Strategies for flavonoid application on etched dentin: Bond stability, enzymatic activity, and biofilm inhibition

This study evaluated the effects of different flavonoid application strategies either as dentin primers or incorporated into a universal adhesive system (SFA) on microtensile bond strength (μTBS), matrix metalloproteinase (MMP) inhibition, biofilm formation, and degree of conversion.

Baicalein, kaempferol, and naringin were tested at 20 mM, either incorporated into a commercial adhesive or dissolved in 50 % ethanol and applied as primers, forming six experimental groups. Three controls were used: Negative (commercial adhesive), Positive (0.2 % chlorhexidine), and Ethanol (50 %). Dentin specimens were analyzed for μTBS (n = 10), dentin-adhesive interface morphology (DAM) (n = 3), and in situ zymography (n = 3). Streptococcus mutans biofilm was grown on adhesive surfaces to assess bacterial viability, and FTIR spectroscopy evaluated the degree of conversion. μTBS data were analyzed using generalized linear models; other data were analyzed by one-way ANOVA followed by Bonferroni or Tukey tests (α = 0.05).

All flavonoid-treated groups showed significantly higher μTBS than the Negative Control after one year. Adhesives with incorporated flavonoids also outperformed the Positive Control. No adverse effects were observed on DAM, bacterial viability, or degree of conversion. All SFA strategies reduced MMP activity, with complete inhibition seen only in the Baicalein primer group.

The use of flavonoids, either as a dentin primer or incorporated into adhesives, offers clinicians a simple and effective strategy to enhance the longevity of adhesive restorations by stabilizing the hybrid layer and reducing collagen degradation without altering application protocols or compromising material performance.