Effective application duration of sodium ascorbate antioxidant in reducing microleakage of bonded composite restoration in intracoronally-bleached teeth

Photon-Induced Photoacoustic Streaming Activation of the Postbleaching Antioxidant Application Rapidly Improves Bonding to Pulp Chamber Dentin

Objective: This study explored whether the erbium/yttrium/aluminum/garnet (Er:YAG) laser irradiated through the photon-induced photoacoustic streaming (PIPS) method would impact on the resin bonding to pulp chamber dentin when used to activate bleaching and/or postbleaching antioxidant treatment. Materials and methods: One hundred five dentin samples prepared from freshly extracted human incisors were randomly assigned to seven groups (n = 15): control (no bleaching/antioxidant); CB (conventional bleaching only); MB (modified bleaching only); CB-NI (conventional bleaching+antioxidant with needle irrigation); MB-NI (modified bleaching+antioxidant with needle irrigation); CB-PIPSI (conventional bleaching+antioxidant with PIPS-activated irrigation); and MB-PIPSI (modified bleaching+antioxidant with PIPS-activated irrigation). Bleaching (40% hydrogen peroxide) lasted for 20 min. Modified bleaching groups were irradiated with Er:YAG laser using the PIPS tip (2940 nm, 0.90 W, 30 Hz, 30 mJ/pulse, 50-μsec pulse duration) during the first 60 sec of the procedure. The antioxidant treatment with 10% sodium ascorbate lasted for 60 sec. PIPS-activated antioxidant groups were irradiated with Er:YAG laser using the PIPS tip (2940 nm, 0.30 W, 15 Hz, 20 mJ per pulse, 50-μsec pulse duration) throughout the procedure. After completing the composite restorations, all samples were subjected to 5000 thermocycling and the shear bond strength (SBS) test at a crosshead speed of 1 mm/min. SBS data were analyzed using the Kruskal-Wallis test with Bonferroni correction (α& 0.05). Results: No significant difference was detected among the control, CB-PIPSI, and MB-PIPSI (p > 0.05), which presented a significantly higher SBS compared with the other groups (p < 0.05). Conclusions: Irrespective of the application mode of the initial bleaching, PIPS-activated irrigation of the antioxidant improved SBS to bleached dentin to the level of the control in 1 min. Postbleaching antioxidant treatment combined with the PIPS method might be a promising approach to enable immediate resin restoration of bleached dentin.

Hypericum perforatum L.: A Potent Antioxidant Source for the Treatment of Oxidized Dentin: An Experimental In Vitro Study

Aim:

To evaluate the therapeutic antioxidant effect of Hypericum perforatum L. (HPL) extract on oxidized dentin as well as to address the following research question: Is experimental HPL-derived antioxidant treatment protocol as effective as sodium ascorbate in terms of reversing the compromised resin bonding to bleached dentin?

Materials and Methods:

Eighty bovine permanent mandibular incisors were included in the shear bond strength (SBS) test and randomly assigned into four groups ( n = 20) as follows: negative control (NC), positive control (PC), sodium ascorbate (SA), and Hypericum perforatum L. (HPL). Group NC did not receive bleaching treatment. All specimens except the NC group were oxidized by bleaching with 35% hydrogen peroxide. Experimental antioxidant solutions were prepared from SA powder and HPL extract at 10% concentrations. The bleached specimens in the SA and HPL groups were treated with respective antioxidant solutions. The SBS test was performed at a crosshead speed of 1 mm/min. The SBS data were analyzed with one-way analysis of variance using the post-hoc Bonferroni correction. The total phenolic content and the antioxidant activity of HPL extract were assessed by using the Folin–Ciocalteu assay and the 2,2-diphenyl-1-picrylhydrazyl free-radical scavenging activity test, respectively.

Results:

Considering the SBS test results, statistically significant the highest and the lowest mean values were observed in NC and PC, respectively ( P <.05). SA and HPL were not significantly different ( P > .05). The total phenolic content (104 ± 1.740 mg gallic acid equivalents (GAE)/gram (GAE/g) dry HPL extract) and the antioxidant activity of the HPL extract were demonstrated.

