without any trouble, and their appearance is discovered by the mother or nurse with some degree of surprise: but when the growth of the teeth is too rapid for the absorption of the gums, dentition is often attended with much pain and derange- ment of the whole system. At this early period of life, as I have already observed, the constitution is so delicate, and the irritability so great, that the least cause of irrita- tion produces an universal sympathy throughout the whole system. It is well known to many adults, that the WHICH ATTEND DENTITION. Ill pain attending the protruding of the dentes sapientiae is very great, and it therefore cannot excite surprise that this cause of irritation should in children produce so many distressing symptoms, and even be the cause of destroying so many. When the formation of the tooth goes on very rapidly, and the absorption of the parts which cover it does not proceed in proportion, it becomes confined; this pro- duces a distension of the membrane, and occasions pres- sure upon the pulp, nerves and vessels at the bottom of the socket. The tooth continues to grow, and the in- creased pressure, which is occasioned by this augmenta- tion, produces inflammation, and a variety of symptoms of general irritation. [If the theory advanced, just before, with regard to the mechanism of dentition be correct, and that it is, seems more than probable, the irritation produced by it cannot be caused by pressure of the tooth upon the 'pulp, nerves and vessels at the bottom of the socket,' but must result from inflammation produced by the pressure of the tooth against the sac and superincumbent gums.] Few children obtain all their teeth without undergoing some degree of suffering: in many, the symptoms are merely local, in others they often arise to a very alarming height, and not unfrequently terminate fatally. When the symptoms are merely local, the gums be- come very tender, and look redder than ordinary, the child is restless, and rather fretful: these symptoms with some children are of short duration, and always go off as soon as the tooth appears. Nature operates in a very salutary manner for their relief, by occasioning an in- crease in the secretion of the saliva, which generally is discharged in large quantities, and thus diminishes the action of vessels. In other cases a gentle diarrhoea takes 112 OF THE DISEASES place, which also reduces the state of irritability. They also find relief from rubbing or pressing the gums, which is best done by themselves. The coral, though used as a common appendage to a child's dress, is a very injurious and a very improper substance: children ought to have nothing hard; they will put their fingers into the mouth and bite upon them; or they may have a soft crust of bread; this slight pressure will expedite the absorption of the gum, and consequently the passage of the tooth; while that produced by a harder substance will increase the irritation and inflammation. When the constitution becomes affected, all the symp- toms of general irritation occur, and there is scarcely any affection we do not meet with in one case or other of difficult dentition. Fever is a frequent attendant, and it often comes on very suddenly; at first there is a heaviness about the eyes, the child then becomes hot, having the skin dry and tongue white; it gets very restless, putting the hand into the mouth, and can neither eat nor sleep. Some- times these symptoms are so much aggravated that de- lirium will take place, and convulsions supervene. In other children, the skin is more particularly affected; a little fever arises, which is soon followed by some kind of eruption. There are several appearances seen upon the skin during childhood, and which are the conse- quence of irritation during the time of dentition. A very common eruption is a rash, which resembles the measles, and which appears in spots about the face and neck, sometimes extending over other parts of the body. This rash is like an aggregate of small pimples, so that when the finger is pressed over the red part, from the skin which is healthy, a small rising may be felt. This has been called the red gum, and is very common WHICH ATTEND DENTITION. 113 to children during the early months. It may in general be esteemed beneficial; for the blood being carried to the skin, takes off any improper determination to important parts, and prevents more serious disease. Sometimes postules arise in different parts of the body; they are at first transparent, from being filled with a limpid fluid, which afterwards becomes purulent, a scab forms, and the changes afford an appearance not unlike a mild small-pox. There are other eruptions which form very unpleasant and extensive scabs; they break out upon the corners of the mouth, or on the cheek. Sometimes they begin upon the forehead, and spread over part of the scalp; they form large loose scabs, which drop off, but are soon succeeded by others. These scabs, however, leave no scar, and therefore are to be considered only as trouble- some, and not dangerous. Other children are subject to an inflammation, and a discharge from behind the ears; this may always be re- garded as salutary, since from its contiguity to the teeth, it tends to divert the inflammation. A gentle diarrhoea, during teething, is a beneficial effort of nature; it takes off the excitement from the constitution, and diminishes the febrile symptoms. But sometimes it becomes so excessive as to produce the most alarming symptoms; the discharges are of a green colour, very frequent, and attended with excessive griping; the rest is so much disturbed that no strength is gained by it; the child is continually starting, and