Background: An association between periodontal disease and metabolic syndrome based on cross‐sectional and case‐control studies was recently reported, but their causal relationship has not been fully clarified. The objective of this cohort study is to investigate the association between periodontal disease and changes in metabolic‐syndrome components to accumulate evidence of the causal relationship between the two conditions.Methods: The study subjects consisted of 1,023 adult employees (727 males and 296 females; mean age: 37.3 years) who underwent medical and dental checkups between 2002 and 2006 and in whom all metabolic‐syndrome components were within the standard values in 2002. The association between the presence of periodontal pockets and the positive conversion of metabolic‐syndrome components was investigated using multiple logistic‐regression analysis, odds ratios (ORs), and 95% confidence intervals (CIs).Results: The presence of periodontal pockets was associated with a positive conversion of one or more metabolic components during the 4‐year observation period (OR: 1.6; 95% CI: 1.1 to 2.2). The ORs for a positive conversion of one component and two or more components were 1.4 (95% CI: 1.0 to 2.1) and 2.2 (95% CI: 1.1 to 4.1), respectively, and the difference was significant for two or more positive components. Of the metabolic‐syndrome components, positive conversions of blood pressure and the blood‐lipid index were significantly associated with the presence of periodontal pockets.Conclusion: The presence of periodontal pockets was associated with a positive conversion of metabolic‐syndrome components, suggesting that preventing periodontal disease may prevent metabolic syndrome.

To clarify the basic properties of a color-changeable chewing gum to determine its applicability to evaluations of masticatory performance under different types of dental status. Ten participants with natural dentition aged 26-30 years chewed gum that changes color during several chewing strokes over five repetitions. Changes in color were assessed using a colorimeter, and then L*, a*, and b* values in the CIELAB color system were quantified. Relationships between chewing progression and color changes were assessed using regression analysis and the reliability of color changes was assessed using intraclass correlation coefficients. We then measured 42 dentate participants (age, 22-31 years) and 47 complete denture wearers (age, 44-90 years) to determine the detectability of masticatory performance under two types of dental status. Regression between the number of chewing strokes and the difference between two colors was non-linear. The intraclass correlation coefficients were highest between 60 and 160 chewing strokes. Dentate and edentulous groups significantly differed (Wilcoxon rank sum test) and values were widely distributed within each group. The color of the chewing gum changed over a wide range, which was sufficient to evaluate the masticatory performance of individuals with natural dentition and those with complete dentures. Changes in the color values of the gum reliably reflected masticatory performance. These findings indicate that the color-changeable chewing gum will be useful for evaluating masticatory performance under any dental status.