The effect of glutathione on 2-hydroxyethylmethacrylate cytotoxicity and on resin-dentine bond strength

In Vitro Investigation of the Effects of Various Reducing Agents on Dentin Treated with Hydrogen Peroxide

We assessed the effect of non-protein thiols (NPSH), reduced glutathione (GSH) and n-acetylcysteine (NAC), on resin shear bond strength (SBS) to hydrogen peroxide (H2O2)-treated dentin, and their effects on the characteristics of dentin in comparison to ascorbic acid (AA) and sodium thiosulfate (STS). H2O2-treated dentin was conditioned with 5% AA, GSH, NAC, or STS applied for 1 or 5 min. The positive control group received H2O2 without antioxidant application, and the first negative control group received distilled water (DW). The specimens received resin bonding immediately after treatment except for the second negative control group (delayed bonding). Microhardness, roughness, and topography were studied. The SBS values of all antioxidants were statistically greater than the positive control group (p < 0.05); however, NAC and AA applied for 1 min demonstrated the highest values, which were comparable to delayed bonding. All treatments removed the smear layer except DW, H2O2, and STS. The negative effect of H2O2 on resin-dentin bonding was mitigated by the application of the antioxidants; however, their efficiencies were dependent on the antioxidant type and time of application. NAC was more effective in optimizing resin bonding to bleached dentin compared to GSH at 1 min application and STS at both application times but was comparable to AA. Negligible negative effects on the substrate's roughness and microhardness were detected. The antioxidant properties of the agent and its capacity to remove the smear layer are the processes underpinning the ability of a certain antioxidant to reverse the effect of H2O2 on bonding.

In Vitro and In Vivo Efficacy of New Composite for Direct Pulp Capping

Objectives

To investigate physicochemical properties, dentin bonding, cytotoxicity, and in vivo pulp response of experimental self-adhesive composites tailored to direct pulp capping.

Materials and Methods

Experimental composites were prepared with beta-tricalcium phosphate and hydroxyapatite nanoparticles adsorbed with simvastatin and glutathione added at 0% (control resin), 1 wt% (Res 1%), and 10 wt% (Res 10%). A commercial light-curable calcium hydroxide (Ca(OH)₂) (Ultra-Blend Plus) was used as control material. The physicochemical properties investigated were flexural strength and modulus, calcium release, and degree of conversion. Dentin bonding was assessed by the push-out test. Proliferation and cell counting assays were performed to evaluate in vitro cytotoxicity using fluorescence microscopy. In vivo pulp capping was performed on molars of Wistar rats, which were euthanized after 14 days and evaluated by histological analysis.

Results

No statistical difference was observed in flexural strength and cell viability (p > 0.05). Res 10% presented higher modulus than control resin and Ca(OH)₂. Also, Res 10% attained statistically higher degree of conversion when compared to other experimental composites. Ca(OH)₂ showed higher calcium release after 28 and 45 days of storage, with no statistical difference at 45 days to Res 10%. All experimental composites achieved significantly higher bond strength when compared to Ca(OH)₂. While no significant difference was observed in the cell proliferation rates, resins at lower concentrations showed higher cell viability. In vivo evaluation of pulp response demonstrated no pulp damage with experimental composites.

Conclusions

The experimental composite investigated in this study achieved adequate physicochemical properties with minor in vivo pulpal inflammation and proved to be a valuable alternative for direct pulp capping.