Tooth biomechanics of the non-mammalian synapsid Dimetrodon using two- and three-dimensional finite element analysis

Major changes in tooth morphology can be tracked throughout the evolutionary history of the Early Permian non-mammalian synapsid Dimetrodon (295-270 Mya). Teeth changed from the ancestral condition of folded roots (plicidentine) and crowns with smooth cutting edges (carinae) to a morphology with elongate roots and blade-like ziphodont crown morphology with serrated denticulate carinae, typical of other extinct apex predators. We created virtual models of individual teeth to investigate the functional differences between these morphological conditions through a combination of 2D and 3D finite element analyses (FEA). Material properties based on extant values of enamel, dentine and bone were applied to models loaded with point forces directed at the tooth tips. Results show that in the crowns, denticles convey energy non-homogeneously, funnelling stress and strain to the thinnest enamel layers between the denticles. Increased surface area of the expanded tooth roots resulted in lower stress values than present in the crowns. Similar areas in a short, folded root did not significantly alter energy transmitted to the cortical bone when compared with elongated, smooth roots. FEA results support the hypothesis that denticles and elongated, non-folded roots were all adaptations that would assist Dimetrodon in the oral processing of larger prey items.