A Study of Posterior Mandibular Movements from Intercuspal Occlusal Position

¹ School of Dentistry, University of Washington, Seattle

All subjects demonstrated posterior movement from their intercuspal occlusal position. The retrusion varies from 0.2 to 1.8 mm. Considerable variance was observed in the direction of posterior movement. The direction of retrusion appears to be dependent primarily on cuspal planes rather than on the articulating surfaces of the temporomandibular joint. Retrusion obtained by the use of retraction was generally the same as that obtained in voluntary movement; therefore, it does not appear that temporomandibular joint structures are noticeably compressible from forceful retrusion. Rotary motion could not be consistently demonstrated with or without the mandible under retraction. The retractor is, however, effective in producing the posterior border position, but, once motion begins, some translation occurs. This study appears to indicate that the rest position does not represent a true border position. The intercuspal position is anterior to the most retruded position demonstrated in this study.