Nanoleakage and microshear bond strength in deproteinized human dentin

Abstract

This study evaluated the influence of dentin deproteinization with NaOCl on the microshear bond strength (microSBS) and the nanoleakage patterns of three dentin bonding systems (DBS). Occlusal dentin surfaces, obtained from extracted noncarious human molars, were divided into two experimental groups, according to dentin surface treatment: Group I-37% H(3)PO(4)/15s and Group II-37% H(3)PO(4)/15s + 10% NaOCl/1 min. The dentin surfaces were bonded with one of the following DBS: Scotchbond Multipurpose-SBMP, Prime & Bond NT-PB and Clearfil SE Bond-SE. After 1 week storage in water at 37 degrees C, the specimens were subjected to the microSBS test. The data were analyzed by two-way ANOVA and Student-Newman-Keuls' test (p = 0.05). The nanoleakage was evaluated using scanning electron microscopy (SEM) in backscattered electron imaging regime. No significant difference in microSBS between dentin treatments was found for SBMP. For PB, microSBS increased after NaOCl dentin treatment. SE showed a reduction in microSBS in deproteinized specimens. SEM analysis showed different nanoleakage patterns for each DBS. Irrespective of dentin treatments, all SBMP specimens showed nanoleakage. SE did not show nanoleakage with the two dentin treatments. PB showed nanoleakage within the hybrid layer only in acid-etched specimens. The influence of dentin deproteinization was dependent on the dentin bonding system formulation.

Effect of Storage and Compressive Cycles on the Bond Strength After Collagen Removal

“…This better adaptation is supported by a previous study that verified a good adaptation of PBNT using nanoleakage. 15 These assumptions are also supported by two main outcomes in the current study. The first is related to maintenance of the µtbs values over time for the groups treated with NaOCl (comparing 2A and 2B; comparing 4A and 4B), which was not observed for the groups treated with the conventional technique (comparing 1A and 1B; comparing 3A and 3B).…”

“…30 These defects may be more susceptible to fracture caused by loading forces than fracture resulting from the aforementioned defects created within the resinous layer. On the other hand, for the NaOCl-treated group (Group 4A), mixed failures were predominant, and this effect is perhaps minimized due to 1) the lower amount of water (important to avoid the collapse of organic structure when using the conventional technique) caused by removal of the collagen fibrils, 15 2) the higher homogeneity of the resultant bonding interface, since the risk of solvent trapping is probably reduced 31-33 and 3) not using HEMA, known to be a very hydrophilic monomer. 2,4,[6][7]15 Furthermore, the higher amount of Ca ions from hydroxyapatite on the deproteinized dentin surface could increase the effectiveness of PENTA, as the interaction between these two components has already been described.…”

“…[19][20][21] The differences in the performance of adhesives in previous studies can be partially attributed to the variety of compositions tested (solvents and monomers, types and concentrations). 15,[22][23] This assumption is supported by studies which demonstrated that acetonebased adhesives had a significant increase in bond strength when applied on deproteinized dentin surfaces, as opposed to what happened with ethanol/ water-based adhesives, which showed significant reduction in bond strength. [16][17]24 Furthermore, a previous study concluded that NaOCl-treated dentin might be more compatible with hydrophobic resins than dentin treated by the conventional acid etching technique.…”

“…While some studies showed that deproteinization did not affect the bond strength of the adhesive systems, [13][14] other studies verified an increase in bond strength when the collagen was removed. [15][16][17][18] Consequently, this effect may be attributed to alterations in the collagen-depleted dentin surface, such as higher mineral content, increased tubular aperture and the appearance of secondary tubules in intertubular dentin. [19][20][21] The differences in the performance of adhesives in previous studies can be partially attributed to the variety of compositions tested (solvents and monomers, types and concentrations).…”

“…25 Consequently, adhesive systems that do not have HEMA in their compositions would be more efficient. 15 Since the presence of fewer hydrophilic monomers can be important for the formation of polymers that are less susceptible to hydrolytic degradation, the technique of collagen removal could be helpful in stabilizing bonding efficiency.…”