Assessing the use of 35 percent sodium ascorbate for removal of residual hydrogen peroxide after in-office tooth bleaching

The effect of resveratrol application on the micro-shear bond strength of adhesive to bleached enamel

The aim is to investigate the effect of resveratrol on micro-shear bond strength (µSBS) of adhesive to enamel after 40% hydrogen peroxide application. For µSBS test, 50 teeth were obtained, 2/3 of crowns were embedded into acrylic resin. After application of hydrogen peroxide twice, teeth were randomly allocated to control group and 9 groups (n = 15) according to concentrations (0.5, 1, 2 µM) and application periods (10, 30, 60 min) of resveratrol. Following, composite resin was placed onto enamel surfaces using 3 tygon tubes for each tooth. µSBS test was performed and failure modes were displayed. To analyze µSBS values, Kruskal Wallis and Mann-Whitney U tests were performed. µSBS values of 1 µM resveratrol for 10 min applied group were statistically higher than control group (p < 0.05). 1 µM resveratrol showed higher µSBS values than 0.5 µM and 2 µM (p < 0.05). No significant difference was detected between application periods (p > 0.05). The improvement of µSBS values with 1 µM resveratrol application may be promising for clinical problems related to reduced bond strength after bleaching.

Comparison of various methods of restoring adhesion to recently bleached enamel

AIM

This study compared the effectiveness of several techniques in restoring compromised bonding to recently bleached enamel.

METHODS

Seventy-five healthy bovine incisors were divided into five groups (n = 15). Fifteen teeth (Group 1) remained intact, whereas 60 (Groups 2 to 5) underwent at-home bleaching with 16% carbamide peroxide. The bonding procedures were as follows: Group 1: Bonding of resin composite to unbleached enamel; Group 2: Bonding immediately after bleaching; Group 3: Application of a 10% sodium ascorbate solution for 10 min before bonding; Group 4: Enamel removal to the depth of 0.5 mm; and Group 5: Increased curing time of the bonding agent to 80 instead of 20 s. After 24 h, the specimens were subjected to micro-shear testing, and the failure mode was determined.

RESULTS

ANOVA revealed a significant difference in bond strength among the groups (P < 0.001). The mean bond strength was significantly lower in group 2 than in other groups (P < 0.05), which showed comparable bond strength to each other (P > 0.05). Adhesive failure was the most predominant failure type in all groups. The mixed failure occurred with a frequency of 26.7% in groups 3 and 5. The Fisher's exact test revealed a significant difference in failure modes among the groups (P = 0.047).

CONCLUSIONS

The three experimental procedures used in this study, including the application of 10% sodium ascorbate before bonding, enamel removal to the depth of 0.5 mm, and increasing the curing time of the bonding agent to 80 s, were effective in restoring the compromised bonding to recently bleached enamel.

Reduction of surface treatment time by combination of citric acid and ascorbic acid while restoring shear bond strength of metal brackets bonded to bleached enamel: a pilot study

BACKGROUND

To investigate the effect of a 50% ascorbic acid with 50% citric acid solution on the immediate shear bond strength (SBS) of metallic brackets after tooth bleaching. The enamel etching pattern and the required quantity of these combined acids as antioxidants following 35% hydrogen peroxide (HP) bleaching were also determined.

METHODS

The stability of the solution at room temperature was assessed at various time intervals. Fifty teeth were randomly divided into five groups: non-bleached (G1), bleached then acid etched (G2), bleached followed by a 10-minute treatment with 10% sodium ascorbate and acid etched (G3), 5-minute treatment with 50% ascorbic acid (G4), and 5-minute treatment with a combination of 50% ascorbic acid and 50% citric acid (G5). Groups G2, G3, G4 and G5 were bleached by 35% HP gel for a total of 32 min. Acid etching in groups G1, G2, and G3 was performed using 37% phosphoric acid (Ormco®, Orange, CA, USA) for 15 s. In all groups, metal brackets were immediately bonded using Transbond™ XT primer and Transbond™ PLUS adhesive, with light curing for 40 s. The SBS was tested with a universal testing machine, and statistical analysis was conducted using one-way ANOVA followed by Tukey's HSD test. The level of significance was set at p < 0.05 for all statistical tests.

RESULTS

Stability tests demonstrated that the combined acids remained effective for up to 21 days. Group G5 significantly increased the SBS of bleached teeth to the level of G1 (p < 0.05), while G3 did not achieve the same increase in SBS (p > 0.05). SEM analysis revealed enamel etching patterns similar to those of both control groups (G1 and G2). Kinetic studies at 6 min indicated that the antioxidation in G5 reacted 0.2 mmole lower than in G3 and G4.

CONCLUSION

5-minute application of the combined acids enhanced the SBS of bleached teeth comparable to unbleached teeth. The combined acids remain stable over two weeks, presenting a time-efficient, single-step solution for antioxidant application and enamel etching in orthodontic bracket bonding.

