Effect of chlorhexidine varnish application on mutans streptococci counts in orthodontic patients

Introduction: Enamel demineralization occurs frequently around orthodontic brackets. High levels of mutans streptococci (MS) increase the risk of caries. The hypotheses tested in this study were that high-frequency application of 40% chlorhexidine varnish (40%CHX) results in lower levels of MS in plaque of orthodontic patients compared with low-frequency application, and that bimonthly application of 40%CHX results in lower levels of MS in plaque compared with 1% chlorhexidine/1% thymol varnish (1%CHX). Methods: Eighty adolescent patients were randomly allocated to 4 treatment groups: monthly, bimonthly, and quarterly 40%CHX application, and bimonthly application of 1%CHX. Plaque samples were collected monthly and processed for MS counts. Twenty patients dropped out before the evaluation time at 1 month. Data from the remaining 60 adolescents were analyzed by using linear regression models with the plaque bacterial ratio (PBRx) as the dependent variable. The trial was ended after 5 months because of a high number of dropouts. Results: High-frequency application of 40%CHX did not provide lower mean PBRx than low-frequency application. Mean PBRx after 40%CHX application was lower than 1%CHX after 1 month (P = .002). This reduction was undiscernible 2 months after the application. Conclusions: 40%CHX application results in greater reduction of MS in plaque than 1%CHX a month after application. A follow-up study with a larger study population is warranted to test the first hypothesis.