Changes in electromyographical activity during different phases of orthodontic treatment: pilot study results

Electromyography is a useful tool in orthodontics to evaluate and monitor muscle activity for diagnosis and during treatment Objectives: The aim of this study was to determine changes in electric muscular activity during different phases of orthodontic treatment. Material and methods: We performed a cohort study and measured bilateral electromyographic activity (EMG) for 30 seconds in maximum intercuspation. EMG activity was measured monthly for 15 months during 4 phases in orthodontic treatment: preatreatment (P0), splint wear (P1); leveling and aligning (P2); space closure (P3); and fi nishing stage (P4). EMG was measured using a digital electromyograph developed by our group (hardware and software) to determine μV every 0.002 seconds. The root mean square (RMS) value was estimated as a mean value of EGM. Patients were treated at the Orthodontics Department and the Physiology Laboratory of UNAM during 2014-2016. We performed a descriptive, bivariate analysis and a random effects linear regression model for repeated measurements adjusted by age, gender, malocclusion and extractions. Results: Our pilot study included 10 patients (6 female and 4 male); mean age was 20 years. At baseline, maximum median EMG was recorded (median 239 μV, IQR 143 μV-561 μV), Multivariate analysis showed that EMG measurements decreased at P1 (regression coeffi cient [Coef]. -180.97; 95% CI -330.37, -31.56; p = 0.018), P3 (Coef. -168; 95% CI -332.36; -3.76; p = 0.045) and P4 (Coef. -184.21; 95% CI -326.91, -41.5; p = 0.011). Conclusions: EMG changes decreased randomly during orthodontic phases and not constantly as generally believed.