The effect of 0.12% chlorhexidine gluconate rinsing on previously plaque-free and plaque-covered surfaces: a randomized, controlled clinical trial.

BACKGROUND Previous in vitro studies showed little bactericidal effect on structured oral biofilm after exposure to chlorhexidine (CHX). In vivo evidence of a CHX effect against structured biofilm is scarce. The purpose of this study was to compare the efficacy of 0.12% CHX gluconate on previously plaque-free and plaque-covered surfaces. METHODS This study had a single-masked, randomized split-mouth, 21-day experimental gingivitis design including 20 individuals who refrained from all mechanical plaque control methods for 25 days. On day 4 of plaque accumulation, the individuals had two randomized quadrants cleaned; the other two quadrants served as the plaque-covered surfaces. Also, on day 4, the individuals started rinsing with 0.12% CHX gluconate for 21 days. The Quigley and Hein plaque index (PI), gingival index (GI), and gingival crevicular fluid (GCF) volume were assessed at baseline and days 21 and 25. The PI also was assessed at days 4, 11, and 18. RESULTS Intergroup comparisons showed statistically higher PI throughout the study on the plaque-covered surfaces compared to the plaque-free surfaces. When the inflammatory response over time was analyzed, a statistically greater increase in GI (from 0.21+/-0.02 to 0.93+/-0.03 versus from 0.18+/-0.01 to 0.52+/-0.03 on plaque-covered and plaque-free surfaces, respectively) and GCF volumes (from 48.09 to 94.28 microl versus from 46.94 to 64.99 microl on plaque-covered and plaque-free surfaces, respectively) occurred on plaque-covered surfaces after 21 days of plaque accumulation. CONCLUSIONS A 0.12% CHX gluconate mouthrinse had little antiplaque and antigingivitis effect on previously plaque-covered surfaces. These results confirm the diminished effect of CHX on structured biofilm and reinforce the necessity of biofilm disruption before the initiation of CHX mouthrinse.