Polymerization of a dual-cured cement through ceramic: LED curing light vs halogen lamp

Abstract

The aim of this study was to investigate the influence of light source, LED unit and halogen lamp (HL), on the effectiveness of Enforce dual-cured cement cured under a ceramic disc. Three exposure times (60, 80 and 120 s) were also evaluated. Two experimental groups, in which the polymerization of the dual-cured cement was performed through a ceramic disc, and two control groups, in which the polymerization of the dual-cured cement was performed directly without presence of ceramic disc were subdivided into three subgroups (three different exposure times), with five specimens each: G1A- HL 60s; G1B- HL 80s; G1C- HL 120s; G2A- LED 60s; G2B- LED 80s; G2C- LED 120s; and control groups: G3A- HL 60s; G3B- HL 80s; G3C- HL 120s; G4A- LED 60s; G4B- LED 80s and G4C- LED 120s. Cement was applied in a steel matrix (4mm diameter, 1.2mm thickness). In the experimental groups, a ceramic disc was placed on top. The cement was light-cured through the ceramic by a HL and LED, however, the control groups were cured without the ceramic disc. The specimens were stored in a light-proof container at 37ºC for 24 hours, then Vickers hardness was determined. A four-way ANOVA and Tukey test (p£ 0.05) were performed. All specimens cured by LED for 60s showed inferior values compared with the halogen groups. In general, light-curing by LED for 80s and 120s was comparable to halogen groups (60s and 80s) and their control groups. LED technology can be viable for light-curing through conventional ceramic indirect restorations, when curing time is increased in relation to HL curing time.

A critical analysis of the degree of conversion of resin-based luting cements

“…Moreover, the higher the DC% of resin-based cements, the better their physicomechanical properties 14 . Several studies have analyzed the polymerization of resin-based cements 3 , 11 - 13 , 18 , 23 - 25 . Most of these studies, however, have used Knoop or Vickers hardness as indicative of their degree of polymerization.…”

Resistência de união entre uma cerâmica e o esmalte de dente bovino, efetuada por diferentes sistemas adesivos e técnicas de cimentação

“…Em muitos dos estudos a este respeito os resultados observados apresentaram valores semelhantes aos de dentes humanos (NAKAMICHI;IWAKU;FUSAYAMA, 1983;ROMANO et al, 2004;MOTA et al, 2003). Há consenso, na literatura, de que restaurações indiretas de cerâmicas com espessuras superiores a 2mm deveriam ser fixadas com cimentos autopolimerizáveis ou de cura dupla (LOPES et al, 2004;AKGUNGOR;AKKAYAN;GAUCHER, 2005;KRAMER et al, 2008;ACQUAVIVA et al, 2009 Crêem que, clinicamente, a fotopolimerização simultânea de adesivo e cimento seja vantajosa. Estão de acordo com o raciocínio de que a espessura da camada adesiva polimerizada causará a desadaptação da peça restauradora, ocasionando discrepâncias marginais e interferências oclusais (HIKITA et al, 2007).…”

Resistência ao micro-cisalhamento de cimentos resinosos fotoativados através de diferentes espessuras de cerâmica

“…Os altos valores de resistência de adesão estão relacionados com a maior taxa de polimerização. Inadequada polimerização estaria associada às menores propriedades mecânicas, aumento da sorção de água e solubilidade e instabilidade da cor , Lopes, 2004. A polimerização dos cimentos resinosos está relacionada com o sucesso das restaurações indiretas uma vez que a resistência de união entre a cerâmica e cimento, e entre o cimento e esmalte e/ou dentina será dependente da obtenção de polimerização adequada do cimento resinoso.…”