spasms of various parts are occasionally seen; at length the whole system becomes so reduced that convulsions of the whole body take place, which continue until nature becomes com- pletely exhausted. In some children, the irritability of the nervous system 114 OF THE DISEASES is so great, that convulsions supervene in a very short time after the appearance of any febrile symptom, and this is constantly the case with the cutting of every tooth. Besides these different affections, there are so many other anomalous symptoms, that it may be truly said, that every symptom of general irritation which can be mentioned, may be met with during the time of dentition. In some children the lungs are much affected, and they are troubled with difficult breathing; in others, the continual derangement of health is often the cause of scrofula, rickets, or consumption. Mr. Hunter mentions a remark- able sympathetic affection in a child, which arose from the irritation excited by teething. Formerly children were often placed under most dangerous circumstances, when they happened to be attacked with the small-pox at the same time as they suffered from dentition; but happily now, they may be defended from that dreadful malady, by the shield which has been raised by the admirable discovery of Dr. Jenner; and we have the certain pros- pect, that this most horrible of human maladies is about to withdraw its pestilential influence from the world for ever. In the treatment of any affection incident to children during the progress of dentition, if the teeth are at all suspected to be concerned, the removal of the cause of irritation ought to be first attended to. This must be done by opening the gum, so as to take off the confine- ment from the tooth, and enable it to pass through. This operation ought always to be had recourse to in the first instance, and then other remedies should be applied ac- cording to the various symptoms which may appear. When there is fever, the antiphlogistic regimen must be adopted. The bowels should be evacuated. The best medicine for children is calomel, which may be WHICH ATTEND DENTITION. 1 15 combined with rhubarb or scammony; or some of the neutral salts may be exhibited. After these, saline draughts or gentle antimonials should be administered, in order to produce a determination to the skin. If the head should be much affected, a blister to the nape of the neck would be very useful. In all cases of rash, or eruptions, the child should be kept warm, and be particularly preserved from taking cold, as great danger often follows the sudden disappearance of any af- fection of the skin. If this should happen, the child should be put into the warm bath, and some medicines administered to produce diaphoresis; also attention is to be paid to the bowels, that no costiveness be suffered. In general, slight eruptions are to be regarded as bene- ficial, and particularly those occurring behind the ears, at- tended with moderate discharge. In cases of difficult dentition, when no sore ear has arisen spontaneously, much benefit has followed the practice of rubbing a small quantity of blister ointment behind the ears, and thus inducing a slight discharge. If scabs are extensive and become dry and hard, they may be washed with wTarm milk and water, and touched with a little oil. They also may occasionally be wetted with the hydrargyrus muriatus, in aqua calcis, in the proportion of 1 gr. to 1 oz.: the scabs should never be picked off, but left to separate of themselves. When they extend over the head and are moist, much trouble and pain is occasioned by the sticking of the cap; they should then be dusted with a little powder, or some fine fuller's earth, and a singed rag should be laid over them. In these cases much good has been seen to attend the use of an oiled silk cap, or a piece of oiled silk laid over the part, this prevents evaporation, and the scabs do not dry and become so troublesome. 116 OF THE DISEASES All eruptions are to be regarded as salutary, for so great a sympathetic connection exists between the skin and the stomach, that it often happens, that the repelling of any eruption from the skin, immediately produces considerable derangement of that organ, which ought to be regarded as a sort of centre of sympathetic action. This is very strikingly seen in a variety of diseases in which the stomach sympathizes with the other parts of the body, and therefore during dentition it is of conse- quence not to check any mild eruption which may appear. If a diarrhoea be only moderate, it should not be checked; it tends to diminish fever, and takes off the excitement from the constitution. As it is usually con- nected with acidity, a little magnesia, or some of the tes- taceous powders maybe exhibited; but when the diar- rhoea runs on for a great length of time, and seems to be causing weakness, which threatens fatal atrophy, serious endeavours must be made to subdue it. The treatment of this complaint is attended with many difficulties, and medicines which succeed in some cases will totally fail in others. If the abdomen be much en- larged, two grains of calomel every night, purged off in the morning with ten grains of rhubarb and half the quantity of magnesia, will generally be found beneficial. This should not be persevered in more than three or four days successively, and should be succeeded by eight grains of the pulvis cretce, comp. cum opio, and four or five grains of columba root. The patient should be warmly clothed, especially on the abdomen and lower extremi- ties. On some occasions the pulv. trag. comp. appears preferable to the pulv. cretce comp.; and the syrup, or decoct, alihce, with 20 drops of paregoric elixir, have suc- ceeded when the other usual means have failed. The warm bath may be considered as another perfect species WHICH ATTEND DENTITION. 