Effect of Sodium Ascorbate or Alpha-Tocopherol on the Resin-Dentin Interface and Bond Strength after Endodontic Treatment and Bleaching / Efecto del Ascorbato de Sodio o Alfa-Tocoferol sobre la Interfaz Resina-Dentina y la Fuerza de Unión Después del Tratamiento de Endodoncia y Blanqueamiento

The objective of this in vitro study was to assess the effects of two antioxidants (sodium ascorbate [SA] and alpha-tocopherol [AT]) on the adhesive interface and dentin bond strength immediately after bleaching with 38 % hydrogen peroxide (38HP) in endodontically-treated teeth. Two stages of experimentation were carried out. Bovine incisors were allocated into four groups (n = 10/group for each experiment): NB, non-bleached restored crowns; 38HP, bleached and immediately restored crowns; 38HP-SA, bleached crowns and SA use; and 38HP-AT, bleached crowns and AT use. Hybrid layer length in dentin (μm) and bond strength (MPa) were assessed with confocal microscopy laser and micro-shear bond strength (μSBS) test, respectively. Failure mode was determined by stereomicroscope. Data analysis was performed with analysis of variance (ANOVA) and Kruskal-Wallis, Dunn, Tukey, and Fisher-exact tests (a = 0.05). Higher values of hybrid layer length were observed similarly in the NB and 38HP-SA groups. The highest μSBS mean values were observed in the NB group (18 .51 ? 1.33), whereas the SBS values for 38HP-AT (1.68 ? 0.32) were similar to the 38HP group (1.61 ? 0.51) (p > 0.05) and significantly lower than the 38HP-SA group (5.78 ? 0.71). Adhesive failures were predominant in the 38HP and 38HP-AT groups. Cohesive and mixed failures were mostly observed in the NB and 38HP-SA groups, respectively. In conclusion, AT has no immediate effect on the hybrid layer formation and μSBS of dentin. Although SA promotes an increase in hybrid layer formation, it was not reflected in the μSBS values.

El objetivo de este estudio in vitro fue evaluar los efectos de dos antioxidantes (ascorbato de sodio [AS] y alfa-tocoferol [AT]) sobre la interfaz adhesiva y la fuerza de unión de la dentina inmediatamente después del blanqueamiento con peróxido de hidrógeno al 38 % (38HP) en endodoncia. -Dientes tratados. Se llevaron a cabo dos etapas de experimentación. Los incisivos bovinos se dividieron en cuatro grupos (n = 10 / grupo para cada experimento): NB, coronas restauradas no blanqueadas; 38HP, coronas blanqueadas y restauradas inmediatamente; 38HP- AS, coronas blanqueadas y uso SA; y 38HP-AT, coronas blanqueadas y uso de AT. La longitud de la capa híbrida en dentina (μm) y la fuerza de unión (MPa) se evaluaron con láser de microscopía confocal y la prueba de fuerza de unión por micro-cizallamiento (μSBS), respectivamente. El modo de falla se determinó mediante estereomicroscopio. El análisis de los datos se realizó con análisis de varianza (ANOVA) y pruebas de Kruskal-Wallis, Dunn, Tukey y Fisher (α = 0,05). De manera similar, se observaron valores más altos de longitud de capa híbrida en los grupos NB y 38HP-AS. Los valores medios más altos de μSBS se observaron en el grupo NB (18,51 ? 1,33), mientras que los valores de SBS para 38HP-AT (1,68 ? 0,32) fueron similares a los del grupo 38HP (1,61 ? 0,51) (p> 0,05) y significativamente más bajos que el grupo 38HP-AS (5,78 ? 0,71). Las fallas adhesivas fueron predominantes en los grupos de 38HP y 38HP-AT. Las fallas cohesivas y mixtas se observaron principalmente en los grupos NB y 38HP-AS, respectivamente. En conclusión, la AT no tiene un efecto inmediato sobre la formación de la capa híbrida y el μSBS de dentina. Aunque AS promueve un aumento en la formación de capas híbridas, no se refleja en los valores de μSBS.

