Objective: To clarify whether altering temporomandibular joint (TMJ) condyle and disc positions by occlusal splint (splint) therapy relieves TMJ pain and to determine whether splint therapy facilitates improvement of the ranges of condyle and articular disc motions. Study design: A total of 150 joints of 75 patients admitted with TMJ pain/discomfort were evaluated. A visual analog scale for TMJ pain was administered during visits following the start of splint treatment. At the start of splint treatment, MRI was performed with/without splint insertion, after which condyle/disc movements were evaluated. Disc position and function, disc configuration, joint effusion, osteoarthritis, and the bone marrow were evaluated. Pearson's correlation coefficients, linear regression, and multiple regression analyses were used for statistical analysis. Results: Splint-related anterior movement of the condyle was related to TMJ pain. With a biconvex disc and/or bone marrow abnormality, splint treatment was ineffective for reducing TMJ pain. Conclusion: Splint therapy was not likely to be successful for any kind of TMJ abnormalities, such as bone marrow abnormalities and/or a biconvex disc appearance on MRI. (C) 2017 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.