Dentistry, the art of the dentist, or that of treating disease in the teeth (Dental Surgery), and of replacing these organs when lost (Mechanical Dentistry). The art is a very ancient one. The Laws of the Twelve Tables (5th century B.C.) provided for the case of 'teeth bound with gold,' it being lawful in this connection to burn or bury gold with the dead person. An Etruscan skull found in 1885 had a set of animal's teeth artificially fixed in it. The dentistry of the United States has in recent times become specially celebrated.
(1) Dental Surgery.—The disorders to which the teeth are liable are those arising from defective development, such as imperfections in form or structure, irregularity of position, &c.; those, again, constituting diseases more properly so called, such as caries or dental decay, necrosis or death of a tooth, inflammation of the soft tissues, such as the gum, the central pulp or nerve, as it is popularly called, neuralgic affections, &c.; lastly, those arising from accidents of various kinds, such as blows, falls, and the like. For the constitution and diseases of the teeth, see TEETH.
The object of the dentist, in treating decayed teeth, is twofold: he either attempts to arrest the decay, and repair its ravages; or he removes the diseased tooth altogether. These operations, along with supplying artificial teeth when the natural ones are lost, constitute the main offices of dentistry.
Scaling.—This is a little operation, by which the accumulation of a substance termed 'tartar' is removed from the teeth. Tartar or salivary calculus is of different densities and colours, and is a deposit from the saliva. It is most frequently found at the necks of the teeth, and lodges in greatest quantity most commonly behind the lower front-teeth. Where it accumulates it is generally accompanied by absorption of the gums, whereby the necks of the teeth are exposed, and they become loosened. Its removal is effected by little hoe-shaped steel instruments, bent in a manner to reach more easily those situations in which the tartar is found. Their mode of use is by inserting the point of any one of them under the free edge of the mass of tartar, at the gum, and lifting it away from the backs of the teeth to which it is adherent. The teeth are then freed from any particles still sticking about them, and their surface smoothed by being rubbed with pumice-powder or chalk. In certain diseased conditions of the structures about the necks of the teeth, considerable purulent discharges occur, and tartar frequently becomes largely deposited.
Regulating.—The teeth of the second, or permanent or adult set, are very liable to be crowded and misplaced, one overlapping the other, or those of the upper jaw falling behind those of the lower when the mouth is closed, thus producing the prominent condition of the under jaw denominated 'under-hung.' To remedy these defects, a variety of means have been adopted by dentists; the principle upon which all of them act, however, being that of pressing the displaced tooth or teeth into the natural position. This, of course, requires that room or space should exist for them to be thus adjusted; and where this is not the case, the usual procedure is to remove one or more of the back-teeth, or any others which it is less desirable to preserve. In other cases the dental arch itself is malformed, and may be enlarged by regulated pressure so as to afford more accommodation for the teeth, as well as to improve its contour. Some considerable time is necessary to complete the regulation of misplaced teeth; and even after they have assumed their proper position, they require to be carefully maintained there, otherwise a tendency to resume their former irregularity soon manifests itself.
Stopping or Filling.—This is one of the most important and delicate operations the dentist has to perform. The first step to be taken in filling or 'stopping' a tooth, is to clear away all decayed and decaying substance. For this purpose, a number of slender digging and excavating steel instruments, termed 'excavators,' are required. The 'dental-engine' is another valuable means of preparing the cavity for filling, and acts by means of small drills and file-headed points rapidly rotating, so as to cut away what is desired of the tooth substance. With these, the hollow in the tooth is scooped out and thoroughly cleaned. If pain be occasioned by this process, the obtunding of the tooth's sensitiveness, or 'destroying the nerve,' as it is called, had better at once be resorted to. This is performed in several ways. Where the tooth is single-fanged, as in front-teeth, the nerve, or more correctly the pulp, may be removed by passing a slender broach, or square and pointed brad-shaped, or slender serrated steel probe up into the central cavity of the tooth, with a slight rotary motion, so as to break up and remove the pulp. Where this cannot be done at once the best plan is to destroy the pulp by some caustic application, such as arsenious acid, chloride of zinc, carbolic acid, &c., carefully applied, a variety of other substances being used for the same purpose.
