Regarding degenerative joint disease, few methods have been developed for objectively estimating deformation of the mandibular condyle. If the anterior functional area of the mandibular condyle, from the front-most point of the mandibular condyle to the mandibular condyle parietal area, can be quantitatively evaluated, it would be beneficial for methods for objectively estimating sequential bony deformity. In this study, 15 patients, 2 men and 13 women, were selected, aged from 10 to 70 years old (average age: 29.2 years; median age: 19 years). The anterior functional area of the mandibular condyle was examined using MRI. Using Aze Win (AZE, Tokyo), a total of 30 joints were measured by three examiners. Each measurement was carried out two times at an interval of more than one week. Statistical analysis was performed using Spearman's correlation (p<0.01) between the first and second functional areas of the mandibular condyle levels, and intraclass and interclass correlations (ICCs) were confirmed at a significance level of p<0.05.
From Spearman's rank test, strong correlations were found between the first and second areas at 0.981, 0.915, and 0.921 (p<0.001). Excellent ICCs were observed between 0.974 and 0.985 (interclass: first and second measurements) and among 0.993, 0.968, and 0.955 (intraclass: three examiners). Therefore, both intraclass and interclass measurements would be reliable as an objective estimation method.

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A 59-year-old female patient consulted our hospital in May 2011 complaining of right temporomandibular joint (TMJ) pain and malocclusion. Her rheumatoid arthritis (RA) has been medically managed in the Internal Medicine Department since 2007. Oral examination showed a limited mouth-opening of 32 mm, with sole occlusal contact in the right mandibular molars. MRI and CT imaging of TMJ revealed irreducible anterior disc displacement with joint effusion in association with erosive bone changes in the right mandibular condyle. Left TMJ showed reducible disc displacement. Medical management was initiated with MTX application, but recurrence of arthritis including that of TMJ was observed as the dose was reduced to alleviate its side effects. Combined medication with Tacrolimus was not sufficiently effective. In 2011, an appropriate dose of 6 mg/week MTX showed good control of RA after resolving adverse effects, but TMJ symptoms recurred soon thereafter. Splint therapy was started, and molar and premolar occlusal contact was confirmed after five months of treatment. TMJ pain and limited jaw opening were alleviated, and when the occlusal state became favorable after ten months, the splint was removed. MRI follow-up study revealed favorable bone remodeling of the right mandibular condyle.

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