Finite element modeling of occlusal variation in durophagous tooth systems

Abstract

In addition to breaking hard prey items, the teeth of durophagous predators must also resist failure under high loads. To understand the effects of morphology on tooth resistance to failure, finite element models were used to examine differences in total strain energy (J), first principal strain and the distribution of strains in a diversity of canonical durophagous tooth morphologies. By changing the way loads were applied to the models, I was also able to model the effects of large and small prey items. Tooth models with overall convex morphologies have higher in-model strains than those with a flat or concave occlusal surface. When a cusp is added to the tooth model, taller or thinner cusps increase in-model strain. While there is little difference in the relationships between tooth morphology and strain measurements for most models, there is a marked difference between effects of the large and small prey loads on the concave and flat tooth morphologies. Comparing these data with measurements of force required by these same morphologies to break prey items illustrates functional trade-offs between the need to prevent tooth failure under high loads by minimizing in-tooth strain versus the drive to reduce the total applied force.

A large carnivorous mammal from the Late Cretaceous and the North American origin of marsupials

“…Its broad, convex premolars with the protocone as a stress concentrator closely approximate an ‘ideal' crushing form37. They require less force than concave shapes to induce crack formation in prey items and are more resistant to tooth fracture than tall- or narrow-cusped shapes37. Even the flat premolars of later wear stages, while not as effective at crushing, incur lower strain values37.…”

“…They require less force than concave shapes to induce crack formation in prey items and are more resistant to tooth fracture than tall- or narrow-cusped shapes37. Even the flat premolars of later wear stages, while not as effective at crushing, incur lower strain values37. Moreover, the RPS25 of D .…”

Tooth occlusal morphology in the durophagous marine reptiles, Placodontia (Reptilia: Sauropterygia)

“…Placodus gigas has maxillary teeth with a larger RoC than the maxillary teeth of Paraplacodus broilii , but still more rounded than the palatine teeth. Based on predictions from previous works, these teeth would have been less likely to break while still effectively crushing prey (Chai et al 2009; Lee et al 2011; Qasim et al 2005; Crofts and Summers 2014; Crofts 2015). The average RoC of the palatine teeth is much larger than the RoC for the maxillary teeth—approaching a predicted optimal tooth shape for crushing while resisting failure (RoC normalized by tooth width ≥0.8; Supplementary Table 1).…”

“…This suggests that these organisms may, in fact, have had a different dietary specialization than the other placodonts or have specialized for durophagy in a different way. The shallow concavity may dissipate in-tooth strain and localize any damage that might occur (Qasim et al 2005; Crofts 2015), whereas the cusp, which has a relatively small RoC, concentrates stress applied to the prey item (Crofts and Summers 2014). Alternatively, these teeth may have worked in a way similar to the system that has been proposed for bunodont molars, where stress is applied to food items by a dull cusp that also dissipates in-tooth stress, while three additional cusps, or the concavity in placodonts, serve to hold food items in place (Berthaume et al 2014).…”

“…Flat teeth have been shown to break shelled prey items with less force than concave or cupped tooth morphologies and with as much or less force than convex or cusped teeth (Crofts and Summers 2014). However, a more convex occlusal surface (pointier teeth) will make tooth failure more likely under high loads compared with flatter or even concave surfaces (duller or cupped teeth), which are better able to diffuse in-tooth strain and can localize damage (Qasim et al 2005; Chai et al 2009; Lee et al 2011; Crofts 2015; for a discussion of cusp morphology in multicusped teeth, see Berthaume et al 2013, 2014).…”