Journal of Dental Medicine

Background and Aims: Internal derangement of the Temporomandibular joint (TMJ) is the most common form of Temporomandibular disorders, which represents an abnormal internal strucural and functional change of the disk, as well as an abnormal relationship of the disk to the condyle, glenoid fossa and articular eminence when the teeth are in the closed- mouth position. The aim of this study was to evaluate the correlation between eminence steepness and condyle disk movements in TMJs affected by internal derangements using magnetic resonance imaging (MRI).

Materials and Methods: In this cross-sectional study, digital MRI files of 90 joints belong to 45 patients in open and closed-mouth positions were evaluated. Patients were subdivided into two groups: 64 individuals with anterior disk displacement with reduction and 26 individuals with anterior disk displacement without reduction. Appropriate oblique sagittal sections were selected and printed. Outlines of the fossa, eminence, condyle and disk were traced on matte acetate sheets and evaluated by an oral and maxillofacial radiologist and a postgraduate student of oral and maxillofacial radiology. Disk rotation, condyle rotation, condyle translation and eminence steepness were measured. The data were analyzed using T-test.

Results: In this study, no significant difference was found in measurements between the two groups, (for steepness P=0.64, for Disc rotation P=0.77, for condyle rotation P=0.28 and for condyle translation P=0.12). Disk rotation showed statistically significant correlation with eminence steepness in the anterior disk displacement with reduction group
(P=0.034). Although this correlation was weak (r=0.27) no statistically significant correlations were found between other variables and eminence steepness in this group (for condyle rotation P=0.3 and for condyle translation P=0.98). Disk rotation and condyle translation had statistically significant relationship in the anterior disk displacement without reduction group (P=0.011, r=-0.49). In addition, a significant difference was found between disk rotation and condyle rotation in this group (P=0.004, r=0.54). The relationship between other variables and eminence steepness were not statistically significant (for disc rotation P=0.06, for condyle rotation P=0.72 and for condyle translation P=0.73).

Conclusion: According to the results of the present study, there is no obvious relationship between eminence steepness and movements of the condyle- disk assembly in patients with TMJ internal derangements. Therefore, the hypothesis that a steep articular eminence of the TMJ is a predisposing factor for disk displacement without reduction could not be verified. Performing prophylactic Eminectomy as a part of patient treatment plan is doubtful and need further evaluations.

Background and Aims: Because of high prevalence of TMJ dysfunctions , increased promotion of diagnostic and treatment methods is necessary. In many cases, in addition to disc position, morphology of other joint components such as articular eminence can be changed and therefore the probable correlation between disc position and morphology of hard tissue components can be used for prediction of internal derangements. The aim of this study was to evaluate the correlation between the position of disc and morphology of articular eminence of TMD`s patients using magnetic resonance imaging (MRI).

 Materials and Methods: In this cross sectional study by evaluation of digital MRI files, ultimately 78 joint images were identified which had sufficient quality and resolution for review. Then the MRI images, were observed and evaluated by 3 oral and maxillofacial radiologists to determine the disc position (normal, anterior displacement with and without reduction, and posterior displacement) and morphology of articular eminence (Box, Sigmoid, Flattened). Ultimately the results that were reported at least by 2 observers were included as the final results and were recorded in the check list. Data were analyzed using Chi-Square test and Fisher test.

 Results: In this study, no case of posterior disc displacement was found and therefore was excluded from the study. Articular eminence morphology (Flattened versus Sigmoid) showed statistically significant correlation with anterior disc displacement with and without reduction (P-values for anterior displacement with and without reduction were 0.03 and 0.002, respectively). No significant difference was found between the sigmoid and box types in relationship with disc displacement (P-values for anterior displacement with and without reduction were 0.72 and 0.70. In this study, no significant difference between the anterior disc displacement with reduction and anterior disc displacement without reduction in relationship with the morphological changes of articular eminence in any of the cases were found.

 Conclusion: The results showed that flattening of articular eminence had significant relationship with anterior disc displacement.