Abstract
Background: Bleaching procedures affect surface enamel structure and decrease its bonding ability to resin composite restorative materials. The application of re-hardening materials to bleached enamel surfaces may prevent this decrease in micro-hardness. Objective: This in-vitro study aims to evaluate the surface micro hardness of human teeth enamel subjected to bleaching with Zoom Advanced Power 2 AP (Phillips, USA), and Opalescence Boost (Ultradent, USA) and compare the re-hardening effects of 10% Sodium Ascorbate, 2% acidulated phosphate fluoride gel, and a 5% Potassium nitrate 0.22% Sodium Fluoride + Calcium Nitrate gel. Methods: Ninety human third molar teeth were used. The specimens were randomly assigned to 5 groups. After the bleaching procedure, the specimens were treated with APF, Sodium Ascorbate or Relief gel as re-hardening agents with 30 teeth in each group. Enamel micro-hardness was measured with Vickers Micro-hardness Tester. The data were evaluated with Kolmogorov-Simirnov, one-way ANOVA, Dunnett’s test, post-hoc Tukey and T-tests. Results: Statistical analysis revealed no significant differences among initial enamel groups’ micro-hardness values (P>.05); however, significant differences occurred between initial and after bleaching treatment group value for G3 (P< .05). After re-hardening, only the Sodium Ascorbate group showed a statistically significant increase with hardness values (P< .05) for G4 and G5. Conclusion: Bleaching treatment conducted with light had no adverse effect on enamel micro-hardness. Sodium Ascorbate can be useful after bleaching to change the adverse effects of bonding on the enamel.
Highlights
Bleaching treatment conducted with light had no adverse effect on enamel micro-hardness
Sodium Ascorbate can be useful after bleaching to change the adverse effects of bonding on the enamel
The current patient population is more demanding of restorations that preserve the aesthetic, and provide aesthetically preferred tooth color [1 - 4]
Summary
The current patient population is more demanding of restorations that preserve the aesthetic, and provide aesthetically preferred tooth color [1 - 4]. Renewal of old composite restorations is usually not made immediately after bleaching procedures, due to the negative effects of bleaching on the bonding of composites [4]. There are a number of protocols that have been described in the literature for bleaching vital teeth [1, 4]. Among these methods, in-office bleaching technique has some advantages. Bleaching procedures affect surface enamel structure and decrease its bonding ability to resin composite restorative materials. The application of re-hardening materials to bleached enamel surfaces may prevent this decrease in micro-hardness
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