title: Influence of light-activation protocol on methacrylate resin-composite evaluated by dynamic mechanical analysis and degree of conversion.
abstract: The aim of this study was to evaluate the degree of conversion (DC) and to identify the viscoelastic properties: storage modulus (E'), loss modulus (E"), tangent delta (tan δ), and glass transition temperature (T g ) of a microhybrid resin-composite light-activated by three different protocols. A Filtek Z250 (3 M ESPE) shade A3 was inserted in a Teflon mold (21 mm × 5 mm × 1 mm for viscoelastic properties; and 5 mm × 1 mm for DC) and light-activated according to the following light-activation protocols: (S) 1,000 mW/cm(2) × 19 s, (HP) 1,400 mW/cm(2) × 14 s, and (PE) 3,200 mW/cm(2) × 6 s, all set up to deliver 19 J/cm(2). Viscoelastic properties was assessed by dynamic mechanical analysis (DMA) (n = 3), performed in single cantilever clamped mode. DC (n = 5) was measured by FTIR on top (T) and bottom (B) surfaces, and the data was submitted to a split-plot one-way ANOVA. For DC, there was a significant effect for surface factor and light-activation protocols factor. Top surface showed higher DC than B in all experimental conditions. Light-activation protocols S and HP resulted in higher DC than PE and were similar between them. Viscoelastic properties (E', E", tan δ, T g ) were not affected by light-activation protocols. It could be concluded that light-activation protocols influenced DC but not influenced the viscoelastic properties.
authors.affiliation: Department of Restorative Dentistry, Piracicaba Dental School, University of Campinas (UNICAMP), Avenida Limeira, 901 Bairro Areião, Piracicaba, SP, 13414-903, Brazil, cecilia.giorgi@yahoo.com.
authors.forename: Maria Cecília C
authors.initials: MC
authors.lastname: Giorgi
authors.forename: Vinícius
authors.initials: V
authors.lastname: Pistor
authors.forename: Raquel S
authors.initials: RS
authors.lastname: Mauler
authors.forename: Débora A N L
authors.initials: DA
authors.lastname: Lima
authors.forename: Giselle M
authors.initials: GM
authors.lastname: Marchi
authors.forename: Flávio H B
authors.initials: FH
authors.lastname: Aguiar
mesh_terms: D003188:Composite Resins / Q000737:chemistry*; D055119:Elastic Modulus; D008027:Light; D008422:Materials Testing; D055668:Photochemical Processes; D011109:Polymethacrylic Acids / Q000737:chemistry*; D044366:Transition Temperature; D014783:Viscosity
chemical_list: D003188:Composite Resins; C444701:Filtek Z250; D011109:Polymethacrylic Acids
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