Durability of solvent-free one-step self-etch adhesive under simulated intrapulpal pressure

Effect of air-blowing temperature and water storage time on the bond strength of five universal adhesive systems to dentin

The purpose of this study was to evaluate the air-blowing temperature and water storage time on the micro-tensile bond strength (μTBS) of five universal adhesive systems to dentin. The bond strength with two different air-blowing temperatures (60±2ºC and 23±2ºC) was measured after water storage at 37ºC for 24 h and 100 days respectively. The fracture surface on dentin side was observed by scanning electron microscope (SEM). Three-way ANOVA revealed a significant effect of universal system (p<0.001) and air-blowing temperature (p<0.001) on bond strength to dentin except water-storage time (p=0.145). The interaction within three factors was significantly different (p<0.001). It could be concluded that the μTBS of universal systems to dentin was material-depended. The higher and more stable bonding performance of universal systems on dentin could be achieved by air-blowing at 60±2ºC temperature. In addition, the quantity of voids in the adhesive layer of aceton-based universal adhesive was significantly reduced by higher temperature.

[Effect of intrapulpal pressure on the bonding strength of resin cement to dentin]

OBJECTIVE

To evaluate the effect of intrapulpal pressure simulation on the micro-tensile bond strength (μTBS) of resin cement to dentin.

METHODS

Thirty extracted human third molars were selected. Occlusal enamel was removed to expose dentine surface and teeth with residual dentin thickness of 0.5-2.5 mm were selected. Dye permeation through dentin tubules with or without intrapulpal pressure (IPP) simulation, or after Single Bond Universal (SBU) application on dentin surface with IPP simulation were observed at the end of 0 min, 5 min, 30 min and 2 h. The teeth with residual dentin thickness of (1.0±0.1) mm were divided into 2 groups with IPP simulation of 15 or 0 cmH₂O (1 cmH₂O=0.098 kPa), which was maintained for 30 min before bonding procedure. SBU was applied on the dentin surface and light cured, then RelyX Ultimate (RLX) cement was heaped on the dentin surface (diameter=10 mm, height=4 mm) and light-cured. After the dentin-resin cement samples were stored in distilled water for 24 h at 37 °C, the samples were cut into beams with cross sectional area of 0.9 mm×0.9 mm for μTSB testing (n=100). The data were analyzed with two independent samples t-test (α=0.05). The fracture mode was observed using scanning electron microscopy (SEM). The results were analyzed with Fisher exact test (α=0.05). The rest of dentin-resin cement samples (five samples for each group) were cut perpendicular to the bonding interface and the morphology of the bonding interface was observed using SEM.

RESULTS

The dye permeation through dentin tubules with IPP simulation was faster than those without IPP simulation. The μTSB of RLX to dentin with and without IPP simulation were (26.26±9.78) MPa and (28.70±9.0) MPa, respectively. The most frequent fracture mode was mixed-fracture mode. There was no significant difference between the two groups for neither bond strength nor fracture types distribution (P>0.05). Regarding the morphology of dentin-resin cement bonding interface, both groups showed 4-8 μm finger-like resin tags.

CONCLUSION

With SBU pretreatment, the IPP simulation had no influence on the immediate bond strength of RLX to dentin.

Are self-etch adhesives reliable for primary tooth dentin? A systematic review and meta-analysis

The purpose of this study was to systematically evaluate the dentin bond strength of etch-and-rinse and self-etch adhesives to primary teeth. In this study, PubMed, ISI (all databases), Scopus, and Cochrane Database were searched according to the selected keywords up to May 11, 2016. The full texts of published articles that appeared to meet the primary criteria for inclusion in this study were obtained. Due to the variation in the methods used, the studies were divided into 2 groups: Group 1 - studies that evaluated the micro-tensile bond strengths (MTBSs) of two-step etch-and-rinse adhesives and two-step self-etch adhesives and Group 2 - studies that evaluated the MTBSs of two-step etch-and-rinse adhesives and one-step self-etch adhesives. The initial search yielded 1447 publications. After a methodological assessment, 8 publications were selected. The results of this study showed that the MTBS of the etch-and-rinse adhesives and the two-step self-etch adhesives were similar (P = 0.34), and both were significantly higher than that of the one-step self-etch adhesive (P = 0.001). This meta-analysis showed that the application of two-step self-etch adhesives performs well when used for primary dentin and can be used to save time in pediatric dentistry.

Effect of Tannic Acid on Bond Strength of Etch and Rinse and Self-etch Adhesive Systems in Dentin of Primary Teeth

INTRODUCTION

One of the possible mechanisms for the gradual destruction of bond strength in dentin-resin interface, could be due to the demineralized unstable collagen matrix. Use of protease inhibitors, such as tannic acid (TA) could prevent destruction of collagen fibers. The aim of this study was to compare the TA effect on bond strength of etch and rinse and self-etch adhesive systems in the dentin of primary teeth.

MATERIALS AND METHODS

This in vitro study was done on 40 extracted primary molar teeth. The teeth were sectioned in the mesiodistal direction, and enamel of buccal and lingual surfaces was removed. Samples were randomly divided into four groups: Single bond (SB) + TA, SB, Clearfil SE Bond (CSB) + TA, and CSB. Then, Z250 and Clearfil AP-X composites were cured on the surfaces of SB and CSB groups respectively. After that, all samples were divided into aging and non-aging groups. For 3 months, samples were placed under 1,000 thermal cycles in aging group. Subsequently, the shear bond strengths of all groups were measured by the International testing machine, and failure mode was evaluated by an optical stereomicroscope. Data were analyzed with paired t-test and independent t-test.

RESULTS

Tannic acid induced a significant reduction in the immediate bond strength of adhesive SB. Meanwhile, TA had no significant effect on shear bond strength of the CSB system.

CONCLUSION

Based on our findings, use of TA is not recommended with SB and CSB adhesives on primary teeth.

CLINICAL SIGNIFICANCE

Tannic acid may not be considered in resin restorations of primary teeth.