Use of two kinds of antioxidants to restore the bond strength of bleached enamel / 华西口腔医学杂志

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 (@*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.

Improving shear bond strength of metallic brackets after whitening

ABSTRACT Objective: To evaluate a protocol for bonding metallic brackets after bleaching with hydrogen peroxide (HP). Methods: 60 extracted maxillary premolar were randomly divided into an unbleached control group and two groups bleached with a solution of 35% hydrogen peroxide prior to bonding. The teeth in one of the treated groups were bonded immediately after bleaching; while the other group was treated with 10% sodium ascorbate immediately after bleaching and before bonding. The teeth in all groups were stored in an artificial saliva solution for 7 days after bonding. The shear bond strength data was measured in megapascals (MPa) and the fail attempts were verified. The significance level was established at p< 0.05. Results: The unbleached group, in which brackets were bonded to untreated enamel, had the highest bond strength values (11.0 ± 5.7MPa) in comparison to the bleached group (7.14 ± 40MPa), in which brackets were bonded to recently bleached enamel. Slightly improved bond strength was observed in the antioxidant group (8.13 ± 5.4MPa), in which the teeth were bleached and then the antioxidant was applied to the teeth before bonding. Unbleached and bleached groups showed statistically significant difference for shear bond strength (p=0.03) and load strength (p=0.03); no significant differences were noted between unbleached and antioxidant groups (p=0.52). Conclusion: The antioxidant treatment applied immediately after bleaching was effective in reversing the reduction in shear bond strength of brackets after tooth bleaching.

RESUMO Objetivo: Avaliar um protocolo para colagem de braquetes metálicos após clareamento com peróxido de hidrogênio (PH). Método: Sessenta pré-molares superiores extraídos foram aleatoriamente divididos em um Grupo Controle (sem clareamento) e dois grupos que receberam clareamento, antes da colagem, com solução de peróxido de hidrogênio a 35%. Em um dos grupos tratados (Grupo Clareamento), os braquetes foram colados imediatamente após o clareamento, enquanto o outro (Grupo Antioxidante) foi tratado com ascorbato de sódio a 10%, imediatamente após o clareamento e antes da colagem. Os dentes, em todos os grupos, foram armazenados em saliva artificial por 7 dias após a colagem. As informações relativas à resistência da colagem foram registradas em megapascals (MPa) e as tentativas fracassadas foram verificadas. O nível de significância foi estabelecido em p < 0,05. Resultados: O Grupo Controle, no qual os braquetes foram colados ao esmalte não clareado, apresentou os valores mais altos de força de adesão (11,0 ± 5,7 MPa), em comparação ao Grupo Clareamento (7,14 ± 40 MPa), no qual os braquetes foram colados ao esmalte recém-clareado. Uma suave melhora na força de adesão foi observada no Grupo Antioxidante (8,13 ± 5,4 MPa), no qual, após os dentes serem clareados, foi aplicado antioxidante aos dentes, antes da colagem. Os Grupos Controle e Clareamento apresentaram uma diferença estatisticamente significativa para a resistência da colagem (p =0,03) e a resistência à carga (p= 0,03); porém, nenhuma diferença significativa foi notada entre os Grupos Controle e Antioxidante (p =0,52). Conclusão: O tratamento antioxidante aplicado imediatamente após o clareamento foi efetivo em reverter a diminuição da resistência da colagem dos braquetes após o clareamento dentário.

