Effect of sodium fluoride pretreatment on the efficacy of an in-office bleaching agent: An in vitro study

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.

[Laboratory evaluation of the effectiveness and safety of the Chairside Light Whitening System fläsh]

THE AIM OF THE STUDY

Optimization of methods for treating dental discoloration using whitening systems based on hydrogen peroxide by laboratory studying their chemical properties.

MATERIAL AND METHODS

The effectiveness of the bleaching system was assessed by quantitatively assessing the color change of model samples of hydroxyapatite (HAP) in the CIE L*a*b* system on a Spectron-M color analyzer after exposure to coloring food media. Safety assessment was carried out on samples made from teeth removed according to indications.

RESULTS

The results of laboratory tests allow us to conclude that the Chairside Light Whitening System professional teeth whitening system fläsh. (WHITEsmile GmbH, Germany) has high whitening efficiency with a whitening degree of ~84%, which significantly exceeds the norm of GOST R 702.3.004-2021. the microhardness of the enamel of samples exposed to the whitening gel for 15 minutes changes extremely little. After exposure of the studied samples to the Chairside Light Whitening System fläsh whitening system for 45 minutes, an increase in digital microhardness indicators is observed, which indicates the dynamics of processes demineralizing the hard tooth structure.

CONCLUSIONS

Chairside Light Whitening System fläsh professional teeth whitening system has high whitening efficiency with minimal impact on the teeth structure and high safety.

Efficacy of Tooth Bleaching With Prior Application of Two Different Desensitizing Agents: An In Vitro Study

Objective To compare and evaluate the efficacy of tooth bleaching with prior application of two different desensitizing agents such as sodium fluoride and 5% potassium nitrate. Materials and methods A total of 108 extracted human maxillary central incisors were stained in black coffee solution and stored in artificial saliva for colour stabilization. The specimens were randomly divided into three groups (n = 36) according to the following protocols: (a) bleaching without desensitizer, (b) bleaching with prior application of sodium fluoride, and (c) bleaching with prior application of 5% potassium nitrate. After fabricating customized trays, desensitizers were applied for 10 minutes followed by 16% carbamide peroxide bleaching gel, which was in contact with the teeth for three hours. The bleaching efficacy was evaluated at baseline (after staining), 3rd day, 7th day, and 14th day using a digital spectrophotometer. Results There was an increase in the overall colour change (∆E) from baseline to 14th day, which was statistically significant at cervical, middle, and incisal thirds of the teeth between the three groups with the sodium fluoride group showing decreased ∆E. Conclusions Carbamide peroxide (16%) showed improved whitening efficacy from baseline to the 14th day with increasing median values at all time periods. The sodium fluoride group showed decreased ∆E value when compared to other groups.

Effect of Neodymium-Doped Yttrium Aluminum Garnet (Nd:YAG) Laser Enamel Pre-Treatment on the Whitening Efficacy of a Bleaching Agent

BACKGROUND

There are a number of different substances and treatments that are effective in mitigating the negative effects of tooth bleaching. It is essential, however, to consider whether or not the presence of these factors affects the efficiency of the bleaching agent.

AIM

The purpose of this study is to determine how the pretreated enamel with a Neodymium-Doped Yttrium Aluminum Garnet (Nd:YAG) laser affects the bleaching effect of hydrogen peroxide at a concentration of 35%.

METHODS AND MATERIALS

Thirty samples were prepared from human-extracted permanent anterior teeth and stained using a tea solution. Based on the pre-treatment protocol, the samples were split into two equal groups (n = 15): In Group I, samples were submerged in saline solution for five minutes, while in Group II, Nd:YAG laser treatment was performed. Following pretreatment, samples from both groups were bleached with 35% hydrogen peroxide. Colour analysis of all samples was done before and after bleaching using a spectrophotometer. For the colour analysis, the CIE L*a*b* (Commission Internationale de l'Eclairage) System of colour measurement was used. For statistical analysis, Student t-tests (two-tailed, unpaired) were used to compare the means of two groups on a continuous scale.

RESULTS

Samples from both groups became lighter in colour following bleaching. After bleaching, there was no discernible difference in the total colour change between the two groups.

CONCLUSION

The application of the Nd:YAG laser before bleaching did not influence the whitening efficacy of 35% hydrogen peroxide.

