AN APPROACH TO DIFFERENTIATE BETWEEN ANTIBACTERIAL AND ANTIADHESIVE EFFECTS OF MOUTHRINSES IN-VIVO

An experimental set-up allowing differentiation in vivo between antiba cterial and antiadhesive properties of mouthrinses is described. The p ercentage of vital bacteria (= microbial vitality) and the bacterial c ounts were microscopically evaluated in saliva and in supragingival de ntal plaque both collected simultaneously at various times during de n ovo plaque formation. In a cross-over design, 12 healthy participants refrained from all oral hygiene for four separate periods of 2 x 4 h a nd 2 x 72 h after having rinsed with either an amine fluoride/stannous fluoride solution (Meridol(R)) or 0.9% NaCl (placebo). Stimulated who le saliva was collected before and after the rinse. Together with whol e-saliva samples, representative 4, 24 and 72-h-old plaque samples wer e separately taken from defined vestibular tooth surfaces that had bee n either exposed to the mouthrinse (unprotected sites) or temporarily covered with inert plastic films (protected sites) during rinsing. The pooled plaque and saliva were stained with fluorescent dyes to differ entiate vital from dead micro-organisms which permitted the estimation of the percentages of vital bacteria. The total bacterial counts were quantified under the darkfield microscope. The Wilcoxon lest was used for selected pairwise comparisons (alpha = 0.05). The percentage of v ital bacteria in saliva fell significantly from 80-95% to about 50-60% as a result of the antibacterial activity of the test solution. These baseline values and those found in the presence of 4 and 24-h-old pla que were frequently lower than those recorded after the placebo rinse. In comparison to the placebo, microbial vitality was significantly re duced in early supragingival plaque formed on unprotected sites after applying the test solution. The similar total bacterial counts in 4-h- old plaque recorded after the use of the test solution on the unprotec ted and the protected areas did not point to an antiadhesive effect of the agent. It is concluded that this new experimental set-up allows d ecoding of the mode of action of a mouthrinse. (C) 1998 Elsevier Scien ce Ltd. All rights reserved.