Effectiveness of Intra-oral Non-skeletally Anchored Appliances in the Correction of Skeletal Class III Malocclusion in Growing Patients: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

Extra-oral appliances used for correcting skeletal Class III malocclusion are often bulky, unaesthetic, and heavily reliant on patient compliance, which can negatively affect treatment outcomes, particularly in growing patients. As a result, intra-oral alternatives have gained increasing attention due to their improved comfort, better acceptance, and reduced visibility. The objective of this systematic review was to examine and appraise existing evidence concerning the effectiveness of intra-oral, non-skeletally anchored appliances for correcting skeletal Class III malocclusion in growing individuals. A comprehensive and systematic search was conducted across five major electronic bibliographic databases, with no language restrictions, to ensure the broad inclusion of relevant studies. Only randomized controlled clinical trials (RCTs) assessing intra-oral non-skeletally anchored appliances were included in the review. A total of eight RCTs involving 336 growing patients met the inclusion criteria, although only two studies were suitable for quantitative meta-analysis. Among the evaluated appliances, the removable mandibular retractor (RMR) demonstrated forward movement of key skeletal landmarks, including point A (mean difference (MD) = 1.92 mm), point B (MD = 0.13 mm), prosthion (Pr) (MD = 1.97 mm), and infradental (Id) (MD = 0.16 mm). Additionally, RMR use was associated with a significant increase in the facial convexity angle (MD = 4.92°) and a reduction in the nasolabial angle (MD = 5.18°), indicating favorable soft tissue profile changes. The lower-clear-plate-based intermaxillary traction (LCP-IMT) appliance demonstrated the most significant improvement in sagittal skeletal relationship. It showed the greatest increase in the ANB angle, the largest reduction in the SNB angle, and the smallest increase in mandibular length, suggesting effective restriction of mandibular growth. Overjet increased significantly with all evaluated appliances, whereas overbite increased only with LCP-IMT. A consistent decrease in lower incisor inclination was observed across all appliances. Soft-tissue adaptations across the appliances included increased facial convexity, forward positioning of the upper lip, and posterior repositioning of the lower lip, all of which contributed to improved facial esthetics. In conclusion, LCP-IMT and reverse twin block (RTB) appliances demonstrated the most favorable skeletal improvements in the sagittal dimension. These were followed by the modified RMR, conventional RMR, modified tandem appliance (MTA), and Frankel’s function regulator III. However, the overall strength of evidence was between low and very low due to methodological limitations, small sample sizes, and heterogeneity among the included studies, highlighting the need for further high-quality research.