117 of warm clothing, and is attended with good effects, by relaxing the pores of the skin and relieving the bowels. If the above mentioned remedies cannot be taken by the patient, opiate frictions of the abdomen or back should be used, and the following formula will answer very conve- niently. R. Ung. hydr. fort. 5i.—pulv. opii puri. Gi. olei oliv. 5 iij. fiat linimentum bis terve in hebdomade in- fric; but the quantity and repetition must be regulated by the judgment of the practitioner. If the patient is much distressed by tenesmus and stools streaked with blood, clysters of starch, with 20 drops of tr. opii, and twice that number of tr. catechu or kino, should be given every evening. When convulsions have taken place, we must endea- vour to remove what appears to be the exciting cause. If the stomach have been overloaded with improper food5 or there be signs of indigestion, a gentle emetic should be given. If there is costiveness, or the bowels are af- fected, they should be cleansed by a clyster: when the stools are offensive, or the breathing at all affected, a few grains of calomel and scammony may be given with ad- vantage. If those medicines do not succeed, antispas- modics should be administered. It often happens that the deglutition is much affected, then it will be right to give an enema with asafoetida: or if not, in a draught, a drop or two of tinct. opii should be given. The back may be rubbed with oil of amber, or aqua ammoniae.— During the fit it is always proper to put the lower parts of the body into warm water, which by exciting a greater flow of blood to the legs, takes off too great a determina- tion to the head; a blister should be applied to the back of the neck, and leeches may be applied to the temple. Other symptoms which arise, must be met according to their urgency; but we ought never to lose sight of what 16 118 OF THE DISEASES may appear to be the principal exciting cause, viz. the inability of some teeth to pass through the gums. Under every circumstance of indisposition, arising from dentition, the lancing of the gums ought never to be omit- ted. The benefit which attends the operation is so sud- den, and if performed sufficiently early, is so certain, that it ought never to be neglected. As soon as the gum is lanced and the membrane is divided, the tooth obtains an increase of room, the pressure is immediately taken off from the socket, and the cause of irritation is removed. It is very surprising that, notwithstanding the manifest advantage which attends the lancing of the gums, in cases of painful dentition, there are persons who entertain strange prejudices against this safe and important source of relief. But the uniform experience of its good effects, and no in- stance of its doing harm ever having occurred, should produce an unanimous consent for adopting it. Some persons object to the operation on account of the pain which it will occasion to the child, not considering that the inflammation produced by the resistance of the gum to the tooth, is far more acute than dividing the gum with a sharp instrument. Others suppose that the formation of the teeth is injured, and that they are more liable to decay; but neither of these circumstances can occur; for at the time that the teeth is about to pass through, the enamel is completely formed, and no injury can be done to the formation of the fang, which is always continued for some time after the appearance of the crown. When it is necessary to lance the gums some time be- fore the teeth are quite ready to appear, they unite, and in this case the cicatrix has been said to impede the pro- gress of the tooth, presenting a greater resistance than the gums in their natural state; but it is now certainly known that a newly formed part always gives way sooner to the WHICH ATTEND DENTITION. 119 process of absorption than the surrounding parts, and hence the passage of the tooth is facilitated. The haemorrhage which is occasioned by the operation is never considerable, but is always beneficial; the vessels become unloaded, and the inflammation is always soon diminished. The most convenient instrument for this purpose is a round edged- gum lancet; this cuts much easier than a pointed one. It is necessary that the tooth be felt with the edge of the instrument, else the membrane may still be left upon the stretch, and no other benefit be derived than that which proceeds from the topical bleeding. In lancing the incisores it will be proper, in dividing the gum, to pass the lancet down on the anterior part of the tooth: for if it be carried deep on the posterior part oi the tooth, there may be a danger of dividing the membrane which connects the pulps of the permanent teeth to those of the temporary, and the formation of the former may be injured.* [When the incision is made directly through the summit of the gums covering the alveolar ridge, the lancet passes behind the teeth, and to prevent which it should be made about the twelfth or sixteenth part of an inch anterior to it.] When the gums of the molares are to be lanced, a crucial incision may be made, or two semilunar incisions, the gums soon separate, and the tooth shortly makes its appearance. The symptoms which usually precede any indisposition arising from teething ought to be universally known, because then the certain remedy may be applied in time, and a great deal of suffering be spared to the child. If the nurse be attentive, she will find the child does not take the nipple with the same degree of force as ordinary, or it holds it only for a short time, and soon ♦Plate IX. Fig. 5. 