Effects of Flavonoid-Containing Natural Products on Dentin Adhesion: A Literature Review

Flavonoid-containing natural products have gained increasing attention in restorative dentistry due to their potential to improve the durability of dentin bonding. The stability of the resin–dentin interface remains a critical challenge, as dentin’s hydrated and heterogeneous structure, along with enzymatic activity of matrix metalloproteinases (MMPs), contributes to hybrid layer degradation over time. Flavonoids, a group of polyphenolic compounds found in sources such as green tea, grape seed extract, and propolis, exhibit antioxidant, anti-inflammatory, and collagen-stabilizing properties that may enhance adhesive performance. These compounds improve dentin adhesion primarily through two mechanisms: collagen cross-linking and MMP inhibition. By reinforcing the collagen network, flavonoids increase its resistance to enzymatic degradation and improve resin infiltration stability. Additionally, flavonoids such as epigallocatechin gallate (EGCG) and proanthocyanidins suppress MMP activity, thereby reducing collagen breakdown within the hybrid layer. Experimental studies have demonstrated increased bond strength and improved resistance to aging procedures, including thermocycling and water storage, in dentin treated with flavonoid-rich solutions. However, despite promising laboratory findings, clinical evidence remains limited, and standardized application protocols have not yet been established. In conclusion, flavonoids represent promising natural biomodifiers that may enhance the longevity of adhesive restorations, although further clinical research is required to validate their routine use in dentistry.