Disc displacement with reduction treated by modified Twin-block

To investigate the morphology and position changes of displaced disk with reduction after treatment by modified Twin-block.

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.

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 diskcondylar angle were decreased significantly after treatment (P＜0.01). The disk morphology as hemiconvex (16) and biplanar (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.

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.