Patients with chronic gum disease who quit smoking in addition to undergoing nonsurgical therapy not only demonstrated a lower abundance of harmful oral pathogens, but also an increase in health-associated bacteria. The researchers from The Ohio State University, Columbus Ohio, and Newcastle University, United Kingdom report their findings in the July 2010 issue of the Journal of Clinical Microbiology.

It is well established that oral bacteria play an important role in the origin of chronic gum disease and that smoking tobacco contributes to a pathogen rich environment. Although prior studies indicate that quitting smoking can alter the oral microbial community, it is unknown if pathogenic colonization can actually be reversed.

In order to determine the effect of quitting smoking on select oral bacteria researchers launched a long-term study, at the beginning of which, plaque samples were collected from 22 initial smokers. Twelve months following nonsurgical periodontal therapy and counseling samples were again taken from all 22 participants, however, 11 were quitters and 11 still smoked. Results showed decreased levels in various bacterial pathogens as well as an increase in health-associated species in those patients who no longer smoked.

“Following nonsurgical periodontal therapy and smoking cessation, the subgingival microbiome is recolonized by a greater number of health-associated species and there are a significantly lower prevalence and abundance of putative periodontal pathogens,” say the researchers. “These results indicate a critical role for smoking cessation counseling in periodontal therapy for smokers in order to effectively alter the subgingival microbiome.”

(S.L. Delima, R.K. McBride, P.M. Preshaw, P.A. Heasman, P.S. Kumar. 2010. Response of subgingival bacteria to smoking cessation. Journal of Clinical Microbiology, 48. 7: 2344-2349.)