抄録
The relationship between the muscle fiber conduction velocity (MFCV), EMG frequency parameters and the occlusal vertical dimension was studied in the human masseter muscle in three normal subjects (24-27yr.). Occlusal vertical dimension was changed from the intercuspal position (ICP) to the maximum bite-raising position (12.8mm) using five different occlusal splints on the habitual opening-closing movement path. Each subject was instructed to clench on each vertical dimension at 10, 30 and 50% maximum voluntary contraction. EMG signals were detected with a surface linear electrode array with 13 contacts placed along the muscle fibers. The MFCV was calculated from the time delay between adjacent EMG signals. The frequency parameters were 10, 25, 50 and 75% cumulative power functions and mean power frequency.
The results obtained were as follows:
1. The MFCV was increased with the contraction level and decreased with the occlusal vertical dimension.
2. The EMG power spectra were slightly shifted to lower frequencies with the occlusal vertical dimension.
3. The MFCV showed a large change in the vicinity of ICP with a slight change of muscle length. It was suggested that the MFCV in ICP was an important index for occlusal reconstruction.
