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Anterior Tooth Attrition in Apes

Attrition is the normal loss of tooth substance due to function and occurs both proximally (leading to a reduction mesiodistally) and occlusally (leading to a reduction in crown or cusp height) . Attrition is a universal primate attribute. Yet with the exception of man, it has been subject to little quantitative appraisal, particularly for the anterior teeth. This study was therefore undertaken to compare incisor and canine dimensions between young and old anthropoid skulls in order to provide some quantitative data on attrition. A total of 32 Gorilla gorilla, 38 Pan troglodytes, and 28 Pongo pygmaeus skulls were included in this study. These skulls were from males and were sexed according to their craniometric features (there were insufficient female skulls to be included in this study). In anthropoids, the first permanent molars frequently exhibit attrition before the completion of permanent tooth eruption. Consequently, the skulls were categorized as young and old according to the following criteria: skulls with complete dentitions but with no attrition on either of the two lingual cusps of the mandibular second molars were considered young; skulls with complete dentitions showing attrition on one or both of these cusps in addition to the three buccal cusps were considered old. Attrition is a complex polymorphism, so that the ageing of skulls on this parameter is arbitrary. Nevertheless, in the absence of written records, the eruption sequence or fusion of sutures provide no preferential means of ageing skulls. Also, in no instance were old skulls with gross attrition selected; all the young skulls showed little or no attrition of their anterior teeth. Estimates of proximal (mesiodistal diameter) and incisal (crown heights) attrition were computed by comparing the tooth dimensions between young and old skulls. The mesiodistal