Bond Strength Of Bleached Enamel Research Articles

Comparative Evaluation of Various Antioxidants on the Shear Bond Strength of Composite Resin to Bleached Enamel - An In Vitro Study.

To evaluate and compare the effect of various antioxidants on the shear bond strength of composite resin to bleached enamel. Labial enamel surfaces of 90 extracted human maxillary central incisors were randomly divided into five groups based on the antioxidant used as follows: Group I ( n = 20): Bleaching with 40% hydrogen peroxide gel for 10 min, without the use of an antioxidant; Group II ( n = 20): Bleaching followed by the use of 10% sodium ascorbate solution; Group III ( n = 20): Bleaching followed by the use of 5% grape seed extract solution; Group IV ( n =20): Bleaching followed by the use of 5% pine bark extract solution; and Group V ( n =20): Control group in which no bleaching was done. Groups I-IV were further subdivided into two subgroups of 10 teeth each, whether the antioxidant application and composite build-up was done immediately (subgroup A) or after 2 weeks of postbleaching (subgroup B). Shear bond strength of the specimens was tested under a universal testing machine. One-way analysis of variance followed by Mann-Tukey posthoc multiple comparison test was used to analyse the data. The level of significance was established at P < 0.05. Within the limitations of this study, it was observed that the use of antioxidants effectively reversed the compromised bond strength of bleached enamel. Among the antioxidants, 5% pine bark extract application after bleaching showed better bond strength.

Assessment of the Micro-Tensile Strength of the Composites for the Various Antioxidants: An In Vitro Study

ABSTRACT Introduction: The application of the antioxidants after the teeth are bleached has been advocated to fasten the restorative process post-bleaching. The motive of this study was to examine and assess the micro-tensile binding strength of bleached enamel to the resin using a variety of antioxidant solutions. Finding the reason for the tooth fracture was the secondary outcome measured. Materials and Methods: An in vitro study was planned with 100 human extracted teeth, with 20 in each group with one as controls and 4 others tested for the antioxidants sodium ascorbate, epigallocatechin gallate, chitosan, and proanthocyanidin application. The bond strength of bleached enamel to the resin was well as the failure type was assessed after the values were noted and compared using the ANOVA and Tukey’s methods keeping P &lt; 0.05 as significant. Results: Epigallocatechin gallate specimens displayed the maximum micro-tensile bond strength under the investigational circumstances, whereas controls displayed the lowest micro-tensile bond strength. There was statistical alteration in micro-tensile bond strengths between all the groups except between epigallocatechin gallate vs chitosan and sodium ascorbate vs proanthocyanidin. High statistical significance was seen between the control and the antioxidant groups as well as between sodium ascorbate and epigallocatechin gallate and chitosan. Conclusion: The antioxidant chemicals significantly augmented the bond strength of bleached enamel to the resin that had been bleached. Also, when compared to the other experimental groups, epigallocatechin gallate and chitosan treatment displayed the greatest mean bond strength values.

Effect of Sodium Ascorbate, Grape Seed Extract, and Aloe Vera Application after In-Office Bleaching on the Bond Strength of Enamel: A 3-Year Evaluation

Introduction. Dental bleaching is the first choice to improve smile esthetics, but, in some cases, it needs to be associated with resin composite restoration to obtain a satisfactory result. Unfortunately, the bonding of resin-based materials can be impaired due to residual oxygen molecules, which can decrease the durability of the restoration. Objectives. To evaluate the effect of the antioxidant application on the bond strength of bleached enamel after 24 hr and 3 years of water storage. Methods. In total, 84 bovine teeth were used in this study. Of these, 77 were bleached with 35% hydrogen peroxide in a single session for three cycles of 15 min. Then, the specimens were divided into groups (n = 7 each): control (without bleaching), without antioxidant (WA) use; application of 10% sodium ascorbate (SA) gel, grape seed (GS) extract, and aloe vera (AV). The restorative procedure was performed immediately after bleaching, 7 and 14 days after bleaching. Specimens were sectioned and evaluated using microtensile bond strength (μTBS). Half of the resin-enamel sticks were tested after 24 hr, and the remaining half after 3 years of water storage. µTBS data were analyzed using a three-way analysis of variance, Tukey’s test, and Dunnett’s test. Results. The lowest µTBS values were observed when the restoration was performed immediately after bleaching in the AV, GS, and WA groups when compared with the SA group ( p &lt; 0.005 ). However, no significant differences were observed among all groups after 3 years of water storage ( p &lt; 0.001 ). Conclusions. SA at 10% was the most effective antioxidant agent for improving the immediate bond strength. However, independent of the antioxidant agent used, the bond strength values were maintained or recovered after 3 years of water storage. SA at 10% could be used to avoid delayed bonding procedures after in-office whitening without compromising bond strength over time. Clinical Significance. The use of antioxidants after dental bleaching can be effective in improving the bonding durability of the adhesive restorations.

