The Joint Space In Unilateral Posterior Crossbite Patients And Correlation Between Three Dimention Of Condylar Differences And Transverse Discrepancy

Objective:To investigate the condylar position differences in three dimensions between centric relation (CR) and maximum intercuspation (MI) in unilateral posterior crossbite patients(UPCB) and to determine if there was possible correlation between transverse discrepency and CR-MI displacement;To measure joint space of two groups and to estimate condyle fossa relationship of unilateral posterior crossbite group; providing guideline for orthodontic treatment planning.Methods:1.Fifty UPCB cases (experimental group) and fifty normal occlusion cases(control group) were evaluated. Mounting dental casts on articulator with CR bite wax, taken by Roth centric registration method. Measuring three dimensional condylar displacements between CR and MI by measures condyle displacement (MCD),and analysis occlusion interference position with articulator. To make comparison of CR-MI differentiation between two group,and comparative analysis the difference of CR-MI discrepency between crossbite side and uncrossbite side in experimental group.2.Measurement the skeletal base widths of UPCB group,and the arch width of the first molar in two groups.To comparative analysis the differences of arch width between two groups and to explore possible correlation between transverse discrepancy and the amount of CR-MI differences in experimental group.3.All cases of UPCB group and control group were taken CBCT examination.The data was fed into three-dimensional measurement software Invivo5.0 to measure joint spaces,and comparative analysis of condyle fossa relationship between experimental group and control group.Results:1.The positive rate of CR-MI discrepency in the UPCB group was higher than that in the normal occlusion group(x 2=52.174, p<0.001),the value of CR-MI discrepency in three dimention were largerr than control group; In the UPCB group, the distraction of the condyles was significantly greater on the crossbite side than on uncrossbite side in the vertical plane(t=3.394,p<0.05),the condylar displacement observed in sagittal plane showed no significant difference between two sides(t=0.012,p>0.05);The positive rate of occlusion interferences in UPCB group was significant higher than that in control group(,x2=5.482, p<0.05),the occlusion interferences were mostly found on the posterior teeth;The occlusion interference rate in crossbite side and uncrossbite side were 50% and 36%.2.The upper intermolar width in crossbite group was significantly smaller than that in the control group(t=-4.629,P<0.001); the lower arch width showed no significant differences between groups(t= 1.943, p> 0.05).There was no significant correlation between transverse discrepency and CR-MI displacement in three dimensional directions.3.The joint spces(AJS、SJS、PJS)demonstrated no significant differences in two groups (p>0.05);Pearson correlation coefficients were done for the relative condyle position of the right and left sides,crossbite and noncrossbite sides.Correlation was found between right side and left side in control group (P<0.05),however no correlation was discovered between the crossbite and noncrossbite sides in experimental group (P> 0.05).The API of the condyle indicated a significant anterior position in crossbite group.In control group,the condyle were slight anterior position in right side and concentric position in left side.Conclusions:In UPCB,the incidence of occlusion interference was high.Transverse discrepency influence CR-MI differences in the vertical plane the most,however the correlation between transverse discrepency and CR-MI shifting in three dimensional directions was insignificant. The condyle in patients with UPCB were in anterior position and there was asymmetry condyle position between two sides.Therefore it is crucial to correct thansverse discrepancy in UPCB patients In order to get better treatment effects,it is necessary to measure the condylar displacement and unmask real jaw relationship before the comprehensive orthodontic treatment starts.