Vitamin C is important for preventing and slowing the progression of many diseases. There is significant evidence linking periodontal disease and vitamin C. We aimed to systematically review the studies addressing the relationship between vitamin C and periodontal disease, and the preventive ability of vitamin C against periodontal disease. Electric searches were performed using PubMed, EMBASE, Cochrane Library, and Web of Science. Studies addressing the relationships between periodontal disease and vitamin C in adults aged over 18 years were included. Quality assessment was done using the Critical Appraisal Skills Program guideline and GRADE-CERQual. There were 716 articles that were retrieved and 14 articles (seven cross-sectional studies, two case-control studies, two cohort studies, and three randomized controlled trials (RCT)) were selected after reviewing all of the articles. The vitamin C intake and blood levels were negatively related to periodontal disease in all seven cross-sectional studies. The subjects who suffer from periodontitis presented a lower vitamin C intake and lower blood-vitamin C levels than the subjects without periodontal disease in the two case-control studies. The patients with a lower dietary intake or lower blood level of vitamin C showed a greater progression of periodontal disease than the controls. The intervention using vitamin C administration improved gingival bleeding in gingivitis, but not in periodontitis. Alveolar bone absorption was also not improved. The present systematic review suggested that vitamin C contributes to a reduced risk of periodontal disease.

A substantial number of adults suffer from obesity, that is caused by the risk factor, masticatory dysfunction. The association between mastication and obesity, however, is inconclusive. This systematic review aims to provide literature regarding the association between mastication and factors affecting masticatory function, and obesity in adults. Four electronic databases (PubMed, EMBASE, Cochrane Library, and Web of Science) were used to search for publications that met the following criteria: published between 2007 and 2016, written in English, and assessed the associations between mastication and obesity among the population aged ≥18 years. The included publications were analyzed based on the study design, main conclusions, and strength of evidence identified by the two authors who screened all the abstracts and full-text articles and, abstracted data, and performed quality assessments by using a critical appraisal tool, the Critical Appraisal Skills Programme Cohort Studies Checklists. A total of 18 articles (16 cross-sectional, 1 cohort studies, and 1 randomized controlled trial [RCT]) met our inclusion criteria and were evaluated. Poorer mastication was associated with obesity in 12 out of 16 cross-sectional studies. One cohort study showed that the obesity group displayed higher tooth loss than the normal weight group. One RCT demonstrated that gum-chewing intervention for 8 weeks significantly decreased waist circumference. Most studies revealed a positive association between mastication and obesity among adults. Nonetheless, most of them are cross-sectional studies, which are insufficient to demonstrate a causal relation. Further advancement requires RCT, especially an intervention of improvement of mastication and obesity needed to confirm this association.

As tooth loss is the high end of periodontal problems and edentulous individuals are at higher risk of nutritional problems like obesity, understanding the association between tooth loss and hypertension is important for improving cardiovascular health. We searched for publications from the last two decades using three electronic databases (PubMed, Web of Science and Scopus) and conducted a systematic review and meta-analysis on the association between tooth loss and hypertension according to PRISMA-P guidelines. Quality assessments were performed using the Newcastle–Ottawa Scale and the GRADE approach. Twenty-four studies (20 cross-sectional, and 4 cohort) met the inclusion criteria for this review. Most cross-sectional studies showed that subjects with more tooth loss exhibited a greater proportion of hypertension and higher systolic blood pressure than those with less tooth loss. Meta-analyses revealed a statistically significant association between tooth loss and hypertension. The pooled odds ratios of hypertension for having tooth loss with no tooth loss and for edentulous with dentate were 2.22 (95% CI 2.00–2.45) and 4.94 (95% CI 4.04–6.05), respectively. In cohort studies, subjects with more tooth loss had a greater incidence of hypertension than those with less tooth loss during the follow-up period. The present systematic review and meta-analysis suggests that tooth loss is associated with an increased risk of hypertension and higher systolic blood pressure.