120 OF THE DISEASES lets it go; the gums feel hot, and are redder than usual; the cheeks appear flushed, the eyes look heavy, and the child is uneasy. When these symptoms appear, the mouth should be examined, and if there be any fulness of the gums, or they have the appearance of inflammation, they should be lanced at that part. The order in which the teeth appear should always be kept in mind, and then there will be little probability of mistake, as to the spot where the cause of irritation is seated. As a child increases in strength, the symptoms arising from dentition diminish, and often become merely local; but the diseases to which infants are liable, frequently keep them in weak health, and much disposed to be af- fected by any exciting cause of irritation. To delicate children there is often danger attending the cutting of the cuspidati and the first molares. These teeth advance in growth nearly at the same time, so that there are eight teeth making pressure upon the mem- branes and the gums at the same period. If at this time a child should be at all indisposed, one or other of these teeth may be the cause of convulsions, or some other se- rious disease; therefore, when any of these teeth appear to be in a state of forwardness, the gum should be lanced. This is the only method of treatment to be relied on to bring a weakly child through this period. During the second dentition, with one exception, scarcely any pain is felt; the constitution has acquired such a degree of strength that the sympathetic action is with more difficulty excited, and the only inconvenience ever experienced is, when the permanent teeth, which are placed at the base of the temporary ones, by the increase of their growth make pressure against them; this more particularly happens when the bicuspides are endeavouring to come forward, and being resisted, by the continuance WHICH ATTEND DENTITION. 121 of the temporary molares, a tenderness and pain are occa- sioned, which can only be relieved by extracting the tem- porary teeth, and thus giving way for the passage of the permanent. The exception to which I have alluded with respect to pain during the second dentition, is in the dentes sapien- tiae; very often a great deal of pain attends the progress of these teeth. When there is scarcely sufficient space for them to grow, or the gum being very thick is firmly bound over them, considerable inflammation, and some- times swelling of the face takes place. In many cases the pain is so severe as to excite a considerable degree of fe- ver and indisposition. I have known persons confined from this cause only, during several weeks. If the den- tes sapientiae of the upper jaw pass through first, it very much increases the inflammation, because whenever the mouth is closed, the' gums which cover the teeth in the under jaw are bitten upon by the upper, and being con- tinually pinched, the patient suffers extremely. Generally it is only necessary to lance the gums with a crucial incision; there is often a good deal of hemorrhage, which is very useful in reducing the inflammation; the gum soon retracts, and the tooth gradually passes through. When the upper dentes sapientiae appear first, it is some- times necessary to cut off the piece of gum which covers the under tooth. In many cases the gum is very thick, and will often close and unite again after the operation; this produces a necessity for repeating it; but which might always be pre- vented, by inserting a small piece of lint between the edges of the divided gum, which then cannot unite; they remain separated, and gradually receding, the^tooth has no longer any obstruction. Sometimes, in these cases the gum is exceedingly 122 DISEASES WHICH ATTEND DENTITION. swelled over the tooth, and when divided by the lancet, a considerable quantity of glairy fluid escapes; in some instances I have met with considerable quantity of matter, and in one case the gum was ulcerated to a great extent. [But neither lancing the gums nor cutting out a piece from over the tooth, will always afford relief, the extrac- tion of the tooth itself is often necessary, or the antagoniz- ing one in the other jaw, which, having made its appear- ance first, strikes the gums covering this, at each occlusion of the mouth, causing it to inflame and swell and often- times to become exceedingly painful. The extraction of the second molaris will generally give relief, and when this is very much decayed, it is better to remove it, than the dens sapientiae. So great is the irritation sometimes produced by the dentition of these teeth, that trismus has been known to result from it. Two cases of this sort have fallen under my own observation. In cases of this sort, the treatment should be addressed to the general system. Copious bleeding, warm bath and small doses of emetic tartar should be had recourse to, for the purpose of inducing a relaxation of the muscles of the jaw, and so soon as this is accomplished, the tooth should be ex- tracted.] CHAPTER ELEVENTH. Being desirous to render this work as complete as possible, I requested the favour of my friend, Mr. Pepys, to make a chemical analysis of the teeth, and from the accuracy with which all his experiments are conducted, I flatter myself that the following observations will not a little enhance the value of the publication. THE ANALYSIS OF HUMAN TEETH. BY W. H. PEPYS, JR. Mr. Charles Hatchet, in his valuable paper on shell and bone, [Phil. Transact, for 1799] enumerated the several substances which enter into the composition of the human teeth; it is to be regretted that the nature of his subject did not render it necessary for him to ascertain the