Effects of alpha-tocopherol antioxidant on fracture strength and adhesion of endodontically treated teeth restored after dental bleaching.

This study evaluated the effect of different concentrations of alpha-tocopherol in gel form on fracture strength, hybrid layer formation, and microtensile bond strength of endodontically treated teeth bleached with 40% hydrogen peroxide (H2 O2 ). Sixty bovine incisors were randomized into one of six groups (n = 10 incisors per group) defined by the interventions carried out after endodontic treatment. In the control group, no additional intervention was carried out, while all teeth in the five intervention groups were bleached with 40% H2 O2 and subsequently treated with alpha-tocopherol at concentrations of 15% (15AT), 20% (20AT), or 25% (25AT), with 10% sodium ascorbate (10SA), or with nothing (40HP). Fracture strength was evaluated in a mechanical testing machine, hybrid layer formation was assessed using scanning electron microscopy, and bond strength was determined using microtensile bond-strength testing. Data were analyzed using Kruskal-Wallis and Dunn's tests. No statistically significant difference regarding fracture strength was observed among groups. Hybrid layer formation was greater in the 15AT group than in groups 40HP and 10SA. Teeth in groups 15AT, 20AT, and 25AT demonstrated higher bond strength than teeth in groups 40HP and 10SA. Alpha-tocopherol, preferably at 15%, effectively reverses the deleterious effects, of bleaching, on hybrid layer formation and bond strength to dentin.

Effect of antioxidants after post-space irrigation on the adhesive interface of glass fiber post cementation.

OBJECTIVE: This study evaluated the effects of antioxidants, 10% sodium ascorbate (SA) or 20% alpha-tocopherol (AT), after post-space irrigation with 2.5% sodium hypochlorite +17% EDTA (SH) or 1% peracetic acid (PA) on the adhesive interface after glass fiber post cementation. MATERIALS AND METHODS: Sixty bovine roots were endodontically treated. After preparation, the post-space was irrigated with SH or PA followed or not by the use of antioxidants (SA or AT) (n = 10). Push-out bond strength test, failure mode, and dentin penetrability analysis using confocal laser microscope were performed in the cervical, middle, and apical thirds. Data from bond strength and dentinal penetrability were evaluated by one-way ANOVA and Tukey post hoc test (p < 0.05). RESULTS: SH showed the lowest bond strength regardless of the third (p < 0.05). In apical third, mixed failure was the most incident in all groups. Only in the cervical third of the post-space, SH-AT provided the greatest tag extension of the cementation system into dentin (p < 0.05). However, in the middle and apical thirds, SH-AT, SH-SA, and PA-SA provided the largest tag extensions (p < 0.05), but similar to each other (p > 0.05). CONCLUSIONS: The use of antioxidants only favored bond strength when SH was used and dentin penetrability of the adhesive and conventional resin cementation, regardless of the solution used to irrigate the post-space. CLINICAL SIGNIFICANCE: The use of antioxidants (10% sodium ascorbate and 20% alpha-tocopherol) after post-space irrigation with sodium hypochlorite appears to increase the bond strength favoring the glass fiber post-cementation.

Laponite Composites: In Situ Films Forming as a Possible Healing Agent.

A healing material must have desirable characteristics such as maintaining a physiological environment, protective barrier-forming abilities, exudate absorption, easy handling, and non-toxicity. Laponite is a synthetic clay with properties such as swelling, physical crosslinking, rheological stability, and drug entrapment, making it an interesting alternative for developing new dressings. This study evaluated its performance in lecithin/gelatin composites (LGL) as well as with the addition of maltodextrin/sodium ascorbate mixture (LGL MAS). These materials were applied as nanoparticles, dispersed, and prepared by using the gelatin desolvation method-eventually being turned into films via the solvent-casting method. Both types of composites were also studied as dispersions and films. Dynamic Light Scattering (DLS) and rheological techniques were used to characterize the dispersions, while the films' mechanical properties and drug release were determined. Laponite in an amount of 8.8 mg developed the optimal composites, reducing the particulate size and avoiding the agglomeration by its physical crosslinker and amphoteric properties. On the films, it enhanced the swelling and provided stability below 50 °C. Moreover, the study of drug release in maltodextrin and sodium ascorbate from LGL MAS was fitted to first-order and Korsmeyer-Peppas models, respectively. The aforementioned systems represent an interesting, innovative, and promising alternative in the field of healing materials.

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.

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.

Is α-Tocopherol or Sodium Ascorbate Effective as Antioxidant on Fracture Resistance of Bleached Teeth?

AIM: To evaluate the effect of two antioxidant formulations (sodium ascorbate and α-tocopherol) on fracture resistance of endodontically treated teeth. MATERIALS AND METHODS: Sixty human premolars were endodontically treated and divided into six groups (n = 10): G1 (negative control)-unbleached and restored with composite resin; G2 (positive control)-bleached in three sessions, using hydrogen peroxide (15 H2O2) plus titanium dioxide (TiO2) nanoparticles, photoactivated by LED laser system and restored with composite resin; G3-bleaching similar to G2, after the use of 10% sodium ascorbate gel for 24 hours and restored with composite resin; G4-similar to G3, but with the use of 10% sodium ascorbate solution and restored with composite resin; G5 and G6-similar to G3, but with the use of 10% α-tocopherol in alcohol or carbopol, respectively, and was also restored. A mechanical fracture resistance test was performed and the Kruskal-Wallis test was used to evaluate the results (α = 0.05). RESULTS: No statistical difference was observed in fracture resistance between groups (p > 0.05). Regarding the antioxidant and pharmaceutical formulation applied, no statistical difference was detected in any comparison (p > 0.05). The frequency of fractures considered favorable was higher in G1 and G3 compared to the other groups. CONCLUSION: The endodontically treated teeth bleached with 15 H2O2 plus TiO2 nanoparticles and photoactivated with the LED laser did not decrease the fracture resistance and the use of sodium ascorbate or α-tocopherol did not increase the crown fracture resistance. CLINICAL SIGNIFICANCE: The literature reports a significant reduction in the bond strength of restorations on the bleached dentin. Therefore, the use of antioxidant agents may have a promising effect on fracture resistance of endodontically treated teeth.