Evaluation of antioxidant application on bond strength of composite resins to bleached enamel

Abstract Aim: This study aims to assess and evaluate the application of 10% sodium ascorbate, 5% green tea extract, 5% pomegranate peel extract, and 5% grape seed extract on shear bond strength of composite to bleached enamel. Materials and Methods: Sixty extracted human maxillary central incisors were randomly divided into seven groups. The enamel surface of these specimens was bleached with hydrogen peroxide (35%), except group VII (control group). Postbleaching, the specimens of group II were placed in artificial saliva for 2 weeks before restoration and the specimens of groups III and IV and groups V and VI underwent antioxidant application; 10% sodium ascorbate, 5% green tea extract, 5% pomegranate peel extract, 5% grape seed extract, respectively, for 10 min, followed by composite resin restoration, respectively. The specimens of group I were restored with composite resin immediately after bleaching. The specimens’ shear bond strength was tested using universal testing equipment. The data obtained were statistically analyzed using a one-way analysis of variance and the Tukey post hoc test. Results: There was no statistically significant difference in the effects of various antioxidants on the shear bond strength of bleached enamel. Conclusion: Within the constraints of the study, it was concluded that the application of antioxidants efficiently recovered the bond strength of bleached enamel. The application of 5% grape seed extract treatment demonstrated better bond strength among the antioxidants tested. Clinical Significance: Antioxidants can be used immediately following bleaching to restore resin composite bond strength without the requirement of delay in the treatment to reduce the nascent oxygen species in bleached teeth.

Effect of 3% Grape Seed Extract on the Bond Strength of Bleached Enamel with Natural and Commercially Available Bleaching Agents: An In-vitro Study

Introduction: Following bleaching with natural and commercial bleaching agents, to reverse the bond strength of enamel various antioxidants are used. The 3% Grape Seed Extract (GSE) has been more potent to be used as an antioxidant and has shown the immediate improvement in the Shear Bond Strength (SBS) values. Aim: To evaluate the effect of 3% GSE as an antioxidant on the bond strength of bleached enamel with natural {Sweet Potato Extract (SPE)}, commercial {35% Hydrogen Peroxide (H2 O2 )} bleaching agents. Materials and Methods: This experimental in-vitro study was conducted at Sibar Institute of Dental Sciences, Guntur, Andhra Pradesh, India, over a period of 1 week in January 2021. According to the bleaching agent used, the labial surfaces of 40 extracted maxillary central incisors have been divided into two groups. Group I (n=20) include teeth bleached by SPE (natural) for about 30 minutes. Group II (n=20) included teeth bleached using 35% H2O2 (Pola office) for about 8 minutes. Each group were again divided into two subgroups (n=10) based on the application of 3% GSE. After bleaching procedures, composite resin cylinders were bonded incrementally on the labial surface and stored in artificial saliva at 37°C for 24 hours. The samples were subjected to SBS under Universal Testing Machine. Data obtained were analysed using One-way Analysis Of Variance (ANOVA) and Tukey’s post-hoc test. Results: On comparison of mean SBS values, statistically significant difference (p-value&lt;0.05) was observed in all groups. The SBS values observed in 35% H2O2 bleached teeth were highly significant than the teeth bleached using 3% GSE application. Conclusion: Application of 3% GSE immediately after bleaching the enamel surfaces neutralizes the deleterious effects of bleaching and increases SBS significantly.

