ANIMAL DENTISTRY. 



177 



of more serious import. They may be unilateral or bilateral. 

 If the temporary tooth is already shed the condition must 

 be treated on the expectant plan. Blisters and time will 

 remove the condition in from two months to one year. They 

 seldom persist longer. Removal of the greater portion of 

 the tumor by trephining it from apex to base with a large 

 trephine will hurry the recovery, but there is some danger 

 of producing a chronic fistula that is difficult to heal. 



DENTAL CYSTS. 



Dental cysts is the name we apply to cystic growths oc- 

 curring along the course of the artery supplying the tooth. 

 They vary in size from small sacs the size of a marble to 

 growths that entirely fill the sinuses and even cause bulging 

 of the facial bones. They are probably the result of athero- 

 matous degeneration in the wall of the nutrient artery of the 

 molar tooth. They frequently become infected and cause 

 alveolar-periostitis, chronic nasal catarrh, or both. Regard- 

 less of size, they completely destroy the nutrition of the 

 tooth by obliterating the nutrient vessel, and after they ex- 

 pel their contents the dead tooth, entirely stripped of its 

 peridental covering, is left projecting into the sinus. During 

 the early stages of the resulting catarrh a diagnosis of the 

 real condition, before operation, is impossible. A tooth so 

 afifected will finally become loosened and thereby for the 

 first time reveal the true cause of the catarrh. In rare in- 

 stances the projecting root becomes encysted in a new mass 

 of fibrous tissue and remains intact through life. The dental 

 cyst explains the nature of the cause of some of these ob- 

 scure cases of chronic nasal catarrh which are described as 

 primary. When recognized these cysts are treated by re- 

 pulsion of the afifected tooth, which is located by palpation 

 or inspection after the skull has been trephined. The disease 



