The author studied masticatory muscle activity and bite force in normal persons without T romandibular Disorders(TMD) signs and symptoms. The number of subjects was 15, and the of them was from 22 to 25 years.
Electromyography was used to record the muscle activity in tapping and cienching movement wit or without occb´sal splint. 3 splints were made from 3 different mandibular positions, that is, cerft occlusion position, Rocabado´s mandibular rest position, Dawson´s centric relation position. The thi. kness of splint was 3.0-3.5mm at molar region.
The muscle examined were Masseter and Anterior Temporalis attached with surface elecbvdd and the device used to measure the EMG level was Bioeiectric processor Model EM2.
After recording the EMG, the author measured the bite force level in clenching movement- t& bite force meter Model MPM-3000 iri the sarhe´positions used in the EMG experiment.
The obtained results were as follows
1. With occlusal splints insertion, the amount of decreased muscle activity- iii Anterior Temp= was more than those in Masseter.
2. In the three maxillomandibular relationships with ocdueal splints, Masseter showed slightly increased level of muscle activity in centric occlusion position but Ant. Temporalis showed decreased Ievd of muscle activity reversely in that position.
3. Muscle activities between Rocabado´s rest position and Dawson´s centric relation position wet
generally similar whatever the muscles or the movements the author examined.
4. Bite force in clenching movement increased with splints insertion, especially with the splint registered
in centric occlusion position.
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