Effect of epigallocatechin-3-gallate and thermal cycling on the bond strength of resin cements to the root dentin.

This study evaluated the effect of epigallocatechin-3-gallate (EGCG) solution and thermal cycling on the bond strength (BS) of fiber posts to the root dentin using two different resin cements (conventional or self-adhesive). One hundred and forty-four bovine roots were endodontically treated. After post space preparation, specimens were randomly divided into six groups (n = 24) according to dentin pretreatment [distilled water, 0.05% EGCG solution or 2% chlorhexidine (CHX) solution] and resin luting agent used for fiber post cementation (RelyX ARC or RelyX U200-3 M ESPE). Then, the samples were separated into two subgroups (n = 12): storage in distilled water at 37 °C for 24 h and thermal cycling (5 °C/55 °C, dwell time 30 s-12,000 cycles) during 6 months. After that, the specimens were subjected to the pull-out BS test (Universal Testing Machine-0.5 mm/min) and the failures pattern was analyzed in a stereomicroscope. According to the BS results (three-way ANOVA, Tukey's test, α = 0.05), the highest values were reported in the group EGCG + RelyX U200, showing significant statistical differences compared to all the other experimental groups. For Control and CHX groups BS values, there was no significant difference (p > .05) between the resin cements. For conventional resin cement, there was no significant difference among treatment solutions (p > .05). The thermal cycling did not influence the BS results (p > .05). As reported by the failure mode analysis, adhesive failure was predominant in all groups. EGCG solution improved the bond strength of self-adhesive resin cement to root dentin.

Apatite-like forming ability, porosity, and bond strength of calcium aluminate cement with chitosan, zirconium oxide, and hydroxyapatite additives.

This study evaluated the effect of chitosan, zirconium oxide, and hydroxyapatite on the apatite-like forming ability, porosity, and bond-strength of calcium-aluminate cements (C). Three hundred bovine root-slices were assigned to one of five groups, according to the material: MTA, C, C + chitosan (Cchi), C + zirconium oxide (Czio), and C + hydroxyapatite (Chap), and within each group, two subgroups, according to the immersion: deionized water or phosphate-buffered saline (PBS) up to 14 days. Assessments (n = 10) of apatite-like forming ability were performed using scanning-electron microscopy, energy-dispersive x-ray spectroscopy, Fourier-transform infrared spectroscopy, and x-ray diffraction. PBS was evaluated for pH and Ca2+ release (n = 10). Bond-strength was analyzed by push-out test (n = 10) and porosity by micro-CT (n = 10). Chemical and push-out data were analyzed by ANOVA and Tukey's tests (α = .05). Porosity data were analyzed by the Kruskal-Wallis and SNK tests (α = .05). Similar Ca/P ratios were observed between all groups (p > .05). The pH of MTA and Cchi were higher than that of other cements at d 3 and 6 (p < .05). Cchi had a higher release of Ca2+ up to 6 days (p < .05). All cements had lower porosity after PBS (p < .05). Cchi and Chap had similar porosity reduction (p > .05), and were higher than MTA, C, and Czio (p < .05). Cchi had higher bond-strength than the other groups (p < .05). PBS samples had higher bond-strength (p < .05). All cements had hydroxyapatite deposition and the chitosan blend had the lowest porosity and the highest bond-strength.