Brazilian red propolis as a potential antimicrobial additive in orthodontic primers

This study evaluated the effect of adding ethanolic extract of red propolis (EERP) on antimicrobial activity, polymerization kinetics (PK), degree of conversion (DC), and shear bond strength (SBS) of the orthodontic adhesive system. Transbond XT Primer was the control group (G1). The experimental adhesives contained 3.25 mg/mL (G2) and 6.50 mg/mL (G3) EERP. Minimum inhibitory concentration and biofilm assay against Streptococcus mutans, and bacterial and exopolysaccharide (EPS) evaluation by confocal laser scanning microscope were performed. PK and DC were evaluated by Fourier Transform Infrared Spectroscopy. The bracket-tooth SBS was evaluated by a universal testing machine. Both antimicrobial and SBS results were analyzed by ANOVA and Tukey's post-hoc test (p<0.05). PK and DC data were submitted to ANOVA and Bonferroni post-hoc test. G3 presented better antimicrobial activity, inhibiting more than 95% of planktonic S. Mutans, 25% of biofilm dry-weight, and 50% of EPS production (p<0.05). PK was different among the groups. DC after 40 seconds of photoactivation ranged from 68.62% for G1 to 76.85% for G2 (p<0.05). SBS data was not presented as statistically significant (p>0.05). Transbond XT Primer modified with 6.5 mg/mL EERP demonstrated antimicrobial activity with no reduction of the bracket-tooth SBS. Propolis-modification did not influence the physic-chemical properties of the orthodontic adhesive.