Electromyographic patterns and masticatory muscles activity changes in patients with dentoskeletal deformities before and after orthognathic surgery: a pilot study

PURPOSE: Orthognathic surgery involves repositioning the skeletal bases to correct dentoskeletal deformities and malocclusions. While its impact on occlusion is well documented, its effects on masticatory muscle activity remain under investigation. This pilot study evaluates changes in static electromyographic (sEMG) patterns of masseter and temporal muscles, and explores correlations with TMJ-related muscular symptoms before and after surgery. METHODS: A surface electromyography (sEMG), by employing TeethanTM, based on occlusal contacts, was performed recording the activation patterns of masseter and temporal muscles, in ten patients with dentoskeletal malocclusions, undergoing orthognathic surgery. The registration assessed the muscles patterns sEMG preoperatively (T0), postoperatively at one month (T1), and at six months (T2) after surgery. RESULTS: Across the cohort, temporal POC increased by 6.76 ± 8.36 from T0 to T1 and by 5.68 ± 5.33 from T1 to T2. Masseter POC rose by 8.74 ± 7.38 (T0-T1) and 8.12 ± 7.42 (T1-T2). Barycentre values shifted by 7.36 ± 4.13 (T0-T1) and 10.65 ± 9.17 (T1-T2), indicating progressive rebalancing of occlusal force distribution. Patients with Class III malocclusion showed greater masseter activation post-surgery, while Class II patients exhibited increased temporal muscle activity. Three patients with preoperative muscular discomfort reported complete symptom resolution at T2, while one patient experienced mild residual symptoms. CONCLUSION: Data obtained from this preliminary study seem to confirm that skeletal bases repositioning modifies the occlusal contacts and, consequently, the neuromuscular proprioceptive stimuli and the activation of the masticatory muscles. sEMG may provide useful complementary information on neuromuscular adaptation following orthognathic surgery. However, larger controlled studies with standardized outcomes and statistical analyses are required before drawing definitive conclusions or recommending its routine clinical use.