Abstract: Objective　To apply Cone-Beam CT (CBCT) and MRI to analyze the imaging differences of patients with temporomandibular joint disorder (TMD) before and after the anterior repositioning splint (ARS), and to explore the clinical effects of ARS in the treatment of TMD. Methods　A total of 86 TMD patients were collected and divided into ARS group (n=60) and non ARS group (n=26). The non ARS group used muscle function training for six months, and the ARS group was treated with ARS for 6 months with the cooperation of muscle function training. The average maximal mouth opening (MMO), joint snapping percentage, pain visual analogue scale (VAS), CBCT three-dimensional data of temporomandibular joint, joint disc length and disc-condyle distance measured under MRI scan of TMD patients were analyzed before and after treatment in the two groups. The changes in bone quality and morphology of the condyle before and after treatment were analyzed in the ARS group (20 patients) and the non-ARS group with degenerative joint disease (10 patients). Results　Compared with the non ARS group, the MMO increased and the joint snapping and pain VAS decreased after treatment in the ARS group (P＜0.05). Results of CBCT showed that the horizontal angle of the condyle decreased, the anterior joint space narrowed and the posterior joint space widened (P＜0.05). There were no significant differences in the supra-joint space, the anteroposterior diameter of the condyle, the internal and external diameter between the two groups (P＞0.05). Compared with the non ARS group, 20 patients with degenerative joint disease showed a significant improvement in condyle bone quality after ARS treatment in the ARS group, and the bone change score decreased (P＜0.05). MRI results showed that there was no significant difference in the length of the joint disc before and after treatment in the ARS group (P＞0.05), whereas the length of the joint disc was significantly shorter after treatment than that in the non ARS group (P＜0.05). Conclusion　CBCT and MRI can confirm the clinical effect of ARS on the position and morphology of the condyles and articular discs in TMD patients.

Key words: temporomandibular joint dysfunction syndrome, cone-beam computed tomography, magnetic resonance imaging, temporomandibular joint disc, anterior repositioning splint