Malocclusion

Overgrowth of the incisor teeth occurs sporadically in rats. The condition occurs secondary to poor alignment of the upper and lower incisor teeth, with resultant failure to wear in the normal manner. The condition may be secondary to a broken upper or lower incisor tooth but is more often a spontaneous event and in many cases is considered to be due to genetic factors. Depending on the duration and severity of the problem, affected animals are frequently thin due to their inability to prehend and masticate food normally, and in advanced cases, severely affected lower or upper incisors may penetrate into the soft tissues of the palate or jaw (Fig. 2.70).