Relationship of cigarette smoking to the subgingival microbiota

Background: The relationship of cigarette smoking to the composition of the subgingival microbiota is not clear. Some studies indicated higher levels of certain species in smokers, while other studies failed to detect differe nces in the microbiota between subjects with different smoking histories. T hus, the purpose of the present investigation was to examine the prevalence , proportions and levels of the subgingival species in adult subjects who w ere current, past or never smokers. Method: 272 adult subjects ranging in age from 20-86 years with at least 20 teeth were recruited for study. Smoking history was obtained using a quest ionnaire. Clinical measures were taken at 6 sites per tooth at all teeth ex cluding third molars at a baseline visit. Subgingival plaque samples tr;ere taken from the mesial surface of all teeth excluding third molars in each subject at baseline and assayed individually for counts of 29 subgingival s pecies using checkerboard DNA-DNA hybridization. Subjects were subset accor ding to smoking history into never (n = 124), past (n = 98) and current smo kers (n = 50). Uni-variate and multi-variate analyses were used to seek ass ociations between smoking category and the counts, proportions and prevalen ce of subgingival species. Results: Greater differences were observed for the prevalence (% of sites c olonized) of the test species in the 3 smoking groups than were observed fo r counts or proportions of total counts. Members of the orange and red comp lexes including E. nodatum, F. nucleatum ss vincentii, P. intermedia, P. mi cros, P. nigrescens, B. forsythus, P. gingivalis and T. denticola were sign ificantly more prevalent in current smokers than in the other 2 groups. The difference in prevalence between smokers and non-smokers was due to greate r colonization at sites with pocket depth <4 mm. Stepwise multiple linear r egression analysis indicated that combinations of the prevalence of 5 micro bial species and pack years accounted for 44% of the variance for mean pack et depth (p < 0.000001), while the prevalence of 3 microbial taxa along wit h age, pack years, current smoking and gender accounted for 31% of the vari ance in mean attachment level (p < 0.000001). The difference in prevalence between current and never smokers of all members of the red complex and 8 o f 12 members of the orange complex was significantly greater in the maxilla than in the mandible. Conclusions: The major difference between the subgingival microbiota in sub jects with different smoking history nas in the prevalence of species rathe r than counts or proportions. The greater extent of colonization in smokers appeared to be due to greater colonization at pocket depths <4 mm. Differe nces in colonization patterns between current and never smokers were greate r in the maxilla than in the mandible.