Effect of chemical degradation followed by toothbrushing on the surface roughness of restorative composites

OBJECTIVES: The aim of the present study was to assess the effect of the exposure to food-simulating liquids prior to brushing simulation on the surface roughness of five composite materials (Quixfil, Filtek Supreme, Esthet-X, Filtek Z250, Tetric Ceram). Material and METHODS: Twenty cylinders (5 mm diameter and 4 mm height) of each composite were randomly allocated to 4 groups (n=5), according to the food-simulating liquid in which they were immersed for 7 days at 37°C: artificial saliva, heptane, citric acid, and ethanol. After this period, the top surface of composite cylinders was submitted to 7,500 brushing cycles (200 g load). Measurements of the surface roughness (Ra, »m) were carried out before and after the exposure to the chemicals/brushing simulation. Changes on the morphology of composite surfaces were observed through scanning electron microscopy (SEM). RESULTS: The statistical analysis (ANOVA with cofactor / Tukey's test, α=5 percent) detected a significant interaction between solutions and composite resins. Esthet-X, Filtek Z250 and Tetric Ceram were not affected by the food-simulating liquids/toothbrushing. Citric acid and ethanol increased the surface roughness of Quixfil and Filtek Supreme, respectively. SEM images corroborate the surface roughness findings, demonstrating the negative effect from chemical solutions and mechanical abrasion. CONCLUSIONS: The surface roughness of composite resin materials are differently affected by the food-simulating solutions, depending on the immersion media.

Associação de técnicas no tratamento restaurador em dentes posteriores: onlay cerâmico X resina composta / Association of techniques in restorative treatment of posterior teeh: ceramic onlay x composite resin

O aumento da demanda por restaurações estéticas é uma realidade na clínica odontológica, sendo que essa tendência é observada não só no tratamento de dentes anteriores, mas também na região posterior. Alternativas restauradoras, como o uso de resinas compostas diretas, inlays, onlays e coroas em resina ou cerâmica, visam o equilíbrio funcional e estético dos dentes posteriores. Entretanto, a escolha da técnica empregada está principalmente associada à técnica empregada, está principalmente associada à condição do remanescente dentário. Assim, através do relato de um caso clínico, esse artigo busca conceituar importantes aspectos quanto ao uso de resinas compostas e restaurações indiretas do tipo onlay cerâmicos, enfatizando a importância na indicação desses dois tratamentos restauradores estéticos para dentes posteriores.

Effect of different light-curing devices and aging procedures on composite knoop microhardness

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.

Efeito dos períodos de armazenamento na resistência de união de um sistema adesivo autocondicionante à dentina bovina / Effect of the storage periods on the bond strength of a self-etch system to bovine dentin

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.