Influence of repeated chlorhexidine varnish applications on mutans streptococci counts and caries increment in patients treated with fixed orthodontic appliances.

The occurrence of new carious lesions is among the most detrimental side effects in subjects undergoing orthodontic therapy with fixed appliances. The present study evaluated the efficacy of repeated applications of a 40% chlorhexidine varnish in this patient group with regard to long-term suppression of elevated mutans streptococci levels and the frequency and location of new carious lesions. Thirty-three prospective orthodontic patients age 11 to 18 harboring more than 10(5) mutans streptococci per ml saliva at the initial examination participated in the study. At baseline the previous carious involvement in each subject was recorded using the DMFS index, and extensive information on caries prevention was given. Using a random assignment 18 subjects were included in the test group while the remaining 15 subjects were assigned to the placebo group. From the time of banding until removal of the fixed appliances (median: 21 months) salivary mutans streptococci counts were recorded once every 8 weeks in both groups. At the same appointments all teeth and introaral appliances in the test group were coated with a 40% chlorhexidine varnish. Subjects in the placebo group were treated in the same way, using a placebo varnish with the same varnish base. After debanding, the DMFS score of each participant was recorded again. Analysis of the data revealed that mutans streptococci counts in the test group were only temporarily suppressed and were restored almost to baseline levels by the end of the study. In both groups a clinically relevant increase in the average DMFS score was recorded. Inter-group differencies were not significant.