Comparative evaluation of reversal of shear bond strength on bleached enamel-resin nanocomposite using antioxidants – sodium ascorbate, salicylic acid &amp; N-acetyl cysteine

Aim: The aim of this study was to compare the reversal of shear bond strength of bleached enamel using 3 antioxidant agents. Methods and Materials: 60 labial enamel blocks of maxillary central incisors were prepared, divided into six groups (n=10). Group I is control group without bleaching and without antioxidants, all the other groups were bleached with 30% carbamide peroxide. Group II, composite bonding done immediately without antioxidants application, Group III, composite bonding done after 7 days of storage in artificial saliva without receiving antioxidants. Group IV, bleached enamel receive sodium ascorbate (SA) antioxidant application for 10 minutes, followed with composite bonding immediately, similarly Group V and VI bleached enamel samples received salicylicacid(SAC) and N-acetylcysteine(NAC) antioxidants application for 10 minutes and composite bonding immediately. All the teeth were subjected to shear bond testing in universal testing machine. Statistical analysis used: The shear bond strength data was analyzed by ANOVA test and multiple comparisons by Tukey’s post-hoc tests at a significance level of P &lt; 0·05. Results: The result of this study showed that for shear bond strength, unbleached normal enamel (group I) showed highest SBS value among all the groups.

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

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. 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. 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. 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.

“Effect of three vitamin antioxidants on reversal of shear bond strength of bleached enamel: An in-vitro Study.”

ABSTRACT&#x0D; Aims and objectives: To evaluate the effect of Sodium ascorbate, Alpha-tocoferol and Beta-carotene vitamins antioxidant on reversing the bond strength between resin composite and bleached enamel surface.&#x0D; Materials and methods: The study focussed on use of three vitamin antioxidants. All the groups in the study were subjected to bleaching containing 35% Hydrogen peroxide. Resin restoration were done after 1 week and immediately after bleaching without any antioxidant in Group 1 and 2 respectively. While in Group 3, 4 and 5, following bleaching treatment, samples were exposed to Beta-carotene gel, Sodium Ascorbate solution and Alpha-tocoferol gel respectively for 10 minutes, before resin restoration was done. Specimens were then subjected to Universal Testing Machine. The results were statistically analysed using ANOVA test and Tukey Honest Significant Difference (HSD) test, to comparatively analyse statistical differences between the groups.&#x0D; Results: The mean shear bond strength values of Group 4 (Sodium Ascorbate solution) showed significantly high bond strengths than Groups 3 (Beta-carotene gel) and 5 (Alpha-tocoferol gel).&#x0D; Conclusion: Treatment of bleached enamel with Sodium ascorbate and Alpha tocoferol antioxidants has significantly improved the shear bond strength of composite resin to enamel.&#x0D; Keywords: alpha-Tocopherol, Antioxidants, Ascorbic Acid, beta Carotene

Comparative Evaluation of the Microtensile Bond strength of composite resin to Bleached Enamel: An In vitro Experimental Study

Aim: Comparative evaluation of the effectiveness of 10% sodium ascorbate solution and delayed treatment on the microtensile bond strength of nanocomposite to bleached enamel using two step etch and rinse and self-etch adhesive technique. Materials and methods: Forty extracted human maxillary central incisors were decoronated, and the crown portion was embedded in acrylic resin with the buccal surface facing upwards. The specimens were randomly allocated to four groups which were further sub-divided into two groups according to the adhesion protocol. Group I- (control group): No bleaching followed by restoration. Group II: Bleaching followed by immediate restoration. Group III: Bleaching followed by surface treatment with 10 % sodium ascorbate for 30 mins followed by restoration. Group IV: Bleaching followed by restoration after 14 days. Result: Statistically significant differences were found between microtensile bond strength of bleached enamel with surface treatment with 10% sodium ascorbate solution and no surface treatment group. Conclusion: Bleaching followed by surface treatment with 10 % sodium ascorbate for 30 mins followed by restoration showed similar strength as compared the control group.

