Edition V16N05 | Year 2011 | Editorial Article | Pages 54 to 61
Aim: The purpose of this study was to make an electromyographic comparison of the action potentials of the upper and lower segments of the orbicularis oris muscle, bilaterally, in youngsters with Class II, Division 1 malocclusion and youngsters with normal occlusion in order to verify whether or not there is a difference between the two groups with regard to the electromyographic activity that occurs. Methods: The sample consisted of 50 girls, in the age-range from 8 to 10 years, with no previous orthodontic treatment, divided into two groups: 25 with Class II, Division 1 malocclusion and 25 with normal occlusion. Electromyographic signals of the orbicularis oris muscle were acquired using Ag/AgCl surface electrodes. Muscle activity was recorded in the resting position, in the isometric contraction and in the isotonic contraction and the Root Mean Square (RMS) values of each movement were determined. The data collected were submitted to statistical analyses of variance and Tukey test (?=0.05). Results: The results showed that there was a difference in electromyographic activity between the young girls with Class II, Division 1 malocclusion and those with normal occlusion. Muscle activity was higher in the girls with malocclusion than in those with normal occlusion. Conclusion: This suggests lower competence of the orbicularis oris muscle in the girls with Class II, Division 1 malocclusion.