DENTISTRY 



763 



now one made in imitation of this, in a species of 

 pottery-ware called iiunrrul tn-th. I'sually this 

 tin. th is accurately fitted to the mm l>\ means of a 

 gold j>in, inserted into the open central canal exist- 

 ing in tin- runt, the other extremity of the pin 

 being attached to the sulwtitute tooth. 



Where more than one tooth i required, and 

 occasionally even where only one is necessary, a 

 ' plate 1 or ' base ' is very exactly fitted either to the 

 gum and palate as in 'suction' sets, or t<> the 

 remaining teeth where they are to IHJ the supports, 

 mure 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 intro- 

 ducing unset Paris plaster, beeswax, or other 

 modelling compound, softened by previous heat- 

 ing, into the patient's mouth, and pressing it 

 forcibly upon those parts of which an impres- 

 sion is desired. On removing the wax or other 

 substance from the mouth, Paris plaster is poured 

 into the mould thus procured, and on its hard- 

 ening, 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 ex- 

 tending 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 ita 

 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, witli 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 inclos- 

 ing mould of it, thus secured, maybe 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 I'M titu. The wax i 

 tin ii replaced by raw vulcanite, which, on the 

 mould being recloftcd, w subjected to the usual 

 process of vulcanising. 



A !>ase which is now itomctimefl used w cheoplantv, 

 or cast-metal, an alloy usually of tin and bUmuth. 

 This base is especially adapted for mouth* in which 

 the lower alveolar ridge in very flat, as it- grout 

 weight tends to keep the denture in position. The 

 method of construction is the Maine, in the pre- 

 liminary stages, as for a vulcanite net. After the 

 wax has been boiled out, the two halve* 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 earned on principally in London and the United 

 States. A great many of the most important pro- 

 cesses are mainly due to American invention or 

 development. Principal among these are the pro- 

 cess 01 vulcanising, the dental-engine, the rubuer- 

 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 oase 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. Elec- 

 tricity has recently been introduced as a motor for 

 the dental-engine and other purposes. 



To show how elaborately every possible require- 

 ment of the dentist is provided for by the manu- 

 facturers, 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 Phila- 

 delphia keeps in stock nearly six hundred 

 varieties of the 'plugger' (instruments for stop- 

 ping teeth). There is l>esides an equally liberal 

 choice in excavators, sealers, &c., while the varieties 

 in the makes of teeth are innumerable. It has 

 been estimated that sixteen thousand ounce* of 

 line gold are annually used for filling teeth ; ten 

 millions of mineral teeth are annually disposed of 

 throughout the civilised world ; and for the im- 

 plantation 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 illus- 

 trated works specially devoted to the subject, such 

 as Litth's System of Dentutry, Tomes s Dental 

 Xitriieri/, Taf't's Operative Dentistry, Richardson's 

 Mechanical Dentistry ; with the lesser works of 

 Coleman, Hunter, Oakely Coles, J. Smith, Sewill, 

 llynies, and others. 



Latcs 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 medi- 

 cal practitioners and those boixt fiat engaged in 

 the practice of dentistry at the time of the act's 

 parsing can take or use the title 'dentist,' or any 

 title signifying that he is registered, under a pen- 

 alt v of '20. And in future any person desiring 

 to oecome a dentist must undergo a certain course 

 of studv, and have taken a degree or license The 

 curriculum of study and the conduct of the exam- 

 ination are under the regulations of the General 

 Council of Medical Education ; and various dental 

 hospitals and school* have Wen established for the 

 instruction of the dental student. The degree in 