Comparative Analysis of Different Flavonoids on the Immediate Shear Bond Strength of Bleached Enamel Surface: An ex-vivo Study

INTRODUCTION: Bleaching, although considered as the first choice of treatment for discoloured teeth, can be utilized in conjunction with composite resin bonding or veneering and porcelain laminate veneers, to provide a more esthetic result. AIM: The aim of the ex-vivo study is to obtain a comparative analysis to evaluate the effectiveness of antioxidants on the immediate composite bond strength on bleached enamel surface.MATERIALS AND METHOD: Freshly extracted human permanent maxillary central incisors were selected and prepared for the respective study. All the specimens then were randomly divided into two control groups and three experimental groups, each group consisting of 20 specimens each. Among these were three experimental groups 10% Sodium Ascorbate, 5% Grape Seed extracts (Proanthocyanidin, PA) &amp; 10% Green tea extracts (catechins and epigallocatechin gallate, CA and EG) and two control groups (Positive control &amp; Negative control).RESULTS: When compared to Group 1 (positive control, 26.24 ± 0.90 MPa ), Group 3 (5%Grape seed extract; 32.17 ± 1.52 MPa), Group 4 (10% Sodium Ascorbate; 28.91 ±1.50 MPa ) and Group 5 (5% Green tea extract; 24.10 ± 1.21MPa ) showed significantly higher shear bond strength values.CONCLUSION: The present study indicated that the shear bond strength of the antioxidant group (Group3) is higher than all three experimental groups. In addition, the shear bond strength of the bleached group (Group 2) is significantly lower than all the other groups. This implies that immediate use of antioxidants, contributes in reversal the bond strength of bleached enamel.

Effect of Photodynamic therapy and Er,Cr: YSGG laser on bond strength of bleached enamel to composite resin

ObjectiveThe purpose of the present study was bleached enamel reversal using conventional ascorbic acid (AA) and contemporary methods including Photodynamic therapy (PDT), Er, Cr: YSGG (ECL) on bond integrity to composite resin. Material and methodForty sound permanent mandibular premolars were collected from a dental clinical setting and disinfected. All forty samples were mounted vertically in a rubber mold exposing only the clinical crown. All samples were bleached using Opalescence Boost Professional Teeth Whitening. After the bleaching procedure, each sample was randomly allocated into four groups according to surface treatment. Samples in group 1 were treated with methylene blue photosensitizer (MBP). Samples in group 2 were exposed to 10% sodium ascorbate. Samples in group 3 were treated with Er, Cr: YSGG laser (ECL). Samples in group 4 were not treated (control). All Samples were treated with 37% phosphoric acid and a bonding agent was applied. A bulk-fill composite was cured to all specimens and all samples were treated in a thermocycler. Specimens were placed in a universal testing machine for shear bond strength (SBS) testing. Descriptive statistics were associated by analysis of variance (ANOVA) and Tukey's post hoc test maintaining level of significance (p<0.05) ResultsThe lowest SBS scores were achieved in the bleached enamel (BE) group (15.25±1.745 MPa). Whereas, the highest bond integrity was attained by AA group (32.23±1.854 MPa). Samples treated with ECL (31.87±1.659 MPa) and AA (32.23±1.854) were comparable (p>0.05). Samples treated with PDT exhibited significantly different SBS (22.41±1.258) compared to other experimental groups ConclusionECL showed a reversal effect of BE compared to AA and has the potential to be used in clinical settings. BE reversal using MBP needs further investigation.

