The correlation between Balkwill angle and occlusal plane angles and temporomandibular joint morphology

Objective To investigate the correlation between the Balkwill angle and occlusal plane angles and temporomandibular joint (TMJ) morphology in adults with skeletal Class Ⅱ division 2 malocclusion. Methods Thirty-five adult patients with skeletal Class Ⅱ division 2 low angle (study group) and 35 adult patients with skeletal Class Ⅰ average angle (control group) were included. The Invivo Dental 5 software was employed to acquire the data of Balkwill angle, occlusal plane angle (FH-OP), posterior occlusal plane angle (FH-POP), mandibular occlusal plane angle (FH-MOP), DPO (vertical distance from condylar center to the MOP) and the TMJ measurement items. Results The mean values of FH-OP, FH-POP and FH-MOP were lower in the study group than control group (P<0.05). The average value of Balkwill angle and DPO were higher in the study group than the control group (P<0.05). Significant differences were found in the measurement results of the mediolateral diameters of the condyle, width of condylar head, the articular eminence inclination and height, superior joint space between two groups. DPO had a medium correlation with mediolateral diameters of the condyle, glenoid fossa depth and articular eminence height. And FH-MOP angle had a medium correlation with mediolateral diameters of the condyle and articular eminence height. There was a medium correlation between the Balkwill angle and articular eminence height, a weak correlation with mediolateral diameters of the condyle, articular eminence inclination, condylar length and glenoid fossa depth. Conclusion The results indicated that the DPO had a significant impact on TMJ morphology, followed by FH-MOP, and finally Balkwill angle in skeletal Class Ⅱ division 2 low angle malocclusion.