Abstract
Objective: To evaluate the effect of 35% hydrogen peroxide (35% HP) combined to different concentrations of nanohydroxyapatite (nHA) on the effectiveness of dental bleaching (superficial enamel and deep dentin) and enamel bond strength. Material and Methods: Fifty bovine dental specimens (5x5x2mm) were divided into 5 groups, according to the treatments (n = 10): no bleaching (negative control); 35% HP (positive control); 35% HP+ 5% nHA; 35% HP + 10% nHa; and 35% HP + 15% nHA. Three in-office bleaching sessions were made. The color analysis was performed on the enamel surface and the opposite dentin, using a spectrophotometer. The results were expressed in the CIE L*a*b* system. After this, the adhesive system was applied to the tooth structure, and the dental specimens received a composite restoration. The microshear bond strength test was performed 24 h after the restoration. Data were submitted to ANOVA and Tukey's test (?=0.05). Results: For the enamel color analysis, all bleached groups differed statistically from the unbleached group, with increasing L* values and decreasing b* values. The addition of different concentrations of nHA did not interfere with the bleaching effectiveness for the enamel and opposite dentin. For microshear bond strength, no statistically significant differences were presented between groups. The adhesive failure rate of the 35% HP + 10% nHA group was lower than the 35% HP group and similar to the negative control. Conclusion: The addition of different concentrations of nHA in 35% of hydrogen peroxide did not interfere with the bleaching efficacy of enamel and deep dentin and did not affect the enamel bond strength after bleaching KeywordsEnamel; Shear strength; Tooth bleaching.
Highlights
The growing concern with aesthetics and the search for the perfect smile have made tooth whitening the treatment of choice for the removal of intrinsic and extrinsic stains
The association of hydrogen peroxide with nanohydroxyapatite may correspond to an innovative option to reduce post-bleaching demineralization; there are no studies that assess the effects of this association on bond strength and deep dentin whitening efficacy. This in vitro study evaluated the influence of 35% hydrogen peroxide (HP) containing different concentrations of nHA on the effectiveness of dental bleaching and enamel bond strength
- Negative Control: No bleaching, - 35% HP: Dental bleaching with 35% hydrogen peroxide
Summary
The growing concern with aesthetics and the search for the perfect smile have made tooth whitening the treatment of choice for the removal of intrinsic and extrinsic stains. Tooth whitening is an effective treatment, adverse effects can be observed in the teeth, such as a reduction in the bond strength of restorations performed immediately after bleaching [2], increased enamel surface roughness [3] and morphological and structural alterations in the enamel [4] and dentin [5]. These changes are attributed to hydrogen peroxide–based agents that modify the organic and inorganic composition of the enamel [4]. This in vitro study evaluated the influence of 35% hydrogen peroxide (HP) containing different concentrations of nHA on the effectiveness of dental bleaching (superficial enamel and deep dentin) and enamel bond strength
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