Influência do pré-aquecimento e do modo de ativação na resistência máxima à tração e no grau de conversão de dois cimentos resinosos de dupla ativação.

AUTOR(ES)
DATA DE PUBLICAÇÃO

2010

RESUMO

This study evaluated the degree of conversion (DC) using Fourier transformed infrared analysis (FTIR) and ultimate tensile strength (UTS) of pre-heated dual-cured resin cements (RCs) exposed to different activating modes: light-activation through a glass slide (GS) or through a pre-cured 2-mm thick resin composite disc (A2 - A2 shade), or specimens were allowed to self-cure (SC). Two dual-cured RCs were used: Rely X ARC (RX) and Variolink II (VII). Disc-shaped specimens (1 mm thick and had 5 mm in diameter) were obtained for DC analysis while hourglass shape specimens (1 mm thick and 1 mm wide at the constriction region) were created for UTS test from addition silicon mold. The RCs were manipulated at 25oC or were preheated to 50oC prior to manipulation. For GS and A2 groups, specimens were exposed to light for 40 seconds. All specimens (n=10) were stored dry in the dark at 37oC for 15 days. For FTIR analysis, the material was placed into the mold on the center of a horizontal diamond ATR element in the optical bench of a FTIR spectrometer. FTIR spectra (n=5) were collected between 1680 and 1500 cm-1 (4- cm-1 resolution) and DC was calculated by standard methods using changes in the ratios of aliphatic-to-aromatic C=C absorption peaks from uncured and cured states. For UTS test, specimens were tested in tension on a universal testing machine (crosshead speed of 1 mm/min) until failure. DC and UTS data were submitted to 2- way ANOVA, followed by post-hoc Tukeys test (pre-set alpha of 5%). Both RCs showed higher DC at 50oC than at 25oC. In RX at 25oC and 50oC and in VII at 25oC, DC values depended on the activating mode, while VII did not show significant difference in DC values between GS and A2 groups at 50oC. No significant difference in UTS values was noted between A2 groups at 25oC and A2 groups at 50oC. SC groups showed higher UTS at 50oC than at 25oC (p<0.05), but SC groups exhibited lower UTS values than light-activated groups at both temperatures (p<0.05). The preheating increased the DC of RCs in all activating modes and improved UTS only when RCs depended on the self-curing mode..

ASSUNTO(S)

odontologia polymerization. dual-cured resin cements curing temperature degree of conversion cimentos resinosos duais, temperatura, grau de conversão, resistência máxima à tração. ultimate tensile strength

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