Effects of 35% hydrogen peroxide solution containing hydrated calcium silicate on enamel surface

Effect of the calcium silicate and sodium phosphate remineralizing products on bleached enamel

Context and Aims

This study evaluated the effect of calcium silicate and sodium phosphate (CSSP) dentifrice and serum on the surface of enamel bleached with hydrogen peroxide (H2O2).

Materials and Methods

A total of 160 bovine enamel slabs were bleached with 35% H2O2 and treated with sodium fluoride (NaF) dentifrice-GI, CSSP dentifrice-GII; CSSP dentifrice + CSSP serum-GIII, or NaF dentifrice + NaF gel-GIV. The dentifrices were applied using a brushing machine three times daily for 7 days. After brushing, sodium phosphate gel and CSSP serum were applied. The microhardness (KNH, n = 14), surface roughness (Ra, n = 14), energy dispersive spectroscopy (n = 6), and scanning electron microscopy (n = 6) were assessed at t0 (before bleaching), t1 (after bleaching), and t2 (after postbleaching treatments).

Statistical Analysis Used

The data were subjected to a two-way analysis of variance and Bonferroni's test.

Results

The KNH decreased at t1 (P < 0.001) but recovered at t2 for all treatments, although only GII showed restored baseline values (P = 0.0109). The surface roughness increased at t1 (P < 0.001) and reduced at t2 (P < 0.001) for all groups, with no significant differences among groups. Enamel composition and morphology did not differ after the treatments, except for silicon accumulation in GIII.

Conclusions

Postbleaching treatment with CSSP dentifrice and serum yielded superior remineralizing effects on bleached enamel.

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.

Chemical, morphological and microhardness analysis of coronary dentin submitted to internal bleaching with hydrogen peroxide and violet LED

BACKGROUND

Violet LED has been used for internal bleaching, however its implications on coronary dentin composition are unclear. The present study aims to evaluate the effect of bleaching with violet LED, either associated with 35 % hydrogen peroxide or not, on microhardness, chemical composition, and morphological characteristics of coronal dentin.

METHODS

Thirty maxillary canines were selected to obtain 30 blocks of coronal dentin, distributed in 3 groups (n = 10): 35 % hydrogen peroxide (HP); violet LED (LED); HP 35 % + LED, (HP+LED). The chemical analysis was performed by FTIR and the morphological evaluation of the dentin structure by confocal laser scanning microscopy before (T0) and after treatment (T1). The microhardness analysis was performed by microdurometer after bleaching. The data were submitted to repeated measures ANOVA test (P> 0.05).

RESULTS

The intensity of the inorganic peaks decreased after bleaching for all groups (P = 0.003). There was an increase in the organic peak intensity after bleaching with HP, a decrease for LED, while HP+LED did not change the intensity (P = 0.044). Moreover, the inorganic/organic ratio decreased for HP (P = 0.022), while for LED and HP+LED there was no significant changes (P>0.05). HP and HP+LED showed lower microhardness values compared to LED (P< 0.05). Regarding morphological changes, an increase in the perimeter of the dentinal tubules was found for all groups, with the smallest increase being observed for LED.

CONCLUSION

HP bleaching decreased the chemical stability and microhardness of the coronal dentin, while the violet LED treatments had no significant impact on dentin stability. In all groups, there was an increase in exposure of the dentinal tubules after bleaching, which was less pronounced with the violet LED bleaching.

The bleaching effect of office bleaching agents containing S-PRG filler evaluated by pH value and electron spin resonance

OBJECTIVES

Surface reaction-type pre-reacted glass-ionomer (S-PRG) filler releases six types of ions with a neutralizing ability. This study evaluated the effect of S-PRG filler incorporation in an H₂O₂-based bleaching material on the bleaching efficacy, pH, and reaction state.

MATERIALS AND METHODS

The experimental bleaching material was formulated by the addition of 5% or 10% S-PRG fillers to the powder part. The stained bovine teeth were treated with the prepared bleaching paste. Commission internationale de l'éclairage (CIE) L*a*b* color space values were recorded before and after bleaching, and the color difference (ΔE) and whiteness index (WI_D) were calculated. Moreover, the used bleaching formulations were assessed for their pH values and reaction state by evaluating the oxidation state of manganese (Mn⁺²) using electron spin resonance (ESR).

RESULTS

The results of ΔE and WI_D showed that the addition of S-PRG filler increased the bleaching effect, but there was no significant difference between the groups with 5% and 10% S-PRG filler. A significant increase in pH in S-PRG filler groups (5% pH 6.7, 10% pH 6.8) was found compared to the 0% group (pH 4.8). ESR measurements showed that the signal emitted from Mn⁺² decreased over time. The S-PRG filler groups showed a significantly higher reduction in Mn⁺² compared to the 0% group, with no significant difference between the 5% and 10% S-PRG groups.

CONCLUSIONS

S-PRG filler addition resulted in improved bleaching efficacy, higher reaction rate, and pH values that are close to neutral.

CLINICAL RELEVANCE

S-PRG filler addition may be effective on the bleaching outcome of H₂O₂-based materials.

