title: Light shielding effect of overlaying resin composite on the photopolymerization cure kinetics of a resin composite and a dentin adhesive.
abstract: OBJECTIVE
  The purpose of this study was to simultaneously determine the impact of exposure times and incremental resin composite overlaying thickness on the cure kinetics of a light activated composite and a dentin adhesive at selected depths of a simulated restoration.
  
  
  METHODS
  Levels and kinetics of polymerization of a light activated resin composite (Z250, 3M-ESPE) and dentin adhesive (Excite, Ivoclar) cured with a halogen light unit (Demetron, Kerr, USA) operating at low/medium intensity (500 mW/cm2) for different exposure durations (20 and 60 s) were measured at selected depths (0.3, 0.6 and 1mm) using a modified calorimetric analyzer (DSC 25, METLLER-TOLEDO).
  
  
  RESULTS
  Final polymerization levels of materials up to 1mm through the composite are not significantly different while the light shielding effect of incremental resin composite overlaying progressively reduces their reaction rates.
  
  
  CONCLUSIONS
  Prolonged irradiation time at low/medium energies is effective for proper conversion of a resin composite and dentin adhesive; 60 s irradiation time provides the maximum obtainable conversion through the dental resin composite for thicknesses up to 1mm.
authors.affiliation: CRIB Centro di Ricerca Interdipartimentale sui Biomateriali, University of Naples, Federico II, Naples, Italy. apicella@unina.it
authors.forename: Antonio
authors.initials: A
authors.lastname: Apicella
authors.forename: Michele
authors.initials: M
authors.lastname: Simeone
authors.forename: Raffaella
authors.initials: R
authors.lastname: Aversa
authors.forename: Alessandro
authors.initials: A
authors.lastname: Lanza
authors.forename: Davide
authors.initials: D
authors.lastname: Apicella
mesh_terms: D002152:Calorimetry, Differential Scanning; D003188:Composite Resins / Q000737:chemistry* / Q000528:radiation effects; D017220:Dentin-Bonding Agents / Q000737:chemistry* / Q000528:radiation effects; D006801:Humans; D007700:Kinetics; D008027:Light; D008029:Lighting / Q000295:instrumentation; D008422:Materials Testing; D008689:Methacrylates / Q000737:chemistry / Q000528:radiation effects; D011108:Polymers / Q000737:chemistry / Q000528:radiation effects; D011829:Radiation Dosage; D013499:Surface Properties; D013997:Time Factors
chemical_list: D003188:Composite Resins; D017220:Dentin-Bonding Agents; C420130:Excite cement; C444701:Filtek Z250; D008689:Methacrylates; D011108:Polymers