pro- portions in which they are respectively found, as it could not have failed to have proved highly useful, and his known accuracy would have precluded the necessity of any other person undertaking such a labour. Several good analyses of bone have been published, but I believe no accurate analysis of the teeth has yet been offered. Bone, it has been observed, when exposed to the ac- tion of acid menstrua, becomes dissolved; that is to say, the solid or constituent substance of them is abstracted, and a gelatinous matter is left of the form of the original bone. 124 THE ANALYSIS OF HUMAN TEETH. Nitric, muriatic, and acetic acids are capable of produ- cing this change, which is accompanied with a liberation of an aeriform fluid, that precipitates lime in lime water, changes vegetable blues red, and by its gravity is known to be carbonic acid gas. These acid solutions yield a co- pious precipitate with pure ammonia, which is again solu- ble in either of the acids. After the precipitation by pure ammonia, the solution of the carbonate of ammonia will still produce a new precipitate. The precipitate of the first solution, by pure ammonia, as noticed above, is soluble again in the acids before men- tioned ; these solutions yield, with a solution of acetite of lead, a copious precipitate, proving the presence of phos- phoric acid. The precipitate obtained by the carbonate of ammonia is also soluble in either of the above acids, but writh effer- vescence; and these solutions are not precipitated by ace- tite of lead; they fall, however, with oxalate of ammonia, carbonate of ammonia, or any precipitant of lime. The great solubility of the phosphate of lime, in even the weakest of the acids, is very extraordinary. Phos- phate of lime mechanically suspended in water, is speedily and completely dissolved by passing a copious stream of carbonic acid gas through it. With these facts before me, I have ventured to exam- ine the several specimens of the human teeth; as the enamel, the bone, or roots, the teeth of adults, and the shedding teeth of children. Previous to an account of the analysis, it may not be uninteresting to notice the action of some of the articles of the materia chemica on the teeth. Sulphuric acid, of the specific gravity 1.83, appears at first to have no action; in the course of an hour small bubbles are perceived, the roots become blackened, and ANALYSIS OF THE ENAMEL. 125 in twelve hours the enamelled part bursts, cracks, and separates, accompanied with an evident formation of sele- nite, by the action of the acid on the lime, which enters into the composition of the teeth. Nitric and muriatic acids of the specific gravity of 1.12, act instantly on the tooth, accompanied with an evolution of a quantity of small air bubbles from the whole of the surface; about eight times their weight of these acids are sufficient for the solution of the solidifying principles of the teeth. The mass left undissolved has nearly the ori- ginal form of the tooth, is flexible, semi-transparent, and easily divided by the nail. The dilute acetous acid (distilled vinegar) has a very trifling action, but when concentrated, acts both on the phosphate and carbonate of lime. Boiling nitric acid acts strongly on a tooth, with the evolution of carbonic acid, and a considerable quantity of azotic gas. The gelatine and solid substance are dis- solved as the surfaces present themselves; but the opera- tion being stopped at any part of the process, the resi- duum is firm and hard, but reduced in size proportioned to the time the tooth has been acted upon. ANALYSIS OF THE ENAMEL. One hundred grains of the enamel of human teeth, (carefully rasped) were placed in 600 grains of nitric acid of the specific gravity of 1.12. Slight effervescence ensued, and after twelve hours 200 grains more of the acid were added. Allowing for the loss by evaporation in a corresponding vessel, after thirty-six hours it was found to have lost four grains and a half. 17 126 ANALYSIS OF THE ENAMEL. It was then diluted with four ounces of distilled water, precipitated by pure ammonia, and then filtered. The precipitate obtained being dried in a water bath, at 212°, weighed 102 grains. It was then ignited, after which it was found to weigh 78 grains. The filtered solution was then precipitated by carbo- nate of ammonia in solution, and filtered: The separated precipitate being dried in a heat of 212°, weighed six grains. Enamel then consists of Phosphate of lime, ... 78 Carbonate of lime, ... 6 84 Water of composition and loss, . 16 100 A loss of 16 grains here takes place, which is easily ac- counted for, from the impossibility of directly ascertaining • the state of dryness in which the ingredients existed originally in the enamel; for we have seen, that by drying the phosphate of lime in a heat of 212°, (after which it had the appearance of being as dry as possible) it yet contained so much moisture, as to yield a gain of 8 grains in the analysis. On the other hand, when ignited, its state is driven to the opposite extreme, and there is a loss of 16 grains. It is impossible, however, that the materials could exist in the teeth, in a state of dryness to be compared with that produced by exposing them to such a high temperature. And it appears but reasonable to conclude, that the real quantity of moisture lies nearer to that given by the heat of 212°, than to that given by ignition, and consequently that the 16 grains lost by exposure to such a high tem- perature, were chiefly water. ANALYSIS OF THE ENAMEL. 127 Bone, or roots of teeth, yielded by analysis in 100 grs.; Phosphate of lime, Carbonate of lime, 58 4 Gelatine, ..... 