Modeling tooth enamel in FEA comparisons of skulls: Comparing common simplifications with biologically realistic models

Bite force is often associated with specific morphological features, such as sagittal crests. The presence of a pronounced sagittal crest in some tapirs (Perissodactyla: Tapiridae) was recently shown to be negatively correlated with hard‐object feeding, in contrast with similar cranial structures in carnivorans. The aim of this study was to investigate bite forces and sagittal crest heights across a wide range of modern and extinct tapirs and apply a comparative investigation to establish whether these features are correlated across a broad phylogenetic scope. We examined a sample of 71 specimens representing 15 tapir species (5 extant, 10 extinct) using the dry‐skull method, linear measurements of cranial features, phylogenetic reconstruction, and comparative analyses. Tapirs were found to exhibit variation in bite force and sagittal crest height across their phylogeny and between different biogeographical realms, with high‐crested morphologies occurring mostly in Neotropical species. The highest bite forces within tapirs appear to be driven by estimates for the masseter–pterygoid muscle complex, rather than predicted forces for the temporalis muscle. Our results demonstrate that relative sagittal crest height is poorly correlated with relative cranial bite force, suggesting high force application is not a driver for pronounced sagittal crests in this sample. The divergent biomechanical capabilities of different contemporaneous tapirids may have allowed multiple species to occupy overlapping territories and partition resources to avoid excess competition. Bite forces in tapirs peak in Pleistocene species, independent of body size, suggesting possible dietary shifts as a potential result of climatic changes during this epoch.

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“…2010), tooth material properties (Herbst et al . 2021), and jaw kinematics during mastication (Kuninori et al . 2014).…”

Section: Discussionmentioning

confidence: 99%

Sagittal crest morphology decoupled from relative bite performance in Pleistocene tapirs (Perissodactyla: Tapiridae)

et al. 2022

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“…In addition, the mechanical properties of these internal structures, like dentine has been found to vary with tooth height [ 91 ]. Future studies should employ micro-CT to create canine tooth models with accurate differences in the thickness and distribution of enamel and dentine or the size of the pulp cavity, which may help to reveal structural mechanisms among species that help counter stresses, similar to previous studies on fish and reptile taxa, and humans [ 38 , 92 , 93 ]. Moreover, the path of a canine tooth during a bite is not unidirectional, as we modelled in our static simulations.…”

Section: Discussionmentioning

confidence: 98%

Taking a stab at modelling canine tooth biomechanics in mammalian carnivores with beam theory and finite-element analysis

et al. 2022

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Canine teeth are vital to carnivore feeding ecology, facilitating behaviours related to prey capture and consumption. Forms vary with specific feeding ecologies; however, the biomechanics that drive these relationships have not been comprehensively investigated. Using a combination of beam theory analysis (BTA) and finite-element analysis (FEA) we assessed how aspects of canine shape impact tooth stress, relating this to feeding ecology. The degree of tooth lateral compression influenced tolerance of multidirectional loads, whereby canines with more circular cross-sections experienced similar maximum stresses under pulling and shaking loads, while more ellipsoid canines experienced higher stresses under shaking loads. Robusticity impacted a tooth's ability to tolerate stress and appears to be related to prey materials. Robust canines experience lower stresses and are found in carnivores regularly encountering hard foods. Slender canines experience higher stresses and are associated with carnivores biting into muscle and flesh. Curvature did not correlate with tooth stress; however, it did impact bending during biting. Our simulations help identify scenarios where canine forms are likely to break and pinpoint areas where this breakage may occur. These patterns demonstrate how canine shape relates to tolerating the stresses experienced when killing and feeding, revealing some of the form–function relationships that underpin mammalian carnivore ecologies.

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“…These values were averages of the published values for rodent enamel and dentine 28 as the two tissues were not distinguished during the segmentation process as a consequence of insufficient CT resolution in some specimens. Furthermore, it has been noted that representation of separate dental tissues in FE models has very limited impact on overall stress distributions 35 . Post-incisor dentition was not segmented as a separate material from bone as the focus of this study was directly on variation in mechanical strength of the mandible as a result of changes in incisor length.…”

Section: Methodsmentioning

confidence: 99%

The biomechanical significance of the elongated rodent incisor root in the mandible during incision

Morris

Cox

Cobb

2022

Sci Rep

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Rodents are characterised by a distinctive masticatory apparatus which includes a single pair of enlarged and continually growing incisors. This morphology, termed diprotodonty, has also independently evolved in a number of other mammals, including the aye-aye. This study examined the functional significance of the internal “root” of the elongated rodent-like incisor. The mandibles of four rodents and an aye-aye were modelled to exhibit incrementally shorter incisor roots. Finite element analysis was used to predict stress and strain patterns across the jaw to determine whether the length of the incisor root contributes to the resistance of mechanical forces encountered in the mandible during incision. It was found that von Mises stresses increase in the region of the mandible local to where the incisor is removed, but that the stress distribution across the wider mandible is only minimally affected. Thus, the long internal incisor appears to play a small role in resisting bending forces close to the incisor alveolus, and may act with the arch-like mandibular shape to strengthen the mandible in this region. However, the impact across the whole mandible is relatively limited, suggesting the highly elongate incisor in diprotodont mammals may be principally driven by other factors such as rapid incisor wear.

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Modeling tooth enamel in FEA comparisons of skulls: Comparing common simplifications with biologically realistic models

Cited by 12 publications

References 58 publications

Sagittal crest morphology decoupled from relative bite performance in Pleistocene tapirs (Perissodactyla: Tapiridae)

Sagittal crest morphology decoupled from relative bite performance in Pleistocene tapirs (Perissodactyla: Tapiridae)

Taking a stab at modelling canine tooth biomechanics in mammalian carnivores with beam theory and finite-element analysis

The biomechanical significance of the elongated rodent incisor root in the mandible during incision

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