Self-adhesive resin luting : effect of curing mode on degree of conversion, biaxial flexure strength and bond strength to dentin / Cimentos resinosos autoadesivos : efeito do modo de polimerização no grau de conversão, na resistencia flexural biaxial e na resistencia de união a dentina

AUTOR(ES)
DATA DE PUBLICAÇÃO

2009

RESUMO

The use of materials that enable excellence in esthetics, coupled with a reduction in the number of steps in the adhesive luting protocol, have aroused the interest of professionals in the use of self-adhesive resin luting. As these materials have appeared only recently, it is necessary to study the physical and chemical properties as well as the mechanism of bonding to dental substrate. Thus, the purpose of this study was to evaluate the effect of curing mode (dual and self-polymerizing) of four resin cements, of which three were self-adhesive resin cements (RelyX Unicem (RX), 3M ESPE, Seefeld, Germany; BisCem (BC), Bisco Inc., Schuamburg, IL, USA e G-Cem (GC), GC Corp., Tokyo, Japan) and one convenctional resin cement (Panavia F 2.0 (PF), Kuraray Medical Inc., Kurashiki, Japan) with regard to the degree of conversion, biaxial flexural strength and bond strength to dentin. For microtensile bond test, occlusal dentin surfaces of third human molars were used and the fractured surfaces of tested specimens were examined by scanning electron microscopy. In other tests, resin cement specimens of standard dimensions were prepared in accordance with each test applied. To study the degree of conversion, the behavior of resin cements was observed with regard to evaluation time (5, 10 and 15 minutes) and statistical difference was observed for the time of evaluation and curing mode. The mean values for RX and BC were increased when the resin cement was dual-polymerizing; however, PF showed no significant differences. With regard to the time of evaluation, the highest degree of conversion was observed 15 minutes after the cement was manipulated for all the groups evaluated, except when BC was auto-polymerized after 5 and 10 minutes. For the resin cement G-Cem it was not possible to calculate the degree of conversion, because no aromatic carbon ring was shown during the initial measurement of the monomer. For biaxial flexural strength, dual-polymerizing of the resin cement produced higher flexural modulus and strength; however, the resin cement BC always showed the lowest values. The tensile bond strength showed higher bond strength for PF and GC when light polymerized. The resin cements RX and BC were not influenced by the polymerization mode. However, when the systems were self-polymerizing, PF and RX showed the best results and RX was similar to GC. The failure pattern presented a predominance of adhesive failures between dentin and resin cement, except when RX was self-polymerized and G-Cem light polymerized, followed by mixed fractures, involving adhesive failure and cohesive fractures of the resin cement. It was concluded that light activation of the dual-polymerized resin cements used, showed highest degrees of conversion, biaxial flexural strength and microtensile bond strength. However, the better performance of some cementing systems may be associated with the chemical characteristics inherent to the material

ASSUNTO(S)

materiais dentarios cimentação cimentation dental materials

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