The 84th Annual Meeting of the American Association of Physical Anthropologists (2015)


Variable response of masticatory function on mandibular form

NATHAN E. HOLTON1,2 and THOMAS E. SOUTHARD1.

1Department of Orthodontics, The University of Iowa, 2Department of Anthropology, The University of Iowa

March 27, 2015 , Archview Ballroom Add to calendar

Comparative studies of human populations have documented a predictable relationship between dietary variation and measures of mandibular size and robusticity. Recent work, however, has highlighted variability in form-function relationships in recent humans suggesting that the influence of function on mandibular form is not homogeneous across populations. To better understand variation in the morphological response to masticatory function, we examined two mouse models that exhibit baseline differences in mandibular cortical bone thickness. “Robust” (C3H/HeJ) and “gracile” (C57BL/6J) strains were both separated into hard-diet and soft-diet trial groups. The hard-diet trial groups were fed normal pelleted mouse chow, while the soft-diet trial groups were fed ground chow mixed with water. The experimental protocol began at 5 weeks of age and continued for 60 days. Using microCT images we assessed mandibular cortical bone area in the molar region and mandibular shape variation using geometric morphometric methods. The effects of dietary variation were evident in the robust mouse model. The hard-diet group exhibited relatively more cortical bone compared to the soft-diet group and there were considerable differences in mandibular shape between the groups associated with the morphology of the muscular processes. In contrast, the gracile mouse model trial groups did not exhibit any differences in mandibular cortical bone area or in mandibular shape. These results indicate that the skeletal response to mandibular loading is variable. With respect to human comparisons, this suggests that there may be important population differences in form-function relationships and that mandibular form may reflect loading history only in some comparisons.