Performance of cone-beam computed tomography filters for detection of temporomandibular joint osseous changes

The temporomandibular joint (TMJ) is a complex anatomic structure and a variety of morphological changes can occur on its osseous surfaces. This study aimed to evaluate the influence of cone-beam computed tomography filters for detection of surface osseous changes of the TMJ to verify the best conditions for evaluating this area. Images of 100 TMJs were analyzed without filter application (WOF) and with the following filters for XoranCat(A (R)) software: Sharpen (F1); Angio_Sharpen_Low 3 x 3 (F2); Angio_Sharpen_High 5 x 5 (F3); and Smooth (F4). Two oral radiologists classified the images according to the presence of osseous changes. A score was also given for image quality assessment. The filters were subjected to pairwise comparisons for each osseous change using McNemar's test, and the image quality among all filtered images was compared using the Kruskal-Wallis test. For the mandibular condyle, there were significant differences (P < 0.05) for sclerosis between WOF x F3 and F1 x F3. Regarding the articular eminence, there were significant differences (P < 0.05) for sclerosis between all filters and F3. No images were considered inadequate for diagnosis. F1 and F2 showed the highest frequencies of "excellent diagnostic conditions", while F3 had the highest frequency of "poor diagnostic conditions". Application of F3 significantly complicates the diagnosis of sclerosis for the mandibular condyle and articular eminence, and it received the worst image quality scores. F1 and F2 were judged to produce images of excellent quality and may be feasible alternatives for evaluation of surface osseous changes in the TMJ.