The cavity being properly shaped and cleaned out until its walls are of sound and hard tooth-bone, is to be well dried, and the plug of stopping-material inserted. Various substances are employed for this purpose, and the mode of using each is somewhat different. For temporary stoppings, pure gutta-percha is a serviceable material. A quantity sufficient to fill the cavity, and somewhat more, is to be gently warmed over a spirit-lamp—not in hot water—and when quite plastic is to be firmly pressed with a blunt-pointed stopping-instrument or 'plugger' into all the interstices of the hollow in the tooth—more and more being pressed in, until the surface of the plug so formed is on a level with the surface of the tooth, when all superfluous portions should be removed, and the solid plug smoothly finished. Osteo-plastic fillings consist of varieties of the metallic oxychlorides and phosphates. They are inserted in a soft condition into the tooth, where they harden in the course of a few minutes.
Another variety of stopping-material consists of amalgams of different kinds. Many absurd statements have been made regarding the evil effects of amalgam stoppings, but the only real disadvantage attending their use is shrinkage, and that many of them get black in the mouth, and discolour the tooth, while some that do not get black are friable, and crumble away in a short space of time. Some of those containing copper exercise a beneficial action on the tooth-bone, but darken its colour very much. The amalgam is rubbed up with mercury to a firm, plastic consistence, and carefully introduced into the dried cavity in the same way as the gutta-percha plug.
Gold-stopping is an operation of a much more complicated and difficult description. The materials used here are either gold-foil—that is, thick gold-leaf—or the peculiar form in which gold exists known as sponge-gold; or again, 'pellets' of gold made up in a soft spongy condition of various sizes ready for use. In stopping a tooth with gold, even more care is necessary in preparing the cavity than what has been already inculcated. Its shape and condition must now be particularly taken into account, and the nearer it approaches to a cylindrical form the better. Various modes of packing the gold are adopted according to two conditions in which gold exists—namely adhesive, where each portion can be welded to the other; or non-adhesive, where they are securely fixed merely by tightly wedging them together. Non-adhesive gold can be made adhesive by heating it to redness. The surface of a gold plug, formed in any of these ways, should be well consolidated by hard pressure with a blunt plugger, or lightly hammered with a suitable mallet, and the superfluous portion being removed, it ought to be burnished until it assumes a brilliant metallic lustre.
Remedies.—Many remedies, more or less service- able, are in use for what is termed toothache—a disorder which, however, is not always one and the same in its nature. Their intention, in general, is either to destroy the nervous fibres existing in a tooth, or to narcotise and render them insensible. Among those acting in the former manner are such as creasote, arsenious acid, carbolic acid, pepsine, chloride of zinc, nitrate of silver, alum, tannin, &c.; among those acting in the latter mode are chloroform, laudanum, ether, spirit of camphor, menthol, cocaine, &c. In all cases the decayed cavity should previously be well cleaned out, otherwise the remedy employed may be altogether prevented from reaching the spot where it is intended to act.
Extraction.—This is the principal surgical operation falling to the dentist. It is performed by means of instruments adapted to the special peculiarities of the tooth requiring removal, or to the circumstances in which it exists. The great matter is, that each tooth should be extracted in accordance with its anatomical configuration; and to accomplish this of course requires an intimate knowledge of the natural form proper to each of these organs individually; without this, it is impossible to extract any tooth upon a correct principle. The tooth is grasped, as far as the instrument can be made to do so, by that portion of the root or fang which just emerges from, or perhaps which is just within, the socket; it is then loosened, not exactly by pulling, but rather by moving it in a lateral or in a rotatory manner, in strict accordance with the respective character of fang possessed; and finally, on its being thus detached from its connection with the jaw, it is, with very little force, easily lifted from its socket.
