RESUMO
The purpose of this research is to find out the activity level and function of the mentalis and orbicularis oris (superior and inferior) in individuals with Angle's Class II division 1 malocclusion. Ten individuals with Angle's Class II division malocclusion were analysed and the findings compared to those obtained from eight individuals with clinically normal occlusion. The electromyographic analysis was performed in the Research Laboratory of Electromyography - Department of Morphology, Federal University of Santa Maria, using a device composed by an amplifier for electromyography a digital-analogic conversion board - CAD 10/26 type and a specific software developed by Lynk Electronic Technology in order to acquire data formathematical processing. Apparatus calibrations was 1000 mV, samples frequency channel 4000 Hz and speed of bundle dislocation was 15 ms/division. Recordings were obtained using Beckman's surface electrodes attached to chin, upper and lower lips during rest and speech movements. The signals recorded were quantified in root mean square (RMS) expressed in microvolts. The results obtained showed that individuals with Angle's Class II division 1 malocclusion undergo alterations in normal patterns of muscular activation . It was found an increase in the postural activity of the inferior orbicularis in individuals with Angle's Class II division 1 malocclusion. During the speech, individuals with Angle's Class II division 1 malocclusion were more active than normal ones.