Comparative evaluation of 6% cranberry, 10% green tea, 50% aloe vera and 10% sodium ascorbate on reversing the immediate bond strength of bleached enamel: In vitro study

ObjectivesThe present study aimed to assess antioxidant activity of herbal antioxidants namely 6% cranberry extract, 10% green tea, 50% aloe vera and 10% sodium ascorbate and their effect on reversal of bond strength in bleached enamel. Materials and methodFrom one hundred and twenty extracted maxillary central incisors enamel blocks of 5 ​× ​5 ​mm were prepared and arbitrarily divided into six experimental groups (n ​= ​20): Group A: no bleaching, Group B: only bleaching protocol, Group C – bleaching ​+ ​6% cranberry extract solution, Group D – bleaching +10% Green Tea extract, Group E − bleaching ​+ ​50% aloe vera extract, Group F – bleaching ​+ ​10% Sodium Ascorbate. After bleaching antioxidants were applied for 10 ​min and were subjected to bonding procedures. The specimens were sectioned into 120 small strips of size (1 ​× ​1 ​× ​8 ​mm). Sixty sticks were analyzed to micro tensile bond strength using Universal testing machine and fractured segment were observed for failure modes (Adhesive, Cohesive and Mixed) under stereomicroscope. Remaining 60 sticks were observed for interface gap between tooth and composite resin under SEM. The %AA (antioxidant activity) was assessed with spectrophotometric analysis. ResultsData was statistically analyzed using ANOVA and Post Hoc Tukey’s test. Group A (91.68 ​± ​2.24 Mpa) showed higher mean micro tensile bond strength versus group D (82.14 ​± ​1.45 Mpa), followed by group E (75.26 ​± ​1.92Mpa), group F (63.89 ​± ​1.95Mpa), group C (57.58 ​± ​1.96 Mpa) and least in group B (31.5 ​± ​1.27 Mpa). The %failure mode inferred maximum adhesive mode of failure (86.25%). ConclusionAll the four antioxidants were able to reverse the compromised bond strength comparatively after bleaching maximum being green tea followed by aloe vera, sodium ascorbate, and minimum in cranberry. Clinically significance-Easily available, biocompatible, cost effectual, and potent herbal antioxidants could be used considerably for immediate esthetic cases where time is a restricting factor.

Comparative evaluation of the effect of 10%, 20%, and 30% guava seed extract on reversing compromised resin bond strength after enamel bleaching in 120 min, 10 min, and 5 min: An in vitro study.

Background:Bonding of composite with enamel and dentin gets compromised if the tooth is restored with composite immediately post bleaching. The application of antioxidants has shown to have a positive effect on it.Aim:The aim of this study was to evaluate and compare the effect of guava seed extract solutions in various concentrations on the shear bond strength (SBS) of composite resin to bleached enamel when applied for 5 min, 10 min, and 120 min.Materials and Methods:Fifty-five maxillary incisors were procured, and labial surfaces of 50 specimens were bleached with 37.5% hydrogen peroxide. These specimens were divided into 3 experimental groups: Group 1–3 comprising 15 specimens each (n = 15), and the remaining specimens were divided into two groups: Group 4 (positive control group) and Group 5 (negative control group). Groups 1–3 were further divided into 3 subgroups according to the application period of antioxidant: subgroups A, B, and C. Specimens were stored in distilled water for 24 h. SBS testing was done using the universal testing machine. Data were tabulated and subjected to statistical analysis using a three-way analysis of variance with post hoc Tukey's test.Results:Guava seed extract showed a complete reversal of the compromised bond strength, and promising results were seen with increased concentration.Conclusion:The use of antioxidants effectively reversed the compromised bond strength of bleached enamel, and an increase in the concentration of antioxidants reduces the duration of its application.

Reversal of Compromised Bond Strength of Bleached Enamel Using Cranberry Extract as an Antioxidant: an In Vitro Study.

