Engineering analyses of the link between occlusion and temporomandibular joint disorders
The roles of occlusion in various aspects of clinical dentistry have been the subjects of long-standing debates. The purposes of this study were to examine the fundamental engineering-based relationships between occlusion, a clinical principle of occlusion, the forces experienced by the temporomandibular joint and temporomandibular joint disorders.
The governing equations of static equilibrium, based on Newton’s laws, were applied to the mandible to compute the forces on the temporomandibular joint and to relate those forces to the alignment of occlusal forces with the long axes of teeth, the principle of occlusion in question. Calculations were performed for 48 combinations of 4 teeth (maxillary and mandibular incisors and molars) with 3 angulations of each and 4 prescribed sets of muscle forces.
The analyses indicate that (1) anatomic dimensions are inherent variables in the equations of equilibrium and (2) the 48 combinations of teeth and muscle forces yielded forces on the joint with an approximately 23:1 range in magnitudes and directions that spanned the entire 360°.
Because mandibular dimensions in the equations of equilibrium translate directly into factors of occlusion (e.g., cusp angulation, vertical dimension of occlusion, occlusal plane height and anterior–posterior occlusal contact location) it is concluded that occlusion is a determinant of joint force and hence, it is fundamentally involved in temporomandibular joint disorders. Flawed contemporary principles of occlusion have made it impossible to prove or disprove a link between occlusion and temporomandibular joint disorders.