Effects of Green Tea Application Time on Bond Strength after Enamel Bleaching

Abstract

This study evaluated the effect of green tea application time on the bond strength of enamel after enamel bleaching. Enamel samples were obtained from 80 third molars and randomly divided into 7 experimental groups (G1-G7) and 1 group without treatment (G8): G1, bleached with 10% carbamide peroxide (CP); G2, CP + 10% sodium ascorbate gel (SA) for 15 min; G3, CP + SA for 30 min; G4, CP + SA for 60 min; G5, CP + 10% green tea gel (GT) for 15 min; G6, CP + GT for 30 min; G7, CP + GT for 60 min. The CP was applied onto the enamel surface for 8 h for 14 days. The SA was applied in groups 2, 3 and 4, and the GT was applied in groups 5-8 according to the above described application times. Immediately after treatment, the specimens were bonded with Adper Single Bond 2 and Filtek Z350XT. The specimens were prepared to microtensile bond strength analysis. Fracture mode analysis was performed using a stereoscopic loupe. The data were statistically analyzed by two-way analysis of variance, the Tukey's and Dunnett's tests (=5%). The means (standard deviation) were: G1, 23.3 (3.2); G2, 25.2 (3.9); G3, 26.4 (5.4); G4, 30.2 (4.5); G5, 26.6 (3.4); G6, 22.0 (5.4); G7, 31.4 (3.3); G8, 31.4 (3.2). All groups had a high percentage of adhesive failures. In conclusion, the bond strength values were higher than the value in the bleached group only when the antioxidants were applied for 60 min.

Correlation between antioxidant activity and bonding strength on bleached enamel

“…The results on bond strength, using 10% GT, corroborate previous studies,[13,14] which found that 10% GT applied for 1 h to enamel bleached with 10% CP was able to reverse the bond strength values. The same was observed in several studies using 10% SA,[6,14,21,22] which reported a reversal in enamel resistance, reverting to values similar to those obtained in enamel with no bleaching treatment.…”

“…[2,4,5] Antioxidant agents have been used to overcome this time delay. [6,8–10,13,14] Thus, in this context, this study compared different concentrations of antioxidants and correlated with %AA. Ascorbic acid was used as the gold standard, because it has been well evaluated in the literature.…”

“…Approximately 0.02 mL of 10% GT (60% catechins and 5% caffeine; Fragon, São Paulo, SP, Brazil) or 10% SA (Fragon) were applied to the samples immediately after bleaching, as described above. The individual trays were placed over the samples to prevent dilution of the antioxidant gel in the artificial saliva, as reported in previous studies,[13,14] to simulate the clinical application of this technique. The antioxidant agents were used for 1 h at 37 ± 1 °C.…”

“…Consistent studies have been published recently that evaluate these antioxidants, including sodium ascorbate (SA),[7] grape seed extract,[8] alpha-tocopherol (vitamin E),[9] catalase, sodium bicarbonate,[10] ethanol,[11] acetone,[12] and, more recently, green tea (GT). [13,14] A study by Berger et al. [13] showed that 10% GT in gel form presents similar results to 10% SA, and concluded that this could be an alternative to reversing the bond strength values for bleached teeth; however, the antioxidant power of GT has not yet been verified.…”

The effect of green tea on the shear strength of brackets after home whitening treatment

“…structure have been studied, including sodium ascorbate [6,7], catalase [8], alphatocopherol [9], grape seed extract [10], and, more recently, green tea [11,12]. Although sodium ascorbate is the most studied antioxidant [6,7,13], its use is still not clinically feasible.…”