Effect of antioxidant on tooth sensitivity after bleaching

OBJECTIVES

This study aimed to investigate the effect of antioxidant (sodium ascorbate) on tooth sensitivity after two in-office bleaching techniques (light-activated and chemical bleaching).

MATERIALS AND METHODS

Ten patients aged 18-25 were bleached in four groups according to bleaching materials and/or antioxidant used. Group A: Maxillary right quadrant received light-activated bleaching with antioxidant. Group B: Maxillary left quadrant received light-activated bleaching without antioxidant. Group C: Mandibular right quadrant received chemical bleaching without antioxidant. Group D: Mandibular left quadrant received chemical bleaching with antioxidant. The tooth sensitivity was recorded using Numerical Rating Scale (NRS) and Schiff Scale (SS) immediately after treatment, 1 day, 1 week, 2 weeks, and 1 month follow-up periods.

RESULTS

Group B exhibited higher sensitivity values than Group A. This difference was statistically significant on the first day after treatment (p = 0.027* in NRS and p = 0.046* in SS). Furthermore, antioxidant incorporation in Group D led to a reduction in teeth sensitivity values compared to Group C. This disparity was highly significant on the first day after treatment (p = 0.001* in NRS and p < 0.001** in SS).

CONCLUSIONS

The antioxidant (10% sodium ascorbate) reduces the intensity of tooth sensitivity at the different follow-up periods, especially after 1 day from bleaching.

CLINICAL SIGNIFICANCE

Using 10% sodium ascorbate after bleaching is advisable to reduce post-operative tooth sensitivity.

Does the Elapsed Time from Bleaching and the Use of Sodium Ascorbate Influence the Bond Strength of Resin Cement to Bleached Enamel?

The objective of this study was to evaluate different delaying times after bleaching and the use of different sodium ascorbate (SA) concentrations (10% and 35%) in the bond strength of adhesive cementation to enamel. This study used 54 sound bovine incisors, which were randomly assigned to the following groups: G1 (unbleached/control+ adhesive cementation (AC)); G2 (bleached + AC after 7 days); G3 (bleached + 10% SA + AC after 24 h); G4 (bleached + 10% SA + AC after 7 days); G5 (bleached + 35% SA + AC after 24 h); and G6 (bleached + 35% SA + AC after 7 days). After bleaching, G3, G4, G5, and G6 received an application of SA before the cylinders build up with RelyX Veneer cement. The samples were subjected to microshear test, and the results were analyzed by two-way ANOVA with Tukey's post hoc test. Group one presented the highest mean bond strength (19.1 MPa) and G3 the lowest (16.96 MPa). There was no statistical difference between the groups tested (p ˃ 0.05). The fracture pattern observed was predominantly mixed. The adhesive cementation may be performed 24 h after bleaching when SA (10% or 35%) is used or after 7 days, without compromising bond strength.

Effect of green tea extract antioxidant on dentin shear bond strength and resin-tag penetration depth after non-vital bleaching

Background: 35% Hydrogen peroxide (H 2O 2) as an active material for internal bleaching can produce free radicals that can affect resin tag penetration into the dentinal tubules. Application of 10% and 35% green tea (GT) extract as an antioxidant after 2 minutes are expected to remove free radical residues and increase dentin shear bond strength and resin tags penetration depth after non-vital bleaching. Methods: 30 extracted healthy human premolars were cut horizontally 2 mm from the Cemento Enamel Junction margin to the crown part, then cut in a mesio-distal direction into two parts. The specimens were divided into five groups: normal dentin, post bleaching dentin, delayed 2 weeks, 10% GT, and 35% GT group. Non-vital walking bleach with 35% H 2O 2 gel was done to all groups except control group. Soon after, 10% and 35% GT extract gel were applied on dentin for 2 minutes, then the specimens were rinsed-off with aquabidest for 2 minutes and dried. All specimens were etched and bonded with an etch-and-rinse adhesive system and filled with resin composite. The shear bond strength assessment was carried out using a Universal Testing Machine (UTM) with a cross-head speed of 0.5 mm/minute. Confocal laser scanning microscopy (CLSM) with a wavelength of 560 nm and a lens magnification of 40x was used to analyze the resin tag penetration. Data were analyzed by one way ANOVA and t-test. Results: There was a significant difference in resin tag penetration depth and shear bond strength between applying 10% and 35% GT extract (p < 0.05). The 35% GT extract group resulted in a significantly longer resin tag penetration than the 10% GT extract group. Conclusions: The application of 35% GT extract is more effective than 10% GT extract as an antioxidant for increasing the shear bond strength of composite resin after internal bleaching.

