Congenital and Neoplastic Abnormalities

Connate teeth arise either from a process of fusion of two tooth germs or from the partial splitting or dichotomy of a tooth primordium. It remains unclear if either or both processes take place. Other terms, such as gemination or double tooth, essentially describe the same phenomenon. Connation of deciduous incisor teeth has been reported in both Pan and Gorilla and rare cases of distomolars (M4) connated with M3 have been described in great apes. Premolar and molar teeth with extra cusps are common, but some great ape molars have been described with as many as nine cusps. In both humans and great apes, the third molar is notorious for variation in size, shape and cuspal number. Deciduous and permanent molars occasionally have additional roots or tall pulp chambers where bifurcation of the root trunk has occurred late in tooth development (taurodontism). Odontomes are tumour-like masses found within the jaws that contain dental tissues (enamel, dentine cementum) in varying proportions and at varying stages of development. Odontomes occur in humans and have been identified in many other animals including one in Papio but their rarity probably explains why none have been identified in great apes. Similarly, other congenital dental anomalies such as enamel pearls (beads of isolated enamel on the roots of teeth) and invaginated teeth, where deeply dilated pits extend into the substance of the tooth are sufficiently rare as not to have been identified in great apes. Teeth and tooth tissues can grow at sites beyond the jaws in ovarian teratomas (dermoid cysts). Teeth with apparently normal morphology and histology, as well as others that are harder to identify, are found mixed with other tissues such as skin, and hair in these tumours.