Effect of Dentin Biomodification Using Naturally Derived Collagen Cross-Linkers: One-Year Bond Strength Study

Purpose. This study investigated the long-term resin-dentin bond strength of dentin biomodified by proanthocyanidin-rich (PA) agents. Materials and Methods. Forty molars had their coronal dentin exposed, etched, and treated for 10 minutes with 6.5% grape seed extract (GSE), 6.5% cocoa seed extract ethanol-water (CSE-ET), 6.5% cocoa seed extract acetone-water (CSE-AC), and distilled water (CO). Samples were restored either with One-Step Plus (OS) or Adper Single-Bond Plus (SB). Bond strength test was performed immediately or after 3, 6, and 12 months. Results. Higher μTBS were observed for GSE immediately (SB- 62.9？MPa; OS- 51.9？MPa) when compared to CSE-ET (SB- 56.95？MPa; OS- 60.28？MPa), CSE-AC (SB- 49.97？MPa; OS- 54.44？MPa), and CO (SB- 52.0？MPa; OS- 44.0？MPa) ( ). CSE outcomes were adhesive system and solvent dependant. After 12 months storage SB results showed no difference among treatment types (GSE- 57.15？MPa; CSE/ET- 54.04？MPa; CSE/AC- 48.22？MPa; CO- 51.68？MPa; ),while OS results where treatment dependent (GSE- 42.62？MPa; CSE/ET- 44.06？MPa; CSE/AC- 41.30？MPa; CO- 36.85？MPa; ). Conclusions. GSE and CSE-ET agents provided enhanced immediate adhesion and stabilization to demineralized dentin after long-term storage, depending on adhesive system. 1. Introduction The presence of cross-links in solubilized collagen provides strength, reinforcement, and stabilization to the fibrils [1] and is important feature of the use of collagen as biomaterial [2]. Collagen cross-links can be induced by either physical or chemical reagents; however, biocompatibility and low cytotoxicity are essential properties [3]. A more resistant, stable, and insoluble network is an important feature for a specific biofunction of collagen to serve as a stable substrate for dental adhesive restorations [4]. Type I collagen is the main constituent of the dentin matrix, and collagen fibrils of the mantle and intertubular dentin occupy most of the space filled by extracellular dentin matrix [5]. The three-dimensional network of demineralized collagen following acid etching serves as substrate for the application of primers or adhesive resins that infiltrate the interfibrillar spaces and promote mechanical retention, via hybrid layer (HL) formation after resin polymerization [6]. The stability of the adhesive interface relies on a compact and homogenous HL [7]. The incomplete infiltration and encapsulation of collagen fibrils by resin monomers [8], the elution of unpolymerized resin monomers overtime, and factors inherent to the oral environment [9] can cause exposure and