Comparative evaluation of effects of natural antioxidants on the shear bond strength of composite resin to bleached enamel

Context: The use of antioxidants immediately after bleaching showed increased bond strength. Aims: This study aimed to compare the effects of natural antioxidants on the shear bond strength of composite resin to bleached enamel. Materials and Methods: Fifty extracted single-rooted upper incisors were decoronated by sectioning the roots 2 mm below the cementoenamel junction, and then, crowns were embedded in autopolymerizing acrylic resin block (3.0 cm × 3.0 cm × 3.0 cm) with the labial surface exposed. They were randomly divided into five groups, depending on the type of antioxidant used (n = 10): (i) Group 1: control (no bleaching), (ii) Group 2: bleaching only, (iii) Group 3: bleaching + 10% sodium ascorbate (antioxidant), (iv) Group 4: bleaching + green tea, and (v) Group 5: bleaching + white tea. Labial surfaces of 40 teeth were bleached with 38% hydrogen peroxide for 20 min following manufacturer's instructions. After that, the experimental groups (Groups 3, 4, and 5) were treated with respective antioxidant solutions before composite restorations were done using a cylindrical plastic mold (3 mm × 5 mm). Shear bond strength of the specimens was tested under universal testing machine. Statistical Analysis: Data were analyzed with ANOVA and Tukey's post hoc test. Results: There were statistically significant differences between shear bond strength of control groups (Groups 1 and 2) and experimental groups (P < 0.05), but no significant difference in bond strength was observed among the antioxidants used. Conclusion: Application of antioxidants immediately after bleaching showed increased bond strength. Green tea and white tea extract can be used as alternative antioxidants in improving the bond strength of enamel.

Effects of an Antioxidant on the Shear Bond Strengths of Orthodontic Brackets After Conventional and Laser-Assisted Extra-Coronal Bleaching / Efecto de un antioxidante sobre la fuerza de unión de brackets de ortodoncia posterior al blanqueamiento convencional y asistido por láser

RESUMEN El objetivo del presente estudio fue evaluar los efectos de la aplicación de un antioxidante sobre las fuerzas de unión (SBS) de brackets de ortodoncia posterior al blanqueamiento con peróxido de hidrógeno (HP). Metodología: Cincuenta premolares recién extraídos se dividieron aleatoriamente en tres grupos. El Grupo 1 se trató con 40% de HP (n=20), el grupo 2 con 40% de HP y se activó con láser de Nd: YAG (n=20) y un grupo de control (Grupo 3) no recibió tratamiento (n=10). Después del blanqueamiento, los Grupos 1 y 2 se dividieron en dos subgrupos (Grupo 1a, Grupo 1b, Grupo 2a y Grupo 2b). Las muestras en los subgrupos 1a y 2a (n=10) no recibieron ninguna aplicación del antioxidante. Se aplicó una solución de ascorbato de sodio al 10% a las muestras en los Grupos 1b y 2b (n=10). Luego, los brackets se adherieron a las superficies de esmalte de todos los grupos experimentales. Las muestras se sometieron a pruebas de SBS y los datos analizados estadisticamente. Resultados: La fuerza de unión de los grupos 1 y 2 fue significativamente más baja que el grupo de control (p <0.001); sin embargo, no se observaron diferencias estadísticamente significativas en SBS entre los grupos 1 y 2 (p>0.001). Las muestras tratadas con antioxidantes de los grupos 1b y 2b fueron significativamente mayores que las de los grupos 1a y 2a (p <0,001). Conclusion: La aplicación de 40% HP tuvo un efecto negativo en la resistencia de unión de los brackets. El uso de antioxidante durante 15 minutos mejoró significativamente la SBS.

ABSTRACT Purpose: The purpose of this study was to evaluate the effects of the application of antioxidant on the shear bond strengths (SBS) of orthodontic brackets bonded to human enamel after extra-coronal bleaching with hydrogen peroxide (HP). Materials and methods: Fifty freshly extracted premolars were randomly divided into three groups. One group (Group 1) was bleached with 40% HP (n=20), another group (Group 2) was bleached with 40% HP and activated with an Nd: YAG laser (n=20), and a control group (Group 3) received no treatment (n=10). After the bleaching procedure, Groups 1 and 2 were further divided into two subgroups (Group 1a, Group 1b, Group 2a, and Group 2b). Specimens in Groups 1a and 2a (n=10) received no antioxidant application. A 10% sodium ascorbate solution was applied to specimens in Groups 1b and 2b (n=10). The brackets were then bonded with light-cure adhesive paste to the enamel surfaces of all experimental groups. Specimens were subjected to SBS tests for debonding. Results: The SBS of brackets bonded in Groups 1 and 2 were significantly lower than those of brackets bonded to the control group (p<0.001); however, no statistically significant differences in SBS were noted in Groups 1 and 2 (p>0.001). The antioxidant-treated SBS of brackets in Groups 1b and 2b were significantly higher than those of Groups 1a and 2a (p<0.001). Conclusions: The application of 40% HP had a negative effect on the bond strength. The use of antioxidant for 15 min resulted in the reversal of failed bond strength.

