Abstract
Clinically, occlusal equilibrations are conducted for children with functional occlusal interferences to improve the occlusal relationship. However very few studies regarding to the neuromuscular effects after occlusal equilibration have been ever made.
The purpose of this study was to examine the influences of occlusal interferences on masticatory muscles and to evaluate the effects after occlusal equilibration electromyographically. Eight children, including six with deciduous dentition and two with mixed dentition were the subjects, all of whom had shown unbalanced EMG activities of the temporal muscles on the tonic neck reflex elicited by dorsal flexion of the head. All of them manifested occlusal interferences clinically during the movements of mandible. On the other hand, nine children found to have functionally normal occlusions with the deciduous dentition were selected as a control.
The results obtained were as follows:
1. The analysis made on the model disclosed that six children out of 8 exhibited an asymmetrical relationship of the occlusion at the canine compared bilaterally and the rest of the children showed a symmetrical relationship.
2. The grade of overbite and overjet found in the occlusal equilibration group was greater compared with that of the control group.
3. As far as the ratio between mandibular arch vs. maxillary arch in terms of intercanine distance and arch length is concerned, it was smaller in the occlusal equilibration group compared with the control group.
4. The occlusal interferences were most commonly observed at the region of the deciduous canine.
5. After the occlusal equilibrations were conducted, six children were found electromyographically to have improved, but in the rest of children, hypertonicity in masticatory muscles still remained.
