Background: The aim of this systematic review was to identify, evaluate, and provide a current literature about the influence of heritability on the determination of occlusal traits. Materials and methods: MEDLINE, SCOPUS, Web of Science, LILACS, and Google Scholar were searched without restrictions up to March 2020. Studies with twin method were considered and the risk of bias assessment was performed using quality of genetic association studies checklist (Q-Genie). The coefficient of heritability (h 2), modelfitting approaches, and coefficient correlation were used to estimate the genetic/environmental influence on occlusal traits. The GRADE tool was used to assess the quality of the evidence. Results: Ten studies met the eligibility criteria. Three studies presented good quality, five moderate quality, and two poor quality. Most studies have found that the intra-arch traits, mainly the maxillary arch morphology, such as width (h 2 16-100%), length (h 2 42-100%), and shape (h 2 42-90%), and the crowding, mainly for mandibular arch (h 2 35-81%), are under potential heritability influence. The traits concerning the inter-arch relationship, as overjet, overbite, posterior crossbite, and sagittal molar relation, seem not to be genetically determined. The certainty of the evidence was graded as low for all outcomes. Conclusions: Although weak, the available evidence show that the heritability factors are determinant for the intraarch traits, namely, arch morphology and crowding. Possibly due they are functionally related, the occlusal traits concerning the maxillary and mandibular relationship seem to have environmental factors as determinants. In this scenario, early preventive approaches can offer a more effective and efficient orthodontic treatment.

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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 patientcentred outcomes need to be conducted to guide clinical management. PROSPERO (CRD42019147436).

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Objectives To investigate the association between the management of mandibular arch perimeter during development of the dentition and its effects on second permanent molar (M2) eruption. Materials and Methods Seven electronic databases were searched without restrictions up to June 2020. Assessment was performed using the Risk Of Bias In Non-randomized Studies of Interventions (ROBINS-I) tool for non-randomized clinical trials (non-RCT). Odds ratio (OR) with 95% confidence intervals was calculated from random-effects meta-analyses. The Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) tool was used to assess the certainty of the evidence. Results Five non-RCTs, with serious to moderate risk of bias, were included. A low certainty of evidence indicated that individuals undergoing mandibular arch perimeter management by controlling the position of the first molar had a high prevalence of M2 eruption difficulties. The odds of eruption disorders was 7.5 times higher (OR: 7.57, [3.72, 15.41], P &lt; .001) in treated individuals. Subgroup analysis revealed that appliances that increased the arch perimeter lead to a greater chance of eruption disorders compared to appliances that only maintained the perimeter. The predictive factors for the M2 eruption difficulty were its previous mesioangulation in relation to the first molar (&gt;24°) and the treatment time (&gt;2 years). Conclusions Mandibular arch perimeter management during development of the dentition leads to an increase in the occurrence of M2 eruption difficulties. The identification of possible risk factors as well as the choice of the appropriate appliance type and the monitoring of these individuals seems to be essential to avoid undesirable effects with this therapy.