Surface Electromyographic Analysis of Masticatory and Neck Muscles in Skeletal Class II Division 1 Malocclusion with EMG Indices - A In Vivo Study

Background amp Objectives To evaluate the activity of oro-facial and neck muscles in skeletal class II division 1 malocclusion with horizontal and vertical growth patterns using surface electromyography.Methods Twenty non-growing patients comprising males and females 18-30 years were selected and grouped into horizontal and vertical growth patterns using lateral cephalograms. sEMG of masseter temporalis sternocleidomastoid and anterior belly of digastric muscles were performed and percentage overlapping coefficient activity Index asymmetry Index and torque Index were recorded.Results The percentage overlapping coefficient was recorded as 112.3 in horizontal and 92.35 in vertical growers. The activity index for horizontal growers was 14.28 microVsec indicating a predominance of the masseter muscle and in vertical growers it was -8.94 microVsec indicating a predominance of anterior temporalis. The asymmetry index for horizontal growers observed was 17.75 microVsec indicating the predominance of rightside muscles and was -10.77 microVsec showing the dominance of left-side muscles in vertical growers. Torque index in horizontal and vertical growth patterns were 24.56 and -43.76 respectively inferring a right-sided mandibular movement in horizontal growers and vice versa. The mean value of sternocleidomastoid muscle observed was 18.74 microVsec in horizontal growers and 14.15 microVsec in vertical growers. The mean values of the anterior belly of digastric muscles were 18.87 microVsec in horizontal growth pattern and 19.57 microVsec in vertical growers.Conclusion There was symmetry between muscles and an increased predominance of the masseter group in horizontal growers while an increased predominance of the temporalis muscle was observed in vertical growers. There was increased activity of right-sided muscles and right-sided mandibular movement in horizontal growers while an increased activity of left-sided muscles and left-sided mandibular movements was noted in vertical growers.