Effects of a chlorhexidine varnish on the mutans streptococci and on dental caries

The purpose of this study was to determine the effects of a chlorhexidine varnish-sealant on the mutans streptococci and on caries outcome variables, in 113 female school-children 10 to 15 years-old, in Rio de Janeiro, Brazil. Subjects were randomly allocated to control (C) and treatment (T) groups, n=55 and n=58, respectively. At baseline the number of decayed, restored, and white spot lesions on teeth surfaces was determined by a calibrated examiner, and the salivary levels of the mutans streptococci were assessed with a dip-slide test. Both groups had their existing carious lesions restored and they were given a prophylaxis. Subjects who belonged to the T group had a 10% chlorhexidine varnish-sealant applied to their entire dentition once or twice (with a 1 week interval) if they had = or smaller then 2.5 x 10^5 CFU of mutans streptococci/dip-slide, respectively. The same procedures performed at baseline were performed after 3 months for each group. After 6 months all subjects received caries examination and salivary analysis for the mutans streptococci. Results showed significantly lower levels of the mutans streptococci in the T group when compared to the C group after 6 months (p less then 0.0001). No significant differences were observed between T and C groups from baseline to 6-month examinations in caries scores. Treatment group was the only predictor (p less then 0.0001-final model) of the salivary levels of the mutans streptococci after 6 months. It is concluded that the use of a chlorhexidine varnish-sealant in the T group when compared to the C group had a significant effect in reducing the levels of the mutans streptococci after 6 months which could not be translated into a significant effect on caries outcome variables when T and C groups were compared. Therefore, we suggest that protocols with multiple applications of chlorhexidine varnishes for a finite period of time may be necessary in longitudinal studies of the effects of chlorhexidine varnishes on the mutans streptococci and on caries outcome variables.