Influence of heritability on occlusal traits: a systematic review of studies in twins.

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 (h2), model-fitting 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 (h2 16-100%), length (h2 42-100%), and shape (h2 42-90%), and the crowding, mainly for mandibular arch (h2 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 intra-arch 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.

Childhood Obesity and Delayed Gratification Behavior: A Systematic Review of Experimental Studies.

OBJECTIVE: To evaluate the extent of the association between instant gratification behavior and childhood obesity. STUDY DESIGN: PubMed, Scopus, EMBASE, EBSCOhost, and Cochrane databases were searched for the terms delayed gratification, children, and obesity. Studies were eligible if they included a sample of at least 100 children who were made to choose between an immediate reward and a larger one later, with the authors comparing the response in different populations and observing some relationship with obesity. A specifically designed data extraction form was used, following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. The methodologic quality of the included studies was assessed with the methodologic index for nonrandomized studies. RESULTS: Nine articles were included after we applied the inclusion and exclusion criteria. Almost all studies conducted the test in populations of preschool children and offered food and/or nonfood rewards. The studies found a clear relationship between an inability to defer gratification and overweight and obesity. The quality assessment of the publications was ranked high in 5 studies and medium in 4. CONCLUSIONS: Children with the inability to delay gratification are more likely to be overweight or obese. Observation of such trends is useful in its implications for reeducation programs. Although the methodologic quality of the eligible studies was acceptable, additional experimental controlled studies are required to associate these behaviors with other aspects.