Influencia da distancia da ponta ativa do fotopolimerizador no grau de dureza Knoop de compositos odontologicos

AUTOR(ES)
DATA DE PUBLICAÇÃO

1998

RESUMO

The purpose of this study was to investigate the effect af light-tip distance on Knoop hardness degree, in different depth, of two composite resms. Two composite resins (Z100 and Silux Plus, colors A3 and U (3M) and a light-curing unit XL 3000 (3M) with 750 mW/cm2of light intensit were used in this study. Specimens with 5 mm in diameter and 2,5 mm thick were polimerizated by visible light for 40 seconds, with light-tip distance of O, 6 and 12 mm from the composite. Four specimens for each composite and distance were prepared. The specimens were stored for 24 hours, in 37°C and 100% .of relative humidity. After, the specimens were vertically positioned and embebed in poliester resin. The specimens were wasted to attain the central region and polished with decrescent grif sandpaper 220, 320, 400, 5 00, 600 and 1000 (3M) and diamond paste (0,05 J..Lm).The Knoop hardness measurements were obtained in six depth Pl to P6, by a Microhardness Tester FM (Future Tech Corp), with a load of 50 g and 30 seconds for each indentation. The results indicated that: (1) - for the composite Z 100, as larger as the distance of the light-tip in relation to the material, less the values of hardness Knoop. And as bigger as depht of the layer in relation to the surface, less the values of hardness knoop; (2) - for the Silux Plux composite, as larger as the distance of light-tip do not produce estatitcally diference on the Knoophardness number in the surface. And the more depth is the layer less will be the polimerization, exept for the situation where the liht-tip were. in contact of the especiments, (3) - the composite Z 1°° was superior statistically in relation to Silux Plus in the three distances of the ligth-curing and in all the depths (p<0,05).

ASSUNTO(S)

compositos polimericos materiais dentarios

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