Incremental or maximal mandibular advancement in the treatment of class II malocclusion through functional appliances: A systematic review with meta-analysis.

To systematically review the effects of functional appliances (FA) using incremental vs maximal mandibular advancement regarding cephalometric measurements in class II malocclusion individuals and to assess patient-centred-outcomes. Six electronic databases were searched without restrictions up to April 2020. We included randomized and non-randomized controlled trials using identical FA. Trials involving participants who used adjunct appliances, inter-maxillary elastics, who received surgical treatment or that recruited individuals with cleft lip/palate or craniofacial deformity/syndrome were excluded. Risks of bias assessments were performed using the Cochrane risk of bias tool-2 and ROBINS-I tools. Mean differences (MD) with their 95% confidence intervals were calculated from random-effects meta-analyses. The GRADE tool was used to assess the certainty of the evidence. Six studies were included. Low to very low certainty of evidence indicated that incremental mandibular advancement resulted in greater gains in mandibular length (MD = 0.89 [0.38, 1.34], P = .0005), anterior mandibular displacement (MD = 0.73 [0.40, 1.06], P < .0001) and SNB angle (MD = 0.44 [0.02, 0.85], P = .04). No significant differences were found for maxillary, dento-alveolar and upper airway outcomes between construction bite protocols (P > .05). Study design and appliance-related factors influenced the results of the subgroup analyses. Existing evidence is inadequate to assess patient-related response and long-term outcome could not be assessed. Currently, there are a heterogeneous number of studies with low quality and methodological issues can lead to biases that strongly limit an evidence-based conclusion. Weak evidence suggests gains in mandibular skeletal parameters in the short term using FA with incremental mandibular advancement. Randomized trials evaluating key topics such as patient-centred outcomes need to be conducted to guide clinical management. PROSPERO (CRD42019147436).