Introduction

Injuries of the teeth are common in animals, and their study is both instructive and interesting. To facilitate description, these injuries will be divided into two groups; injuries to developing teeth and injuries to teeth that have erupted, further divided into (a) teeth of continuous growth and (b) teeth of limited growth.

Injuries to developing teeth

The effect of injury on a tooth in its crypt depends upon the stage of growth and the character of the injury. If the tooth is partly formed, for instance when the crown is formed and mineralized and the root is about to be formed, the crown may be displaced by an injury leaving the formative soft parts still in position but, because the formed and unformed parts are still connected, a bend is introduced between the two which may be quite acute. When recovery occurs and formation recommences, the bend and any associated deformity of the soft parts will be reproduced in the completed tooth. Such specimens often look as if they have been divided and then stuck together; hence this condition is often categorized as dilaceration.

Figure 19.1 shows an example of this condition. The left I3 of a captive, sub-adult polar bear is lying horizontally along the floor of the nasal fossa covered only by a thin layer of bone. About one-third of the crown of the tooth had been mineralized at the time of injury and had been bent backwards, forcing it slightly into the as yet unformed portion (Fig. 19.1B).