ABSTRACT
The aim of this study was to evaluate the effect of light-curing devices (Halogen/HAL, Light Emitting Diodes/LED, Argon Laser/LAS and Plasma Arc/PAC) and aging procedures (Mechanical Cycling/MC, Thermal Cycling/TC, Storage/S, MC+TC and MC+TC+S) on the micro-hardness of bottom/B and top/T surfaces of 2-mm-high composite resin cylinders. The Knoop microhardness test (25 g, 20 s) on both B and T was performed before and after each aging procedure. For B and T, before aging procedures, PAC showed reduced polymerization effectiveness when compared with HAL. In the T, after TC, PAC and LAS had also showed reduced polymerization effectiveness when compared to HAL and LED. For all light-curing devices, MC+TC+S and S affected the Knoop microhardness values. In the B, no difference could be observed among the aging procedures for PAC. From all light-curing units, PAC may have rendered composites of reduced quality and the storage aging procedures were the most harmful to the polymer hardness.
Subject(s)
Curing Lights, Dental , Composite Resins/radiation effects , Hardness Tests , Light-Curing of Dental Adhesives/methods , Analysis of Variance , Composite Resins/chemistry , Dental Stress Analysis , Lighting/instrumentation , Materials Testing , Polymers/chemistry , Surface Properties , Time FactorsABSTRACT
O objetivo do presente estudo foi avaliar o efeito do armazenamento de dentes bovinos, em diferentes períodos, na resistência de união de um sistema adesivo autocondicionante de dois passos. Para essa avaliação, 40 incisivos bovinos (n = 10) foram armazenados em solução de timol 0,10 g.mL 1(um negativo) durante os seguintes períodos: 24 horas (controle), 15 dias, um mês e seis meses. Após esses períodos de armazenamento, cada dente foi desgastado até a exposição da dentina superfcial, um sistema adesivo autocondicionante (Clearfl SE Bond/Kuraray) foi aplicado e um bloco de resina composta (TPH Spectrum, Dentsply DeTrey) foi confeccionado sobre o substrato dentinário. Os materiais restauradores foram aplicados segundo as instruções do fabricante. Os espécimes foram seccionados a fim de se obterem fatias de 1 mm de espessura e constrições foram realizadas para obtenção do formato de ampulheta com área adesiva de 1 mm2. As fatias foram testadas sob tensão em uma máquina de ensaio universal a uma velocidade de 0,5 mm.min 1(um negativo) e o padrão de fratura foi analisado em microscopia eletrônica de varredura (MEV). Os seguintes resultados foram obtidos (MPa): 24 horas - 11,73 ± 5,2; 15 dias - 9,66 ± 3,6; 1 mês - 11,01 ± 6,7, e 6 meses - 9,43 ± 4,7. Não foi observada nenhuma diferença estatística signifcante (ANOVA, p = 0,79). Falhas na interface adesiva foram mais frequentemente observadas. Pode-se concluir que os períodos de armazenamento avaliados não infuenciaram a união do sistema adesivo autocondicionante à dentina bovina.
The aim of this study was evaluate the effect of the storage of bovine teeth in different periods on the microtensile bond strength of a two-step self-etch system. For this, forty bovine incisors (n = 10) were stored in 0.10 g.mL 1(one negative) thymol solution during the following periods: 24 hours (control), 15 days, 1 month, and 6 months. After these storage periods, each tooth was fattened until superfcial dentin exposure, the bonding system (Clearfl SE Bond/Kuraray) was applied and a composite block (TPH Spectrum, Dentsply DeTrey) was built over the dentin substrate. Restorative materials were used following manufacturer's instructions. The specimens were sectioned to obtain 1 mm thick slabs, which were trimmed to an hour-glass shape with cross sectional area of 1 mm2. Slabs were tested under tension in a universal testing machine at 0.5 mm.min 1(one negative) and their failure mode was analyzed with scanning electron microscopy (SEM). The following results were obtained (MPa): 24 hours - 11.73/5.2; 15 days - 9.66/3.6; 1 month - 11.01/6.7, 6 months - 9.43/4.7. Signifcant differences among experimental groups were not observed (ANOVA, p = 0.79). Failures within the adhesive interface were the most frequently observed. May be concluded that the storage periods did not infuence the bonding of the two-step self-etch system to dentin.
Subject(s)
Cattle , Dental Cements , Dentin , Microscopy, Electron, Scanning , Analysis of Variance , Dentin-Bonding Agents , Shear Strength , IncisorABSTRACT
O objetivo deste estudo é revisar a literatura sobre as estratégias clínicas para minimizar os efeitos adversos da contração de polimerização dos compósitos, dentre elas, a forma de inserção da resina composta, o uso de materiais intermediários com propriedades elásticas e as técnicas de fotoativação. De acordo com a literatura, a combinação de mais de uma estratégia parece ser o método mais eficiente para garantir o sucesso clínico das restaurações diretas. Além disso, o julgamento crítico do adequado emprego dos compósitos pode influenciar o resultado final do tratamento restaurador.
Subject(s)
Composite Resins , Dental Materials , Dental Restoration, PermanentABSTRACT
The aim of this study was to evaluate the microleakage of class II resin composite restorations polymerized with light-emitting diodes (LEDs) with different numbers of blue diodes. One hundred sixty-eight class II cavities were prepared in bovine teeth. A one-bottle adhesive system (Single Bond/3M ESPE) was applied. The microhybrid or packable resin composites were inserted in three horizontal increments and cured for 40 seconds each, according to the following groups (n=21): G1- Z250 + LED light curing unit with 19 LEDs (3M ESPE); G2- Surefil + LED light curing unit with 19 LEDs; G3- Z250 + LED light curing unit with 7 LEDs (DMC); G4- Surefil + LED light curing unit with 7 LEDs; G5- Z250 + LED light curing unit with 6 LEDs (MM Optics); G6- Surefil + LED light curing unit with 6 LEDs; G7- Z250 + conventional halogen light curing unit (Demetron-Kerr); G8- Surefil + conventional halogen light curing unit. After thermocycling, the specimens were immersed in 2% methylene blue solution and then evaluated for microleakage. The Kruskal-Wallis and non-parametric Multiple Comparison tests (p<0.05) showed statistically significant differences among groups median: G1: 1(d); G2: 4(a); G3: 1(cd); G4: 4(a); G5: 2(bc); G6: 4(a); G7: 1(cd); G8: 4(ab). The blue light-emitting diode units (LEDs) demonstrated similar results to the conventional halogen lamp unit and the microleakage of the packable resin composite was significantly more severe than that of the microhybrid resin composite