The effect of bite plane use on terminal hinge axis location.

The effect of bite phase therapy on the location of hinge axis was observed and compared in a sample of normal subjects and a group of individuals with TMJ dysfunction. The normal group displayed a mean change of 1.0 mm with a range of 0.3 mm to 3.4 mm between bite plane use and its absence. The direction of change with bite plane use was anterior with a tendency for superior component. The same group utilized the bite plane a second time and the axis location was compared with the original determined with bite plane use. This procedure was done to test the reproducibility of hinge axis on normal subjects. The mean change between the two bite plane uses was .87 mm with a range of 0.0 mm to 3.0 mm. The symptomatic patients changed a mean of 1.46 mm with a range of 0.0 to 3.3 mm. The direction of change was definitely posterior following therapy with a strong tendency for a superior component. This study seems to emphasize the need for a relaxed and asymptomatic muscular pattern for individuals on whom occlusal adjustments are to be made. In the presence of erroneous maxillomandibular skeletal relationships inaccuracy is inherent for occlusal equilibration.