One-Step Surface-Treatment Reagent (35% 3-O-Ethyl-l-ascorbic Acid Plus 50% Citric Acid Solution) Restores the Shear Bond Strength of Metal Brackets Bonded to Bleached Human Enamel: An In Vitro Study

This study investigates how a new substance, composed of ethyl ascorbic acid and citric acid, affects the shear bond strength (SBS) of metal brackets when bonded to bleached teeth. Forty maxillary premolar teeth were used and randomly placed into four groups (n = 10): the control group did not undergo bleaching; the remaining groups underwent bleached using 35% hydrogen peroxide. In group A, 37% phosphoric acid was applied after bleaching. In group B, 10% sodium ascorbate was used for ten minutes before 37% phosphoric acid. In group C, 35%3-O-ethyl-l-ascorbic acid plus 50% citric acid solution (35EA/50CA) was applied for 5 min. The subgroups were bonded immediately after bleaching. The SBS was determined with a universal testing machine and analyzed using one-way ANOVA and then Tukey's HSD tests. Adhesive remnant index (ARI) scores were determined with a stereomicroscope and analyzed with a chi-squared test. The significance level was 0.05. Group C demonstrated significantly higher SBS values than group A (p < 0.001), but was not significantly different than the control group or group C (p > 0.05). The ARI scores were significantly different among the groups (p < 0.001). In conclusion, enamel surface treatment using 35EA/50CA improved the reduced SBS to an acceptable clinical level and reduced the clinical chair time.

Can antioxidant treatment replace delay in bracket bonding? An in vitro study

BACKGROUND

Deterioration in shear bond strength has been reported after immediate bracket bonding following hydrogen peroxide bleaching. This study compared the effectiveness of three antioxidant agents, namely, alpha-tocopherol, green tea extract, and sodium ascorbate, in reversing the bleaching effect and as possible alternatives to delayed bonding.

METHODS

A total of 105 extracted human premolars were arbitrarily assigned to 7 groups (n = 15 each), including group 1 as the unbleached control group and six experimental groups, which were bleached with 40% hydrogen peroxide in three sessions of 15 min each. In experimental group 2, bonding was performed immediately after bleaching, whereas in groups 3 and 4, bonding was delayed for 1 and 2 weeks, respectively; meanwhile, the specimens were immersed in artificial saliva at 37 °C. Groups 5, 6, and 7 were treated immediately after bleaching with 10% of alpha-tocopherol, green tea extract, and sodium ascorbate solutions, respectively, for 15 min. Specimens were processed using 500 thermal cycles between 5 and 55 °C, with a dwell time of 30 s after 24 h of bracket bonding, and then tested for shear bond strength. The adhesive remnant index was examined to evaluate fracture mode. One-way analysis of variance, Kruskal-Wallis H, and post hoc Tukey's honestly significant difference tests were used to compare the data. Significant results were subjected to pairwise comparisons with Bonferroni's correction-adjusted of p values ≤ 0.050.

RESULTS

Shear bond strength was significantly lower (p < 0.001) in the immediate bonding and 1-week delay groups than in the control group. However, no significant difference was detected among the 2-week delay, antioxidant-treated, and control groups (p > 0.05).

CONCLUSIONS

Application of 10% alpha-tocopherol, green tea extract, or sodium ascorbate for 15 min could restore shear bond strength after 40% hydrogen peroxide bleaching as an alternative to delay in bracket bonding.

Efficacy of organic and antioxidant agents to regain bond strength to bleached enamel in different dental adhesive solvents

Materials like carbamide peroxide or hydrogen peroxide are commonly used for vital teeth bleaching. However, there have been concerns regarding their effect on composite-to-bleached enamel bonding strength. The study investigated the impact of organic and antioxidant agents on composite bond strength in bleached enamel with different dental adhesive solvents. Human third molar teeth were sectioned into buccal and lingual halves. The two main adhesive solvent groups evaluated were acetone and alcohol. Each main group was divided into six groups. The positive control group received no bleaching, the negative control group consisted of bleaching with no surface deoxidization; and other experimental categories involved post-bleach treatments with 95% ethanol, sodium ascorbate (10%), acetone solution, or sodium fluoride solution (1.1%). Following the surface treatment and enamel bonding procedure, nano-hybrid composite cylinders measuring 3 × 2 mm were directly cured over the bleached enamel substrate. The shear bond test was performed after 24-h storage and 12,000 thermocycles on a universal testing machine. In this study, one-way ANOVA was used along with Tukey's HSD tests at a significance level of 0.05. The negative control groups showed significantly lower bond strength than the positive control group. Ethanol surface treatment had superior mean bonding strength in acetone and alcohol-based adhesive solvent groups. The utilization of sodium ascorbate for surface treatment resulted in a significant enhancement of adhesion between the composite material and bleached enamel surface. Sodium fluoride application showed no significant recovery in shear bond strength in both dental adhesive groups. It was concluded that hydrogen peroxide severely compromised the immediate bond strength of composite resin. Surface treatment of bleached enamel with ethanol, sodium ascorbate, and acetone solutions is an effective option for restoring bond strength.

