MRI findings of working and non-working TMJ during unilateral molar clenching on hard bolus

The aim of this study is to evaluate with MRI the TMJs behavior during one-side clenching on a hard bolus. The sample consisted of 13 patients. an MRI of TMJ using a 1.5 Tesla superconducting magnet and a dedicated surface coil was performed in all patients. Parasagittal scans of the TMJ (perpendicular to the long axis of the condyles) were made with the mouth closed, open and with a plastic thickness 10 mm high, 15 mm wide and 20 mm long always interposed between the molars of the left side; TSE T2W and DPW sequences were used. The working condyle is always positioned behind the non-working contralateral condyle and the morphology of the retrodiscal tissue upper lamina was curvilinear in all TMJs examined. This work confirmed that, during clenching on a unilateral hard bolus, the working condyle translates less than the balancing one and that the condyle-disc ratios are substantially the same in both sides. The study of the retrodiscal tissue imaging in the different functional phases, suggest that it does not exert any pulling force towards the disc.