S.G. SHERIDAN, D.M. MILLER, D.P. VAN GERVEN, H.H. COVERT.
Department of Athropology, University of Colorado

The human mandible-as-lever model (Hylander 1975) predicts a mechanical relationship between bite forces passing through the teeth and those passing through the mandibular condyle.   The present research was conducted to test the hypothesis that unilateral chewing as evidenced by dental wear asymmetry, corresponds to dental pathology and asymetric bony changes in the temporomandibular joint.

Analysis was undertaken on 147 adult crania from the Medieval Christian site of Kulubnarti (Sudan).  Skeletal changes in the TMJ were assessed for indications of dislocation, bone on bone rubbing, infection, and condylar malformation.  Evidence for abscess and dental caries, as well as antemortem tooth loss was also collected.  Degree of dental wear was then scored following Brothwell (1972).

The present results indicate a strong correlation between side-dominant chewing and left-right asymmetry in the TMJ.  When disorders appear at the condyle, unilateral chewing results on the injured side, directing forces through the teeth rather than the condyle.  Individuals with dental pathologies favor chewing on the healthy side of the mouth.  Forces passing through the teeth occur on the healthy side; forces passing through the condyle occur on the diseased side.  Tooth wear patterns associated with TMJ and dental pathologies fit those predicted using Hylander's lever-action model.