The relationship between skull morphology, masticatory muscle force and cranial skeletal deformation during biting

Toro‐Ibacache, Viviana; Muñoz, Víctor Zapata; O’Higgins, Paul

doi:10.1016/j.aanat.2015.03.002

Cited by 58 publications

(56 citation statements)

References 81 publications

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“…Indeed, despite an overall weak relationship between muscle force and skull shape in humans, individuals with an orthognathic maxilla have larger temporalis muscles and thus higher muscle forces than prognathic individuals (Toro‐Ibacache et al. ).…”

Section: Discussionmentioning

confidence: 99%

Congenital muscle dystrophy and diet consistency affect mouse skull shape differently

et al. 2017

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The bones of the mammalian skull respond plastically to changes in masticatory function. However, the extent to which muscle function affects the growth and development of the skull, whose regions have different maturity patterns, remains unclear. Using muscle dissection and 3D landmark-based geometric morphometrics we investigated the effect of changes in muscle function established either before or after weaning, on skull shape and muscle mass in adult mice. We compared temporalis and masseter mass and skull shape in mice with a congenital muscle dystrophy (mdx) and wild type (wt) mice fed on either a hard or a soft diet. We found that dystrophy and diet have distinct effects on the morphology of the skull and the masticatory muscles. Mdx mice show a flattened neurocranium with a more dorsally displaced foramen magnum and an anteriorly placed mandibular condyle compared with wt mice. Compared with hard diet mice, soft diet mice had lower masseter mass and a face with more gracile features as well as labially inclined incisors, suggesting reduced bite strength. Thus, while the early-maturing neurocranium and the posterior portion of the mandible are affected by the congenital dystrophy, the late-maturing face including the anterior part of the mandible responds to dietary differences irrespective of the mdx mutation. Our study confirms a hierarchical, tripartite organisation of the skull (comprising neurocranium, face and mandible) with a modular division based on development and function. Moreover, we provide further experimental evidence that masticatory loading is one of the main environmental stimuli that generate craniofacial variation.

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Section: Discussionmentioning

confidence: 99%

Congenital muscle dystrophy and diet consistency affect mouse skull shape differently

et al. 2017

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“…An FE model of the cranium of a male human aged 43, with full dentition, was built from segmented CT data used in previous studies (Toro‐Ibacache et al, ; Toro‐Ibacache et al, ), where muscle CSAs were also directly measured. The image data comprise a medical CT scan of a living patient taken at the Teaching Hospital of the University of Chile (Hospital Clínico de la Universidad de Chile, Santiago de Chile).…”

Section: Methodsmentioning

confidence: 99%

“…Cancellous bone was omitted, and hence all bone was modelled as a solid material with a Young's modulus of 17 and 50 GPa for teeth, both with a Poisson's ratio of 0.3. This model building approach has been used in previous studies of cranial FE models (Wroe et al, ; Bright and Gröning, ; Fitton et al, ; Jansen van Rensburg et al, ; Toro‐Ibacache et al, ) and is relevant in cases where model resolution, fossilization or taphonomic processes do not allow to accurately model cancellous bone (Bright and Gröning, ; Fitton et al, ; Toro‐Ibacache et al, ), or when models are generated via 3D surface warping (O'Higgins et al, ).…”

Section: Methodsmentioning

confidence: 99%

“…Static bites were simulated at I 1 and unilaterally at the left or right M 1 . As noted above, the maximum muscle forces from the temporal, masseter and medial pterygoid muscles were estimated from their CSAs measured in previous studies (Toro‐Ibacache et al, ; Toro‐Ibacache et al, ) using a protocol based on that of Weijs and Hillen () and the formula, Force = CSA × 37 N cm −2 , where the last term is an estimate of the magnitude of intrinsic muscle strength for human masticatory muscles (Weijs and Hillen, ; O'Connor et al, ). The estimated values of CSA and maximum forces are presented in Table .…”

