The impact of remineralization agents on dental bleaching efficacy and mineral loss in bleached enamel

Effect of different remineralization agents on the optical properties of bleached enamel

BACKGROUND

The aim of this study was to evaluate the effect of different remineralization agents applied immediately after bleaching on the colour stability, whiteness index and whiteness index difference of enamel.

METHODS

One hundred enamel samples from bovine incisors were divided into two groups for at-home and in-office bleaching. The samples were further divided into five subgroups: (1) Acidulated phosphate fluoride (APF), (2) Casein phosphopeptide amorphous calcium phosphate fluoride (CPP-ACPF), (3) Calcium glycerophosphate, fluoride (CaGP, F), (4) Hydroxyapatite, fluoride (HAp, F), and (5) control. After treatment, all samples were stained with red wine. Color measurements were taken at baseline, after bleaching, after remineralization, and after staining using a dental spectrophotometer. Optical parameters included L*, a*, b*, CIEDE2000 color difference (ΔE00), whiteness index for dentistry (WID), and whiteness index difference (ΔWID). Statistical analyses were performed with Kruskal Wallis, Friedman, and Dunn tests.

RESULTS

Color and whiteness differences after bleaching were statistically similar between in-office and at-home bleaching (p > 0.05). Remineralization protocols had no significant effect on enamel color or whiteness across all groups (p > 0.05), but significant differences were found between the CPP-ACPF, CaGP, F, HAp, F, and control groups (p < 0.05).

CONCLUSION

Application of remineralization agents after bleaching was found to be ineffective on color and whiteness change of bleached enamel. Remineralization agents containing HAp, CPP-ACP and CaGP, respectively, were found to be more successful in terms of color stability.

Effect of bleaching and repolishing on whiteness change and staining susceptibility of resin-based materials

BACKGROUND

The aim of this study was to investigate the effects of different types of bleaching methods and repolishing on the whiteness index and staining susceptibility of additive and subtractive production resin-based materials and direct composite resins.

METHODS

In this study, a total of 96 samples (8*8*2m) were prepared using a nanohybrid composite resin (Neo SpectraTM-ST (NS)), a subtractive-manufactured nanoceramic resin (CerasmartTM270 (CS)), and an additive-manufactured permanent resin (Saremco print Crowntec (CT)). The samples were randomly divided into four treatment groups: control (distilled water, 14 days), in-office bleaching (Opalescence Boost-40% HP, 3*20min), at-home bleaching (Opalescence PF-16% CP, 6 h, 14 days), and toothpaste group (Opalescence Whitening, 2*5min, 14 days) (n:8). After each the bleaching procedure was completed, the samples were kept in coffee solution for 7 days. Following, all samples were repolished. The color of the samples was measured with a spectrophotometer at baseline (T0), after bleaching (T1), after staining in coffee (T2) and after repolishing (T3). The whiteness index change (∆WID, T1-T0), staining susceptibility (∆E1, T2-T1) and color change after repolishing (∆E2, T3-T1) of the samples were calculated in the CIE (Commission International De I'Eclairage) system. The data were analyzed by SPSS software One-Way ANOVA, post-hoc Tukey, post-hoc Tamhane's-T2 and Paired-samples T test (α = 0.05).

RESULTS

The ∆WID of all tested materials was significantly different in the in-office bleaching group compared to the control group (p < 0.05). Among the bleaching groups, the highest ∆WID was obtained in-office bleaching group of CT (2.91 ± 4.12). Staining susceptibility after bleaching (∆E1) was higher in the in-office and at-home bleaching groups compared to the control group in all tested materials. However, the difference between the treatment groups was statistically significant in NS and CS (p < 0.05). The highest ∆E1 was obtained in the in-office group of CT (7.36 ± 4.82). Color changes after repolishing (∆E2) of the tested materials were less in all groups compared to ∆E1.

CONCLUSION

In-office and at-home bleaching can increase the whiteness index change and stain susceptibility of materials. Among the tested materials, the color stability of additive-manufactured CT was comparatively poorer. The repolishing was found to be beneficial in reducing staining.

Biomaterials based on advanced oxidation processes in tooth whitening: fundamentals, progress, and models

The increasing desire for aesthetically pleasing teeth has resulted in the widespread use of tooth whitening treatments. Clinical tooth whitening products currently rely on hydrogen peroxide formulations to degrade dental pigments through oxidative processes. However, they usually cause side effects such as tooth sensitivity and gingival irritation due to the use of high concentrations of hydrogen peroxide or long-time contact. In recent years, various novel materials and reaction patterns have been developed to tackle the issues related to H2O2-based tooth whitening. These can be broadly classified as advanced oxidation processes (AOPs). AOPs generate free radicals that have potent oxidizing properties, which can thereby increase the oxidation power and/or reduce the exposure time and can probably minimize the side effects of tooth bleaching. While there have been several reviews on clinical tooth whitening and the application of novel nanomaterials, a review based on the concept of AOPs in tooth bleaching application has not yet been conducted. This review describes the common types and mechanisms of AOPs, summarizes the latest research progress of new tooth bleaching materials based on AOPs, and proposes a model for tooth bleaching and a rate control step at the molecular level. The paper also reviews the shortcomings and suggests future development directions.

Do Different Tooth Bleaching-Remineralizing Regimens Affect the Bleaching Effectiveness and Enamel Microhardness In Vitro?

Objective

Tooth bleaching may negatively affect the enamel surface properties, such as reduction in hardness values, and remineralizing agents can reverse these effects. This study evaluated the effect of remineralizing agents before, during, and after the bleaching process on enamel's whitening effectiveness and microhardness.

Methods and Materials

The initial color of 104 bovine incisors after immersion in tea solution was recorded, and then, the teeth were randomly divided into eight groups (n = 13). Group 1 (NC) was considered the control with no treatment, and Group 2 (B) was bleached with 40% hydrogen peroxide gel. The 3% fluorohydroxyapatite (FHA) and 2% sodium fluoride (NaF) were applied before (FHA/B, NaF/B), during (FHA + B, NaF + B) and after (B/FHA, B/NaF) the bleaching process in other groups. The final color and microhardness in three depths of 20-30, 50-60, and 100-120 µm were measured. Data were analyzed using Shapiro-Wilk, one-way ANOVA, Tukey, Games Howell, repeated measurement, and LSD tests.

Results

The FHA + B presented the lowest ΔE, significantly lower than other groups, except B/FHA. The ΔE in B/FHA was significantly lower than B/NaF. The bleaching significantly reduced the enamel hardness in three depths. The highest microhardness values were reported for B/NaF and NaF + B, which have no noticeable difference with NC, while FHA/B showed the lowest hardness in three depths, which was significantly lower than NC.

Conclusion

The application of NaF before, during, and after the bleaching improved the microhardness of bleached enamel as the unbleached one with no adverse effect on whitening effectiveness.