28 90 Water of composition and loss, 10 100 teeth of adults yielded on analysis in Phosphate of lime, ^ . Carbonate of lime, 100 grains, 64 6 Gelatine, ..... 20 90 Water of composition and loss, 10 Specific gravity of adults' teeth, 100 2.2727. The shedding, or primary teeth of children, yielded on analysis in 100 grains, Phosphate of lime, ... 62 Carbonate of lime, ... 6 Gelatine, ..... 20 88 Water of composition and loss, . 12 100 Specific gravity of children's teeth, . 2.0833. In these analyses, as in the former, the phosphate of lime was also exposed to a red heat, and consequently was reduced to a greater degree of dryness than that in which it existed in the tooth. In all of them the carbonate of lime was dried in a heat of 212° (above which it would have been liable to de- composition) and the gelatine of the three last in the same temperature. EXPLANATION OF PLATES TO PART FIRST. PLATE I. THE RUDIMENTS OF THE ALVEOLAR PROCESSES AND THE PULPS OF THE TEETH. Fig. 1. The under jaw of a foetus at three or four months. In the anterior part, processes of bone are shooting across to form the alveoli for the incisores. Fig. 2. The gums removed from the same jaw bone, exhibiting the first appearance of the pulps, those of the incisores being the most distinct. Fig. 3. The under jaw of a foetus at six months, in which the alveolar processes are seen more advanced. Fig. 4. The pulps removed from the same jaw, dis- tinctly formed, each contained within its pro- per membrane. Fig. 5, 6. The upper jaws of foetuses of the same age, as in Fig. 1, 2; exhibiting the alveolar pro- cesses and pulps. PLATE II. THE PROGRESS IN THE FORMATION OF THE TEETH FROM THE TIME OF BIRTH, UNTIL BETWEEN TWO AND THREE YEARS OF AGE. *#* The figures on the left side of the plate represent the teeth as naturally situated; those on the right side as taken out from the sockets; the dotted lines represent the gums. Fig. 1. The teeth at the time of birth, when they are only shells, having the form of the crowns of teeth. a. The central incisores. b. The lateral incisores. c. The cuspidati. d. The first molares. e. The second molares. A. Points of ossification upon the tips of the pulps of the permanent incisores. B. Points of ossification upon the points of the per- manent molares. Fig. 2. The teeth of a child about six or eight months after birth. At this time the central incisores of the upper jaw, and the central and lateral incisores of the lower jaw, have made their appearance; the other teeth are considerably advanced in growth. PLATE II. 133 abode. The temporary teeth. A. The permanent central incisores. B. The permanent lateral incisores. C. The permanent cuspidatus of the lower jaw. D. The first permanent molares. Fig. 3. The teeth of a child at sixteen months. The incisores in each jaw, and the first molares, have passed through the gums. A. The permanent incisores much increased. B. The cuspidati. C. The first permanent molares. Fig. 4. The temporary set of teeth have all passed through the gums, and in addition to the per- manent teeth already described are, A A. The points of the first bicuspides. 18 PLATE III.* THE TEETH OF A CHILD BETWEEN FOUR AND FIVE YEARS OF AGE. Fig. 1. A side view. Fig. 2. A front view. Of the temporary set. aaaa. The central incisores. bbbb. The lateral incisores. c c c c. The cuspidati. dddd. The molares. Of the permanent set. e e e e. The central incisores. ffff. The lateral incisores. g g gg. The cuspidati. hhhh. The first bicuspides. iiii. The first molares. k k. The second molares. The formation of the second bicuspides has not yet commenced. * For the references to this Plate, and Plates IV. and V. see the outline Plate VI. PLATE IV. THE TWO SETS OF TEETH AT SIX YEARS OF AGE. Fig. 3. of Plate VI. Of the temporary set. aaaa. The central incisores. bbbb. The lateral incisores. cccc. The cuspidati. dddd. The molares. Of the permanent set. eeee. The central incisores. //. The lateral incisores. gggg. The cuspidati. hhhh. The first and second bicuspides. i i. The first molares. k k. The second molares. PLATE V. THE TEETH AT EIGHT OR NINE YEARS OF AGE. THE INCI- SORES HAVE BEEN CHANGED, AND THE FIRST PERMANENT MOLARES HAVE APPEARED. Fig. 4. of Plate VI. Of the temporary set. a a. The cuspidati. bbbb. The molares. Of the permanent set. cccc. The central incisores. dddd. The lateral incisores. e e. The cuspidati. ffff The bicuspides. g g. The first molares. h h. The second molares. i i. The third molares, or dentes sapien- tiae, beginning to form. PLATE VII. (FROM GOODSIR.) Fig. 1. Mucus membrane. Fig. 2. Mucus membrane with a granular mass rising up from it. Fig. 3. Primitive dental groove. Fig. 4. A papilla on the floor of the groove. Fig. 5. The papilla enclosed in a follicle, and the se- condary dental groove forming. Fig. 6. The papilla assuming the shape of a pulp, the opercula forming and a depression for a cavity of reserve behind the inner operculum. Fig. 7. The papilla after it has become a pulp, the follicle a sac by the adhesion of the lips of the oper- cula, and the secondary dental groove in the act of closing. Fig. 8. The secondary groove adherent, except behind the inner operculum, where there remains a shut cavity of reserve for the formation of the pulp and sac of the permanent tooth. Fig. 9. The last change more complete by the deposition of the granular body, deposition of tooth-bone commencing. Fig. 10. The cavity of reserve receding, its bottom in which the pulp is forming dilating. Fig. 11. The cavity of reserve becoming a sac with a 138 PLATE VII. pulp at its bottom, and further removed from the surface of the gum; the temporary tootli covered with a layer of bone, and the granular substance absorbed. Fig. 12. The temporary tooth getting its