The Effects of Chlorhexedine Rinses in the Presence of a Plaque-free Zone Associated with Supragingival Plaque Formation

A plaque free zone (PFZ) is observed during early stages of supragingival plaque formation. Its disappearance is associated with plaque build-up and down-growth subgingivally. Objectives: the aim of the present study was to assess the effect of chlorhexedine on the presence of PFZ associated with supragingival plaque build-up. Material and Methods: Prior to the experiment a test panel was carried out to assess intra and inter-examiner variability. Ten male volunteers, average age 22 years, participated in two periods of plaque build-up with readings at 72 and 96 hours. Presence of plaque and PFZ were assessed by three clinicians. Intra-examiner agreement varied from 83% to 93%. Inter-examiner Kappa values between one reference examiner (RE) and the two others varied between 0.6 and 0.64. The rinsing experiment was then carried out in a crossover, double-blind study controlled by a quinine sulphate placebo. The same test panel, following a prophylaxis at start, rinsed twice daily with 15 ml of 0.12% chlorhexedine for 1 minute or the placebo. The presence of plaque and PFZ were assessed, by the RE, after 72 and 96 hours in the buccal aspects of teeth. Results were analyzed with the Wilcoxon test (p<0.05). Results: Chlorexedine was associated with significantly more plaque free areas or plaque with PFZ present as compared to the placebo rinses. Out of 357 surfaces examined, 202 were plaque free and 154 had plaque and PFZ 72 hours following rinses with chlorexedine. In contrast only 38 surfaces were plaque free and 77 surfaces had supragingival plaque extending subgingivally, i.e.without PFZ after placebo rinsing. After 96 hours 5.60% of the surfaces following chlorehexedine and 44,26% following quinine presented plaque extending subgingivally. Conclusion: it can be concluded that chlorehexedine inhibits the subgingival down-growth of supraginvival plaque as compared to a quinine placebo.