Study on equilibrium and stabilization of mandibular intercuspal position in Class Ⅱ Division Ⅰ malocclusions

Objective To analyze the dynamic occlusal contacts in ClassⅡDivision Ⅰ Malocclusions during mandibular movement from muscular contact position(MCP)to intercuspal position(ICP),and to investigate the equilibrium and stabilization of ICP as well as dental morphological factors related to the MCP-ICP discrepancy.Methods 60 subjects with Class Ⅱ Division Ⅰ Malocclusions with no history of orthodontic treatment were employed.T-scan Ⅱ system was used to record and analyze the dynamic occlusal contacts during mandibular movement from MCP to ICP.Dental morphological data were determined by measuring plaster mold.SPSS 12.0 was used for statistics.Resuits There was no significant difference among three repeated measurements of the vertical distance from the center of occlusive force to the midline,D-value of occlusive force between the right and the left side,the numbers of occlusal contacts in the intercuspal position.Significant difference of the posterior arch-widths was observed between the group with and without ICP-MCP discrepancy.There was no significant difference between the groups in the depth fluency of curve of spee,and index of molar relationship.Conclusions Class Ⅱ Division Ⅰ Malocclusions is characterized by stability with intercupided occlusion.ICP-MCP discrepancy maybe associate with abnormal posterior arch-width,and is independent of the vertical and sagittal discrepancy.