Etching a Fiber Post Surface with High-concentration Bleaching Agents

Introduction: Commonly, resin composites/cements fail to achieve proper bonding to fiber posts when their surfaces have not been previously etched. This study evaluated the effect of the concentration and application mode of hydrogen peroxide on the surface topography and bond strength of resin composite to glass-fiber posts. Methods and Materials: Fiber posts were immersed in 24% or 35% solutions (a high-concentration bleaching agent) of hydrogen peroxide (H2O2), or these solutions were applied over the post surface using a microbrush (n=10). Posts without any treatment were used as a control. After etching, the posts were silanated and an adhesive was applied. The posts were positioned in a mold, and a resin composite was incrementally inserted and light-cured. The post/resin assembly was serially sectioned into several beams that were subjected to a tensile bond strength test. The data were subjected to the two-way analysis of variance and Tukey test (α=0.05). The Dunnet's test was used to compare the experimental conditions to the control. The surface topography was analyzed using scanning electronic microscopy. Results: The non-etched post presented a relatively smooth surface without fiber exposure. Except for the application of 24% H2O2, the other experimental conditions increased the number of exposed fibers and bond strength in relation to the control. Although immersion resulted in higher values for the 24% H2O2 application, the mode of application did not alter bond strength when 35% H2O2 was used. Conclusions: The effect of the mode of application of H2O2 depended on its level of concentration. A high-concentration bleaching agent improved the bond strength of the resin composite to the post surface, regardless of which mode was used

Influence of Matrix Metalloproteinase Synthetic Inhibitors on Dentin Microtensile Bond Strength of Resin Cements

This study evaluated the effect of dentin pretreatment with 2% chlorhexidine (CHX) or 24% ethylenediamine tetra-acetic acid gel (EDTA) on the dentin microtensile bond strength (mu TBS) of resin cements. Composite blocks were luted to superficial noncarious human dentin (n=10) using two resin cements (RelyX ARC [ARC] and RelyX U100 [U100]) and three dentin pretreatments (without pretreatment-control, CHX, and EDTA). CHX was applied for 60 seconds on the acid-etched dentin in the ARC/CHX group, and for the same time on smear layer-covered dentin in the U100/CHX group. EDTA was applied for 45 seconds on smear-covered dentin in the U100/EDTA group, and it replaced phosphoric acid conditioning in the ARC/EDTA group for 60 seconds. After storage in water for 24 hours, specimens were prepared for microtensile bond strength testing. The results were submitted to two-way analysis of variance (AN-OVA) followed by Tukey test. ARC produced significantly higher mu TBS (p<0.05) compared to the U100, except when EDTA was used. For ARC, no pretreatment and CHX produced higher mu TBS than EDTA. For U100, EDTA produced higher mu TBS; no statistical difference occurred between CHX pretreatment and when no pretreatment was performed. While CHX did not affect immediate dentin bond strength of both cements, EDTA improved bond strength of U100, but it reduced dentin bond strength of ARC.37438639

Influence of chlorhexidine on dentin adhesive interface micromorphology and nanoleakage expression of resin cements

This study focused on adhesive interface morphologic characterization and nanoleakage expression of resin cements bonded to human dentin pretreated with 1% chlorhexidine (CHX). Thirty-two non-carious human third molars were ground flat to expose superficial dentin. Resin composite blocks were luted to the exposed dentin using one conventional (RelyX ARC) and one self-adhesive resin cement (RelyX U100), with/without CHX pretreatment. Four groups (n = 8) were obtained: control groups (ARC and U100); experimental groups (ARC/CHX and U100/CHX) were pretreated with 1% CHX prior to the luting process. After storage in water for 24 h, the bonded teeth were sectioned into 0.9 x 0.9 mm(2) sticks producing a minimum of 12 sticks per tooth. Four sticks from each tooth were prepared for hybrid layer evaluation by scanning electron microscope analysis. The remaining sticks were immersed in silver nitrate for 24 h for either nanoleakage evaluation along the bonded interfaces or after rupture. Nanoleakage samples were carbon coated and examined using backscattered electron mode. Well-established hybrid layers were observed in the groups luted with RelyX ARC. Nanoleakage evaluation revealed increase nanoleakage in groups treated with CHX for both resin cements. Group U100/CHX exhibited the most pronouncing nanoleakage expression along with porous zones adjacent to the CHX pretreated dentin. The results suggest a possible incompatibility between CHX and RelyX U100 that raises the concern that the use of CHX with self-adhesive cements may adversely affect resin-dentin bond. 2013. (C) 2013 Wiley Periodicals, Inc.76878879