Section: Methodsmentioning

confidence: 99%

“…FEA has been increasingly used to predict the mechanical response of the skull to both muscle and bite forces in terms of deformation, strains and stress. These parameters are then commonly investigated in relation to evolutionary (Strait et al, ; Wroe et al, ; Smith et al, ), developmental (Kupczik et al, ) and physiological or pathological processes and adaptations (Tanne et al, ; Gross et al, ; Koolstra and Tanaka, ; Ross et al, ; Toro‐Ibacache et al, ).…”

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The Effect of Varying Jaw‐elevator Muscle Forces on a Finite Element Model of a Human Cranium

Toro‐Ibacache

O’Higgins

2016

The Anatomical Record

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Finite element analyses simulating masticatory system loading are increasingly undertaken in primates, hominin fossils and modern humans. Simplifications of models and loadcases are often required given the limits of data and technology. One such area of uncertainty concerns the forces applied to cranial models and their sensitivity to variations in these forces. We assessed the effect of varying force magnitudes among jaw-elevator muscles applied to a finite element model of a human cranium. The model was loaded to simulate incisor and molar bites using different combinations of muscle forces. Symmetric, asymmetric, homogeneous, and heterogeneous muscle activations were simulated by scaling maximal forces. The effects were compared with respect to strain distribution (i.e., modes of deformation) and magnitudes; bite forces and temporomandibular joint (TMJ) reaction forces. Predicted modes of deformation, strain magnitudes and bite forces were directly proportional to total applied muscle force and relatively insensitive to the degree of heterogeneity of muscle activation. However, TMJ reaction forces and mandibular fossa strains decrease and increase on the balancing and working sides according to the degree of asymmetry of loading. These results indicate that when modes, rather than magnitudes, of facial deformation are of interest, errors in applied muscle forces have limited effects. However the degree of asymmetric loading does impact on TMJ reaction forces and mandibular fossa strains. These findings are of particular interest in relation to studies of skeletal and fossil material, where muscle data are not available and estimation of muscle forces from skeletal proxies is prone to error. Anat Rec, 299:828-839, 2016. V C 2016 Wiley Periodicals, Inc.Key words: finite element analysis; human cranium; masticatory muscle activity; sensitivity analysisFinite element analyses (FEAs) simulating masticatory system loading in crania of primate hominin fossils and modern humans are increasingly common. However data on muscle forces, required to accurately load a model to simulate a particular function are often lacking. This means that approximations and simplifications are required and the sensitivity of finite element models to these needs to be understood. Muscle force is a parameter that is of relevance in any mechanical analysis of the masticatory system. It is generally agreed

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The evolution of cranial base and face in Cercopithecoidea and Hominoidea: Modularity and morphological integration

Profico

Piras

Buzi

et al. 2017

American J Primatol

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The evolutionary relationship between the base and face of the cranium is a major topic of interest in primatology. Such areas of the skull possibly respond to different selective pressures. Yet, they are often said to be tightly integrated. In this paper, we analyzed shape variability in the cranial base and the facial complex in Cercopithecoidea and Hominoidea. We used a landmark-based approach to single out the effects of size (evolutionary allometry), morphological integration, modularity, and phylogeny (under Brownian motion) on skull shape variability. Our results demonstrate that the cranial base and the facial complex exhibit different responses to different factors, which produces a little degree of morphological integration between them. Facial shape variation appears primarily influenced by body size and sexual dimorphism, whereas the cranial base is mostly influenced by functional factors. The different adaptations affecting the two modules suggest they are best studied as separate and independent units, and that-at least when dealing with Catarrhines-caution must be posed with the notion of strong cranial integration that is commonly invoked for the evolution of their skull shape.

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The relationship between skull morphology, masticatory muscle force and cranial skeletal deformation during biting

Cited by 58 publications

References 81 publications

Congenital muscle dystrophy and diet consistency affect mouse skull shape differently

Congenital muscle dystrophy and diet consistency affect mouse skull shape differently

The Effect of Varying Jaw‐elevator Muscle Forces on a Finite Element Model of a Human Cranium

The evolution of cranial base and face in Cercopithecoidea and Hominoidea: Modularity and morphological integration

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