Functional significance of strain distribution in the human mandible under masticatory load: Numerical predictions I. Ichim a, *, J.A. Kieser a , M.V. Swain a,b a Department of Oral Sciences, Faculty of Dentistry, Otago University, Walsh Building, 310 Great King Street, Dunedin 9001, New Zealand b Biomaterials, Faculty of Dentistry, Sydney Dental Hospital, University of Sydney, NSW 2010, Australia 1. Introduction To preserve its competence bone requires functional mechan- ical stimulation. Absence of functional loading will cause changes to the microstructure of the bone and may possibly lead to atrophy. 1–3 A common feature of studies of mandibular morphology is the assumption that there is some functional relation between the form of the lower jaw and masticatory stress. 4 This relationship between diet and mandibular bone mass was linked to allometric factors in comparative studies. 5–7 Furthermore, it was noted that the local variation in cortical bone thickness in the mandibular corpus appears to be stereotypical among anthropoids. This occurs at sections under the molars, where the lingual cortical plate is thinner than buccal one. 8 The functional significance of this postcanine cortical asymmetry is still obscure. It is widely accepted that local variation in bone area or mass is linked with differences in strain magnitude during function and hence strain analysis can be employed to investigate whether cortical asymmetry is linked with biomechanical demands in mastication. Following a theore- tical analysis, Demes et al. 9 suggested that during mastication, occlusal force combined with the twisting moment can result in an increase of stresses on the buccal cortical region and their decrease on the lingual cortical area. In vitro investiga- tions 8 provided some backing for this approach but strains determined in the lateral midcorpus and alveolar segments were inconsistent and did not support the model. Because of obvious practical reasons, a direct strain measurement in the functioning human mandible cannot be achieved, and hence these have to be inferred. It was suggested that finite element modelling may be used instead to predict real biomechanical responses in mandibular models. 10 archives of oral biology 52 (2007) 465–473 article info Article history: Accepted 21 October 2006 Keywords: Human mandible Strains Mastication Cortical bone FEA abstract A common feature of studies of mandibular morphology is the assumption that there is some functional relation between the form of the lower jaw and masticatory stress. It was noted that the local variation in cortical bone thickness in the mandibular corpus appears to be stereotypical among anthropoids. This occurs at sections under the molars, where the lingual cortical plate is thinner than buccal one. In this study we investigate and contrast the strain pattern along buccal and lingual surfaces of the mandibular corpus during mastica- tion using a numerical model of a human mandible. We show that strain distribution differs in alveolar and mid-corpus segments of the mandible and that the latter develops an alternate pattern between the buccal and lingual aspects of the working and balancing sides of the jaw. We then relate the magnitude of these strains to Frost’s mechanostat. Our results suggest that the cortical asymmetry of the human mandible is in fact not related to strain patterns generated during mastication. # 2006 Elsevier Ltd. All rights reserved. * Corresponding author. Tel.: +64 3 4797084. E-mail address: ionut.ichim@stonebow.otago.ac.nz (I. Ichim). available at www.sciencedirect.com journal homepage: www.intl.elsevierhealth.com/journals/arob 0003–9969/$ – see front matter # 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.archoralbio.2006.10.020