Inhibition of Enzymatic Degradation of Adhesive-Dentin Interfaces

TLDR

Adhesive procedures activate dentin‑associated MMPs, initiating bond degradation, while water sorption remains the main degradation mechanism and enzymes mainly affect etch‑and‑rinse adhesives. The study tested whether adding MMP inhibitors to adhesive primers could prevent enzymatic degradation and improve bond durability. Chlorhexidine (non‑specific) and SB‑3CT (MMP‑2/9‑specific) were incorporated into primers of gold‑standard etch‑and‑rinse and self‑etch adhesives. Gelatin zymography showed MMP‑2 release from the etch‑and‑rinse adhesive but not from the self‑etch adhesive, and the added inhibitors reduced bond degradation only for the etch‑and‑rinse adhesive.

Abstract

Adhesive procedures activate dentin-associated matrix metalloproteinases (MMPs), and so iatrogenically initiate bond degradation. We hypothesized that adding MMP inhibitors to adhesive primers may prevent this endogenous enzymatic degradation, thereby improving bond durability. A non-specific MMP inhibitor (chlorhexidine) and a MMP-2/9-specific inhibitor (SB-3CT) were admixed to the primers of an etch & rinse and a self-etch adhesive, both considered as gold-standard adhesives within their respective categories. For dentin powder exposed to the adhesives under clinical application conditions, gelatin zymography revealed the release of MMP-2 (not of MMP-9) by the etch & rinse adhesive, while no release of enzymes could be detected for the mild self-etch adhesive, most likely because of its limited dentin demineralization effect. The built-in MMP inhibitors appeared effective in reducing bond degradation only for the etch & rinse adhesive, and not for the self-etch adhesive. Water sorption of adhesive interfaces most likely remains the principal mechanism of bond degradation, while endogenous enzymes appear to contribute to bond degradation of only etch & rinse adhesives.