Abstract
Background
Bilateral Class II intermaxillary elastics (CII elastics) are commonly used in orthodontics; however, the effects of CII elastics on masticatory muscle activity and the occlusal contact area have not been studied.
Objectives
To evaluate the short-term effects of CII elastics on masticatory muscle activity balance, occlusal contact area, and masticatory performance in a group of adult orthodontic patients after three months.
Materials and Methods
Forty-three patients with a <3 mm Class II molar relationship receiving ongoing treatment with fixed appliances were recruited. The experimental group (n=21) wore CII elastics (100-150 g/side) full time; the control group (n=22) did not wear CII elastics. Surface electromyography, the areas of occlusal contact and near contact (ACNC), and the median particle size of a test food were assessed prior to (T0), and after one (T1) and three months (T2). Within- and between-group differences were analyzed and the relationships between changes in dependent variables were examined (α=0.05).
Results
At T2, the experimental group showed better masticatory muscle activity balance (P<0.001) and masticatory performance (P<0.05) than controls. Both masticatory muscle activity balance (P<0.001) and masticatory performance (P<0.001) significantly improved in the experimental group between T0 and T2. The changes in masticatory muscle activity balance and masticatory performance were significantly related (P<0.05). No significant changes in cumulative ACNC or ACNC balance were observed (P>0.05).
Conclusion
After three months, CII elastics improved masticatory muscle activity balance, which led to better masticatory performance.
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