Optimal mouth position for magnetic resonance imaging of the temporomandibular joint disk.

Optimal mouth positioning for magnetic resonance imaging of the TMJ is controversial. This study evaluates the closed mouth position and partial-open mouth position for diagnostic accuracy of anterior displacement of the disk. Sixty-two joints were considered abnormal in at least one position. In the positive joints, the closed mouth position sequences were all abnormal and diagnostic, while 34% of partial-open mouth position sequences were falsely normal. It was found that the closed mouth position provides higher diagnostic accuracy for disk displacement, although optimal examinations include imaging in both positions.