Abstract:

Objective  This study aims to evaluate the temporomandibular joint (TMJ) changes in patients with class Ⅱ division 1 subdivision malocclusions before and after Twin-block treatment using a cone-beam CT (CBCT). Methods  Twenty subjects with class Ⅱ division 1 subdivision malocclusions were included in this study. Hand-wrist radiographs were conducted in the FG-G stage. CBCT was performed to determine the changes in the TMJ before and after the Twin-block treatment. The InVivoDental software was used to calculate the relevant parameters from the three-dimensional CBCT images. The acquired data were then analyzed. Results After treatment, the sagittal condylar anterior spaces were reduced, whereas the sagittal condylar superior and posterior spaces as well as the coronal condylar superior space increased (P<0.01). The condylar height, sagittal condylar angles, and condylar anteroposterior diameters also increased (P<0.01). Conclusion After the Twin-block treatment, new bone deposition was observed on the condyle. The condyle height also increased and resulted in adjustments in the condyle position within the glenoid fossa to more downward and forward positions. CBCT can quantify TMJ changes and provide an objective assessment to orthodontic treatment.

Key words: cone-beam CT, class Ⅱ division 1 malocclusion, Twin-block functional appliance, temporomandibu-lar joint