Conclusions:

The natural HPL plant extract was as effective as SA in reversing the compromised resin bonding to bleached dentin. Antioxidant treatment derived from the HPL extract may enable immediate resin restoration of oxidized dentin.

Antioxidant therapy enhances pulpal healing in bleached teeth

Objectives

The purpose of this study was to evaluate the histopathological effects of an antioxidant therapy on the pulp tissue of rat teeth exposed to a bleaching gel with 35% hydrogen peroxide.

Materials and Methods

Forty rats were subjected to oral ingestion by gavage of distilled water (DW) or ascorbic acid (AA) 90 min before the bleaching therapy. For the bleaching treatment, the agent was applied twice for 5 min each to buccal surfaces of the first right mandibular molars. Then, the animals were sacrificed at 6 hr, 24 hr, 3 day, or 7 day post-bleaching, and the teeth were processed for microscopic evaluation of the pulp tissue.

Results

At 6 hr, the pulp tissue showed moderate inflammatory reactions in all teeth of both groups. In the DW and AA groups, 100% and 80% of teeth exhibited pulp tissue with significant necrosis and intense tissue disorganization, respectively. At 24 hr, the AA-treated group demonstrated a greater regenerative capability than the DW group, with less intense inflammatory reaction and new odontoblast layer formation in 60% of the teeth. For up to the 7 day period, the areas of pulpal necrosis were replaced by viable connective tissue, and the dentin was underlined by differentiated odontoblast-like cells in most teeth of both groups.

Conclusions

A slight reduction in initial pulpal damage during post-bleaching was promoted by AA therapy. However, the pulp tissue of AA-treated animals featured faster regenerative potential over time.

Antioxidants in Endodontics: A Strategic Review

Over the past few decades, the free radicals and antioxidants have attracted tremendous importance in the field of dentistry. Depending on the level of free radicals in the body, they can either be harmful or helpful. Antioxidants are the substances that interact with and stabilize free radicals thereby protecting cells from the damage caused by free radicals. The indigenous antioxidants may be useful in preventing the harmful effects of oxidative stress. The present article presents a review on the free radicals formation, their role in disease pathogenesis, antioxidants and their potential role in endodontics.

Pull-out bond strength of a self-adhesive resin cement to NaOCl-treated root dentin: effect of antioxidizing agents

Objectives

This study evaluated the effect of three antioxidizing agents on pull-out bond strengths of dentin treated with sodium hypochlorite.

Materials and Methods

Root canals of 75 single-rooted human teeth were prepared. Fifteen teeth were irrigated with normal saline for a negative control group, and the remaining 60 teeth (groups 2 - 5) with 2.5% NaOCl. The teeth in group 2 served as a positive control. Prior to post cementation, the root canals in groups 3 - 5 were irrigated with three antioxidizing agents including 10% rosmarinic acid (RA, Baridge essence), 10% hesperidin (HPN, Sigma), and 10% sodium ascorbate hydrogel (SA, AppliChem). Seventy-five spreaders (#55, taper .02, Produits Dentaires S.A) were coated with silica and silanized with the Rocatec system and ceramic bond. All the prepared spreaders were cemented with a self-adhesive resin cement (Bifix SE, Voco Gmbh) in the prepared canals. After storage in distilled water (24 h/37℃), the spreaders were pulled out in a universal testing machine at a crosshead speed of 1.0 mm/min. Pull-out strength values were analyzed by one-way ANOVA and Tukey's HSD test (α = 0.05).

Results

There were significant differences between study groups (p = 0.016). The highest pull-out strength was related to the SA group. The lowest strength was obtained in the positive control group.

Conclusions

Irrigation with NaOCl during canal preparation decreased bond strength of resin cement to root dentin. Amongst the antioxidants tested, SA had superior results in reversing the diminishing effect of NaOCl irrigation on the bond strength to root dentin.