Functional mandibular deformation in edentulous subjects treated with dental implants.

PURPOSE: The purpose of this study was to measure medial convergence, dorsoventral shear, and corporal rotation in the human mandible. MATERIALS AND METHODS: Measurements were made using custom-fabricated strain gauge displacement transducers in 6 edentulous subjects who had been treated with mandibular endosseous dental implants. These were mounted on the most distal of the mandibular implants on each side, and measurements were made in real time using a multichannel analogue/digital converter and a personal computer for data storage and analysis. Measurements were made while the implants were loaded, and the subjects opened and closed their mouths and made lateral mandibular excursions. Medial convergence was measured as a linear change at the site of the most distal implant. Dorsoventral shear was expressed as a relative rotation of the right and left mandibular bodies projected onto the median sagittal plane, and corporal rotation was expressed as the relative rotation of the most distal implant. RESULTS: Jaw deformation was found to occur immediately on opening and was related to closing forces and jaw position. Medial convergence of up to 41 microns was observed, with values for corporal rotation of up to 6 degrees and dorsoventral shear of up to 19 degrees. CONCLUSION: The study demonstrated clinically for the first time 3 different and simultaneous patterns of functional mandibular deformation.