40 THE SURGICAL ANATOMY OF THE HORSE 



the incisors of the same jaw, and if sufficient care has been taken in 

 rotating the tooth, extraction is easy. 



Repulsion of Teeth 



A second method of removal is by punching out the tooth, and is 

 termed "repulsion." This method is adopted in the removal of fangs 

 where the crowns have broken away, or in the removal of teeth 

 where the presence of odontomata, etc., renders extraction by forceps 

 unusually difficult. 



In connection with the removal of molar teeth by this method a 

 careful study of the direction which the root of each tooth takes is 

 necessary. The root of the last molar in the upper jaw when the skull 

 is considered with its long axis disposed horizontally, projects in a 

 direction which is much more obliquely upwards and backwards than 

 is the case with the roots of the remaining molars. 



This root forms a projection, the inner aspect of which is entirely 

 in the outer compartment of the superior maxillary sinus, where it 

 is covered by a thin osseous plate. 



The root of the fifth molar forms inwardly an elevation which is 

 only in part visible in this sinus. The remainder of this root, together 

 with tlie elevation formed inwardly by the whole of the root of the 

 fourth molar and also part of that formed by the root of the third molar, 

 is visible in the outer compartment of the inferior maxillary sinus. 



It is evident, therefore, that to be able to apply a punch to the root 

 of the sixth or fifth molars, the operation of trephining into the superior 

 maxillary sinus should be performed. In this case the seat adopted should 

 not be that which is selected when the object is to drain the sinus, 

 because the object is not, as in the latter case, to make the opening as near 

 as possible to the septum separating the superior and inferior maxillary 

 sinuses, but to arrive at a seat which will be immediately over the 

 extremity of the root of the molar which it is desired to remove. 



The root of the sixth molar runs upwards and backwards to within 