The in vitro effect of solutions with or without sugar in dental bleaching

The interaction of bleaching technique (in-office or at-home) and solutions (deionized distilled water with and without sugar, red wine with and without sugar, coffee with and without sugar) on the effectiveness of in vitro dental bleaching was evaluated. Hydrogen peroxide (HP) 37.5% gel was used for in-office bleaching, 3 applications of 8 min each, 3 sessions with an interval of 7 days. At-home bleaching was performed with 10% Carbamide peroxide (CP), 2 h/day, for 30 days. The enamel vestibular surfaces (n = 72) were subjected daily to test solutions for 45 min, washed with distilled water for 5 min and stored in artificial saliva. The enamel color analysis was performed with a spectrophotometer through color variation (ΔE) and luminosity variation (ΔL). Roughness analysis was performed by atomic force microscopy (AFM) and scanning electron microscopy (SEM). Enamel composition was determined by energy dispersive X-ray spectrometry (EDS). The results were submitted to one-way analysis of variance (ANOVA) for ΔE, ΔL and EDS and two-way for AFM. For ΔE and ΔL there was no statistically significant difference. An increase in roughness was observed on the surface when exposed to a sugar-water solution for at-home bleaching and a lower concentration of Ca and P in the deionized water solution with sugar. Solutions containing or not sugar did not influence the bleaching potential, however the presence of sugar in the water solution increased the surface roughness with CP.

Calcium-Polyphosphate Submicroparticles (CaPP) Improvement Effect of the Experimental Bleaching Gels' Chemical and Cellular-Viability Properties

The aim of this research was to develop and characterize the chemical and cellular-viability properties of an experimental high-concentration bleaching gel (35 wt%-H2O2) containing calcium-polyphosphate particles (CaPP) at two concentrations (0.5 wt% and 1.5 wt%). The CaPP submicroparticles were synthesized by coprecipitation, keeping a Ca:P ratio of 2:1. The CaPP morphology, size, and chemical and crystal profiles were characterized through scanning and transmission electron microscopy, energy-dispersive X-ray analysis, and X-ray diffraction, respectively. The assessed bleaching gels were experimental (without CaPP); 0.5% CaPP; 1.5% CaPP; and commercial. The gels’ pH values and H2O2 concentrations (iodometric titration) were determined. The odontoblast-like cell viability after a gel’s exposure was assessed by the MTT assay. The pH and H2O2 concentration were compared through a repeated-measures analysis of variance (ANOVA) and a Tukey’s test and the cell viability through a one-way ANOVA and a Tukey’s test using a GraphPad Prism (α < 0.05). The CaPP particles were spherical (with Ca and P, 135.7 ± 80.95 nm size) and amorphous. The H2O2 concentration decreased in all groups after mixing (p < 0.001). The 0.5% CaPP resulted in more-stable pH levels and higher viability levels than the experimental one (p < 0.05). The successful incorporation of CaPP had a positive impact on the bleaching gel’s chemical and cellular-viability properties when compared to the experimental gel without these particles.

Pilot study on the applicability of boron-doped diamond electrodes for tooth whitening

Objectives

While various approaches are available for tooth whitening, the basic concept employs the use of peroxides in the form of gels, which are applied to tooth surfaces. Previous studies have shown that reactive oxygen species acting as potent disinfectants can be produced using boron‐doped diamond (BDD) electrodes for the electrolysis of water. With these electrodes being applicable, for example, for endodontic treatment, it was the goal of this pilot study to use such electrodes for tooth whitening.

Material and Methods

Two groups (n = 10) of intact clinical crowns were obtained by horizontally cutting off roots of extracted human teeth. The crowns were either bleached by applying a commercially available agent based on 40% hydrogen peroxide or were immersed in saline undergoing electrolysis with BDD electrodes. Whitening of specimens was judged on standardized photographs by examiners with three different levels of experience. Statistical analysis was based on Gwet's AC2 coefficient with quadratic weights, Shapiro–Wilk tests, and two‐way analysis of variance of aligned rank transformed data (level of significance set at α = .05).

Results

Levels of reliability ranging from fair to substantial were recorded for single persons while the level of reliability ranged between fair and moderate for groups of raters. The level of experience had no significant effect on the ratings (p = .2500). The bleaching method had a significant effect on ratings (p = .0005) with BDD electrodes showing less effect.

Conclusions

Bleaching by applying BDD electrodes was possible, but was not as effective as the use of commercially available in‐office whitening gel. A potential explanation may be seen in different concentrations of reactive oxygen species.

Effects of incorporating 45S5 bioactive glass into 30% hydrogen peroxide solution on whitening efficacy and enamel surface properties

OBJECTIVES

This study aimed to evaluate the effects of 30% hydrogen peroxide (HP) solution containing various contents of 45S5 bioactive glass (BAG) on whitening efficacy and enamel surface properties after simulating the clinical bleaching procedure.

MATERIALS AND METHODS

A total of 60 bovine enamel specimens discolored with black tea were divided into five groups treated with distilled water (DW), HP, 0.01 wt.% BAG + HP, 1.0 wt.% BAG + HP, and 20.0 wt.% BAG + HP (n = 12). The pH change was observed for 20 min immediately after mixing the experimental solutions, which were applied for 20 min/week, at 37 °C over 21 days. Color, gloss, roughness, microhardness, and micromorphology measurements were conducted before and after bleaching treatment.

RESULTS

All groups containing BAG experienced an increase in pH from 3.5 to 5.5 in less than 1 min, and the final pH increased as the BAG content increased. The ΔE of all experimental groups was significantly higher than that of the DW group (p < 0.05), but there were no significant differences between different BAG contents (p > 0.05). Gloss significantly decreased in all experimental groups compared to the DW group, and the increased BAG content had significantly affected the decrease in gloss (p < 0.05). There was no statistical difference in surface roughness (p > 0.05), but hardness increased significantly with BAG content after bleaching treatment (p < 0.05).

CONCLUSIONS

HP containing 45S5 BAG showed efficacy in tooth whitening. Also, the pH value of the HP remained acidic near 3.5 for 20 min, while the HP containing the 45S5 BAG showed an increase in pH, which inhibited the demineralization of the enamel surface, and maintained the surface morphology.

CLINICAL RELEVANCE

These novel materials are promising candidates to minimize enamel surface damage caused by HP during bleaching procedure in dental clinic.