A comparison of the effect of application of sodium ascorbate and amla (Indian gooseberry) extract on the bond strength of brackets bonded to bleached human enamel: An In vitro study

Whitening of teeth is a popular choice among dental clinicians and patients. However, the changes in enamel structure and composition induced by the bleaching agents cause a decrease in the shear bond strength of brackets leading to premature bracket debonding. Among several methods to overcome this, the most common is delaying bonding by 2–4 weeks. This waiting period can be eliminated by applying an antioxidant (sodium ascorbate) which causes a reversal in the reduction of bond strength. Aim: This study aims to compare the efficacy of a naturally occurring antioxidant (gooseberry) and sodium ascorbate in normalizing the bond strength of enamel to prebleached levels. Materials and Methods: Seventy-two extracted premolars were divided into 4 equal groups; 1st group – control group – unbleached teeth, bonded directly, 2nd group – bleached with 16% carbamide peroxide (8 h for 1 week), then bonded. 3rd and 4th group – similarly bleached, followed by application of 10% sodium ascorbate and gooseberry extract (3 h respectively), then bonded. Bond strength was checked using Instron Universal Testing Machine. Results: The bond strength of the control group was the highest and that of the carbamide group was drastically reduced. Considerable increase in the bond strength was seen after treatment with sodium ascorbate with negligible difference between sodium ascorbate and control group (P > 0.05). Conclusion: Treatment with gooseberry extract did improve the bond strength but was not as effective as sodium ascorbate postbleaching.

Effects of applying antioxidants on bond strength of bleached bovine dentin

OBJECTIVES: Some antioxidants are believed to restore dentin bond strength after dental bleaching. This study was done to evaluate the influence of antioxidants on the bond strength of bleached bovine dentin. MATERIALS AND METHODS: Thirty incisors were randomly assigned to 10 groups (two unbleached control and eight bleached groups: immediate bonding IB, 4 wk delayed bonding DB, 10% sodium ascorbate treated SA, 10% alpha-tocopherol treated TP groups). Teeth in half of groups were subjected to thermal stress, whereas the remaining groups were not. Resin-dentin rods with a cross-sectional area of 2.25 mm2 were obtained and microtensile bond strength was determined at a crosshead speed of 1 mm/min. Fifteen specimens were prepared for SEM to compare the surface characteristics of each group. The change in dentin bond strength from thermal stress and antioxidant treatment was evaluated using two-way analysis of variance (ANOVA) and Sheffe's post hoc test at a significance level of 95%. RESULTS: The control group exhibited the highest bond strength values, whereas IB group showed the lowest value before and after thermocycling. The DB group recovered its bond strength similar to that of the control group. The SA and TP groups exhibited similar bond strength values with those of the control and DB groups before thermocycling. However, The TP group did not maintain bond strength with thermal stress, whereas the SA group did. CONCLUSIONS: Applying a 10% sodium ascorbate solution rather than 10% alpha-tocopherol solution for 60 sec is recommended to maintain dentin bond strength when restoring non-vitally bleached teeth.

