Impact of orthodontic treatment on masticatory muscle electromyographic patterns in patients with anterior crossbite

Anterior crossbite affects facial aesthetics and may cause temporomandibular joint disorders and masticatory muscle dysfunction. Prolonged abnormal bite positioning may impact muscle activity and affect treatment stability. Although orthodontic therapy aims to realign teeth and correct bite relationships, the neuromuscular adaptations following treatment remain unclear. This study aims to investigate the changes in masticatory muscle activity before and after orthodontic treatment in patients with anterior crossbite using surface electromyography (sEMG).

41 participants were recruited and divided into 3 groups: normal occlusion (n = 18), anterior crossbite without treatment (control, n = 6), and anterior crossbite with orthodontic treatment (experimental, n = 13). Muscle activity of the temporalis, masseter, and anterior digastric muscles was recorded across four stages. Measurements included maximum mouth opening, muscle endurance, and sEMG. Data were analyzed using IBM SPSS (IBM Corp., Armonk, NY, USA) with independent t-tests and repeated measures ANOVA.

After orthodontic treatment, the experimental group showed improved mouth opening and biting force. While no significant differences in resting muscle potentials were found between treated patients and the normal group, statistically significant differences were observed between the experimental and control groups in the clenching activity of both left and right temporalis muscles (P < 0.05) throughout all stages of the study (P < 0.05).

Orthodontic treatment improved muscle function in anterior crossbite patients, but muscle activity does not fully normalize. This suggests that post-treatment muscle adaptation may require more time and highlights the importance of monitoring muscle function as part of comprehensive orthodontic care.