Influencia da posição e do numero de muflas no microondas sobre a liberação de monomero residual, dureza de superficie e porosidade da resina acrilica Acron MC




In attempt to save working time, microwave-polymerized dentures can be processed simultaneously. However, little concern exists about possible uneven acrylic resin polymerization when inserting multiple flasks in a microwave oven. Thus, this .study evaluated the effect of number and position of flasks in the monomer release, Knoop hardness and porosity of a microwave-cured acrylic resin. Samples were made of Acron MC (AMC, GC lnt.) and processed under 500 W. The following flask number-position associations were tested: one simple flask centraI1y placed over the tuming plate (I control); two flasks, one in the center (IIa) and the other marginally placed in the plate (llb); two flasks centrally placed over the plate, one above (IIIa) and the other below (IIIb). The processing time varied according to the number of flasks: 3 minutes or 4.5 minutes for 1 or 2 flasks inserted, respectively. For monomer released in water, each specimen (18 in each group) was put in an assay glass tube containing 6 mL of deionized water, which was daily changed. Monomer levels were obtained by spectrophotometry at 206 nm, after 24, 28, 72, 96, 120 e 144 hours. For hardness test, 12 indentations were done in the surface of 12 specimens in each group, after 144 h of water storage. The porosity was verified by immersing the polished specimens in permanent ink, and counted through a stereo light microscope. The results found were: 1) Monomer release by groups: GI= 82,0(197,4)b, GIIa=44,1(98,l)b, GIIb= 63,9(183,0)b, GIIIa= 189,1 (436,)a, GIIIb= 26,1(88,8)c 2) Monomer release by time: 24h= 335,8(501,3)a, 48h= 66,1 (146,0)b, 72h= 35,7(51,0)c, 96h= 19,6(21,9)c, 120h= 14,5(16,4)d, 144h= 14,7(19,1)d 3) Knoop hardness: GI=18,1(3,5)a, GIIa=17,1(1,9)a, GIIb=16,3(3,2)a, GUIa=16,8(3,9)a, GIIIb=17,6(2,5)a; 4) Porosity: GI=7,2(9,4)a, GIIa=19,3(36,0)a, GIIb=20,8(28,2)a, GIIIa=24,3(42,6)a, GIIIb=13,2(13,9)a There was no statistical significant difference (p


polimerização resistencia dos materiais resinas acrilicas dentarias microondas

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