Evaluation of masticatory muscle activity in forced crossbites children with Asymmetry Index

Abstract

The purpose of this study was to investigate the influence of the forced crossbite on the bilateral balance of the masticatory muscle activity in children. The subject examined in the study were 17 children with forced crossbites (7 boys, 10 girls, mean age 7.6 years old) .
The balance of the temporalis and the masseter muscle acivity was assessed by the asymmetry index (AI), and occlusal deviation and occlusal contacts were evaluated by the occlusal detection system “Occlusogram”.
The results obtained were as follows;
1. The mandible was detected to be laterally deviated to the side of the crossbites from the initial occlusal contacts to the intercuspal position (ICP) .
2. The activity of the temporal muscle during clenching in the ICP tended to be more dominant at the side of the deviated mandible than the other side.
3. When the subjects were classified into two groups; deviation side dominant and opposite side dominant group based on the balance of muscle activity of the masseter, AI of the masseter in both groups showed high correlation with the extent of lateral occlusal deviation.
These results suggest that the occlusal deviation due to the forced crossbites in children affected on the bilarteral balance of masticatory muscle activity.