Effects of black tea tooth staining previously to 35% hydrogen peroxide bleaching

Aim: To determine if the artificial staining with black tea (BT) influences the enamel microhardness before in-office bleaching and if BT staining is necessary to evaluate the efficacy of bleaching with 35% hydrogen peroxide Methods: Enamel/dentin blocks were randomized into groups according to the staining protocol (n=5/group): (CO) control – maintained in artificial saliva solution (AS); (BT4) immersed in black tea solution for 4 h; (BT24) immersed in black tea solution for 24 h. After the staining protocols, all specimens were kept in AS for one week, followed by bleaching (three sessions of HP application for 40 min). Knoop surface microhardness (kgF/mm2) was determined at baseline (T0), after staining (T1), after 7 days of storage in AS (T2), and after bleaching (T3). The color (ΔE00) and coordinate changes (ΔL, Δa, Δb) were measured using a digital spectrophotometer at T0 and T3. Data were submitted to one-way (ΔE00, ΔL, Δa, Δb) or two-way ANOVA repeated measures (kgF/mm2) and Tukey’s test (a=5%). Results: The staining protocols (BT4 and BT24) promoted significantly lower microhardness (T1 and T2, p<0.05) than CO, whereas CO was the only group to maintain microhardness values over time. Bleaching promoted perceptible ΔE00 without a significant difference among the groups regardless of the staining protocol (p=0.122). CO and BT4 showed no differences in terms of ΔL and Δa (p>0.05), but BT4 displayed a higher Δb than CO. Conclusion: The artificial staining with BT negatively affected the enamel surface microhardness and was not essential to evaluate the efficacy of 35% hydrogen peroxide bleaching.

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

OBJECTIVES

The objectives of this study were to develop a novel bleaching material containing hydrated calcium silicate (hCS) particles and investigate the effects of hCS on the bleaching efficacy, microhardness, and surface morphology of bovine enamel.

MATERIALS AND METHODS

To prepare the hCS particles, white Portland cement was mixed with distilled water and ground into a fine powder. The particles in various proportions were then mixed with 35% hydrogen peroxide solution (HP), while HP without hCS was used as a control (HP), and teeth whitening gel was used as a commercial control (CC). Following the thrice application of experimental and control solutions on the discolored bovine enamel surface for 15 min, color change (n = 10), microhardness (n = 10), and micromorphology (n = 2) of the enamel surface were analyzed.

RESULTS

The Δ E^* of the enamel surface treated with the experimental solution containing hCS was significantly higher than that of the CC, but there were no significant differences between the different hCS contents. The experimental solution containing hCS reduced the percentage of microhardness loss on the enamel surface, and the percentage of microhardness loss significantly decreased as the content of hCS increased (p < 0.05). The erosion pattern was only observed on enamel surfaces treated with HP and CC.

CONCLUSIONS

This study suggests that HP containing hCS is effective in bleaching efficacy. In addition, hCS could also minimize the microhardness loss of tooth structure caused by HP and maintain enamel surface morphology.

CLINICAL RELEVANCE

This novel bleaching material is promising for inhibiting demineralization and promoting the remineralization of teeth during bleaching treatment in dental clinics.

Effect of photo-thermal acceleration on in-office bleaching

The purpose is to evaluate the effect of photo-thermal acceleration on in-office bleaching efficiency using a bleaching agent without photocatalysts in vitro. Artificially discolored bovine lower incisors were prepared, and the mixed in-office bleaching material contained hydrogen peroxide 23% was applied by following treatment for 10 min: high-(HI group) and low-intensity LED lights (LI group), oven at 38 °C (OV group), and room temperature at 23 °C (RT group). Color was measured before and after bleaching and color difference (∆E*) was calculated. The data were statistically analyzed using a two-way ANOVA and Tukey’s post hoc test. The temperature change (∆T) of applied bleaching agent in HI and LI groups was measured using a thermography and was analyzed using a T test. The bleaching procedures were repeated 6 times. Irradiation in the HI group resulted in the highest ΔE, followed by the LI group whose ΔE was significantly lower. Both irradiated modes exhibited higher ΔE compared to non-irradiated OV and RT groups which were not significantly different from each other. The average temperature rise of bleaching agents in HI and LI groups after 10 min irradiation was 15.00 °C and 11.80 °C, respectively. The effect of photo-thermal acceleration was proved for an in-office bleaching agent without photocatalysts in vitro.

Influence of light and laser activation of tooth bleaching systems on enamel microhardness and surface roughness

Objective

The objective of this study was to compare the effects of light and laser activation of in-office tooth bleaching systems on enamel microhardness and surface roughness.

Materials and Methods

Twenty-five enamel slabs were divided into three treatment groups: light-activated bleaching, laser-activated bleaching, and control. The baseline data were recorded for enamel microhardness (Vickers microhardness [VMH]) and surface roughness (Roughness average, Ra). The specimens were cured for 10 min upon hydrogen peroxide application for the light-activated bleaching group and activated with a laser source, 8 cycles, 10 s per cycle for the laser-activated group. The changes in VMH and Ra at days 1, 7, and 28 were evaluated. Kruskal-Wallis, Friedman, Wilcoxon, and Mann-Whitney tests were used to analyze both VMH and Ra between the treatment groups at different time intervals.

