Improvement of masticatory kinematic parameters after correction of unilateral posterior crossbite: Reasons for functional retention.

Objective: To evaluate reverse-sequencing chewing cycles (RSCC) and their kinematic parameters on both sides before and after correction with the Function Generating Bite (FOB) appliance. Materials and Methods: Forty-seven patients, 8.3 +/- 1.1 (mean SD) years of age, with unilateral posterior crossbite (35 on the right side, 12 on the left side) and 18 age-matched controls (9.1 +/- 0.8 years) were selected for the study from the orthodontic division of the University of Turin, Italy. The crossbite was corrected in all patients using FGB, and mandibular motion was recorded with a kinesiograph K-7 (Myotronics, Tukwila, Wash), during chewing on both sides of a soft and a hard bolus before and after correction. Results: After correction, the percentage of RSCC significantly decreased for soft and hard (P<.001) boluses and fell within the normal range for 75% of the patients. The indices of the chewing pattern (closure angle, axis, maximum lateral excursion) significantly improved (P<.001), becoming symmetric between sides. Conclusions: The results of this study showed that the functional appliance, FOB, was able to lower the percentage of RSCC significantly, bringing them back to the normal range in 75% of cases, and to improve the kinematic parameters that become symmetric between sides.