Relationship Between Dental Topography, Food Type and Jaw Kinematics in Two Species of Non-Human Primates

Hypothesis: We hypothesize that differences in diets among non-human primates will be reflected in differences in the occlusal tooth morphology and the ability to process foods of different material properties. Objective: The post-canine dentitions of living and extinct primates are enormously diverse, and used for a wide range of behaviors. Here we seek to identify relationships between patterns in the occlusal surface of the teeth with the behavior for which the teeth are most frequently used, feeding. These relationships are important for identifying potential selective pressures driving variation in dental morphology. Methods: Dental topography data were analyzed from Cebus apella (n=12) and Macaca mulatta (n=12) maxillas and mandibles, digitized with a Lythos ™ Digital Impression System. First molars (M1) were isolated, and dental variables were calculated using the MorphoTester software. Feeding time data were calculated from three-dimensional jaw kinematics from both species. Foods were grouped into two categories base on material properties. Custom Matlab scripts calculated the time from ingestion to the first swallow. The effect of species, individuals, and food type on dental topography and feeding time variables were evaluated with ANOVA. Results: Dental variables related to topography of Cebus first molars are lower than Macaca, namely in Dirichlet Normal Energy, surface area, outline area, and orientation patch count. There is no difference in Surface Relief Index. Feeding time data illustrate that food material properties have no impact on time to swallow in Cebus, but macaques take longer to process low toughness/high stiffness foods. Macaca have longer overall feeding times than Cebus. Conclusions: Cebus have dental variables indicative of a frugivorous, hard object diet while Macaca have dental variables indicative of a generalized frugivorous/folivorous diet. Differences in feeding times support the hypothesis that species level differences in tooth morphology influence processing of foods of different material properties. Funding: UIC College of Dentistry, Department of Orthodontics. IACUC: ACUP/Renewal ACUP protocol: University of Chicago IACUC 72154; 71489