The effects of sustained incisal clenching on the temporomandibular joint space

Objective: To determine the effect of sustained incisai clenching on the width of the temporomandibular joint space. Methods: Nine normal subjects clenched on an anterior appliance for 10 min at 49 N. Sagittal tomograms were obtained during comfortable closure in the intercuspal position (ICP) (ICP- Before), comfortable closure on bite force transducer without clenching (BFT-Before), start of clenching (BFT-0), end of 5 min clenching (BFT-5), end of 10 min clenching (BFT-10), comfortable closure on the bite force transducer immediately after clenching (BFT-After) and comfortable closure in ICP after clenching (ICP-After). Joint space dimensions were automatically measured by a computerized image analysis system. Results: The minimum joint space dimension was significantly reduced at BFT-5 (P = 0.0381), BFT-10 (P = 0.0019) and BFT-After (P = 0.0053) in relation to BFT-Before. The condylar position was also significantly shifted upward at BFT-0 (P = 0.0422), BFT-5 (P = 0.0005), BFT- 10 (P = 0.0001), and BFT-After (P = 0.0004) in relation to BFT-Before. Conclusion: Sustained incisai clenching at 49 N causes significant anterior joint space reduction. We believe this is due to marked compression of the articular cartilage and disc.