We aimed to consolidate all available data on worldwide third molar agenesis frequencies, with a particular emphasis on exploring the factors leading authors to find contradictory results for the demographic and morphologic predictors of this anomaly. A total of 12,376 studies were originally identified, then narrowed down to 1,312 for title/abstract screening. On the basis of our inclusion and exclusion criteria, we selected 92 studies, containing 100 effect sizes and 63,314 subjects, for systematic review and metaregression. The worldwide rate of agenesis was found to be 22.63% (95% confidence interval = 20.64% to 24.76%), although the estimates ranged from 5.32% to 56.0%. Our subgroup analyses revealed that women are 14% more likely than men to have agenesis of ≥1 third molars and that maxillary agenesis was 36% more likely than mandibular agenesis in both sexes. Furthermore, we found that having agenesis of 1 or 2 molars was most common, while agenesis of 3 or 4 molars was least common. Finally, we found large differences among agenesis frequency depending on geographic region. This information is expected to be of use not only to clinicians and patients but also to policy makers, given the implications for third molar extraction protocols.

Mexicans and Mexican Americans share culture, genetic background, and predisposition for chronic complications associated with obesity and diabetes making imperative efficacious treatments and prevention. Obesity has been treated for centuries focused-on weight loss while other treatments on associated conditions like gout, diabetes (T2D), and hypertriglyceridemia. To date, there is no systematic review that synthetize the origin of obesity clinics in Mexico and the efforts to investigate treatments for obesity tested by randomized clinical trials (RCT). We conducted systematic searches in Pubmed, Scopus, and Web of Science to retrieve anti-obesity RCT through 2019 and without inferior temporal limit. The systematic review included RCT of anti-obesity treatments in the Mexican adult population, including alternative medicine, pharmacological, nutritional, behavioral, and surgical interventions reporting biometric outcomes such as BMI, weight, waist circumference, triglycerides, glucose, among others. Studies with at least three months of treatment were included in the meta-analysis. We found 634 entries, after removal of duplicates and screening the studies based on eligibility criteria, we analyzed 43, and 2 multinational-collaborative studies. Most of the national studies have small sample sizes, and the studied strategies do not have replications in the population. The nutrition/behavioral interventions were difficult to blind, and most studies have medium to high risk of bias. Nutritional/behavioral interventions and medications showed effects on BMI, waist circumference, and blood pressure. Simple measures like plain water instead of sweet beverages decrease triglycerides and systolic blood pressure. Participants with obesity and hypertension can have benefic effects with antioxidants, and treatment with insulin increase weight in those with T2D. The study of obesity in Mexico has been on-going for more than four decades, but the interest on RCT just increased until this millennium, but with small sample sizes and lack of replication. The interventions affect different metabolic syndrome components, which should be analyzed in detail with the population living on the U.S.-Mexico border; therefore, bi-national collaboration is desirable to disentangle the cultural effects on this population's treatment response.