fang, and ap- proaching the surface of the gum. Fig. 13. Root of the temporary tooth longer, and its sac touching the surface of the gum. Fig. 14. Eruption of the temporary tooth; its sac again a follicle, and the permanent receding further from the surface of the gum. Fig. 15. Completion of the temporary tooth; free portion of the sac become the vascular margin of the gum, and the permanent sac connected by a chord passing through the alveolo-dental canal or foramen. Fig. 16. Lengthening of the root of the permanent tooth, the crown approaching the gum, and the root of the temporary tooth partly destroyed. Fig. 17. The changes last described more advanced. Fig. 18. The eruption of the permanent tooth, and the molting of the temporary. Fig. 19. The permanent tooth perfected. Fig. 20. The primitive dental groove in its non-adherent state. Fig. 21. The papilla and follicle of the first molaris on the floor of the non-adherent portion of the groove, now become the secondary groove. Fig. 22. The papilla a pulp, and the follicle a sac, and the lips of the secondary groove adhering, so that the latter has become the posterior or great cavity of reserve. Fig. 23. The sac of the first molar increased in size, ad- vancing into the coronoid process or maxillary PLATE VII. 139 tuberosity, and the cavity of reserve length- ened. Fig. 24. The sac of the first molaris returning by the same path to its former position, and the cavity of reserve shortening. Fig. 25. The cavity of reserve sending backwards the sac of the second molaris. Fig. 26. The sac of the second molaris passing into the coronoid process or maxillary tuberosity. Fig. 27. The second molar sac returned, and the cavity of reserve shortened. Fig. 28. The cavity of reserve sending off the sac and pulp of the wisdom tooth. Fig. 29. The sac of the wisdom tooth advanced into the coronoid process or maxillary tuberosity. Fig. 30. The sac of the wisdom tooth returned to the extremity of the dental range. PLATE VIII. Fig. 1. The permanent set of teeth complete. Row 1. The temporary teeth of the upper jaw. Row 2. The permanent teeth of the upper jaw. Row 3. The permanent teeth of the lower jaw. Row 4. The temporary teeth of the lower jaw. PLATE IX. Fig. 1. Longitudinal sections of teeth, the bony part of which has been burnt, to render the distri- bution of the enamel more conspicuous. Fig. 2. The transverse section of a molaris. Fig. 3. A tooth magnified, to exhibit the striated ap- pearance of the enamel. Fig. 4. An under jaw, the fore part of which, and of the teeth, have been sawn away to shew the cavities in the teeth. Fig. 5. A section of the under jaw; the nerve is seen giving off branches which enter the cavities of the teeth. Fig. 6. A molaris of the under jaw, having three fangs. Fig. 7. A molaris having on its side a deposit of enam- el like a pearl. Fig. 8. The central incisores of the under jaw united at the sides. Fig. 9. Two views of the second and third molares of the upper jaw, which are united by the inner fangs. Fig. 10. A molaris of the under jaw, having the crown of a bicuspis growing out of its side. Fig. 11. A molaris of the under jaw, having four fangs. Fig. 12. Ther*permanent central incisores of the under jaw, having an exceedingly deformed appear- ance. 19 142 PLATE IX. Fig. 13. A molaris of the upper jaw, having five fangs. Fig. 14. Several teeth, shewing the appearance of the enamel when defective in quantity, the sur- face of the teeth being covered with small indentations. PLATE X. ALL THE FIGURES OF THIS PLATE ARE FROM INJECTED PREPARATIONS. Fig. 1. The under jaw of a child at the time of birth; the fore part has been removed, and the membranes inclosing the teeth are seen to be vascular. Fig. 2. The teeth have been turned out of the sockets, and the inner membranes are also seen to be vascular. Fig. 3. The lower jaw of a foetal calf, in which the vas- cularity of both membranes is seen. The membrane belonging to one tooth has been turned down to exhibit the vascularity on the inner side. Fig. 4. Half of the upper jaw of a boy about eight years of age. Part of the central incisor, the cuspi- datus, the first molaris and the second molaris, (not yet completely formed) has been cut away to show the vascularity of the membrane within the cavities of the teeth. The lateral incisor and the bicuspides are contained within the membranes. Figs. 5, 6, 7, 8, and 9, represent the manner in which permanent teeth are formed. Fig. 5. Half the under jaw of a child soon after birth. The membranes of the teeth are seen, and over the bristle the membranes of the pulps of the incisores and the cuspidatus of the permanent 144 PLATE X. set, which are firmly attached to the membranes of the temporary teeth. Fig. 6. Part of the jaw of a child about three years of age. The permanent teeth are placed deep in the jaw, and their membranes remain at- tached to the gums. The vessels of the mem- branes are derived from the gums. The artery which passes through the jaws sends off branches to the pulps of the teeth. Fig. 7. Teeth which have been removed from the sockets to explain the attachments of the permanent to the temporary teeth. a. The pulp of the temporary teeth inclosed within its membrane. b. The pulp of the permanent teeth attached by its membrane to that of the temporary. c. The temporary tooth completely grown. d. The permanent tooth attached to the gum, the membrane being elongated into a sort of pedicle. Fig. 8. A section of the lower jaw, showing the tempo- rary tooth, with the manner of the situation and attachment of the permanent tooth. Fig. 9. Exhibits the manner in which the pulps of the permanent molares are produced. a. The first permanent molaris inclosed