1995 Volume 39 Issue 1 Pages 135-145
The influence of the occlusal vertical dimension on the muscle fiber conduction velocity (MFCV) and muscle fatigue was studied in the human temporal and masseter muscle in six healthy subjects (22-30years old). Occlusal vertical dimension was changed from the intercuspal position (ICP) to the maximum bite-raising position (21.0mm) by applying three different occlusal splints along the habitual opening-closing movement path. Muscle fatigue was developed until the subject stopped contracting the muscle at each occlusal vertical dimension. The EMG responses were evoked by electrical stimulation of the skin at the mandibular notch. The EMG signals were detected using a surface linear electrode array having seven contacts placed on the muscle fibers. The MFCV was calculated from the time delay between adjacent EMG signals.
The results were as follows:
1. The MFCV was increased with increment of the contraction level but decreased with increment of the occlusal vertical dimension.
2. The MFCV was decreased with muscle fatigue at each occlusal vertical dimension.
3. The endurance time was decreased with increment of the occlusal vertical dimension. The results indicate that occlusal vertical dimension is an important parameter for the propagation velocity of action potentials and for the development of static muscle fatigue.
