The effect of cigarette smoking on gingival bleeding

Background: The purpose of this study was to investigate the dose-dependent effect of cigarette smoking upon gingival bleeding on probing (BOP) in a large representative sample of the United States population (National Health and Nutrition Examination Survey III). Methods: Weighted multiple logistic regression was used to model bleeding on probing of 141,967 mesio-buccal sites in 12,385 individuals with complete case records on all covariates. Adjustments were made for age, gender, race/ethnicity, number of missing teeth, tooth type/jaw, root caries, full crown coverage, socioeconomic status (poverty/income ratio), and survey characteristics. The model stratified by presence of calculus (CALC) and increased probing depth (PD greater than or equal to4 mm). Generalized estimating equations were used to account for dependence of sites within subjects. Results: Smoking had a strong suppressive effect on gingival bleeding. The effect was strongest in heavier smokers (>10 cigarettes/day) and smallest in former smokers. In healthy sites (no CALC, PD: 3 mm), the odds ratio (OR) of bleeding for sites in heavier smokers compared to never-smokers was 0.56 (95% CI: 0.45-0.70). Sites with CALC and/or PD greater than or equal to4 mm were more likely to bleed in never-smokers (OR: 5.7; 95% CI: 4.3-7.6). This relationship was less evident among heavier smokers (OR: 1.3; 95% CI: 0.8-1.9). The effect of smoking did not differ between maxillary and mandibular molars, premolars, or incisors. Conclusion: Smoking exerts a strong, chronic, and dose-dependent suppressive effect on gingival bleeding on probing.