Effect of Sodium Ascorbate or Alpha-Tocopherol on the Resin-Dentin Interface and Bond Strength after Endodontic Treatment and Bleaching

ABSTRACT: 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.

RESUMEN: 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.

Niveles de ascorbato en pacientes quemados durante la fase aguda / Ascorbate levels in burned patients during the acute phase

Introducción y objetivo: Después de la agresión térmica disminuyen los niveles de antioxidantes y se elevan los biomarcadores oxidativos, que junto a los mediadores inflamatorios, participan en las alteraciones de la microvasculatura provocando filtración capilar y shock hipovolémico. La vitamina C modula esta respuesta, por lo que se ha propuesto incorporarla en megadosis al tratamiento inicial del paciente quemado.El objetivo de este trabajo es estimar los niveles de ascorbato sérico que alcanzan los pacientes quemados administrando 3 g diarios de vitamina C durante la fase aguda.Material y método.Estudio descriptivo en 25 pacientes quemados en reanimación a los que se les determinó el nivel de ascorbato sin recibir la primera dosis de vitamina C y a las 72 horas de su administración. Comparamos las concentraciones de ascorbato en esos momentos con el de referencia empleando el Test de Student para una muestra. Determinamos si existía asociación entre el nivel de ascorbato y la extensión de la lesión utilizando el Test de Student para muestras independientes y analizamos el pronóstico de vida utilizando análisis de varianza (ANOVA).Resultados.Los valores promedio de ascorbato estuvieron significativamente disminuidos sin cambios entre el nivel inicial y a las 72 horas de tratamiento. No encontramos relación con la extensión ni con el pronóstico.Conclusiones.La administración de 3 g de vitamina C no fue suficiente para alcanzar los niveles séricos normales. Es necesario administrar dosis superiores a la protocolizada en nuestra institución. (AU)

Background and objective: After thermal aggression, antioxidant levels decrease and oxidative biomarkers rise, which together with inflammatory mediators, participate in alterations of the microvasculature, causing capillary leakage and hypovolemic shock. Vitamin C modulates this response, and it has been proposed to incorporate it in megadoses in the initial treatment of burned patients.The aim of this work is to estimate the serum ascorbate levels reached in burned patients by administering 3 g daily of vitamin C during the acute phase.Methods.Descriptive study in 25 burned patients in resuscitation, in whom the ascorbate level was determined without receiving the first dose of vitamin C and then at 72 hours. Those ascorbate concentrations were compared with the reference one using the Student's test for a sample. It was determined if there was an association between the level of ascorbate and the extension of the lesion using the Student's test for independent samples, and the same was analyzed with the prognosis of life using analysis of variance (ANOVA).Results.Mean ascorbate values were significantly decreased without changes between the initial level and that reached at 72 hours treatment. No relationship was found with the extension or with the prognosis.Conclusions.Administration of 3 g of vitamin C was not enough to reach normal serum levels. It is necessary to administer doses higher than the protocol established in our institution. (AU)

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.

Defense responses of wheat plants (Triticum aestivum L) against brown spot as a result of possible elicitors application / Resposta de defesa das plantas de trigo (Triticum aestivum L) contra a mancha marrom diante da aplicação de possíveis elicitores

The objective of this research was to evaluate the response of wheat plants to the application of possible elicitor compounds against Bipolaris sorokiniana pathogen. This response was measured through the quantification of antioxidant enzymes, malondialdehyde and flavonoids, evaluation of the severity of brown spot disease and productivity in wheat, greenhouse and field crops. The treatments consisted of suspensions of endophytic fungi Aspergillus japonicus and Trichoderma tomentosum, salicylic acid, acibenzolar-S-methyl and fungicide. In the field trials, in 2015 and 2016, the development of the disease was lower and productivity was higher in all treatments, with emphasis on the fungicide. However, endophytic fungi suspensions demonstrated potential as growth promoters, disease severity reducers and protective antioxidant response activators, as they promoted significant increase in superoxide dismutase, catalase, glutathione and flavonoid enzymes.(AU)

O objetivo desta pesquisa foi avaliar a resposta de plantas de trigo diante da aplicação de possíveis compostos elicitores perante o patógeno Bipolaris sorokiniana. Tal resposta foi examinada por meio da quantificação de enzimas antioxidantes, malondialdeído e flavonoides, da análise da severidade da doença mancha marrom e da produtividade na cultura do trigo, em casa de vegetação e em campo. Os tratamentos consistiram em suspensões de fungos endofíticos Aspergillus japonicus e Trichoderma tomentosum, ácido salicílico, acibenzolar-S-metil e fungicida. Nos ensaios em campo, em 2015 e 2016, o desenvolvimento da doença foi menor e a produtividade foi superior em todos os tratamentos, com destaque para o fungicida. No entanto, as suspensões de fungos endofíticos demonstraram potencial como promotores de crescimento, redutores da severidade da doença e ativadores de resposta antioxidante protetora, pois promoveram o aumento significativo das enzimas superóxido dismutase e catalase, das glutationas e flavonoides.(AU)

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.