Quantitative Measurements of the Depth of Enamel Demineralization before and after Bleach: An In Vitro Study

Objective

This study is aimed at determining two main points. First, if the Canary System™ (CS), initially used to assess caries, can measure a decalcification depth of bleached enamel quantitatively, and second, whether or not whitening has a harmful effect on enamel. This device can be considered a useful tool in the clinical assessment of the progression of demineralization after bleaching.

Materials and Methods

This study collected sixty human premolars that are in a good state recently extracted for orthodontic reason. To properly disinfect and preserve the premolars, they were stored in a saline solution and later in distilled water for a period of two weeks to allow the premolars to rehydrate. Later, 24 hours before the experiment, the premolars were introduced into a solution of artificial saliva to acquire back their minerals. The mineral content of the teeth was measured by the Canary System™ before bleaching. The teeth were bleached with 30% hydrogen peroxide (fläsh HP 30%), 30 min per week and for 3 consecutive weeks to simulate the conditions of strong bleaching in the clinic. The extent of demineralized enamel was measured by the Canary System™ at three points on the enamel surface of each tooth. The data were averaged for each application of the bleaching product. The demineralization extent of the teeth was measured by the Canary System™ before and after bleaching. The significance level was set at 0.05, and SPSS version 26 was used. The data were analyzed by using Wilcoxon's and Student's tests.

Results

Mineral loss occurred after the first bleaching session; the Canary System™ detected a decalcification in the first bleaching session (532 ± 322 μm) compared to the other sessions (p ≤ 0.05), while no significant change was detected between the second and the third sessions (p > 0.05).

Conclusion

Based on the findings of the present study, under in vitro conditions, it was possible to measure the demineralization extent of bleached enamel with the Canary System™.

Use of two kinds of antioxidants to restore the bond strength of bleached enamel

OBJECTIVES

This work aimed to evaluate the ability of two kinds of antioxidants, namely, grape-seed extract and sodium ascorbate, in restoring bond strength at the resin-enamel interface after bleaching.

METHODS

Ten groups of samples with 15 teeth per group were prepared for shear-bond-strength test at the resin-enamel interface after bleaching. The groups were as follows: control; no antioxidant; 2.5%, 5%, 10%, or 15% grape-seed extract; and 2.5%, 5%, 10%, or 15% sodium ascorbate. The peak values of shear bond strength when resin was debonded from teeth and the failure modes under a microscope were recorded. Ten other groups of teeth with two teeth per group were prepared and treated in a similar approach before resin bonding. The samples were cut vertically to the bonding interface. The structures of the bonding interface were compared by scanning electron microscopy.

RESULTS

No statistically significant difference in shear bond strength was found among the no-antioxidant, 2.5% grape-seed extract, and 2.5%, 5%, or 10% sodium ascorbate groups (P>0.05), which were statistically significantly lower than the control group (P<0.05). Evidence of marginal gap was observed at the resin-enamel interface, and resin tags in enamel were short, poorly defined, and fragmented. No statistically significant difference in shear bond strength was found among 5%, 10%, or 15% grape-seed extract, 15% sodium ascorbate, and control groups (P>0.05). No evidence of discontinuity was found at the adhesion interface, and resin tags in enamel were long, well defined, and structurally intact. Failure in the adhesive joint was the major debond mode in all experimental groups.

CONCLUSIONS

Immediately after bleaching, the bond strength of dental enamel significantly decreased. Bond strength can be restored by 5% grape-seed extract or 15% sodium ascorbate in 5 min.

Use of antioxidants to restore bond strength after tooth bleaching with peroxides

This review compiles the literature on the antioxidants used after tooth bleaching with either low or high-concentrated carbamide and hydrogen peroxide to recover the bond strength. Antioxidants used in bleached teeth are mainly natural and non-enzymatic, except for catalase. Commonly, antioxidants are applied to remove any reactive oxygen species (ROS) residues left from bleaching gels, which adversely affect adhesive procedures, such as restorations or orthodontic brackets bonding. Even though sodium ascorbate, the most thoroughly investigated antioxidant, showed the most efficient bond strength recovery at 10% concentration, its performance depends on the type of solution and the application time. Natural extracts, such as proanthocyanidins and green tea, showed satisfactory results in the reversal of bond strength at 5% and 10% concentrations, respectively. Sodium ascorbyl phosphate, α-tocopherol, and catalase exhibited promising results, but further research is required. The adhesive system type plays an important role in the outcome of enamel bond strength after the antioxidant application. The postponement of either restorations or orthodontic brackets cementation following bleaching procedures seems to be efficiently replaced by antioxidant application prior to bonding procedures. However, the efficacy of using an antioxidant to recover bond strength depends on its type and application time.

Comparative Analysis of Shear Bond Strength of Composites to the Sodium Ascorbate Hydrogel-treated Bleached Enamel Surfaces: An In Vitro Analysis

Aim

To compare the shear bond strength of composites to the sodium ascorbate hydrogel-treated bleached enamel surfaces.

