BACKGROUND: The effects of pro-inflammatory diets, as measured by the Dietary Inflammatory Index (DII), on periodontal disease among Americans have not been evaluated. OBJECTIVE: This study examines whether the DII is associated with periodontitis in U.S. adults participating in the National Health and Nutrition Examination Surveys (NHANES) 2009-2014. In particular, it evaluates whether an anti-inflammatory dietary pattern is associated with lower prevalence of periodontitis in NHANES and lower severity of periodontitis. METHODS: Dietary Inflammatory Index score was derived from taking the mean of two 24-hour dietary recall interviews. The sample population included 7,480 subjects (3,628 men and 3,852 women), who were 30-80 years old from all racial/ethnic groups. The exclusion criteria were incomplete or missing data regarding clinical periodontal and dental examinations. In addition, participants were also excluded who had diabetes, cancer, pregnancy or breastfeeding status, unreliable dietary information, or elevated alcohol intake. The DII score was classified as Low DII/anti-inflammatory (DII: -5.16≤DII≤0.54) and High DII/pro-inflammatory (DII: 0.54<DII≤4.82). Outcome was measured using case definitions of periodontitis and classified as mild, moderate, severe, and total periodontitis. The prevalence for each was calculated in the overall sample population and sex-specific subgroups. Logistic regression models were used to calculate crude ORs (and 95% CI) for the presence of total periodontitis. Multivariate regression analysis was used to adjust for age, sex, alcohol consumption, and smoking. Chi-square test was used to calculate the ORs for mild, moderate, and severe periodontitis. RESULTS: The prevalence of total periodontitis among subjects with Low DII is 42% and the prevalence of total periodontitis among subjects with High DII is 47.5%. The prevalence of total periodontitis among men with Low DII is 49.8%, while the prevalence of total periodontitis among men with High DII is 57.7%. The prevalence is 32.1% and 41.4% for women with Low DII and High DII, respectively. Based on adjusted logistic regression models, consuming a diet that scores High DII results in 35% increased risk of total periodontitis; for men the risk is 25% and for women 44%. Based on the subtype analysis, consuming a diet that scores High DII results in a statistically significant 21% increased risk of moderated periodontitis and 48% increased risk of severe periodontitis. CONCLUSIONS: Pro-inflammatory diet (High DII) is associated with higher prevalence of moderate, severe, and total periodontitis in both men and women. The prevalence of mild periodontitis is higher among women adhering to High DII, but not among men. The overall cohort has increased odds of having moderate, severe, and total periodontitis when consuming pro-inflammatory foods and nutrients, with women being at greater risk for total periodontitis. Subjects whose diet was pro-inflammatory had statistically-significant increased risk of having moderate or severe periodontitis, but not mild.