Effect of Chlorhexidine Varnish on Mutans Streptococci Counts

None of the studies on the recovery of mutans streptococci (MS) in plaque after chlorhexidine varnish application had follow-up periods exceeding 5 months. Objectives: To assess the duration of suppression of MS in pit and fissure plaque of permanent first molars of 6-7-year-old children after 40% chlorhexidine varnish (EC40) application over an evaluation period of 9 months and to compare the MS inhibiting effect of two application schemes of EC40. Methods: Using a split mouth design, test tooth received EC40 application on occlusal surfaces and pits. EC40 (Group A; n=31) was applied at baseline, 6, 12 and 18 months. Group B children (n=37) received EC40 application at baseline, 3, 12 and 15 months. For group C (n=33) children, one test molar received EC40 with the application frequency of group A, and the contra-lateral molar received the varnish with the application frequency of group B. Plaque samples were taken from pits and fissures of test and control permanent first molars at baseline, 6, 9, 12 and 24 months. A mixed ANOVA model was used to analyse the data. Results: Three and 6 months after the last EC40 application, MS counts were statistically significantly reduced, but 9 months after the last EC40 application MS counts were back to baseline and control site level. Twice application of EC40 (B) instead of one application within 3 months (A) had not a statistically significant different inhibiting effect on MS. Conclusions: EC40 application on pits and fissures of permanent first molars of 6-7-year-old children can significantly reduce MS in pits and fissure plaque for up to 6 months.