title: Pre-heated dual-cured resin cements: analysis of the degree of conversion and ultimate tensile strength.
abstract: This study evaluated the degree of conversion (DC) and ultimate tensile strength (UTS) of dual-cured resin cements heated to 50º C prior to and during polymerization. Disc- and hourglass-shaped specimens of Rely X ARC (RX) and Variolink II (VII) were obtained using addition silicon molds. The products were manipulated at 25º C or 50º C and were subjected to 3 curing conditions: light-activation through a glass slide or through a pre-cured 2-mm thick resin composite disc, or they were allowed to self-cure (SC). All specimens were dark-stored dry for 15 days. For DC analysis, the resin cements were placed into the mold located on the center of a horizontal diamond on the attenuated total reflectance element in the optical bench of a Fourier Transformed Infrared spectrometer. Infrared spectra (n = 6) were collected between 1680 and 1500 cm-1, and DC was calculated by standard methods using changes in ratios of aliphatic-to-aromatic C=C absorption peaks from uncured and cured states. For UTS test, specimens (n = 10) were tested in tension in a universal testing machine (crosshead speed of 1 mm/min) until failure. DC and UTS data were submitted to 2-way ANOVA, followed by Tukey's test (α= 5%). Both products showed higher DC at 50º C than at 25º C in all curing conditions. No significant difference in UTS was noted between most light-activated groups at 25º C and those at 50º C. VII SC groups showed higher UTS at 50º C than at 25º C (p < 0.05). Increased temperature led to higher DC, but its effects on resin cement UTS depended on the curing condition.
authors.affiliation: Department of Operative Dentistry, Guarulhos University, Guarulhos, SP, Brazil.
authors.forename: Flávio Álvares
authors.initials: FÁ
authors.lastname: França
authors.forename: Michele de
authors.initials: Md
authors.lastname: Oliveira
authors.forename: José Augusto
authors.initials: JA
authors.lastname: Rodrigues
authors.forename: César Augusto Galvão
authors.initials: CA
authors.lastname: Arrais
mesh_terms: D000704:Analysis of Variance; D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry; D055117:Curing Lights, Dental; D006358:Hot Temperature; D006801:Humans; D008422:Materials Testing; D011092:Polyethylene Glycols / Q000737:chemistry; D058105:Polymerization; D011109:Polymethacrylic Acids / Q000737:chemistry; D019279:Resin Cements / Q000737:chemistry* / Q000528:radiation effects; D055116:Self-Curing of Dental Resins / Q000379:methods*; D013499:Surface Properties; D013718:Tensile Strength; D013997:Time Factors
chemical_list: D011109:Polymethacrylic Acids; C462240:RelyX ARC; D019279:Resin Cements; C103502:Variolink; D011092:Polyethylene Glycols; D017438:Bisphenol A-Glycidyl Methacrylate