Assessment of oral parafunctional behaviors and electromyographic activities of the masticatory muscles in young female patients with orthodontic Invisalign treatment

Objectives: To evaluate the effect of Invisalign treatment on the oral parafunctional behaviors and the electromyographic activities of masticatory muscles. Methods: Twenty-three female patients (mean age 26.8 +/- 2.4) were included. All patients had received the Invisalign treatment for at least 6 months. The Oral Behavior Checklist (OBC) was completed at T0, i.e., before wearing the aligner; at T1, i.e., after 3 months of treatment; and at T2, i.e., after 6 months of treatment. The surface Electromyographic (sEMG) activities of the bilateral anterior temporal (TA), masseter (MM) and sternocleidomastoid (SCM) were recorded at the mandibular postural position (MPP) and during maximal voluntary contraction (MVC) at T0, T1 and T2, respectively. Results: (1) The OBC score significantly decreased betweenT0 and T1 (P<0.05). (2) When measured at the MPP, the activity of the TA increased significantly between T0 and T1 (P<0.05). During MVC, the activities of the TA and SCM at T1 were significantly higher than those of T0 (P<0.05). At the MPP and MVC, we found no difference in TA, MM or SCM activities between T1 and T2. Conclusions: The clear aligners of Invisalign treatment have a relevant effect on the orofacial system, which suggests that some functional mechanics may underlie this type of the appliance.