Efficacy of propolis varnish in reducing Streptococcus mutans counts

Aim: To evaluate the efficacy of experimental propolis varnish containing 15% green propolis in reducing Streptococcus mutans (SM) from saliva and dental biofilms. Methods: Patients aged 8–11 years were recruited from a preventive program. After prophylaxis, propolis varnish was applied to collect saliva and biofilm samples at regular times (baseline/T0, 2nd day/T1, 3rd day/T2, 4th day/T3, 5th day/T4, 10th day/T5, 15th day/T6, and 30th day/T7). After each sampling, stimulated whole saliva was homogenized for 30 s, and tenfold serial dilutions in saline were plated on mitis-salivarius-bacitracin (MSB) agar and incubated at 37°C for 48 h. Colonies with typical morphology were counted, and the number of colony-forming units (CFU)/mL was compared via an independent sample t test. For quantitative real-time PCR (qPCR), the data were statistically analysed via one-way ANOVA with the Holm‒Sidak post hoc test. Results: There was a significant difference in salivary SM levels between T0/T1 (baseline/2nd day) and T1/T7 (2nd day/30th day), but no difference was observed from the 3rd day onwards. The qPCR results also revealed a decrease in the number of SMs in the biofilm in the first days after varnish application. Conclusions: A single application of green propolis varnish reduced SM in saliva and biofilms for three days. Whether these findings affect the incidence of caries needs to be confirmed through studies, which may improve the original formulation (International Clinical Trials Registry Platform registration code: NCT02052973).