The 82nd Annual Meeting of the American Association of Physical Anthropologists (2013)

Investigating the relationship between mandibular skeletal form and Stafne’s defect using geometric morphometrics


1Department of Integrative Biology, University of California, Berkeley, 2Division of Biophysics, Stockholm University

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Stafne’s static bone defect (SSBD) is a small lesion that can develop in one or both sides of the human mandible, usually in the area below the mylohyoid ridge in the submandibular fossa. In this study, 25 cases of SSBD were observed in a large archaeological sample of ancient skeletal remains from across California (n=855), spanning temporal periods from early human occupation to European contact. The observed SSBD frequency of 2.9 percent is consistent with previously reported frequencies for North Amerindians, but observed frequencies in certain regional subsamples are considerably higher, i.e. 6-7 percent. The cause of SSBD is unknown, although salivary gland size has been suggested as a predominant factor in geographic patterning of SSBD prevalence. The potential influences of size, shape, and asymmetry of the mandibular bone have so far not been examined. To investigate these factors, we here used a geometric morphometrics (GM) approach to analyze 134 mandibles with and without SSBD from three regions of California. Landmarks and sliding semilandmarks along a transverse cross-section of the lower mandible were digitized and aligned with Procrustes superimposition. Statistical analyses of centroid size and symmetric/asymmetric shape data did not show overall differences between mandibles with and without SSBD, although some shape differences were evident among mandibles from the Santa Barbara Channel region. The results indicate that skeletal form alone is not a primary determinant of SSBD formation or frequency. However, between-group variation in submandibular morphology may be one of multiple factors in its pathogenesis and geographic distribution.

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