Relative risk for postoperative pneumonia in relation to periodontal diseases. Presence of periodontal diseases and disease severity were significantly greater in patients with postoperative pneumonia. (A-B): Data were expressed as "box and whiskers: 10–90 percentile" and compared using the non-parametric Mann-Whitney test (A): Disease score: periodontal diseases in every patient were evaluated. A score number was ordered to each diagnose, and the sum of the scores appears as "disease score". * = p = 0.0018 (B): Severity score is the number of co-existing periodontal diseases in each patient. * = p = 0.031; (C): Analysis of Relative Risk: "High score" patients had a Disease Score of ≥ 15 and a Severity Score of ≥ 3. Number of patients is shown in each groups. Chi-square test was performed, one-sided p value was calculated. *p < 0.0001; Relative risk: 3.5; confidence interval (95%): 1.085 to 11.29.