The relevance of temporomandibular joint (TMJ) disc morphologic characteristics to clinical diagnoses and treatment outcomes for internal derangements continue to be debated. Objective: This study compared the MRI characteristics of the disc to both clinically obtained diagnoses and treatment outcomes. Methods: Retrospective analyses were performed on MRIs of 33 TMJs from humans (34.2+11.1 years; 79% female). Subjects were categorized according to their clinical diagnoses based on presenting signs and symptoms of disc internal derangement: asymptomatic normal (control), with reduction, and without reduction. Diagnostic decisions were made prior to MRIs. Digital caliper measurements of intermediate and posterior band thicknesses were taken from the central section of the sagittal MRIs in the closed mouth position. All measures were within instrument resolution (+0.01mm). A ratio of posterior to intermediate band thickness was then calculated. Disc shape was classified as either linear or round. Disc position was categorized into 3 groups according to Drace and Enzmann (1990). Intra-rater reliability was greater than 0.86 for all measures. All symptomatic subjects in this study received intra-oral splint therapy. Treatment outcomes were expressed as improvement and no improvement/worse based on both subjective and objective criteria. Data were analyzed using Kruskal-Wallis (position and shape), ANOVA, and binary logistic regression. Results: Relative to diagnostic categories, increased band thickness was indicative of the asymptomatic normal group (p<0.002). Disc shape and position were not related to clinical diagnoses or treatment outcomes (p>0.05). However, thickness ratio correctly classified positive treatment outcomes in 86.7% of the cases. Specifically, values closer to 6.0 predicted better treatment outcomes. Conclusions: Based on these findings, MRI measures of disc thickness and subsequent ratio calculations show promise as objective measures that could be developed into clinical prognostic indicators. Further study is needed in these areas.

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