title: Influence of different ceramics on resin cement Knoop Hardness Number.
abstract: This study evaluated: (1) the effect of different ceramics on light attenuation that could affect microhardness, measured as the Knoop Hardness Number (KHN), of a resin cement immediately and 24 hours after polymerization and (2) the effect of different activation modes (direct light-activation, light activation through ceramics and chemical activation) on the KHN of a resin cement. Resin cement Rely XARC (3M ESPE) specimens 5.0 mm in diameter and 1.0 mm thickwere made in a Teflon mold covered with a polyester film. The cement was directly light activated for 40 seconds with an XL 2500 curing unit (3M ESPE) with 650 mW/cm2, light activated through ceramic discs of Duceram Plus (DeguDent), Cergogold (DeguDent), IPS Empress (Ivoclar), IPS Empress 2 (Ivoclar), Procera (NobelBiocare), In Ceram Alumina (Vita) and Cercon (DeguDent), having a 1.2 mm thickness or chemically activatedwith-out light application. The resin cement specimens were flattened, and KHN wasobtained using an HMV 2 microhardnesstester (Shimadzu) with a load of 50 g applied for 15 seconds 100 microm from the irradiated surface immediately and after storage at 37 degrees C for 24 hours. Ten measurements were made for each specimen, with three specimens for each group at each time. The data were submitted to ANOVA and Tukey's test (p = 0.05). The KHN of the resin cement was not only affected by the mode of activation, but also by the post-activation testing time. The mean KHN of the resin cementfor chemical activation and through all ceramics showed statistically significant lower values compared to direct activation immediately and at 24 hours. The KHN for 24 hourspost-activation was always superior to the immediate post-activation test except with direct activation. The most opaque ceramics resulted in the lowest KHN values.
authors.affiliation: Department of Dental Materials and Restorative Dentistry, University of Uberaba, Uberaba, MG, Brazil. gilberto.borges@uniube.br
authors.forename: Gilberto A
authors.initials: GA
authors.lastname: Borges
authors.forename: Parul
authors.initials: P
authors.lastname: Agarwal
authors.forename: Benito A S
authors.initials: BA
authors.lastname: Miranzi
authors.forename: Jeffrey A
authors.initials: JA
authors.lastname: Platt
authors.forename: Thiago Assunção
authors.initials: TA
authors.lastname: Valentino
authors.forename: Paulo Henrique
authors.initials: PH
authors.lastname: dos Santos
mesh_terms: D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry / Q000528:radiation effects; D003776:Dental Porcelain / Q000737:chemistry; D006244:Hardness; D055115:Light-Curing of Dental Adhesives; D008422:Materials Testing; D011092:Polyethylene Glycols / Q000737:chemistry / Q000528:radiation effects; D011109:Polymethacrylic Acids / Q000737:chemistry / Q000528:radiation effects; D019279:Resin Cements / Q000737:chemistry / Q000528:radiation effects; D055116:Self-Curing of Dental Resins; D013997:Time Factors
chemical_list: D011109:Polymethacrylic Acids; C462240:RelyX ARC; D019279:Resin Cements; D003776:Dental Porcelain; D011092:Polyethylene Glycols; D017438:Bisphenol A-Glycidyl Methacrylate