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 differences in the microbiota between subjects with different smoking histories. Thus, the purpose of the present investigation was to examine the prevalence, proportions and levels of the subgingival species in adult subjects who were 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 questionnaire. Clinical measures were taken at 6 sites per tooth at all teeth excluding third molars at a baseline visit. Subgingival plaque samples were taken from the mesial surface of all teeth excluding third molars in each subject at baseline and assayed individually for counts of 29 subgingival species using checkerboard DNA-DNA hybridization. Subjects were subset according to smoking history into never (n=124), past (n=98) and current smokers (n=50). Uni-variate and multi-variate analyses were used to seek associations between smoking category and the counts, proportions and prevalence of subgingival species. RESULTS: Greater differences were observed for the prevalence (% of sites colonized) of the test species in the 3 smoking groups than were observed for counts or proportions of total counts. Members of the orange and red complexes including E. nodatum, F. nucleatum ss vincentii, P. intermedia, P. micros, P. nigrescens, B. forsythus, P. gingivalis and T. denticola were significantly more prevalent in current smokers than in the other 2 groups. The difference in prevalence between smokers and non-smokers was due to greater colonization at sites with pocket depth <4 mm. Stepwise multiple linear regression analysis indicated that combinations of the prevalence of 5 microbial species and pack years accounted for 44% of the variance for mean pocket depth (p<0.000001), while the prevalence of 3 microbial taxa along with age, pack years, current smoking and gender accounted for 31% of the variance 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 of 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 subjects with different smoking history was in the prevalence of species rather than counts or proportions. The greater extent of colonization in smokers appeared to be due to greater colonization at pocket depths <4 mm. Differences in colonization patterns between current and never smokers were greater in the maxilla than in the mandible.