Herbst and Twin Block appliances in Class II malocclusion management for children: a systematic review and meta-analysis

Introduction – Class II malocclusion is a common skeletal abnormality in growing patients, often associated with mandibular retrusion. Functional appliances such as Herbst and Twin Block appliances aim to stimulate mandibular growth during puberty. However, evidence comparing their effectiveness remains inconsistent. Objective – To compare the skeletal, dental, and soft tissue effects of Herbst and Twin Block appliances in growing patients with Class II malocclusion through a systematic review and meta-analysis. Methods – Randomized controlled trials (RCTs) comparing both appliances in children ≤16 years of age with Class II malocclusion were included if they reported skeletal, dental, or soft tissue outcomes. Non-randomized studies, case reports, reviews, and those with incomplete data were excluded. PubMed, Scopus, Web of Science, the Cochrane Library, and EMBASE, among other sources, were searched until January 30, 2025, with no language or date restrictions. Risk of bias was assessed using the Cochrane RoB 2.0 tool, and the certainty of the evidence was evaluated using the GRADE method. A random-effects meta-analysis calculated standardized mean differences (SMDs) with 95% confidence intervals. Results – Seven RCTs with 548 participants were included. Both appliances effectively managed Class II malocclusion, with generally similar effects on skeletal and soft tissue parameters. The Herbst appliance showed significant advantages in improving the mentolabial angle (SMD: 0.56; 95% CI: 0.15–0.96) and molar relationship (SMD: −0.31; 95% CI: −0.56 to −0.05). No significant differences were observed in other outcomes. Conclusions – Both the Herbst and Twin Block appliances are effective for Class II correction in growing patients. The Herbst appliance offers modest advantages in certain parameters, but clinical decisions should also consider patient-specific factors such as adherence, comfort, esthetics, and growth stage. Systematic Review Registration – https://www.crd.york.ac.uk/PROSPERO/view/CRD420251011083, PROSPERO: CRD420251011083.