Materials and methods

Sixty-six extracted human maxillary first premolars were sectioned mesiodistally to obtain two nonocclusal surfaces (n = 132). The specimen in the experimental group (n = 80) were divided into four treatment groups depending upon bleaching protocols used: group I (10% FGM home bleach), group II (22% Pola Night home bleach), group III (37% light-activated in-office bleach Pola Office+), and group IV (35% Pola office in-office bleach without light activation). Specimens were subjected to the 1-minute application twice with sodium ascorbate hydrogel and were further divided into two subgroups “a” (acetone-based) and “b”(ethanol-based) depending upon the bonding agents used. The specimens of the control group (n = 52) were further divided into two treatment groups, that is, positive control and negative control. The specimens were tested using universal testing machine.

Results

The result of the present study revealed that the specimens bleached with 10% FGM home bleach showed the greatest shear bond strength and specimens bleached with 35% in-office bleach Pola Office showed the lowest shear bond strength.

Conclusion

A twice 1-minute application of sodium ascorbate hydrogel was effective to reverse the deleterious results of bleaching on enamel shear bond strength. Bonding agent containing acetone as a solvent (Prime and Bond NT) in this present study showed greater shear bond strength values than the bonding agent containing ethanol as a solvent (Adper Single Bond).

Statement of clinical relevance

The shear bond strength of composite restorative materials could be improved by applying sodium ascorbate gel to the bleached enamel surfaces.

How to cite this article

Pathak K, Kumar P, Choudhary A, et al. Comparative Analysis of Shear Bond Strength of Composites to the Sodium Ascorbate Hydrogel-treated Bleached Enamel Surfaces: An In vitro Analysis. Int J Clin Pediatr Dent 2021;14(6):741–747.

Effects of remaining dentin thickness on the bond strength of bleached dentin

Background

The bond strength of resin composites to dentin was reported to be related to either the remaining dentin thickness (RDT) or bleaching treatment. However, information is limited regarding the effects of RDT on the bond strength of bleached dentin. The present study aimed to investigate the effects of RDT on the microshear bond strength (μSBS) of resin cement to bleached dentin.

Methods

A total of 120 dentin specimens were prepared and randomly divided into 2 groups: a bleaching group (group B) and a control group (group C). Hydrogen peroxide with a concentration of 35% (Ultradent, USA) was applied on the dentin surface for 2 × 1 d for group B, while no bleaching treatment was performed for group C. After the treatment, the specimens were finished and polished to obtain different RDTs (2, 1, and 0.5 mm) and divided into 3 groups of 20 specimens each. The bonding procedure was performed using Panavia V5 (Kuraray, Japan) with a bonding area of 0.785 mm². For each group, half of the specimens were subjected to 5000 thermal cycles (subgroup T), while the other half did not receive thermocycling (subgroup N) (n = 10). The specimens were then subjected to the μSBS test using a universal testing machine. Data were analyzed by a three-way analysis of variance (α = 0.05). The fracture modes of the specimens were confirmed with a measuring microscope. Representative specimens with different fracture modes were observed with scanning electron microscopy (SEM).

Results

The μSBS values were significantly affected by bleaching treatment (p < 0.001), whereas no significant effect was observed for thermocycling (p = 0.293). In terms of RDT, a significantly different μSBS value was found among the subgroups with different RDTs in group C (p = 0.003). However, the RDT did not significantly affect the μSBS values of bleached dentin in group B (p = 0.779). The μSBS values were significantly lower in group B than in group C (p < 0.001). A higher percentage of adhesive failure was observed in group B than in group C.

Conclusion

Based on the present findings, it can be concluded that the RDT did not affect the bond strength of resin cement to bleached dentin.

Clinical significance

Since RDT did not affect the bond strength of resin cement to bleached dentin, bonding procedures should not be performed immediately after intracoronal bleaching, even if the dentin is planned to be removed due to a tooth preparation process.

Comparative Evaluation of Two Antioxidants on Reversing the Immediate Bond Strength of Bleached Enamel: In Vitro Study

Background

Tooth bleaching causes a significant decrease in the bonding strength between the resin and human enamel. Nevertheless, the effects of different antioxidant types on the immediate bonding strength of resin and bleached enamel were significantly different. Therefore, the objective of this study was to compare the effects of 2 antioxidants for enhancing the bond strength of the resin to bleached enamel.

Material/Methods

There were 48 enamel blocks performed from 48 recently extracted maxillary central incisors. There were 8 groups: NC (negative control, no bleached specimens restored without antioxidants); NA (no antioxidant, bleached specimens bonded immediately without any antioxidants); SA30, SA60, and SA120 (bleached specimens accepted the management of 10% sodium ascorbate (SA) for 30 minutes, 60 minutes, and 120 minutes, respectively, before restored); PC30, PC60, and PC120 (bleached specimens received treatment of 5% proanthocyanidins (PC) for 30 minutes, 60 minutes, and 120 minutes, respectively, before restored). We measured the micro-tensile bond strength of specimens and used 2-way ANOVA to analyze the data.

