The contribution of different types of polyphenols to bonding performance by enhancing the stabilization of the hybrid layer

Objectives This study aims to investigate how the molecular weight, steric hindrance, number of phenolic hydroxyl groups, and their spatial arrangement in four polyphenols influence the inhibition of matrix metalloproteinase (MMP) activity and the promotion of collagen cross-linking and remineralization through polyphenol pre-treatment, and further analyze how these effects enhance the stability of the hybrid layer. Materials and methods Resin-dentin bonding specimens, collagen membranes, and demineralized dentin slices were prepared with/without pretreatment using four polyphenols: myricetin, resveratrol, proanthocyanidins (PA), and tannic acid, representing stilbenes, flavonoids, condensed tannins, and tannins. Then the microtensile bond strength (µTBS), nanoleakage, and in situ zymography were evaluated. The ability of polyphenols to inhibit MMP activity, promote collagen cross-linking and remineralization was assessed through quantitative MMP activity assays, hydroxyproline assays, cross-linking degree measurements, transmission electron microscopy (TEM), Zeta potential measurements, X-ray diffraction (XRD), and attenuated total reflectance-fourier transform infrared spectroscopy (ATR-FTIR). Results Among the four polyphenols, PA and myricetin demonstrated the strongest bonding enhancement by significantly increasing µTBS, reducing nanoleakage, and inhibiting MMP-9. PA and tannic acid were the most effective in promoting collagen cross-linking, while PA and myricetin showed the best remineralization capacity. Conclusions All four polyphenols promoted collagen cross-linking, inhibited MMP activity, and enhanced remineralization; PA and myricetin ultimately led to more significant increases in µTBS and reductions in nanoleakage. Clinical relevance PA and myricetin have better capabilities for enhancing bonding durability, which is very valuable for future screening of suitable polyphenols and even designing and synthesizing better-performing polyphenol structures artificially.