ALTERATION IN THE BITE FORCE AND EMG ACTIVITY WITH CHANGES IN THE VERTICAL DIMENSION OF EDENTULOUS SUBJECTS

The bite force and EMG activity of jaw closing muscles were studied at seven different vertical jaw positions around the occlusal vertical d imension (OVD) in 10 edentulous subjects. When the masseteric EMG acti vity was maintained at constant values (40% and 20% of the maximum act ivity at the OVD), the bite force increased in proportion to increase of the vertical dimension. On the other hand, when the bite force was maintained at constant values (4 kg and 8 kg), the EMG activities of t he jaw closing muscles decreased, with an increase of the vertical dim ension. These results indicate that the OVD is not the position at whi ch the most efficient exertion of the bite force is obtained.