Objectives: A hypothesis of sequential condylar morphological changes, ranged from flattening, erosion, recortication to osteophytosis, associated with disk kinematics has been proposed. These changes were hypothesized as an adaptation strategy to optimize the unfavorable loads. The aim of this pilot study was to evaluate a possible relationship between TMJ arthrotic changes and the contact mechanics of the eminence/disk/condyle complex by using static and true dynamic MRIs. Methods: Sagittal TMJ MRI series of 49 patients were included for this analysis. All the images were obtained with a 1.5 T MR scanner (Siemens Sonata®). Static images were scanned with a me2d protocol. Dynamic images were with a tfiperf2d protocol at pace of 0.4 sec/frame. With the static MRIs, erosion, recortication and osteophyte etc. arthrotic signs of the condyle were noted. With the true dynamic MRIs, the disks were classified as noon-positioned, displacement with reduction and without reduction. The contact areas among eminence/disk/condyle complex during movements were also recorded. Results: Of the 98 TMJs, 22 were with noon-position disks and all of them had no obvious sign of arthrotic changes; 30 with displaced but reduced disks and only 3 of them with arthrotic changes; 46 had non-reduced disks and 40 of them showed arthrotic changes (p<0.05, ÷2 test). The condylar sites with erosion or recortication seemed to be corresponded to the contact sites with eminence or the non-reduced disks at the end of maximal mouth opening, where resistance was met. Conclusions: The great majority of the TMJs with non-reduce disks have signs of arthrotic changes. These changes seem to relate to the contact mechanics.

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