Anæsthetics are employed in the extraction of teeth in the same manner as for other surgical operations, where it is desirable to abolish pain. See ANÆSTHESIA. Neither ether nor chloroform should be given by inexperienced hands, nor should both the giving of the anæsthetic and the extraction be attempted by one individual on any occasion. Nitrous oxide or laughing-gas is of much service, answering all the purposes of chloroform or ether in short operations. A combination of two or more of these anæsthetics has been employed with apparent success, such as nitrous oxide with ether. Freezing the gum, the injection into it of cocaine, and other modes of inducing insensibility, local or general, have been proposed from time to time, but one after another has been abandoned as unserviceable.
(2) Mechanical Dentistry.—The various conditions of the mouth requiring the adaptation of artificial teeth, range from cases where only one tooth may be wanting, to those where not a single tooth remains in the jaw, above or below. Accordingly, artificial teeth are spoken of as partial or complete sets—a partial set being one for either upper or lower jaw, where some of the natural teeth still remain; a complete set being one for either jaw, where none are left, or for both jaws, when both are in such circumstances.
The transplantation of the teeth of another individual is a very old usage revived every now and again, and equally often falling into desuetude; and implantation is a recent modification of the process.
The simplest form of partial sets is what is termed a pivoted tooth. This is an artificial tooth fixed in the mouth upon the fang or root of one whose crown has been lost by decay or otherwise. The most usual mode of procedure is as follows: An artificial tooth, as near as possible to the colour and form of that to be replaced, is selected. This artificial tooth used to be the crown of a natural human tooth corresponding to that lost, but is now one made in imitation of this, in a species of pottery-ware called mineral teeth. Usually this tooth is accurately fitted to the root by means of a gold pin, inserted into the open central canal existing in the root, the other extremity of the pin being attached to the substitute tooth.
Where more than one tooth is required, and occasionally even where only one is necessary, a 'plate' or 'base' is very exactly fitted either to the gum and palate as in 'suction' sets, or to the remaining teeth where they are to be the supports, more especially in what is called crown and bridge work; and to this base the artificial teeth required are fitted and fixed.
This 'base' is frequently made of gold, silver, or platinum plate, of the thickness of card-board, of vulcanised caoutchouc or vulcanite, or of celluloid—a compound of camphor and gun-cotton. An exact model of the gum and other parts upon which the plate is to rest is obtained by introducing unset Paris plaster, beeswax, or other modelling compound, softened by previous heating, into the patient's mouth, and pressing it forcibly upon those parts of which an impression is desired. On removing the wax or other substance from the mouth, Paris plaster is poured into the mould thus procured, and on its hardening, or 'setting,' this plaster-cast presents an exact counterpart of the gum. It is upon this plaster-model that all the subsequent operations are performed in fitting the artificial set.
Metallic-plate Sets.—Where the framework lying upon the gum is to be of gold or silver plate, or the like, it is necessary to procure, besides the plaster-model, a metal one. This metal-model is generally cast in zinc, gun-metal, or some such material; and a counter-model of a softer metal, generally lead, is taken from this again, so that a complete pair of dies is in this way procured. The gold or other plate, cut of a convenient size, is then stamped between the two metallic dies, until assuming the precise form desired. It is then trimmed, and any more delicate adjustments made upon it, such as fitting and soldering bands or clasps to those parts where it is to embrace any teeth remaining in the mouth. The mode of fastening the teeth to the plate varies. One kind of teeth has a tube extending along their whole length, and these are fastened by means of a pin fixed to the plate, and passing up the tube. The other kind is provided with short platinum pins, fixed in the material of the tooth during its manufacture, to which pins a piece of gold or other plate is soldered, or a mass of gold fused upon them, and this, again, soldered to the framework of the set.
Another form of these plate sets or artificial dentures is where the plate—generally of platinum—has an arrangement suited for fusing a siliceous material to it and the teeth, so as to form an artificial gum. This is termed 'continuous gum work,' and is very effective although it has its disadvantages. Sometimes vulcanite sets are mounted with continuous gum work.
