Short-term effect of orthodontic clear aligners on muscular activity and occlusal contacts: A cohort study

Introduction: The simultaneous presence of maxillary and mandibular clear aligners alters the vertical dimension and the quantity and quality of occlusal contacts. Few data in the literature explain how this occurs and the effects on neuromuscular coordination. This study aimed to evaluate occlusal contacts and muscular balance during treatment with clear aligners over a short follow-up time. Methods: Twenty-six female adult patients were enrolled in this study. The center of occlusal force (COF) was evaluated using a T-Scan II device, whereas muscular symmetry and balance were determined through surface electromyography using a standardized protocol that reduces anthropometric and electrode variations. Both evaluations were performed in centric occlusion and with aligners worn before treatment, after 3 months, and after 6 months. Results: A statistically significant variation in COF position was reported in the sagittal plane but not in the transverse plane. The shift in the COF position was followed by a change in muscular balance evaluated through surface electromyography. Conclusions: Treatment with clear aligners resulted in an anterior shift of the COF when biting in centric occlusion and a posterior shift when the aligners were worn in healthy female patients after 6 months of observation. This change in occlusal contact was followed by an improvement in muscular function symmetry in the short term when aligners were worn, compared with the centric occlusion during treatment.