Masticatory movement path in subjects with Angle Class II malocclusion

Objectives: The purpose of this study was to clarify the characteristics of masticatory function in Angle Class II malocclusion. Methods: The subjects were divided into the two groups. Group 1 consisted of 10 female subjects with Angle Class II malocclusion. Group 2 consisted of 10 female subjects with individual normal occlusion. The movement of incisal point during masticating chewing gum on the habitual side was recorded by using Mandibular Kinesiograph (MKG). With automatic masticatory movement analyzing software system (K-S system), the average path in ten cycles beginning with the fifth cycle of mastication was displayed. The opening distance and masticatory width were calculated from the average path. In addition, the indices representing the stability of masticatory movement path (Standard Deviation/Opening Distance) was calculated as opening lateral component, closing lateral component, vertical component by dividing the average path of the standard deviations in horizon and vertical direction on the average path with opening distance. These indices were compared statistically between the two groups. Results: In the opening distance, Group 1 indicated significantly lower values than Group 2 (P<0.01). In the masticatory width, Group 1 indicated lower values than Group 2, but there was no significant difference between the two groups (P>0.05). In the all indices representing the stability of masticatory movement path, Group 1 indicated significantly higher values than Group 2 (opening lateral component and vertical component: P<0.01, closing lateral component: P<0.05). Conclusion: The results suggested that masticatory movement path in subjects with Angle Class II malocclusion showed narrow tendency, and its stability was less stable than subjects with individual normal occlusion.