Hydrolytic Stability of Self-etch Adhesives Bonded to Dentin

TLDR

Functional monomers, especially 10‑MDP, chemically interact with hydroxyapatite in hybrid layers of mild self‑etch adhesives, with 10‑MDP’s calcium salt showing superior hydrolytic stability compared to 4‑MET and phenyl‑P. We investigated whether additional chemical interaction of self‑etch adhesives improves bond stability. The study found that the 10‑MDP–based adhesive maintained micro‑tensile bond strength and interfacial integrity after 100,000 thermocycles, whereas 4‑MET and phenyl‑P adhesives degraded, confirming that long‑term durability depends on the functional monomer’s chemical bonding potential.

Abstract

Functional monomers chemically interact with hydroxyapatite that remains within submicron hybrid layers produced by mild self-etch adhesives. The functional monomer 10-MDP interacts most intensively with hydroxyapatite, and its calcium salt appeared most hydrolytically stable, as compared with 4-MET and phenyl-P. We investigated the hypothesis that additional chemical interaction of self-etch adhesives improves bond stability. The micro-tensile bond strength (μTBS) of the 10-MDP-based adhesive did not decrease significantly after 100,000 cycles, but did after 50,000 and 30,000 cycles, respectively, for the 4-MET-based and the phenyl-P-based adhesives. Likewise, the interfacial ultrastructure was unchanged after 100,000 thermocycles for the 10-MDP-based adhesive, while that of both the 4-MET- and phenyl-P-based adhesives contained voids and less-defined collagen. The findings of this study support the concept that long-term durability of adhesive-dentin bonds depends on the chemical bonding potential of the functional monomer.