in its mem- brane. b. A small membranous substance given off from the membrane of the first, and which becomes the pulp of the second permanent molaris. Fig. 10. Half of a young jaw, showing the foramina through which the membranes of the perma- nent teeth pass, to be attached to the gums. A bristle is placed in one, and is seen going into the socket of the new tooth. PLATE XI. Fig. 1. The progress of absorption in several of the temporary cuspidati. Fig. 2. The same circumstance exemplified in several of the temporary molares. Figs. 3 and 4. Sections of the lower jaw exhibiting the progress in the formation of the permanent teeth, and the absorption of the fangs of the temporary teeth. Fig. 5. Exemplifies the changes which take place in the teeth at different periods. A. Part of the under jaw of a child at six years, when the temporary teeth only are visible. B. Part of the jaw of a child about eight or nine years of age. The temporary incisores and cuspidatus have been removed; the permanent incisores and the first permanent molaris have grown up. C. In this jaw the first temporary molaris has been re- moved, and is succeeded by the first bicuspis; the cuspidatus and the second permanent molaris are appearing. D. Part of a jaw in the adult state. The second temporary molaris has been succeeded by the second bicuspis. The third molaris, or dens sapientiae, has made its appearance. In this series of jaws, the change of the temporary 146 PLATE XI. teeth for the permanent, and the addition of the permanent molares are clearly elucidated. The teeth which succeed the temporary inci- sores and cuspidati are larger, and those which succeed the temporary molares are smaller. Fig. 6. The upper jaw of a foetus, in which only one incisor had formed. a. The incisor. b. b. The cuspidati. c. c. The first molares. PLATE XII. EXAMPLES OF IRREGULARITY SOMETIMES OCCURRING DURING THE SECOND DENTITION. Those permanent teeth which are acquiring an irregu- lar position, are sufficiently obvious. Those marked a a, are the temporary teeth which ought to be extracted. PLATE XIII. Fig. 1. One central incisor turned in, being placed when the mouth is closed, behind the under teeth. a a. The temporary lateral incisores. Fig. 2. The same circumstance occurring in both the central incisores. The lateral incisores being placed properly. a a. Th^ temporary cuspidati. Fig. 3. The central permanent incisores rightly situa- ted, the lateral ones turned in. a a. The temporary cuspidati. Fig. 4. The four permanent incisores, having the same improper situation. Fig. 5. The bar to be fixed on the teeth, in order to remedy this kind of irregularity. Fig. 6. Represents the bar as fixed in order to bring one of the central incisores forward. Fig. 7. The bar fixed, with ligatures applied to the four permanent incisores, which are to be drawn forward. PLATE XIV. (FROM CATALAN, DELABARRE, ROBERTSON AND NATURE.) Fig. 1. An apparatus invented by M. Catalan to be placed upon the lower teeth, with four in- clined planes fixed to it, and designed to act upon the four incisores of the upper jaw. Fig. 2. The apparatus applied with a view to exhibit the principle upon which it acts. Fig. 3. In this figure, copied from Delabarre, an incisor tooth with one of its approximal surfaces pre- senting anteriorly, is represented. Fig. 4. A cap applied to the deviating incisor writh liga- tures attached to it, for the purpose of turning the tooth in its socket until the front surface shall present anteriorly. This figure is also copied from M. Delabarre. Fig. 5. The manner of correcting irregularity of the teeth by means of ligatures and a metallic grate, as proposed by M. Delabarre. Fig. 6. This figure, representing an apparatus applied to the lower teeth with an inclined plane acting upon a central incisor, is copied from Mr. Robertson's Treatise on the Teeth. Fig. 7. The last named apparatus before being applied to the teeth. Fig. 8. A gold case fitted to the lower teeth with an in- clined plane to act upon a deviating cuspidatus, constructed by the editor. 20 PLATE XV. CASES OF IRREGULARITY FROM SUPERNUMERARY TEETH, &c. Fig. 1. Supernumerary teeth of the conical form. Fig. 2. Supernumerary teeth resembling bicuspides. Fig. 3. A tooth which acquired a distorted shape during its formation, from the resistance of the temporary tooth. Fig. 4. A supernumerary tooth placed between the central incisores. Fig. 5. A supernumerary tooth growing above the central and the lateral incisor. Fig. 6. A remarkable case of irregularity, occasioned by the growth of two supernumerary teeth. Fig. 7. A similar case, the supernumerary resembled bicuspides of the lower jaw. Fig. 8. A case of two lateral incisores on the same side. IRREGULARITY AT AN ADVANCED PERIOD. Fig. 9. The lateral permanent incisores to be ex- tracted. Fig. 10. The most irregular tooth must be removed, when the others will approximate. Fig. 11. A cuspidatus left projecting until a late pe- riod; this being removed, the teeth will appear regular, as the lateral incisor and the first bicuspis are close to each other. Fig. 12. An exfoliation from the upper jaw, containing the temporary molares, and (a a) the bi- cuspides advancing in formation, b. The socket for the permanent cuspidatus. Rate I llg. i P S Duval's Lvth. PkUad* Plate, 2. ....... ""3 ^ - x'±Jks&k P. 'S. Duval*Liih PhJ.au Plate, 3. Ori stone. hrFDanqiion, PSDuvals Liih Phdad Plate *. ?lat*.5 (hi stvn& Iry C. Kudu? J -thplAid Plate b. Fin. 4 On .stone, ly C Kuckd P. S.Duval's Litk. Hulas. EZ>XX On Stone- by FJJavtgrwn P. S.Burnt, Mitk.ru • c Plate 8. Row 1. Row 2 J On stone, fy CJ&ckei P Slhivcds Litn P'hdaxl FU- ! 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