Abstract:

Objective This study investigates the differences in condylar position between centric relation（CR） and maximum intercuspation（MI） in Angle’s Class Ⅱ orthodontic patients before treatment. Methods 80 cases, who were Angle’s Class Ⅱ pretreatment patients, and 50 cases, who were normal（ideal） occlusion were accepted. Dental casts were mounted on Panadent articulator with CR bite record, taken by bilateral manipulation and load testing. The differences in condylar position between CR and MI in all three spatial planes were measured using the Panadent condylar position indication（CPI）. Results 1）The positive rate of CR-MI discrepancy was 92.50%（74 cases） in the group of Angle’s Class Ⅱ malocclusion and 10.00%（5 cases） in the group of normal occlusion（P< 0.001）. 2）74.32%（55 cases） CR-MI discrepancy in 74 cases in the group of Angle’s Class Ⅱ pretreatment patients were coincidence discrepancy. 3）91.25% patients in the group of Angle’s Class Ⅱ malocclusion and 66.00% in the group of normal occlusion present occlusion interferences which located at the posterior teeth. Conclusion The results suggested that orthodontists should be aware of a high incidence of condylar displacement in Angle’s Class Ⅱ pretreatment patients, and measure condylar displacement before the start of comprehensive orthodontic treatment to unmask real jaw relationships and avoid possible misdiagnoses.

Key words: centric relation, Angle’s Class Ⅱ malocclusion, condylar position indication