Effect of occlusal appliances and clenching on the internally deranged TMJspace

Aims: Stabilization appliances and mandibular anterior repositioning applia nces have been used to treat patients with internal derangement of the temp oromandibular joint (TMJ) based on the assumption that these appliances wor k by decompressing the TMJ. The purpose of this study was to indirectly tes t this assumption. Methods: Bilateral TMJ tomograms of 7 subjects with unil ateral anterior disc displacement without reduction (ADDwor) were taken dur ing comfortable closure and during maximum clenching in maximum intercuspat ion; tomograms were also taken with the 2 types of occlusal appliances in u se. Outlines of the condyle and the temporal fossa were automatically deter mined by an edge-detection protocol, and the minimum joint space dimension of the joints with and without ADDwor was automatically measured for each e xperimental condition as the outcome variable. Results: Upon comfortable cl osure and maximum clenching, the minimum joint space dimensions of the ipsi lateral and contralateral joints with the use of stabilization appliances a nd mandibular anterior repositioning appliances were not significantly diff erent from those seen in maximum intercuspation. Conclusion: These findings do not indicate that these appliances induce an increase in joint space du ring closing and clenching in joints with ADDwor.