Objective: To summarize the clinical manifestation and treatment of temporomandibular joint (TMJ) disc ossification, providing reference for clinical diagnosis and treatment of TMJ disc ossification. Methods: From January 2006 to January 2018, 4 patients with TMJ disc ossification (2 males and 2 females, aged 20-55 years with an average age of 35.5 years) which were admitted to the Department of Oral and Maxillofacial Surgery, Shenzhen Second People′s Hospital were analyzed retrospectively. Ossification of TMJ disc was found in 4 cases during TMJ surgery. Two cases underwent partial ossification resection plus disc reduction and anchorage, and two cases underwent discectomy plus temporalis myofascial flap replacement. The causes, clinical manifestations and surgical effects of TMJ disc ossification were analyzed by comparing the maximal interincisal opening, visual analogue scale (VAS) score and MRI imaging indexes before and after operation. Results: The history of anterior disc displacement of TMJ in 4 patients was long (average 11.5 years). In clinic, TMJ disc ossification was characterized by TMJ pain and limitation of mouth opening. The maximal interincisal opening was (32.1±6.1) mm and the VAS score was (7.3±0.4) before operation. MRI showed that the displaced discs of the affected sides were displaced and the condyle bones were worn. During the operation, ossification of TMJ discs was found yellow and hard, and the original elasticity was lost. Pathologic findings showed that the TMJ disc cartilage were ossified to osteoid tissue. Under the microscope, bone cells scattered around the bone cells and red trabecular bone were seen, and there were bone trabecula formed. In a follow-up of one year, TMJ pain was significantly decreased [VAS: (1.7±0.2)], and the maximal interincisal opening was (38.5±2.2) mm. MRI showed that the TMJ disc returned to normal position, and the sign of repairing and reconstruction of condyle bone could be found. Conclusions Long term displacement of TMJ disc may cause ossification with pain and limitation of interincisal opening. According to the degree and extent of ossification, partial ossification plus disc reduction and anchorage or discectomy plus temporalis myofascial flap replacement is feasible, and the clinical effects are satisfactory.

Objective: To investigate the morphology and position changes of displaced disk with reduction after treatment by modified Twin-block. Methods : 19 patients were diagnosed as displaced disk with reduction and they were treated with modified Twin-block from July 2015 to June 2016. 28 temporomandibular joints (TMJ) of these patients were included in the analysis. The disk length, disk-condylar distance, and disk-condylar angle were measured with MRI before and after treatment. Paired t-test was used. Disk morphology before and after treatment was also documented and analyzed by Wilcoxon signed rank test. The statistical significance was set at P<0.01. Results : 28 TMJ disks were anteriorly displaced with reduction. 24 of them were repositioned while the other 4 were still anteriorly positioned after treatment. The disk length was increased significantly (P<0.01) while the disk-condylar distance and disk-condylar angle were decreased significantly after treatment (P<0.01). The disk morphology as hemiconvex (16) and bi planar (9) were the majority before treatment, while biconcave (16) and biplanar (10) were changed to the larger part after treatment. There was improvement on the disk deformation with a statistical significance (P<0.01). Larger disk-condylar distance, disk-condylar angle and severer deformation of disks were observed in the 4 disks without reposition. Conclusion Modified twin-block is an effective appliance for disk displacement with reduction by repositioning the disk and modifying the disk deformation. However the effect is not good for disks with severer deformation and displacement. Further studies with larger sample and stratified group are still needed.