Dentin pretreatment with Er:YAG laser and sodium ascorbate to improve the bond strength of glass fiber post.

Root-filled teeth that received fiber posts most frequently fail at the adhesive interface between resin cement and dentin. The objective of this study is to evaluate the effect of Er:YAG laser and/or sodium ascorbate (SA) on bond strength, microhardness of dentin, and penetration depth of cement into dentinal tubules. Forty-eight bovine incisor roots were endodontically treated, post spaces were prepared and equally divided into four groups (n = 12): G1-distilled water (control); G2-10% SA (10 min); G3-Er:YAG laser (150 mJ/4 Hz/40 s), and G4-Er:YAG laser + 10% SA. Glass fiber posts were cemented and roots sectioned into slices. In the first slice, the push-out bond strength (MPa) and failures were analyzed by confocal laser scanning microscope (CLSM). The second slice was subjected to microhardness test (KHN) and CLSM to assess the cement penetration. ANOVA and Tukey test were used for bond strength and microhardness data and Kruskal-Wallis and Dunn tests for the cement penetration (α = .05). The SA-treated samples had higher bond strength (10.02 ± 5.45a), similar to Er:YAG laser (9.91 ± 4.62a) and Er:YAG laser + SA (8.09 ± 4.07a). The least values (P < .05) were found on control (4.02 ± 2.39b). Significant differences were observed on root thirds (P < .05): cervical > middle > apical. There was a predominance of adhesive failures. The microhardness test revealed no differences between groups (P > .05). The experimental groups (G2, G3, and G4) had highest penetration into dentinal tubules when compared to the control (G1). Dentin pretreatments with Er:YAG laser or SA improved bond strength of cement-post-dentin interfaces; however, no synergistic effect of both treatments combined was observed.

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.

Protocols for sodium ascorbate application on intracoronary dentin bleached with high-concentrated agent.

PURPOSE: Composite resin restorations are normally replaced after the internal bleaching of endodontically treated-teeth because the bleaching agent does not alter the color of the restorative material. This study evaluated the effect of 10% sodium ascorbate (SA) applied at different protocols on bleached dentin. MATERIALS AND METHODS: One-hundred slabs of intracoronary bovine dentin were divided into 5 groups: 2 controls-GI without bleaching (positive), GII bleached with 35% hydrogen peroxide (HP) (negative); and 3 experimentals - GIII. 35% HP + SA at protocol 1 (dripping, washing and drying the solution), GIV. 35% HP + SA at protocol 2 (dripping and aspirating the solution) and GV. 35% HP + SA at protocol 3 (dripping, rubbing and aspirating the solution). Sixty fragments were restored and subjected to shear bond strength test (n = 12). Forty fragments (n = 8) were prepared for chemical analysis (energy dispersive X-ray spectrometry) and surface morphology (scanning electron microscopy). Data were analyzed by ANOVA and Tukey test (P < 0.05). RESULTS: GI (3.169 ± 1.510a) had the highest means values, similar to GIV (2.752 ± 0.961a) and GV (2.981 ± 1.185a) (P < 0.05). Inferior values were obtained in GII (1.472 ± 0.342b) and GIII (2.037 ± 0.742ab) had intermediate values (P > 0.05). Oxygen concentration was reduced in groups treated with SA, and the surface exhibited residual granules of the solution. CONCLUSION: The 10% SA solution reestablishes the bond strength of restorative material to bleached dentin, especially if active protocols of application and aspiration were used.

Protective Effect of Sodium Ascorbate on MDPC-23 Odontoblast-Like Cells Exposed to a Bleaching Agent.

OBJECTIVES: To evaluate the cytotoxic effects of a bleaching agent composed of 0.01% carbamide peroxide (CP; 2.21mug/ml H(2)O(2)) on the MDPC-23 odontoblastic cell line, and to determine whether sodium ascorbate (SA) is capable of reducing, or even eliminating, the toxic effects caused by this bleaching agent. METHODS: The cells were seeded in wells and incubated for 48 hours. CP and SA were dissolved in a culture medium (DMEM) in order to obtain experimental extracts. Six groups of cells (n=10) were treated as follows: G1: no treatment (control); G2: 0.25 mM SA/60 min; G3: 0.5 mM SA/60 min; G4: 0.25 mM SA+0.01% CP/60 min; G5: 0.5 mM SA+0.01% CP/60 min; and G6: 0.01% CP/60 min. The cell metabolism was evaluated by MTT assay, and the cell morphology was assessed by scanning electron microscopy. The data obtained were analyzed by 2-way ANOVA and post-hoc Tukey's test (alpha=5%). RESULTS: THE PERCENTAGES OF CELL METABOLISM WERE AS FOLLOWS: G1 (control)=100%; G2=110.06%, G3=108.57%, G4=90.35%, G5=97.63%, and G6=66.88%. Group 6 presented a statistically lower cell metabolism than did the other groups, and the cells that remained on the substrate exhibited changes in their morphology. SA decreased the cytotoxic effects caused by CP, demonstrating its protective effect against the toxic components of this dental product. CONCLUSIONS: It was concluded that CP gel has cytopathic effects on MDPC-23 odontoblastic cells, even at low concentrations such as 0.01%. SA at 0.25 mM, and that 0.5 mM is able to protect these cultured cells against the cytotoxic effects of CP.