ObjectiveTo evaluate the effects of a Twin-block appliance on the condyles of patients with ClassⅡmalocclusion by conducting a systematic review and a Meta-analysis.MethodsPubmed, Embase, Cochrane Library, Chinese BioMedical Literature Database, China National Knowledge Infrastructure, and VIP Database were electronically searched. Randomized controlled trials, controlled clinical trials, and single-arm trials on condylar changes produced by a Twin-block appliance in patients with ClassⅡmalocclusion were included. Two reviewers independently extracted and assessed the risk of bias. Meta-analyses were conducted with Review Manager 5.3.ResultsEight studies were included; among which, seven were of high quality. After treatment with a twin block appliance, condyles moved anteriorly. The anterior joint spaces decreased (P<0 .000 01), whereas the posterior spaces increased (P<0 .000 01). the superior spaces were not changed (P=0.11). Moreover, a significant difference was observed in the increase of the condylar space index (P<0 .000 01). after treatment, the anteroposterior diameters of the condyles and condylar height increased (P=0.000 2 andP<0 .000 01, respectively). by contrast, no significant changes were discovered in the medial external diameters of the condyles (P=0.42).ConclusionA Twin-block appliance can promote the growth of a condyle in the posterior and upper direction and move it forward in favor of the correction of Class Ⅱ malocclusion.
