Predicted Incidence of Occlusal Errors in Centric Closing Around Arbitrary Axes

Purpose: This study aimed to estimate the frequency of occlusal errors that could be induced in centric closing of casts around arbitrary axes instead of the hinge axes in a group of patients. Materials and Methods: In 57 asymptomatic subjects, individual hinge axis points, arbitrary axis points, and coordinates of occlusal cusps along the lateral dental arches were determined experimentally on each side. Horizontal errors that could emerge when rotating the casts around the arbitrary instead of around the hinge axes were calculated for all persons with 2- and 4-mm changes of vertical dimensions. Results: Mounting of casts in relation to arbitrary axes could induce occlusal errors of less than 300 µm in the second molar area in 87% of patients with a 2-mm change of vertical dimension. In 12% of cases, errors between 300 and 500 µm could occur. In only 1%, errors greater than 500 µm had to be expected. The errors generally decreased from posterior to anterior tooth locations, but strongly increased for widening of jaw gapes. Conclusion: The transfer of casts in relation to arbitrary axes is associated with a negligible risk for inducing errors above clinically relevant limits. If changes of vertical dimension would not exceed 2 mm, the transfer in relation to individual hinge axes would bring no advantage for occlusal therapy.