The Antioxidant Effect of Green Tea, Rosemary, and Their Combination on Resin Bond Strength to Bleach Tooth Structures

Objective: This study aimed to evaluate the effect of four experimental antioxidant protocols on the shear bond strength of a resin-based composite to bleach the enamel and dentin. Materials and Methods: Using extracted bovine incisors, 140 enamel/140 dentin specimens were prepared. Both enamel and dentin samples were assigned into seven groups, individually (n=20): ENC/DNC= negative control, EPC/DPC= positive control, EDR/DDR= delayed restoration, ESA/DSA= sodium ascorbate, EGT/DGT= green tea, ER/DR= rosemary and EGTR/DGTR= green tea and rosemary combination. Experimental antioxidant solutions prepared from sodium ascorbate, green tea, or rosemary extracts were applied to the bleached enamel/dentin samples in the ESA/DSA, EGT/DGT and ER/DR groups, respectively. The mixture of the green tea/ rosemary extract solutions at a 1:1 ratio was applied to the EGTR/DGTR groups to investigate possible synergistic antioxidant interaction. The shear bond strength (SBS) test was conducted at a crosshead speed of 0.5 mm/minute. Failure modes were assessed under a stereomicroscope at x40 magnification. Data were analysed statistically using Welch-ANOVA and Tamhane post-hoc tests. Results: The lowest and highest mean SBS values were obtained in the positive control groups (EPC/DPC) and negative control groups (ENC/DNC), respectively (p0.05). Synergistic antioxidant interaction could not be obtained in the green tea and rosemary combination protocol. Conclusion: Natural plant-derived antioxidants can be an alternative to synthetic sodium ascorbate and may enable immediate resin restorations of bleached tooth structures

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-mu sec 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-mu sec 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 (proportional to 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