Microbiologic changes following administration of locally delivered doxycycline in smokers: A 15-month follow-up

Background: Additional clinical benefits have been reported with the use of locally delivered antimicrobials in the treatment of smokers; however, long-term changes in the subgingival microbiota following the use of these drugs in smokers have not been documented. The aim of this study was to evaluate long-term microbiologic changes following locally delivered doxycycline in the treatment of smokers. Methods: Sixteen smokers with chronic periodontitis presenting a minimum of four pockets (probing depth ≥5 mm) were selected. Patients were assigned randomly to receive scaling and root planing (SRP) or SRP and local doxycycline (SRP-D). Patients were treated at baseline and 12 months. Subgingival plaque samples were collected at baseline; 3, 6, and 12 months; and 45 and 90 days following retreatment. Polymerase chain reaction and DNA-DNA hybridization analyses were performed to detect the presence of selected periodontal pathogens. Results: The reduction in the number of sites positive for Porphyromonas gingivalis and Tannerella forsythia (previously T. forsythensis) was statistically significant for SRP-D at 3 months (68% and 41.3%, respectively) and for SRP at 6 months (75% and 52%, respectively) following treatment. The SRP group showed a greater frequency of P. gingivalis than the SRP-D group at 3 months (58% and 25%, respectively). There also was a greater reduction in the frequency of P. gingivalis at 3 months following retreatment with SRP-D compared to SRP (47% and 8%, respectively). Conclusion: In smokers, adjunctive local doxycycline resulted in a greater reduction in the frequency of P. gingivalis following initial and supportive therapy compared to conventional treatment.