Background and Objectives: Bleaching reduces the bond strength of enamel, if adhesive restorations are carried out immediately. Reversal of compromised bond strength of bleached enamel by application of antioxidant agents has been reported in the literature. The aim of the study is to assess the neutralizing effect of 6% cranberry (CB) solution on the bond strength of bleached enamel compared with that of 10% sodium ascorbate (SA) solution.Materials and Methods: Enamel surfaces of 64 extracted human premolar teeth were randomly divided into four groups based on the antioxidant used. Further subgrouping was done in Groups II, III, and IV dividing each group into subgroup A and subgroup B of eight teeth each based on whether the bonding was performed immediately or after a delay of 14 days postbleaching respectively. Shear bond strength (SBS) of the specimens was measured using a Universal testing machine. The data were then tabulated and statistically analyzed using one-way ANOVA (analysis of variance) and Tukey’s post-hoc parametric tests. A p-value of <0.05 was considered statistically significant.Results: The SBS measurements were compared among the four groups including the subgroups. The SBS was highest in the SA delayed bonding group and lowest in the bleached immediate bonding group.Conclusion: A 10% SA solution has proven superior to 6% CB solution in the reversal of compromised bond strength following bleaching.

Effect of surface removal following bleaching on the bond strength of enamel

BackgroundA reduction in bond strength of bleached enamel has been confirmed in the literature. Although limited information is available, it is conceivable that the veneer preparation process may remove the impacted enamel and further eliminate the compromised bond strength between the composite resin and bleached enamel. This study aimed to evaluate the effect of surface removal following bleaching on the micro-shear bond strength (μSBS) of bleached enamel.MethodsForty-eight specimens were prepared from bovine incisors and were randomly divided into 2 groups (n = 24): group B (bleaching with 40% hydrogen peroxide for 2 × 45 min with a 1-week interval) and group C (control group without bleaching treatment). Immediately after receiving the treatments, 0.5 mm of the enamel was removed from the specimen surface, followed by bonding of composite resin to the enamel surface. Each group was further divided into 2 subgroups of 12 specimens each: subgroup T (with 5000 thermocycles in water baths at 5 °C and 55 °C), and subgroup N (without thermocycling). The μSBS values were measured using a universal testing machine and subjected to two-way analysis of variance (α = 0.05). The fracture modes of the specimens were observed using a stereomicroscope.ResultsThe μSBS values of the different groups ranged from 21.42 to 25.21 MPa. Following a surface reduction of 0.5 mm, bleaching treatment and thermocycling did not significantly affect the μSBS values (P = 0.348 and P = 0.507, respectively). No significant interaction was found between the bleaching treatment and thermocycling (P = 0.514). All the groups exhibited a high percentage of mixed failures. Compared with group C, group B exhibited higher percentage of adhesive failure.ConclusionThe results suggested that the bonding procedure could be performed on the bleached enamel following a surface reduction of 0.5 mm immediately after the bleaching treatment.

Does bond integrity of bleached enamel increases with phototherapy? A systematic review.

The aim of the current systematic review was to evaluate the efficacy of phototherapy (PT) on bond strength of bleached enamel. Electronic databases including MEDLINE (PubMed), ISI Web of Science, Scopus, ScIELO, LILACS and EMBASE until January 2019. The addressed focused question was: "Does PT increase the bond integrity of bleached enamel?" Only in-vitro studies evaluating the effect of PT compared with bleaching agent or no phototherapy were included. The outcome measures of interest was shear bond strength. A total of 5 in-vitro studies were included. Different concentrations of hydrogen peroxide were used in the included studies. The frequency of laser used in the included studies ranged from 20 Hz to 60 Hz. Pulse duration was reported in only 3 studies that ranged from 100 μs to 320 μs. The overall main outcomes of the included studies showed that in 4 studies, application of phototherapy resulted in significantly higher bond integrity of bleached enamel as compared to enamel which underwent acid etching with bleaching alone, while 1 study showed comparable shear bond strength of bleached enamel achieved by PT as compared to bleaching alone. The evidence from the current systematic review suggests that phototherapy increases the bond strength of bleached enamel. Further in-vitro studies should be performed in order to obtain stronger conclusions.

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

BackgroundBleaching 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 MethodsThree 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.ResultsAll 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).ConclusionsThe 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 Er,Cr:YSGG Laser and Ascorbic Acid on the Bond Strength and Microleakage of Bleached Enamel Surface.

