# Biomodification of dentin collagen with hydroalcoholic propolis extract: Impact on resin–dentin adhesion

## TL;DR

This study shows that hydroalcoholic propolis extract can improve the stability of dentin collagen and help maintain the bond between resin and dentin over time.

## Contribution

The novel use of hydroalcoholic propolis extract as a collagen cross-linking agent for dentin adhesion is demonstrated.

## Key findings

- 1% hydroalcoholic propolis extract significantly improved collagen cross-linking and elastic modulus.
- After 6 months, 1% HPE preserved microtensile bond strength better than lower concentrations and the control.
- Fourier-transform infrared spectroscopy confirmed enhanced cross-linking in treated groups.

## Abstract

This in vitro study evaluated the effect of hydroalcoholic propolis extract (HPE) as a collagen cross‐linking agent for preserving the dentin–adhesive interface. Dentin beams from human third molars were demineralized with 10% phosphoric acid and assigned to five treatments: distilled water (control), 6.5% grape seed extract (GSE), and HPE at 0.1%, 1%, or 10%. Elastic modulus (n = 10), dry mass variation (n = 10), and microtensile bond strength (µTBS, n = 8) were assessed after 24 h and after 6 months of storage. Collagen stability was analyzed using Fourier‐transform infrared spectroscopy (n = 10). Elastic modulus was evaluated using Kruskal–Wallis and Friedman tests, dry mass variation, and µTBS with linear mixed‐effects models. GSE produced the greatest increase in elastic modulus, followed by 1% and 0.1% HPE. After 6 months, all experimental groups maintained µTBS, except 0.1% HPE and the control, which showed reductions of approximately 30%. Spectroscopic analysis revealed increased Amide I and decreased Amide II bands in all treated groups, indicating enhanced collagen cross‐linking. Overall, HPE—particularly at 1%—improved dentin collagen stability and contributed to the preservation of the adhesive interface over time.