Magnetic resonance imaging and tomographic evaluation of occlusal appliance treatment for advanced internal derangement of the temporomandibular joint. This study evaluates the positional relationship of the disc and mandibular condyle in patients with late opening clicks treated with appliance therapy. A total of 30 joints (18 patients) were studied. Twenty-seven of these 30 joints were treated with the appliance until the joints were silent to auscultation. The patients were then evaluated with axial corrected tomography and magnetic resonance imaging (MRI) in the centric occlusion position and with their bite appliance (Sved-type) in place. Comparisons were made between condyle position in centric occlusion and with the appliance in place. Magnetic resonance imaging was then used to evaluate disc positional changes. Each imaging procedure was made in the same sagittal plane. Only changes in condyle positioning could be identified. Evidence of disc repositioning with the appliance in place was seen in only three MRI examinations. The remaining 27 joints continued to exhibit disc displacement with various changes in disc morphology. It is concluded that the concept of "disc capture" is a clinical term only, and that such perceived clinical success should not lead to the assumption that an actual change in intra-articular anatomic relationships has occurred. Joint noises may decrease because joint space is increased, allowing smoother condylar translation beyond disc surface irregularities and positional abnormalities. 