The effect of tooth loss on sexual dimorphism of South African mandible using geometric morphometrics

The human mandible is one of several sexually dimorphic bones and provides moderate to high accuracy in the estimation of sex during forensic application. Mandibular morphology changes in response to aging and tooth loss and few studies have considered the effect of these factors on sex estimation. The aim of the study was to assess the effect of tooth loss on the accuracy of estimating the sex of the mandible. The sample includes 196 mandibles of South African Black people of African descent. Seventy-nine mandibles had full dentition and 117 had various degrees of tooth loss. Fixed and semi-sliding 3D landmarks were used to outline non-alveolar mandibular morphology. The alveolar region was scored for the presence or absence of antemortem tooth loss. Two-sample permutation tests assessed the presence of sexual dimorphism and discriminant analysis was used to illustrate sexual dimorphism and to estimate the accuracy of sex allocations. Mandibles with full dentition and tooth loss had higher sex allocation accuracies, but the difference was greater among those with tooth loss than observed in fully dentate mandibles. Males displayed a broader mandibular arch, ramus flexure, ante-gonial notches, and longer coronoid processes compared to females in both the dentate and edentate mandibles. The accuracy of sex estimation was comparable between the tooth loss sample (86.8 %) and the full dentition sample (85.4 %). Thus, mandibles with tooth loss exhibit sufficient sexual dimorphism to estimate sex accurately using both qualitative and quantitative methods in a South African population. (231)