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Changes in the Bilateral Balance of Masticatory Muscle Activity after Surgical Correction of Mandibular Lateral Shift: Report of 2 Cases

Hiroshi Ueda, Masaaki Kato, Atsushi Horihata and Kazuo Tanne

Objective: This case report is designed to present changes in the bilateral balance of masticatory muscle activity during daytime after surgical correction of mandibular lateral shift. Study design: Using a portable EMG recording system, masseter and anterior temporal muscle activities were recorded in two patients with lateral deviation of the mandible for three hours at pretreatment, 6 months and 12 months after surgery. Results: In case 1, the Asymmetry Ideex of masseter muscle activity during mealtime and during daytime was 0.3 at T0, 0.4 at T1and 0.1 at T2, and -0.6 at T0, 0 at T1and 0.2 at T2, respectively. With respect to anterior temporal muscle activity, the AIs were -0.1 and -0.4 at T0, -0.2 and -0.5 at T1, and 0.1 and -0.1 at T2 during mealtime and daytime. In case 2, the AI of masseter muscle activity during mealtime and during daytime was 0.3 at T0, 0.2 at T1and 0.3 at T2, and -0.3 at T0, -0.6 at T1 and -0.1 at T2, respectively. With respect to anterior temporal muscle activity, the AIs were 0 and 0 at T0, 0 and 0.3 at T1, and 0.1 and 0.3 at T2 during mealtime and daytime. Conclusion: The different differing results were shown in two similar cases, although despite the surgical correction of mandibular lateral shift producing produces considerable improvement of the bilateral balance in muscle activity during mealtime and daytime.