Results

The mean±standard deviation bond strength measured were: NC, 29.99±4.00; NA, 14.90±1.97; SA30, 18.60±2.20; SA60, 22.57±2.71; SA120, 26.15±3.85; PC30, 16.78±2.29; PC60, 19.13±2.24, PC120, 23.90±2.01 MPa. In addition, the fracture types were mainly of an adhesive mode (88.75%), followed by mixed (7.5%), and cohesive (3.75%).

Conclusions

10% sodium ascorbate provided a comparatively more promising improvement for immediate bond strength than 5% proanthocyanidins when the same duration of antioxidant was applied.

Influence of simplified, higher-concentrated sodium ascorbate application protocols on bond strength of bleached enamel

Background

Bleaching procedures performed before restorative procedures, due to the oxygen released, affects the quality of bonding restorations. The application of an lower-concentrated antioxidant for one-hour or more can reversal the compromised bonding to bleached enamel, but it was not effective according to the bleaching concentrations applied. The aim of the present study was to evaluate simplified protocol of higher-concentrated sodium ascorbate (35%SA) in bond strength values of enamel bleached with 10%, 16%, 22% carbamide peroxide (CP) or 35% hydrogen peroxide (HP).

Material and Methods

Three hundred and forty enamel surfaces of 85 human third molars were used, divided into 17 groups (n=20), according to the following groups: control = no bleaching and no ascorbic acid application; bleaching (CP10%, CP16%, CP22% at-home and HP 35% in-office) and 35%SA application (no application; 35%SA applied twice for 1-min each [SA2×1], twice for 5-min each [SA2×5] and; twice for 10-min each [SA2×10]). After that, adhesive was applied and composite cylinders were made with Filtek Z350 composite. Microshear test was performed in a universal testing machine. BS values were statistically evaluated using ANOVA and Tukey’s and Dunnet’s (against control) tests, with 5% level of significance.

Results

All bleaching concentrations significantly decrease the enamel bond strength results when compared to control group (p<0.05). More concentrated PC (PC22% and PH35%) showed lower enamel bond strength results when compared to lower concentrated PC (PC10% and PC16%; p<0.05). A significant increase of the enamel bond strength results were only observed when SA2×5 and SA2×10 were applied (p<0.05).

Conclusions

The application of 35% sodium ascorbate for twice 5- and 10-min each was an efficient protocol to reverse the bond strength in bleached enamel at the same level as the no bleaching enamel, independently of the bleaching concentration used.

Key words:Tooth bleaching, hydrogen peroxide, sodium ascorbate, bond strength.

Effect of Non-Vital Bleaching on the Durability of Resin⁻Dentin Bond with an Ethanol-Based Etch-And-Rinse Adhesive

To evaluate the bleaching procedure and application of sodium ascorbate on dentin bond durability, the enamel surface of intact human third molars (n = 18) were removed, and the teeth were randomly divided into two groups for immediate and six-month bond strength evaluation. The specimens were further assigned into three subgroups according to treatment procedure, as follows: subgroup A, no bleaching (positive control) was performed prior to the etch-and-rinse bonding with single bond and subsequent build-up with Z250 composite; subgroup B, the samples were bleached with 20% carbamide peroxide 6 h/day for five consecutive days prior to bonding; and subgroup C, bleaching was performed as in subgroup B, after which 10% sodium ascorbate was applied on dentin surface for 10 min before the bonding procedures. A microtensile bond strength test was performed and the failure modes were evaluated under a stereomicroscope. The data were analyzed using two-way analysis of variance (ANOVA) and Tukey’s post-hoc tests with a level of significance of 0.05. Bleaching significantly decreased the immediate and six-month bond strength. The application of sodium ascorbate had no significant effect on the immediate and six-month bond strength of bleached specimens. We conclude that the bleaching procedure may decrease the durability of the resin–dentin bond of the tested etch-and-rinse adhesive.

Impact of Microabrasion on the Effectiveness of Tooth Bleaching

The aim of the present study was to evaluate the effect of prior microabrasion on the teeth color change and tooth bleaching effectiveness. Eight sound molars were mesio-distally sectioned and the halves were randomly allocated to receive enamel microabrasion or non-abrasion (control) in one of surfaces (buccal or lingual), while the remaining surface received the other treatment. The tooth color on baseline was evaluated by spectrophotometer (CieL*a*b system). After the microabrasion procedure, the tooth color was measured again. Following, the specimens were bleached with 35% hydrogen peroxide for two sessions with one-week interval. The color was re-evaluated 7 days after each section and 30 days after the second session. The effect of enamel microabrasion on color changes was evaluated by paired T-test. Deltas L*, a*, b*, and E were calculated and data submitted to 2-way repeated measure ANOVA followed by Tukey`s test. Paired T-test was also used to assess possible differences on the ultimate color achieved after tooth bleaching. Enamel microabrasion reduced the lightness and increased the redness of specimens. Specimens that received microabrasion presented higher values of ∆L* than control after each bleaching procedure; and higher ∆a* after the 2nd bleaching session. However, the prior enamel microabrasion did not affect the ultimate values of color parameters. Despite enamel microabrasion have modified the tooth color, this procedure did not affect the ultimate results achieved with tooth bleaching using a high-concentrated hydrogen peroxide.

