Abstract
Computational finite element analyses (FEAs) of the skull predict structural deformations under user specified loads and constraints, with results normally presented as stress and strain distributions over the skull's surface. The applied loads are generally a representation of the major adductor musculature, with the skull constrained at bite positions and at the articulating joints. However, virtually all analyses ignore potentially important anatomical structures, such as the fasciae that cover the temporalis muscle and attach onto the zygomatic arch. In vivo experimental studies have shown that removal of the temporal fasciae attachment onto the zygomatic arch in Cebus monkeys results in significant bone adaptation and remodeling in this region, suggesting the fasciae play an important role in stabilising the arch during biting. Here we investigate this potential stabilising role by carrying out FEAs of a macaque skull with and without temporal fasciae included. We explore the extent to which the zygomatic arch might be stabilized during biting by a synchronized tensioning of the temporal fasciae, acting to oppose masseteric contraction forces. According to our models, during temporalis muscle bulging the forces generated within the tensioned temporal fasciae are large enough to oppose the pull of the masseter. Further, a near bending-free state of equilibrium within the arch can be reached, even under forceful biting. We show that it is possible to eliminate the high strain gradients in and around the zygomatic arch that are present in past computational studies, with strains being more uniform in magnitude than previously thought.
Highlights
The skull houses and protects the brain and sensory organs, supports critical functions such as feeding and breathing, and provides a framework onto which muscles and other soft tissues attach and act
Through computational finite element analyses (FEAs), we assess the impact of modeling the temporal fasciae in the primate skull
The motivation for this study was provided by experimental evidence that the temporal fasciae play an important stabilising role in Cebus monkeys (Eisenberg and Brodie, 1965) and by circumstantial and clinical evidence regarding the apparent stability of isolated zygomatic arch fractures in humans (Fujii and Yamashiro, 1983; Werner et al, 2002; Turan et al, 2004; RodriguezVegas and Casado Perez, 2004)
Summary
The skull houses and protects the brain and sensory organs, supports critical functions such as feeding and breathing, and provides a framework onto which muscles and other soft tissues attach and act. The septal cartilage, which stretches from the perpendicular plate of the ethmoid to the external nose, may play some role in transmitting and dampening masticatory loads (Al Dayeh et al, 2009). Another potentially important external structure is the deep temporal fascia, which originates from the periosteum of the superior temporal line and attaches strongly to the superior border and lateral surface of the zygomatic arch (Eisenberg and Brodie, 1965; Wormald and Alun-Jones, 1991; Oxnard and Franklin, 2008). It has been suggested that the fasciae aid the zygomatic arch in resisting the tensions of the masseter muscle, which may be large during forceful biting (Eisenberg and Brodie, 1965)
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