Influence of curing tip distance on resin composite Knoop Hardness Number, using three different light curing units

This in vitro study evaluated the influence of curing tip distance on the Knoop Hardness Number (KHN) of a resin composite when using three different light curing units: (1) a halogen light (XL 1500 curing unit-3M), (2) a "softstart-polymerization" (Elipar Trilight curing in an exponential mode-ESPE) and (3) a PAC (Apolo 95E curing unit-DMD). The resin composite, Filtek Z250 (3M), was cured by these curing units at three. light-tip distances from the resin composite: 0 mm, 6 mm and 12 mm. The resin composite specimens were flattened to their middle portion and submitted to 18 KHN measurements per specimen. The results showed that for the Elipar Trilight unit, the hardness of the resin composite decreased as the light tip distance increased. The XL 1500 unit presented a significant decrease in hardness as the depth of cure of the resin composite increased. Apolo 95E caused a decrease in the resin composite hardness values when the depth of cure and light tip distance increased.28331532

Effect of light curing tip distance and resin shade on microhardness of a hybrid resin composite Efeito da distância da ponta do aparelho de fotoativação e da cor na microdureza superficial de um compósito híbrido

Resin composite shades and resin composite polymerization performed with a distanced light tip are factors that can affect polymerization effectiveness. Thisin vitro study aimed to evaluate the influence of curing tip distance and resin shade on the microhardness of a hybrid resin composite (Z250 - 3M ESPE). Forty-five resin composite specimens were randomly prepared and divided into nine experimental groups (n = 5): three curing tip distances (2 mm, 4 mm, and 8 mm) and three resin shades (A1, A3.5, and C2). All samples were polymerized with a continuous output at 550 mW/cm². After 24 hours, Knoop microhardness measurements were obtained on the top and bottom surfaces of the sample, with a load of 25 grams for 10 seconds. Five indentations were performed on each surface of each sample. Results showed that bottom surface samples light-cured at 2 mm and 4 mm presented significantly higher hardness values than samples light-cured at 8 mm. The resin shade A1 presented higher hardness values and was statistically different from C2. The resin shade A3.5 did not present statistical differences from A1 and C2. For the top surface, there were no statistical differences among the curing tip distances. For all experimental conditions, the top surface showed higher hardness values than the bottom surface. It was concluded that light curing tip distance and resin shade are important factors to be considered for obtaining adequate polymerization.<br>A cor do compósito e a polimerização realizada com a ponta do aparelho de fotoativação distante da superfície do compósito são fatores que podem afetar a efetividade de polimerização. Assim, o objetivo deste estudo in vitro foi avaliar a influência desses fatores na microdureza superficial de um compósito híbrido (Z250 - 3M ESPE). Quarenta e cinco espécimes de compósito foram aleatoriamente preparados de acordo com os nove grupos experimentais (n = 5): três distâncias de fotoativação (2 mm, 4 mm e 8 mm) e três cores de compósito (A1, A3,5 e C2). Todas as amostras foram fotoativadas com aparelho de fotoativação ajustado com intensidade contínua de 550 mW/cm². Após 24 horas, dez medidas de dureza Knoop foram obtidas nas superfícies de topo e fundo de cada amostra, com carga de 25 gramas por um tempo de 10 segundos. Resultados mostraram que, para a superfície de fundo, os grupos com a fotoativação realizada com distância de 2 e 4 mm apresentaram maiores médias do que os grupos com distância de 8 mm, e os grupos de cor A1 apresentaram maiores médias e com diferenças estatísticas que os grupos de cor C2, e o grupo A3,5 não apresentou diferenças estatísticas quando comparado aos outros grupos. Para a superfície de topo, não houve diferenças estatísticas significantes para os fatores estudados. Para todas as condições experimentais, a superfície de fundo apresentou médias de durezas estatisticamente menores do que as da superfície de topo. Pode-se concluir que os fatores cor do compósito e distância de polimerização são importantes fatores a serem considerados para a obtenção de adequada polimerização

Influence of different light-curing units on the surface roughness of restorative materials: in situ study

The aim of this study was to evaluate the influence of different light sources (LED and Halogen lamp) on the roughness (superficial) of composite resin (Filtek Z250, Filtek P60, Charisma and Durafill) varying post-irradiation times, in an in situ experiment. For this purpose, 80 specimens were made in polyurethane moulds. Ten volunteers without medicament use and good oral condition were selected and from them study moulds were obtained. A palatal intra-oral acrylic resin appliance was made for each of the subjects of the experiment. In each appliance, two specimens of each material were fixed (LED/Halogen lamp - control group). Roughness tests were performed immediately and 30 days after initial light-curing. Statistical analysis was performed using ANOVA. Statistically significant difference was observed only between post-irradiation times, where the 30th day showed the highest roughness values. It be concluded that roughness was influenced only by post-irradiation times, presenting the 30- days period inferior behavior