Effect of different light-curing methods and materials for indirect venners on Knoop hardness of resin cements / Efeito dos metodos de fotoativação e dos materiais para facetas indiretas na Dureza Knoop de cimentos resinosos

AUTOR(ES)
DATA DE PUBLICAÇÃO

2005

RESUMO

The increasing demand for esthetic restorations has increased the use of ceramics and composites in oral rehabilitation. The resin-based cement is the material of choice to fix these prosthetic restorations. This material can polymerize by chemical activation, physical activation or by a combination of chemical/ physical activation. In several clinical situations light curing must be performed indirectly through ceramics or composite. Sometimes, in cases in which esthetic is the major goal, light-cured cements are preferred because their longer color stability. However, the chemical activation can guarantee the polymerization of the cement. The present study aimed to evaluate the Knoop hardness of the resin-based cement Enforce, activated by chemical/ physical mode or by physical mode solely, light-cured directly or through 1.5mm of ceramics (HeraCeram) or composite (Artglass) using different light-curing devices. For light-curing the following activation times were used: conventional halogen light (XL2500) applied for 40s - HL; light emitting diodes (Ultrablue Is) for 40s - LED; and light emitted by xenon plasma arc (Apollo 95E) for 3s - PAC. Bovine incisors embedded in polystyrene resin had its buccal faces ground flat and submitted to the hybridization technique. On the hybridized dentin area a rubber mold was seated (1mm thickness and 5mm diameter), into which the manipulated cement was deposited. A disc of one of the prosthetic materials was seated over this set to proceed the light-curing. After storage for 24h at 37oC, the samples were sectioned and submitted to hardness measurements in 3 different depths: near to restorative material, near to dentin and in the center. The hardness (KHN) measurements were performed in a micro-hardness tester after 50gf load by 15s. Data were submitted to ANOVA and to Tukey?s test, with a=0.05. In general, it was verified that dual cement presented higher hardness compared to physical mode, exception to HL in direct light curing and with Artglass and LED with HeraCeram. When the level dual was fixed, higher hardness was observed with LED in direct light curing and with HeraCeram, what was not observed with Artglass, in which similar hardness values were obtained with different devices. For HL, the lowest hardness was observed with HeraCeram and for LED, with Artglass. For PAC, lower hardness was verified in direct light curing and with HeraCeram. When the level physical mode for cement activation was fixed, the highest hardness was obtained with LED in direct light curing and with HeraCeram followed by HL and PAC, respectively. With Artglass, the highest hardness was observed with HL followed by LED and PAC, respectively. It was not possible to determine the hardness of physical activated cement light-cured with PAC through Artglass and HeraCeram. Light curing through HeraCeram showed to be deleterious to HL. For LED, this behavior was noted with Artglass

ASSUNTO(S)

dental resins dental materials resinas dentarias materiais dentarios

ACESSO AO ARTIGO

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