Results

There were a significant reduction in VMH values and significant differences between days 1, 7, and 28 against the baseline in the light-activated bleaching group (P = 0.001). The Ra values revealed significant differences in both light- (P = 0.001) and laser-activated (P = 0.033) groups.

Conclusion

Light activation of a bleaching agent caused a reduction in enamel microhardness and an increase in surface roughness when compared to laser activation.

Effect of pH of bleaching agent on tooth bleaching action in vitro

This study investigated the effect of pH of bleaching agent, photo-irradiation time or application times on bleaching action using hematoporphyrin-stained papers (HSPs) and artificially stained bovine-teeth (BT). 23% H2O2 with pH 5.5, 6.0, 7.0, 8.0 and 9.0 were applied on the specimens. HSP was photo-irradiated for 1, 3 and 5 min. BT were photo-irradiated for 10 min and the bleaching was repeated ten times (n=10). CIE L*a*b* of the specimens were measured before and after the procedure. Data were analyzed by repeated-measures ANOVA followed by multiple comparisons with Bonferroni correction. For the HSP, longer irradiation time and higher pH yielded significantly higher color difference (ΔE). As for BT, increasing application times and higher pH resulted in higher ΔE. It was concluded that the pH of the bleaching agent significantly improved the bleaching effect with increased photo-irradiation time for HSP and with an increase of repeated application times for BT.

Effect of pH conditioners on tooth bleaching

The purpose of this study was to evaluate the effect of pH conditioners on tooth bleaching using hematoporphirin-stained paper and artificially discolored bovine tooth model. Experimental bleaching gels containing 23% hydrogen peroxide, adjusting pH 7.0 by different pH conditioners (NaOH, NaHCO3, Na2CO3, KOH, KHCO3, and K2CO3), were prepared. Each bleaching gel was applied on a hematoporphirin-stained paper, and the light was exposed for 5 min. Before and after bleaching, color was measured and color difference was calculated. Artificially discolored bovine tooth samples were prepared and bleached by four experimental bleaching gels containing NaOH, NaHCO3, Na2CO3, or KHCO3. The bleaching time was 10 min with light exposure, and bleaching was repeated 10 times. The color of bleached surface was measured at each bleaching period, and color difference was calculated. In the experiment using hematoporphirin-stained paper, degrees of color difference were KHCO3 > NaHCO3 > KOH > NaOH > Na2CO3 ≥ K2CO3. In the experiment using bovine teeth, degrees of color difference were KHCO3 > NaHCO3 > NaOH > Na2CO3. It was concluded that the bleaching materials with same pH and different pH conditioners showed different bleaching effects and that both cation and anion in the pH conditioners affected bleaching effect.

Effects of in-office bleaching agent combined with different desensitizing agents on enamel

OBJECTIVE

To analyze color change, microhardness and chemical composition of enamel bleached with in-office bleaching agent with different desensitizing application protocols.

MATERIALS AND METHODS

One hundred and seventeen polished anterior human enamel surfaces were obtained and randomly divided into nine groups (n = 13). After recording initial color, microhardness and chemical composition, the bleaching treatments were performed as G1: Signal Professional White Now POWDER&LIQUID FAST 38% Hydrogen peroxide(S); G2: S+Flor Opal/0.5% fluoride ion(F); G3: S+GC Tooth Mousse/Casein Phosphopeptide-Amorphous Calcium Phosphate (CPP-ACP) paste(TM); G4: S+UltraEZ/3% potassium nitrate&0.11% fluoride(U); G5: S+Signal Professional SENSITIVE PHASE 1/30% Nano-Hydroxyapatite (n-HAP) suspension(SP); G6: S-F mixture; G7: S-TM mixture; G8: S-U mixture; G9: S-SP mixture. Color, microhardness and chemical composition measurements were repeated after 1 and 14 days. The percentage of microhardness loss (PML) was calculated 1 and 14 days after bleaching. Data were analyzed with ANOVA, Welch ANOVA, Tukey and Dunnett T3 tests (p<0.05).

RESULTS

Color change was observed in all groups. The highest ΔE was observed at G7 after 1 day, and ΔE at G8 was the highest after 14 days (p<0.05). A decrease in microhardness was observed in all groups except G6 and G7 after 1 day. The microhardness of all groups increased after 14 days in comparison with 1 day after bleaching (p>0.05). PML was observed in all groups except G6 and G7 after bleaching and none of the groups showed PML after 14 days. No significant changes were observed after bleaching at Ca and P levels and Ca/P ratios at 1 or 14 days after bleaching (p>0.05). F mass increased only in G2 and G6, 1 day after bleaching (p<0.05).

CONCLUSIONS

The use of desensitizing agents containing fluoride, CPP-ACP, potassium nitrate or n-HAP after in-office bleaching or mixed in bleaching agent did not inhibit the bleaching effect. However, they all recovered microhardness of enamel 14 days after in-office bleaching.