Vulcanite Sets.—The first step in the manufacture of a vulcanite set of teeth is to make a pattern set in wax, with the mineral teeth fixed in the wax. This pattern set is made upon and fitted to the plaster-model, and is adjusted to the wearer's mouth precisely as if it were the set to be worn. When everything is thus prepared, a duplicate of the wax-set is made in vulcanite—the vulcanite replacing the wax, and the mineral teeth being retained as they were. The process by which the vulcanite is made to take the place of the wax consists in imbedding the pattern set in Paris plaster, so that the inclosing mould of it, thus secured, may be separable into at least two parts. On these being taken asunder, the wax of the pattern set is melted out with boil- ing water, leaving the teeth in situ. The wax is then replaced by raw vulcanite, which, on the mould being reclosed, is subjected to the usual process of vulcanising.
A base which is now sometimes used is cheoplasty, or cast-metal, an alloy usually of tin and bismuth. This base is especially adapted for mouths in which the lower alveolar ridge is very flat, as its great weight tends to keep the denture in position. The method of construction is the same, in the preliminary stages, as for a vulcanite set. After the wax has been boiled out, the two halves of the mould are placed together, and the melted metal is poured in.
Dental Appliances.—The manufacture of dental apparatus is a very large and important one, and is carried on principally in London and the United States. A great many of the most important processes are mainly due to American invention or development. Principal among these are the process of vulcanising, the dental-engine, the rubber-dam, mineral teeth, the introduction of nitrous-oxide gas, and perhaps also the great improvements in the modern operating-chair. The introduction of the vulcanite base and mineral teeth has been the means of bringing the benefits of dentistry within the reach of thousands who could not afford the expense of gold and silver plates. The dental-engine is an ingenious little machine, whereby the action of a treadle, conveyed through a flexible arm, gives a rotary motion to a drill or burr, for operating in the patient's mouth. Electricity has recently been introduced as a motor for the dental-engine and other purposes.
To show how elaborately every possible requirement of the dentist is provided for by the manufacturers, we may give a few instances. Most makers offer a choice from about a hundred varieties of forceps for the extraction of teeth; the number of drills and burrs for the dental-engine provided by one maker for selection approaches three hundred; while a manufacturer in Philadelphia keeps in stock nearly six hundred varieties of the 'plugger' (instruments for stopping teeth). There is besides an equally liberal choice in excavators, scalers, &c., while the varieties in the makes of teeth are innumerable. It has been estimated that sixteen thousand ounces of fine gold are annually used for filling teeth; ten millions of mineral teeth are annually disposed of throughout the civilised world; and for the implantation of these in the mouth, independent of gold and other bases, sixteen tons of rubber are annually required.
For a more detailed account of dentistry, we must refer to the numerous and beautifully illustrated works specially devoted to the subject, such as Litch's System of Dentistry, Tomes's Dental Surgery, Taft's Operative Dentistry, Richardson's Mechanical Dentistry; with the lesser works of Coleman, Hunter, Oakely Coles, J. Smith, Sewill, Rymes, and others.
Laws as to Dentistry.—In 1878 an act entitled the Dentists Act was passed with a view of amending the laws relating to dental practitioners. In terms of this act, no one except qualified medical practitioners and those bonâ fide engaged in the practice of dentistry at the time of the act's passing can take or use the title 'dentist,' or any title signifying that he is registered, under a penalty of £20. And in future any person desiring to become a dentist must undergo a certain course of study, and have taken a degree or license. The curriculum of study and the conduct of the examination are under the regulations of the General Council of Medical Education; and various dental hospitals and schools have been established for the instruction of the dental student. The degree in
Great Britain and Ireland is L.D.S. (Licentiate in Dental Surgery). The only foreign degrees (both American) qualifying for registration in Britain are D.M.D. (Harvard) and D.D.S. (Michigan). In 1888 there were in practice in Great Britain and Ireland 977 licentiates under the new act, and 3889 practitioners registered as having been in practice before 1878.