Effects of sustained unilateral molar clenching on the temporomandibular joint space

Objective. To measure the effect of unilateral sustained clenching on the temporomandibular joints, changes in the minimum joint space dimension were assessed. Study design. Ten healthy subjects performed a sustained clench on a bite force transducer in the first molar region for 5 minutes with a constant force of 170 N. Three separate sagittal tomograms were bilaterally obtained with the transducer in place before clenching and during the beginning and at the end of the contraction. Changes were quantified with a computerized image analysis system. Results. The minimum joint space of the contralateral temporomandibular joint was significantly reduced both at the beginning and at the end of the contraction task. Further the minimum joint space was also significantly less at the end than at the beginning of the contraction even though bite force level was identical. The ipsilateral condyle images showed no significant shift in the minimum joint space. Conclusions. These data suggest that unilateral molar clenching induces a significant reduction of the minimum joint soace in the contralateral temooromandibular joint and a sustained condition remarkably increases this change.