Ultrasonographic Images And Electromyographic Activity Of Masseter Muscle In Class Ⅲ Malocclusions With Different Vertical Craniofacial Morphology

Objective The purpose of this study was to compare the craniofacial structures of different vertical types of Angle classâ…¢patients to morphous and fuction;evaluate morphous and electromyography changes of masseter muscle of Angle classâ…¢malocclusion.Method The subjects consisted of 30Angle classâ…¢malocclusion(10 high-angle,10 low-angle,10 normal-angle)and 12 normal occlusion.Cephalometric analysis was performed with all cases and 10 measurements were obtained.Ultrasound scanning was used to measure the perimeter,area,width,mean thickness,maximal thickness and length of masseter muscle under posture,maximal clenching and maximal protruding condition. EMG was used to test the changes of activities masseter muscle.All the measurements were compared statistically.Result 1.In the three mandibular positions,the masseter muscle size of high-angle group was smaller than that in low-angle;the maximal thickness at MPP and mean thickness at maximal protruding condition of high-angle group were smaller than that in normal-angle;the mean thickness at ICP and maximal protruding condition of normal-angle group were smaller than that in low-angle.2 At ICP and maximal protruding condition,the EMG activities of high-angle group was lower than that in low-angle;the EMG activities of high-angle group was lower than that in normal-angle;the EMG activities of normal-angle group was lower than that in low-angle.3.The vertical craniofacial structures was related to moand function of masseter muscle.4.The morphous of masseter muscle Angle classâ…¢malocclusion was related to the function.5.The mean thickness and maximal thickness of Angle classIIImalocclusion was smaller than that in normal occlusion at ICP.6.The EMG activities of Angle classâ…¢malocclusion was lower than that in normal occlusion at ICP;the EMG activities of Angle classâ…¢malocclusion was higherthan that in normal occlusion at MPP and maximal protruding condition.Conclusion 1.The vertical craniofacial structures was related to morphous and function of masseter muscle,the morphous of masseter muscle Angle classâ…¢ malocclusion was related to the function.2.The masticatory muscles activity of Angle classâ…¢malocclusion is abnormal,the function of the masseter muscle is less effective than normal occlusion.