Masseter Coordination During Chewing in Unilateral Posterior Crossbite Before/After Therapy

Objectives: Objectives:
To investigate the effect of therapy in children with unilateral posterior crossbite on kinematics and the electromyography (EMG) of the masseter muscle on both the affected and non-affected side during chewing. The therapy involved treatment with the appliance Function Generating Bite (FGB).
Methods: Methods:
Fifty children, ( 9.1 ± 2.3 years) with unilateral posterior crossbite and twenty children (age: 9.5 ± 2.6 years) were selected for the study. Mandibular motion was tracked using a Kinesiograph (K7-I; Myotronics, Tukwila, WA, USA) and surface EMG signals were simultaneously recorded from the masseter muscle bilaterally (EMG amplifier part of the K7-I WIN Diagnostic System) during chewing of hard and soft bolus types, before and after therapy. The percent difference between the ipsilateral and contralateral masseter peak EMG amplitude was determined for each chewing condition as a measure of the coordination between the bilateral masseter muscles. The data were analyzed with an ANOVA with group (crossbite, controls), time (pre and post intervention), and bolus hardness (soft and hard) as factors.
Results: Results:
Post-intervention, the patient group showed a significant reduction in the percentage of reverse cycles during chewing on the crossbite side (P<0.05). The percent difference between ipsilateral and contralateral masseter peak EMG amplitude was dependent on the interaction between group and time (P<0.05). At baseline the percent difference between the ipsilateral and contralateral masseter peak EMG amplitude was lower for the patients with crossbite compared to the controls; however after the intervention there was no difference between groups.
Conclusions: Conclusions:
After therapy, the patients with crossbite displayed coordination between the masseter muscles during chewing which was similar to a group of controls. These findings indicate that the functional intervention induced a favorable change in the neural control of chewing.