ABSTRACT
AIM: The use of bleaching agents, despite being a conservative treatment, can cause a decrease in the surface microhardness of dental resins, affecting their aesthetics and performance. The aim of this study was to evaluate the in vitro effect of polishing on the surface microhardness of nanohybrid composite resins that were subjected to bleaching with 35% hydrogen peroxide. MATERIALS AND METHODS: This cross-sectional, in vitro experimental study consisted of 30 composite resin samples made according to ISO 4049-2019 and divided equally into two groups (A and B) which were subjected to 35% hydrogen peroxide bleaching. Group A was subjected to polishing procedure, whereas group B was the control group. The samples were stored in distilled water at 37°C for 24 h. The Vickers microhardness was determined with a load of 100 g-f for 10 s. The data were analyzed with Student's t-test for independent samples at a confidence level of 95%. RESULTS: The surface microhardness of the group that was subjected to polishing (A) obtained a mean of 78.07 ± 7.96 HV, whereas for the group that was not subjected to polishing (B) the mean was 65.67 ± 5.22 HV. The difference between groups (A and B) was statistically significant (P < 0.001). CONCLUSION: Nanohybrid composite resins previously subjected to 35% hydrogen peroxide gel significantly increased their surface microhardness when subjected to polishing when compared with unpolished nanohybrid composite resins.
ABSTRACT
Objetivos: Comparar in vitro el grado de microfiltración marginal obtenido en las restauraciones de resina compuesta realizadas con la técnica grabado total de tres pasos y con grabado selectivo del esmalte con autograbante de dos pasos. El estudio fue prospectivo, transversal, experimental y comparativo. Material y Métodos: Fueron utilizados 28 premolares, divididos en dos grupos de 14 muestras cada uno a los cuales se les aplicó dos tipos de técnica adhesiva: Un grupo (A) con la técnica grabado total de tres pasos con el sistema adhesivo Optibond FL (Kerr); y grupo (B) con la técnica grabado selectivo del esmalte con autograbante de dos pasos con el sistema adhesivo Optibond XTR (Kerr). Posteriormente obturadas con resina compuesta Filtek Z350 (3M ESPE) y sometidas al proceso de termociclaje durante 500 ciclos de 5°C y 55°C. La microfiltración fue evaluada a través de un índice de profundidad de microfiltración mediante la penetración de azul de metileno al 2 % y observada con microscopio estereoscopio. Resultados: Los datos se analizaron mediante la prueba estadística U de Mann-Whitney, determinándose que no existen diferencias estadísticamente significativas (p≥0,05) entre ambas técnicas adhesivas. Se observó una mayor cantidad de piezas dentarias sin microfiltración en el grupo B (28,6%) sobre el grupo A (7,1 %). Conclusiones: El grado de microlfiltración marginal obtenido en ambas técnicas adhesivas presentó resultados similares.
Objectives: Compare the degree of marginal microfiltration in vitro obtained in composite resin restorations performed with the three-step etch-and-rinse technique and selective enamel etching with two-step self-etch. The study was prospective, transversal, experimental and comparative. Material and Methods: 28 premolars were used, divided into two groups of 14 samples to which were applied two types of adhesive technique: A group (A) with the total three-step etch-and-rinse technique with the Optibond FL (Kerr) adhesive system; and group (B) with selective enamel etching two-step self-etch with the adhesive system Optibond XTR. Later sealed with composite resin Filtek Z350 (3M ESPE) and subjected to the thermocycling process for 500 cycles of 5 ° C and 55 ° C. The microfiltration was evaluated through a depth index of microfiltration through the penetration of 2% methylene blue and observed with stereoscopic microscope. Results: The data were analyzed using the U Mann Whitney test, and it was determined that there were no statistically significant differences (p≥0.05) between the two adhesive techniques. A greater number of teeth without microfiltration was observed in group B (28.6%) over group A (7.1%). Conclusions: The degree of marginal microfiltration obtained in both adhesive techniques presented similar results.
