OPEBATIONS ON THE TEETH. 335 



rapid wearing of various parts of their surfaces, though it seldom 

 reaches the point of caries. 



The different indications which the majority of these patho- 

 logical conditions may impose resemble so nearly those required 

 under similar circumstances for the grinders, that it becomes un- 

 necessary to appropriate a special chapter to their discussion, and 

 we therefore proceed to the consideration of the general opera- 

 tions performed upon the teeth, according to the indications 

 which may be from time to time presented. 



Opeeativb Dental Sukgeey. 



Two pi-incipal indications present themselves under this head- 

 ing. First, the leveling of the frictional dental surfaces, for the 

 removal of any existing asperities or sharp projections, in order 

 to estabUsh a perfect coaptation, as well as the free movement 

 necessary for the execution of their function of attrition. Second, 

 the extraction of the teeth which have undergone such important 

 alterations in their structure, that their conservation becomes in- 

 compatible with the regular execution of mastication, or because 

 of the serious complications they may involve. 



Leveling of the Dental Arches — The original mode of operat- 

 ing to level the molar teeth consisted in making the animal chew 

 on the blacksmith's rasp. It is a simple process, easy to perform, 

 without danger to the animal, and so well answering the purpose 

 that even to-day the process is stUl in extensive use. But this 

 modus operandi is not without its inconveniences, among other 

 objectionable points, requiring to be repeated for several days 

 imtil perhaps the teeth have become smooth by rubbing against 

 the rough surface of the rasp — a result not always as satisfactory 

 as it might be. More appropriate instruments have therefore 

 been invented, though, in point of fact, none of them are other 

 than more or less modified rasps or files, as they are truly called. 

 Their number and variety are to-day very great, and their quali- 

 ties vary very much, according to the taste, the ideas, and often 

 the dexterity of those who use them. Samples of these files are 

 represented in Fig. 340, and according to their general construc- 

 tion may be classified as rough and fine rasps, flat and angular, 

 guarded, double and single on one or other of their edges. Some 

 are simple, and formed of a single piece, while others are jointed 

 and compound, and may be screwed or unscrewed with facility 



