Importance of the hybrid layer on the bond strength of restorations subjected to cyclic loading

Abstract

The present study evaluated the long-term microtensile bond strength of collagen-depleted dentin followed by cyclic loading. Bovine flat, midcoronal dentin received one of the following surface treatments: acid-etch or acid-etched + 5% NaOCl for 2 min. The teeth were restored with Single Bond, Scotchbond Multi-purpose, One-Step Plus, or All-Bond 2 adhesive systems. Half of the specimens were randomly assigned to receive 200,000 cycles (50 N force). Teeth were sectioned into 1 x 1 mm thick slices and stored for 24 h, 1 month, 3 months, or 6 months. Specimens were subjected to tensile testing after elapsed storage time. Samples were analyzed by three-way ANOVA and Fisher's PLSD (p < 0.05). The results showed that the deproteinized groups without cyclic loading presented lower bond strength when compared with the control group, but the difference was only statistically significant for Single Bond and All-Bond 2 (p < 0.05). All adhesives presented a decrease in bond strength over time, regardless of the dentin treatment. When cyclic loaded, the decrease in bond strength for the deproteinized group was even greater when compared with the control group (p < 0.05). The results suggest that the hybrid layer is important as a stress-buffering layer when loading is applied, and thus the presence of collagen is essential.

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

“…The total depth of dentin demineralization is not fully infiltrated by monomers, which leaves an exposed collagen network, susceptible to hydrolytic degradation over time [9]. The removal of dentin matrix, the so-called deproteinization, has already been proposed as a possible treatment to increase bond strength longevity and decrease technique sensitivity [7, 22]. However, a long-term study revealed decrease in the deproteinized dentin-resin bonds [22].…”

“…However, a long-term study revealed decrease in the deproteinized dentin-resin bonds [22]. In addition, the HL is believed to be important as a stress-buffering layer under mechanical loading [7]. Thus a stronger, stable, and resistant collagen layer is more suited substrate for current dental adhesive restorations.…”

“…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 disorganization of collagen fibrils and consequent degradation of the HL [10].…”

Biofilm Formation within the Interface of Bovine Root Dentin Treated with Conjugated Chitosan and Sealer Containing Chitosan Nanoparticles

“…Use of the chemostat-based biofilm fermentor in this study was based on our group's previously established non-destructive experimental model (21), which was subsequently adapted for assessment of the interface of root canal sealers with root dentin in simulation of intraoral pathogenic conditions (22). Unlike in the previous studies (24, 25), bovine roots were used in the current study, because their large canals facilitated standardized application of surface treatments with CSRB and PHCS. Also, the large canals could be bored to produce parallel walls, in order to maximize the focal depth of CLSM while accounting for the transparency of materials (26).…”

Deproteinization stabilises dentin bonding of self-adhesive resin cements after thermocycling

“…Previous reports stated that this adhesive is not capable of effectively filling the pores created by the sodium hypochlorite because its slow diffusion [35,36]. For etch-and-rinse adhesives, such as Single Bond 2, the hybrid layer represents the principal mechanism of adhesion [37][38][39]. Therefore, the presence of collagen is pivotal.…”