Effective application duration of sodium ascorbate antioxidant in reducing microleakage of bonded composite restoration in intracoronally-bleached teeth

OBJECTIVES: The aim of this study was to determine an appropriate application duration of sodium ascorbate (SA) antioxidant gel in reducing microleakage of bonded composite restoration in intracoronally-bleached teeth. MATERIALS AND METHODS: Eighty endodontically-treated human incisors were randomly divided into eight groups: control, no bleaching; IB and DB, immediate and delayed bonding after bleaching, respectively; S10m, S60m, S24h, S3d and S7d, bleaching + SA gel for 10 min, 60 min, 24 hr, 3 day and 7 day, respectively. For bleaching, a mixture of 30% hydrogen peroxide and sodium perborate was applied for 7 day. All access cavities were restored using One-Step adhesive (Bisco Inc.) and then Aelite LS Packable composite (Bisco Inc.). The bonded specimens were subjected to 500 thermal cycles, immersed in 1% methylene blue for 8 hr, and longitudinally sectioned. Microleakage was assessed with a 0 - 4 scoring system and analyzed using nonparametric statistical methods (alpha = 0.05). RESULTS: Group IB showed a significantly higher microleakge than the control group (p = 0.006) and group DB a statistically similar score to the control group (p > 0.999). Although groups S10m, S60m, and S24h exhibited significantly higher scores than group DB (p 0.999). CONCLUSIONS: Application of SA gel for 3 day after nonvital bleaching was effective in reducing microleakage of composite restoration in intracoronally-bleached teeth.

Bond strength of composite-resin and resin-modified glass ionomer to bleached enamel: Delay bonding versus an antioxidant agent.

Objectives: As enamel bond strength of the resin-modified materials is reduced after bleaching, a delay bonding of at least 1 week is recommended. This study investigated the efficacy of 10% sodium ascorbate hydrogel on the bond strength of bleached enamel as an antioxidant agent. Materials and Methods: Ninety-six human, sound molars divided into eight groups. Buccal enamel surfaces of specimens in two negative control groups after preparation were bonded by the Z100 CR using the single-bond adhesive and Vitremer RmGI. Specimens in other groups after enamel preparation were bleached with 9.5% hydrogen peroxide. In two positive control groups, bonding of CR and RmGI was performed immediately after bleaching. Specimens in two other groups were immersed in distilled water after bleaching, and then CR and RmGI were bonded after 1 week. In last two groups, 10% sodium ascorbate hydrogel was applied after bleaching, and then they were bonded by CR and RmGI. The specimens were placed under shear force. Statistics: ANOVA and Duncan's multiple range tests were used for data analysis. Results: Application of 10% sodium ascorbate hydrogel immediately before bonding and delay bonding for 1 week eliminated the negative effects of bleaching on CR and RmGI enamel bond strength. Conclusion: Application of 10% sodium ascorbate hydrogel or 1 week period elapsed after bleaching could significantly increase the enamel bond strength to a normal value.

Comparison of the effect of hydrogel and solution forms of sodium ascorbate on orthodontic bracket-enamel shear bond strength immediately after bleaching: An in vitro study.

Aim: This study compared the effects of hydrogel and solution forms of sodium ascorbate (SA) with two different application times on bracket bond strength subsequent to bleaching. Materials and Methods: A total of 72 sound premolars were randomly divided into six groups (n = 12): An unbleached control group (group one) and five experimental groups of carbamide peroxide. Specimens in group two were bonded immediately after bleaching; specimens in groups three and four were bleached, then treated with SA solution for ten minutes and three hours, respectively, and then bonded. In groups five and six, SA hydrogel was used and the specimens were prepared similar to groups three and four, respectively. Following debonding, bond strengths were recorded in MPa. To evaluate the amount of resin left on the enamel surfaces, adhesive remnant index (ARI) scores were used. Statistical Analysis: The bond strength data were analyzed with ANOVA and pairwise comparisons were made by Tukey test. The ARI data were subjected to Kruskal-Wallis test and two-by-two comparisons were made by the Mann-Whitney U test. Results: There were significant differences in bond strengths between the groups ( P < 0.0005). However, the differences between groups three, four, five and six were not significant. Furthermore, there were no significant differences between group one and groups four and six, whereas the differences between the other groups were significant ( P < 0.05). Regarding ARI, there were significant differences among the groups ( P = 0.004). Conclusion: Bleaching significantly decreased the bracket bond strength. Compromised bonding was reversed with a three-hour application of both forms of SA.