Avaliação da microdureza de quatro cimentos resinosos duais fotopolimerizados através da interposição de diferentes materiais: estudo in vitro

Este estudo avaliou por testes de microdureza o grau de polimerização de quatro cimentos resinosos duais: Bistite II, Enforce, RelyX ARC e Variolink II, fotopolimerizados através da interposição de barreiras confeccionadas com materiais utilizados em retaurações estéticas indiretas. Foram confeccionados 72 espécimes para cada marca de cimento, divididos em 6 grupos, segundo o tipo de barreira utilizada na interposição, durante a sua fotopolimerização: G1: sem barreira; G2: Resina composta Cesead; G3: Inceram alumina/Allceram; G4: IPS Empress; G5: Inceram zirconia/Allceram; G6: fragmento dental. A fotopolimerização foi realizada com luz halógena Optilux 401 (Demetron) com 650 mW/cm2 de potência e os ensaios foram realizados em três períodos: imediata, 24h e 7dias, em um Microhardness Tester FM 700, sob cargas de 50gf durante 15s, cujos valores de microdureza foram obtidos em HV. As médias dos valores em HV foram submetidos à ANOVA e teste de Tukey. As condições de G3 e G5 resultaram em polimerização deficiente do cimento, que não permitiram a realização dos ensaios. O cimento Bistite teve a maior dureza no grupo controle e o menor com a interposição de resina composta. O RelyX ARC teve os valores de microdureza mais estáveis nas condições analisadas em todos os períodos de avaliação. O Enforce e o Variolink foram intermediários e semelhantes entre si. A interposição de materiais durante a fotopolimerização de cimentos resinosos duais, interfere na microdureza dos mesmos. Quando da utilização de alumina ou zirconia, outro modo de polimerização ou tipo de cimento deve ser utilizado.This study evaluated by microhardness tests the curing degree of four dual cured cements: Bistite II, Enforce, RelyX ARC and Variolink II, lightcured through the interference of barriers made with materials used in indirect aesthetic restorations. 72 specimens were made for each cement that was divided into 6 groups, according to the barrier type used in the interference, during the light activation G1: without barrier; G2: Cesead, a composed resin; G3: Inceram alumina/Allceram; G4: IPS Empress; G5: Inceram zirconia/Allceram; G6: dental fragment. The lightcuring was accomplished with a conventional halogen unit, Optilux 401 (Demetron) with 650 mW/cm2 and the measurements were accomplished in three periods: immediate, 24hours and 7days, in a Microhardness Tester FM 700, under loads of 50gf during 15seconds. Microhardness values were obtained in HV. The averages of the HV values were submitted to ANOVA and Tukey test. The G3 and G5 groups resulted in deficient polymerization of the cement, that they didn't allow the accomplishment of the rehearsals. The Bistite cement had the largest hardness in the control group and the smallest with the interference of Cesead. RelyX ARC had the stableer values of microhardness in the analyzed conditions in all of the evaluation periods. Enforce and Variolink were intermediate and similar amongst them. The interference of barriers during the lightcuring of dual resinous cements interferes in the microhardness of the same ones. When a restoration of alumina or zirconia is used, other polymerization way or cement type should be used

Additional chemical polymerization of dual resin cements: reality or a goal to be achieved?

Abstract Introduction This study serves as a warning to dentists and researchers that dual-cured resin cements may not polymerize completely under some prosthetic crowns. Objective The aim of this study was to analyse the polymerization degree of dual-cured resin cements under prosthetic barrier, by microhardness test. Material and method Three cements (Bistite II, RelyX ARC and Variolink II) were light-cured through different barriers, placed between the cement and the light source: G1: without barrier; G2: composite resin (Cesead); G3: Inceram alumina; G4: IPS Empress; G5: Inceram zirconia; G6: tooth fragment. Photopolymerization was carried out using a halogen light unit (650 mW/cm2); microhardness was evaluated using the Microhardness Tester FM 700, under a load of 50gf with a dwell time of 15s, at two evaluation times (30min and 24h). Result The results were submitted to ANOVA and Tukey tests (5%). Both Inceram alumina and Inceram zirconia ceramic barriers hindered polymerization. Bistite, followed by RelyX and Variolink, exhibited the highest microhardness values (p<0.05). As the highest values were obtained without a barrier, it was determined that the barrier, followed by the tooth, influenced microhardness. Both Empress and Cesead had the smallest microhardness values but with no statistically significant difference between them. Conclusion The barrier negatively affected the microhardness of dual-cured resin cements; evaluation time did not affect microhardness values for most of the conditions tested. There is a limited effect of the chemical activator on the polymerization of some dual-cured cements, and their performance is product specific