Introduction

Teeth of continuous growth, such as rodent incisors, are kept to their appropriate functional length by wear; this implies an equilibrium between the rate of formation and the rate of wearing away. Occasionally, this equilibrium is not maintained and there is overgrowth of the teeth which, as in some examples described here, may reach grotesque proportions. It is not worthwhile to catalogue here all the descriptions that exist in the literature of single instances of this condition, some from the wild state, others from breeding colonies of captive animals, so we have restricted ourselves to descriptions that are usefully detailed, where previous literature is reviewed, or where the causation is discussed.

Teeth of limited growth can also to some extent appear to be overgrown beyond the level of the occlusal surfaces of the adjacent teeth when the teeth with which they normally occlude are lost, malposed or absent. This is often over-eruption (Chapter 16, pp. 348–349) but, in hypsodont teeth where wear is a predominant feature, over-eruption may be simulated by non-wear of the affected tooth; that is, it retains its normal overall height while adjacent teeth become shorter (Chapter 16, p. 348. Fig. 22.1).

Overgrowth of incisors in Rodentia and Lagomorpha

One of the most striking examples of overgrowth, seen in Figure 17.1, is of particular interest because it is a specimen collected by John Hunter, and is in the Hunterian Museum of the Royal College of Surgeons.