|Budget Amount *help
¥2,000,000 (Direct Cost : ¥2,000,000)
Fiscal Year 1995 : ¥700,000 (Direct Cost : ¥700,000)
Fiscal Year 1994 : ¥1,300,000 (Direct Cost : ¥1,300,000)
Masticatory muscle activity is affected by various environmental changes inside and outside the oral cavity. The effects of an increase in the occlusal vertical dimension and those of the occlusal contact on masseter muscle activity were evaluated.
Masseter muscle activity during the whole day (24 hours) was analyzed using a "whole day electromyogram recording and analysis system" with a bite plate either for the anterior teeth area (type A plate) or that for all dental arch (type F plate), or without any plate.
Prior to electromyography, the subjects pcrformed maximum clenching,
Setting with 1/16 (level 1), 1/4 (level 2), 1/2 (level 3), and 3/4 (level 4) of the maximum potential as reference levels. The muscle activity time and frequency per hour were examined during the whole day, arousal, and sleep and analyzed by two-way analysis of variance.
1. Only at level 1, significant differences were found in the muscle activity time and frepuency during the whole day, arousal, and sleep among t
2. The muscle activity time during sleep at level 1 was significantly decreased in using a type A or F plate, conpared to that in using any plate.
3. At levels 2 and 3 during sleep, significant differences were found in the muscle activity time and frequency only among the conditions ; muscle activity was significantly decreased using a type A of F plate than without using any plate.
4. At level 4, no significant differences were found among the subjects or among the conditions.
5. significant difference was found between the type A and F plates at any levels during the whole day, arousal, or sleep.
These results showed a significant decrease in masseter muscle activity during sleep with an increase in the occlusal vertical dimension using a bite plate.
No siginificant differences were observed among masseter activities during the whole day, arousal, and sleep between using type A and F plate. However, comparison of the type A and F plates showed a slightly more marked decrease in muscle activity using the type A plate. This indicates that the presence or absence of molar occlusal contact affects masseter activity. Less