An Electromyographic Study on Mandibular Rest Position Induced by Several Methods

하악안정위 유도에 관한 근전도학적 연구

Mandibular rest position is very essential position because in that position, masticatory muscularture can be reciprocally coordinative and unstrained. So obtaining a good ability to establish and maintain rest position in non-functioning state is mandatory for treatment of patient with craniomandibular disorders. In general, many types of mandibulr movement exercise start from rest position and use the sense of muscle relearning, that is, muscle smoothness and relaxation, throughout the exercise period. In this study, 44 normal subjects for control group and 37 patients with craniomandibular disorders for experimental group participated and they were classified into 3 subgroups, respectively. One method to guide mandibular rest position was used for one subgroup, so theree methods were used for this study, 1)self-guided rest position without any education, 2) guided by Rocabado's tongue rest position, 3) guided through swallowing after Dawson's centric relation. To record electromyographic activity, Bioelectric processor EM2 (Myotronics, U.S.A.) was used. The numbers of sessions from start to stable resting electromyographic level and muscle activities in stable state were recorded and two recordings which were first and second, 3 days after first recording, were done, The data were processed with SPSS/PC+package. The obtained results were as follows : 1. Mean number of sessions in second recording were fewer than those in first recording in both groups. In comparison among 3 subgroups, mean number of sessions of subgroup guided through Dawson's method were fewer than those of other groups though it is not statistically significant. 2. There was a difference of mean number of sessions between control and experimental group in first recording, but in second recording there was no difference in any cases. 3. Mean value of muscle activity were generally not different without regard to group and method if once come to stable resting position level. Mean value of muscle activity of guided subgroups showed a tendency of decreasing in second recording than in first recording. However, in self-guided subgroup there was a inconsistent pattern. 4. The amounts of change in session number from first to second recording in control group were fewer than those in experimental group.