It has been observed that in temporomandibular joint (TMJ) disorders, osteoarthritis stimulates bone resorption in subchondral area of condyle. The active bone remodeling likely alters distribution of degree of bone mineralization (DBM). The objective of this study was to examine if analysis of the DBM distribution in condyle can be used to assess the development of TMJ osteoarthritis.
IRB approval was obtained for retrospective analysis of cone beam computed tomography (CBCT) exams of 17 patients (10 males and 7 females, mean age 46 yrs) that showed bony changes in TMJ consistent with osteoarthritis. Both right and left condyles were digitally dissected 7 mm from the top of condylar surface, parallel to the occlusal plane. Non-bone voxels outside condyle were removed using a segmentation method. The DBM histogram of each condyle was obtained by calibrating a CT attenuation value of each bone voxel to a mineral density using known phantoms. Mean and standard deviation (SD) of DBM were obtained. Low and high values (Low and High) of DBM were also determined at the lower and upper 5th percentile values of the histogram, respectively. Correlations of SD with other DBM parameters were tested.
Results: The SD had significant positive correlations with Mean (r=0.48, p<0.003) and High (r=0.84, p<0.001) while no correlation with Low (p>0.194).
Conclusions: The SD accounts for variability of DBM that changes with bone turnover. Low and High represent DBM values for newly forming (less mineralized) and older (more mineralized) bone tissue, respectively. The results of our study indicate that the variability of DBM is determined by highly mineralized parts of condylar bone tissue in TMJ disorder patients. This finding provides an insight that bone resorption in older bone tissue dominates in controlling the progress of TMJ osteoarthritis.
Keywords: Bone, CBCT, Mineralization, Resorption and TMJ and masticatory muscles