1996 Volume 2 Issue 2 Pages 179-187
The purpose of this study was to investigate the relationship between the occlusal stability and the masseter muscle activity in cleft lip and palate patients. Eighteen subjects were selected and divided into 6 groups; children and adults with normal occlusion as normal child group and normal adult group, cleft lip and/or palate child patients and adult patients without constricted upper arch at initial examination as child non-constricted arch group and adult non-constricted arch group, cleft lip and/or palate child patients and adult patients with constricted upper arch at initial examination as child constricted arch group and improved constricted arch group. The occlusal stability of posterior teeth was evaluated by calculating the occlusal stability index, and the masseter muscle activity was measured with the 9 channel EMG analyzing system in the subjects. And also, their symmetries were estimated by the asymmetry index.
The results were as follows:
1) The occlusal stability index and the masseter muscle activity in the child constricted arch group were lower than those of normal child group and child non-constricted arch group. Also, the child constricted arch group showed higher value of asymmetry index than other groups.
2) A strong positive correlation between the occlusal stability index and the masseter muscle activity were admitted in the child groups (r=0.96) .
3) The masseter muscle activity of the child constricted arch group was increased and the asymmetry index was reduced after wearing an occlusal splint for 10 days.
4) Comparing the child subjects with adult subjects, the occlusal stability index and the masseter muscle activity of the adults were higher than those of children.
Especially, the occlusal stability index and the masseter muscle activity were eminently ameliorated in improved constricted arch group. We think this result is due to the improvement of the stability of posterior teeth after orthodontic treatment.
