Electromyographic studies were performed on the action of the masseter muscles. Among the children aged from 6 to 8 years, ten children with normal occlusion and another ten with space maintainer were selected.
The children were divided into 3 groups.
They were:
1) A group: Children who removed space maintainer
2) B group: Children who inserted space maintainer
3) C group: Children with normal occlusion
The electromyogram was recorded with 4 channel polygraph. (Grass model 1) Electrodes which were cup-typed gold disks, 9 millimeters in the diameter, were located on the superficial layer of masseter muscles.
The electromyogram was recorded in the physiologic rest position, molar occlusion, chewing movement, protraction, left lateral movement, and right lateral movement.
The conclusions were as follows.
1. In the physiologic rest position, lateral movement, the electrical potentials of the masseter muscles were not changed clearly in each groups.
2. In molar occlusion, chewing movement, The electrical potentials of the masseter muscles of the B group were almost 10% higher than those of A group, and were almost 60-70% in comparision with C . group.
|