Effect of Two-minute Application of 35% Sodium Ascorbate on Composite Bond Strength following Bleaching

AIM

The aim of this study is to assess the effect of 35% sodium ascorbate on microtensile bond strength of dentin immediately after bleaching with 35% hydrogen peroxide.

MATERIALS AND METHODS

A total of 25 sound human 3^rd molars were collected. Teeth were randomly divided into five groups for different treatments: Group I [bleaching + immediate bonding (i.e., restoration)], group II (bleaching + delayed bonding), group III (bleaching + sodium ascorbate + immediate bonding), group IV (bleaching + sodium ascorbate + delayed bonding), and group V (bonding only). After bleaching, but before bonding, groups II and IV were stored for 1 week in deionized water at 37°C. All samples were bonded using OptiBoned FL (Kerr) and Filtek Supreme (3M/ESPE). Teeth were sectioned into 1 × 1 mm 2 bars, and microtensile bond strength was tested with a universal testing machine (Instron 8841) at a cross-head speed of 0.5 mm/minute.

RESULTS

Microtensile bond strength differed significantly across the five groups, with a significant reduction in microtensile bond strength observed for samples in group I relative to samples in any of the other treatment groups (p < 0.05).

CONCLUSION

The application of a high concentration of sodium ascorbate for a shorter time reversed the negative effect of 35% hydrogen peroxide bleaching on composite bonding strength to dentin.

CLINICAL SIGNIFICANCE

The negative effects of bleaching on composite bonding can be neutralized by the application of the reversing agent sodium ascorbate thus, increasing the efficiency of clinic chair time. This is clinically relevant for those patients requiring restorative treatment immediately after in-office bleaching.

Evaluating the effect of antioxidant agents on shear bond strength of tooth-colored restorative materials after bleaching: A systematic review

PURPOSE

The main objective of the present study was to make a systematic review of how antioxidant agents affect shear bond strength of tooth-colored restorative materials after bleaching.

DATA SOURCES

Electronic search was used to extract the related articles on the targeted key words such as "antioxidant", "dental bleaching" and "shear bond strength" (SBS) from MeSH, PubMed, Medline, and Cochrane electronic data bases. These articles were all published before 2016.

STUDY SELECTION

Inclusion criteria were restricted to English journal articles concerning humans, clinical trials, cohorts and case-control studies. Therefore, systematic reviews, case reports, letters to editors, editorials and congress abstracts were excluded from the analysis.

CONCLUSIONS

Most studies conducted on the issue have produced experimental data which are rather controversial, and there is no general agreement about the reported outcomes. As an illustration, most studies have not considered the relationship between the type of antioxidant materials and the shear bond strength. In point of fact, some researchers (e.g Kimyai et al.) have concluded that antioxidants like gel and solution leave similar effects on SBS. Alternatively, certain studies (e.g., Kunt et al.) have produced inconclusive data regarding the impact of one week postponement of the restorative process on SBS after the bleaching process. The results of the studies evaluating the role of various adhesive systems used after bleaching have demonstrated that regardless of the type of adhesive system used, applying antioxidants before restorative procedures can adversely affect the bleaching agents utilized for SBS. It has also been suggested that the type of the adhesive system used might be correlated with the magnitude of SBS. The results obtained from the systematic review of the articles under investigation reflected that the use of antioxidant agents, regardless of their type, form, concentration and duration of application, can improve SBS after bleaching.

Influence of 10% sodium ascorbate gel application time on composite bond strength to bleached enamel

Objective To analyze bond strength to bleached enamel following application of 10% sodium ascorbate gel. Material and methods Forty third molars were allocated into five groups (n = 8): GP - unbleached specimens restored with composite resin; GN - specimens restored immediately after bleaching; and G15; G30 and G60 (test groups) - bleached specimens treated with 10% sodium ascorbate gel for 15, 30 and 60 min before restoration. The teeth were sectioned and the buccal and lingual faces were restored. After storage in distilled water (37 °C/24 h), sticks of ±0.8 mm² were tested in tensile (0.5 mm/min). Fractures were observed and classified. Data (in MPa) were analyzed with one-way ANOVA and Tukey tests (α = 0.05). Results No differences were found among GP (26 ± 6.0), G15 (23 ± 7.3), G30 (25 ± 6.1) and G60 (25 ± 5.1), with GN (15 ± 5.5) showing the lowest bond strength (p < 0.0001). Conclusion The application of 10% sodium ascorbate gel for 15 min after bleaching with 37.5% hydrogen peroxide restored the bonding to enamel.

