Hypo-Divergent Skeletal Group has Higher Bone Density in the TMJ

Objectives: Condylar position in the glenoid fossa and bone density of the TMJ can be better determined with Cone-Beam CT (CBCT). Position of the condyle in various sagittal skeletal relationships has been previously investigated, however, there are no well-designed studies that associate bone density and position of condyle with vertical skeletal patterns. The aim of this study was to compare the condylar position and the density of condyle and glenoid fossa in hyper-divergent, hypo-divergent, and normal patients using CBCT.
Methods: CBCT was used to assess 180 TMJs from 90 patients that were divided into 3 groups based on vertical skeletal pattern. Using CBCT reconstruction software (In vivo-5) the center of the condyle was taken as a reference point and three angles were constructed (45, 90 and 135 degrees to the true horizontal line) in sagittal and coronal views. The anterior, superior and posterior joint spaces in mid sagittal section of condyle and medial, superior and lateral joint spaces in the mid coronal section were measured from condyle to glenoid fossa along the reconstructed lines. Density numbers of the condyle and glenoid fossa were measured using pixel intensity values (PIV) at specific standardized points.
Results: In the sagittal sections there were significant differences between superior and posterior joint space distances and the PIV values of superior part of condyle and superior and posterior of glenoid fossa. In the coronal view all the joint space distances and PIVs showed significant differences. The Post HOC test revealed significant differences between hypo- divergent and hyper-divergent groups for all the measurements except for PIV value of glenoid fossa.
Conclusions: Hypo-divergent group had the highest condylar head and glenoid fossa bone density and all the joint spaces in coronal view are larger than other groups. Vertical skeletal pattern could affect the position of condyle and bone density of TMJ.