302 DENTAL FISTULA. 



tion of several cases of dental fistula in the horse, dog and cat, see 

 Cadiot and Dollar's " Clinical Veterinary Medicine and Surgery." 



Causes. Fistula?, though generally preceded by alveolar perios- 

 titis, may be produced by complicated fractures or injuries of the 

 maxilla. Hertwig believed pre-molar fistulse in the lower jaw to be 

 commonly caused by wounds inflicted by narrow and inclined 

 mangers. We can support this view, having seen many cases of 

 pre-molar fistula in young animals exhibiting no disease of the 

 alveolus, but traceable to external injury of the lower jaw. The 

 root of the tooth is often thickened, surrounded by actively -growing 

 granulation tissue, which becomes covered with fresh cement ; a 

 periostitis alveolaris ossificans results, with formation of hyperostosis 

 radicis (Fig. 303), and extraction is rendered difficult, or even 

 impossible. 



The symptoms consist in the appearance of a little funnel-shaped 

 depression in the skin of the lower margin of the under jaw, or of 

 the upper jaw at the height of the roots of the pre-molars. Some- 

 times the fistula opens within the mouth near the affected tooth, 

 as may be proved by injecting the channel with a coloured fluid. 

 A fine sound being introduced, meets with a hard substance — tooth, 

 or bone, or it may pass into the mouth. Round the external opening 

 and over the course of the canal the bone is rarefied and swollen. 

 Mastication is not always impeded. Examination usually betrays 

 signs of alveolar periostitis in the affected tooth. 



Prognosis. Removal of the affected tooth is indicated. Hertwig 

 describes a cure after application of the actual cautery and mopping 

 with tincture of aloes, but such recoveries are exceptional. When 

 the lower pre-molars have become diseased from external injury, 

 recovery sometimes takes place without removal of the tooth. But 

 usually infection of the alveolus continues, and pus formation prevents 

 healing. Moreover, in such cases there is generally a difficulty in 

 extracting the tooth. In dental fistula affecting the upper jaw a 

 radical cure is impossible without removal of the tooth. In prognosis 

 account must be taken not only of the disturbances caused by the 

 diseased tooth, but also of the danger of extraction. Where incon- 

 venience is slight, it may appear advisable to refrain from treatment. 

 If, however, the fistula opens into the upper maxillary sinus or nostril, 

 the tooth must be removed and the sinus trephined. Where per- 

 foration into the nostril is attended with necrosis of the turbinated 

 bones, as not infrequently happens, the prognosis is unfavourable. 

 The nasal discharge continues after extraction of the tooth, and 

 betrays the peculiar smell of bone pus. After a time pieces of the 



