Objective: To study the changes of condyle position and occlusion between centric jaw relation (CR) and maximum intercuspation (MI) positions.
Methods: The power centric registration advocated by Roth was used to take centric relation bite registration for 50 patients (25 Angle Class I, and 25 Angle Class II). Diagnostic models were mounted and analyzed with Panadent articulator and condylar position indicator.
Results: Nearly all patients had CR-MI difference in all three spatial planes. Seventy percent of the Sagittal displacement was within 2.0 mm and 87% of the transverse displacement was within 1.0 mm. Movement of most of the condyles was posterior and inferior. Sixty-four percent of the initial contacts in CR occurred on the most posterior molar on one side. When the mandible moved from CR to MI, overbite deepened, overjet decreased, and molar relationship became mesialized. Correlation was found between some variables of condylar displacement and occlusion changes. No significant difference between Angle Class I and Angle Class II patients was observed in condylar position and occlusion changes.
Conclusion: The occlusion in centric jaw relation should be analyzed before treatment to reveal the disharmony between occlusion and jaw position.