The Effect of 3% Phosphate Ascorbyl Gel on Bond Strength of Composite Resin to Enamel treated with 35% Hydrogen Peroxide

OBJECTIVE

To evaluate the effect of 3% phosphate ascorbyl gel (PA) in different times onto the microshear bond strength of composite resin (CR) to bovine enamel treated with 35% hydrogen peroxide (HP).

MATERIALS AND METHODS

Thirty enamel blocks of bovine incisors were made and divided into 5 groups (n = 6) with three specimens per group (n = 18), according to treatment: G1= No bleaching + CR; G2 = HP + CR after 15d; G3 = HP + CR after 24 hours; G4 = HP + PA (15 min) + CR after 24 hours; G5 = HP + PA (2 hours) + CR after 24 hours. The resin cylinders were made by Tygon matrices. Microshear bond strength test was performed using universal testing machine with a 50N load at a speed of 0.5 mm/min. Fracture modes were assessed by a stereomicroscope 40 ×. Microshear bond strength values were submitted to the analysis of variance (ANOVA) one-way and Tukey test (p < 0.05).

RESULTS

G1 had significant results when compared to G3 and G5 (p < 0.01). However, G2, G3, G4 and G5 have showed no significant differences among groups (p > 0.05). Failure modes were categorized into adhesive (90%) and mixed (10%).

CONCLUSION

The use of 3% phosphate ascorbyl gel for 15 minutes was able to improve bond strength of composite resin to bleached bovine enamel, but when 3% phosphate ascorbyl gel was applied during 40 minutes it negatively interfered in the adhesion of the resin to bleached bovine enamel.

Effect of Sodium Ascorbate and Delayed Bonding on the Bond Strength of Silorane and Two-step Self-etch Adhesive Systems in Bleached Enamel

Background and aims. Studies have shown decreased bond strength of composite resin to human and bovine bleached enamel. This study evaluated the effect of sodium ascorbate and delayed bonding on the bond strength of two adhesive systems to bleached enamel.

Materials and methods. The labial surfaces of 150 sound bovine incisor teeth were abraded with abrasive paper. The teeth were randomly divided into 8 groups: A: control; B: bleached with 35% hydrogen peroxide; C: bleached with 35% hydrogen peroxide + sodium ascorbate gel; and D: bleached with 35% hydrogen peroxide + delayed bonding. In groups A‒D, silorane adhesive system and Filtek silorane composite resin were used. In groups E‒H, the same preparation methods of groups A-D were used. Two-step self-etch Clearfil SE Bond adhesive systems and AP-X composite resin were administered. Shear bond strength of each group was measured. Two samples were prepared for each surface preparation for ultra-structural evaluation. Two-way ANOVA and Tukey test were used for data analysis at P<0.05.

Results. The interaction between the adhesive system type and surface preparation protocol was significant (P=0.014), withsignificant differences in shear bond strengths in terms of the adhesive systems (P<0.01). There were significant differences in shear bond strength in terms of surface preparation techniques irrespective of the adhesive system (P<0.01).

Conclusion. The results showed that bleaching with 35% hydrogen peroxide decreased the shear bond strength values with both adhesive systems, and a one-week delay in bonding and 10% sodium ascorbate for10 minutes restored the bond strength in both adhesive systems.

Evaluation and comparison of bond strength to 10% carbamide peroxide bleached enamel following the application of 10% and 25% sodium ascorbate and alpha-tocopherol solutions: An in vitro study

Aim:

To evaluate and compare composite bond strength to carbamide peroxide bleached enamel following the application of 10% and 25% sodium ascorbate and alpha-tocopherol solutions.

Materials and Methods:

Sixty premolars were divided into six groups. Groups I and VI served as unbleached and bleached controls respectively. Groups II, III, IV and V served as the experimental groups and were subjected to 10% carbamide peroxide bleaching followed by 10 min application of 10% and 25% sodium ascorbate and 10% and 25% alpha-tocopherol solutions, respectively. Following composite bonding, shear bond strength was determined and the results were analyzed using ANOVA and Tukey highest significant difference test.

Results:

Only Group IV showed significantly lower bond strength when compared to Group I (unbleached control). When compared to Group VI (bleached control), except Group IV, groups II, III and V showed significantly higher bond strength. However, there was no statistically significant difference between the experimental groups corresponding to 10% and 25% and similar concentrations of sodium ascorbate and alpha-tocopherol solutions.

Conclusion:

Following 10% carbamide peroxide bleaching, except 10% alpha tocopherol, 10 min application of 10% and 25% sodium ascorbate and 25% alpha-tocopherol solutions significantly improves the shear bond strength of composite resin to enamel.