The available evidence of Er,Cr:YSGG lasers on bleached enamel is limited and controversial. It is assumed that Er,Cr:YSGG laser will be effective in reversing the effect of bleaching on adhesive bond integrity of enamel to resin composite. The study aimed to evaluate the efficacy of Er,Cr:YSGG laser on bond strength and microleakage of bleached enamel. From the 80 samples, 60 samples were bleached (40% hydrogen peroxide) and divided into three subgroups. Twenty bleached samples in each subgroup were exposed to 10% sodium ascorbate (Gp A), Er,Cr:YSGG laser (50 Hz and 4.5 W) (Gp L), and no treatment (Gp B), respectively. Twenty samples were not bleached (Control-C). Using etch and rinse technique, resin composite was built-up on enamel and photopolymerized. Ten specimens in each group were tested for shear bond strength at a crosshead speed of 1 mm/min. Ten specimens in each group were tested for microleakage using 2% methylene blue. Data were analyzed using analysis of variance (ANOVA) and Tukey post hoc multiple comparisons test. The mean bond strength of specimens in group L (30.83 ± 1.7000) was comparable with group A (31.38 ± 2.03) and was significantly higher than bleached specimens (9.49 ± 0.86) (p < 0.001). The highest mean microleakage values were observed in bleached group (630.32 ± 156.58). The mean microleakage among control (36.66 ± 27.33) and laser group specimens (55.32 ± 34.98) was comparable (p > 0.05). Treatment of bleached enamel with erbium, chromium:yttrium-scandium-gallium-garnet (Er,Cr:YSGG) laser showed a significant reversal effect on the enamel bond strength and microleakage scores. Er,Cr:YSGG laser (50 Hz, 4.5 W) treatment has the potential to restore the bond strength of bleached enamel to resin composite.

Effect of different antioxidants on reversing compromised resin bond strength after enamel bleaching: An in vitro study.

Objective:The effect of 10% sodium ascorbate, 10% α-tocopherol, 10% grape seed extract, and 10% guava seed extract solutions on the shear bond strength (SBS) of composite resin to bleached enamel was evaluated.Materials and Methods:Labial enamel surfaces of 72 extracted maxillary central incisors were bleached using 37.5% hydrogen peroxide. Sixty-four specimens were divided into four experimental groups (Group I–IV) comprising 16 specimens each and remaining eight specimens were placed in Group V. Groups I–IV were further divided into 2 subgroups: A (10 min) and B (120 min) comprising 8 specimens each. Eight unbleached specimens served as control (Group VI). Immediately following bleaching, Groups IA–IVA and IB–IVB specimens were treated with respective antioxidants for 10 min and 120 min. All specimens were then bonded with composite resin. Specimens were stored in distilled water for 24 h. SBS testing was done. Data were tabulated and subjected to statistical analysis using ANOVA and Tukey's honest significant difference test.Results:Group VI (unbleached) showed the highest SBS followed by Group IV (10% guava seed extract).Conclusion:Use of antioxidants effectively reversed the compromised bond strength of bleached enamel. About 10% guava seed extract application after bleaching showed best bond strength.

Evaluation of 5% proanthocyanidin and 30% alpha-tocopherol on shear bond strength of composite to bleached enamel: An In vitro study

Objective: The aim of this in vitro study is to evaluate and compare the effect of 5% proanthocyanidin and 30% alpha-tocopherol on the bond strength of composite resin to the bleached enamel. Materials and Methods: The labial enamel surface of sixty central incisors was flattened for the purpose of this study. Fifteen teeth served as control group which did not receive bleaching nor antioxidant treatment. The remaining 45 teeth then were randomly divided into three groups of 15 each. They are Group 1: bleaching with 38% hydrogen peroxide for 10 min without the use of antioxidant, Group 2: bleaching followed by treating with 5% proanthocyanidin, and Group 3: bleaching followed by treating with 30% alpha-tocopherol. The bonded specimens were stored in distilled water (37°C, 24 h) and tested for shear bond strength in a universal testing machine. The data were analyzed with one-way ANOVA and Tukey's post hoc test. Results: Higher bond strength values were seen in the control group followed by 5% proanthocyanidin group. Conclusion: Use of 5% proanthocyanidin can effectively reverse the bond strength of bleached enamel.