title: Degree of conversion of dual-cure resins light-cured through glass-fiber posts.
abstract: OBJECTIVE
  To evaluate the degree of conversion (DC) of dual-curing materials used to lute glass-fiber posts in a simulated root canal polymerized by two different modalities.
  
  
  METHODS
  Artificial root canals were used to simulate a clinical condition to lute 45 posts by three different dual curing luting cements (Calibra, Multilink Automix and Variolink II). Two light cure modalities were chosen for each luting cement: standard (S group) 400 mW/cm2 for 120 seconds and high-power (H group) 1200 mW/cm2 for 40 seconds. Raman spectra were collected at different positions in the post surface (1, 3, 5 and 7 mm from the coronal-most portion of the post covered in cement) and the percentage degree of conversion was computed. The data were analyzed using ANOVA and post-hoc Student-Neuman-Keuls t-test (P = 0.05).
  
  
  RESULTS
  The DC of the tested luting composites decreased progressively while increasing the distance from the light tip. Regardless of the polymerization modality (H or S) applied. Conversely, the curing modality significantly influenced the DC of the tested materials, evidencing different responses to the same energy density: Calibra seemed to be less dependent on light-curing than the other tested materials, showing a constant behavior. Multilink Automix reached the highest DCs in the S group compared to the H mode. Variolink II showed an interesting drawback in DC at 7 mm when cured in the H model. Dual-cure materials show adequate monomer conversion but when the distance from the curing light increased, a variable, but significant lowering in conversion rate was observed. In addition, the time and power of curing appeared to be material-dependent and should be calibrated individually.
authors.affiliation: Department of Materials for Engineering, University of Brescia, Italy. fc@francescacerutti.it
authors.forename: Francesca
authors.initials: F
authors.lastname: Cerutti
authors.forename: Pier Antonio
authors.initials: PA
authors.lastname: Acquaviva
authors.forename: Massimo
authors.initials: M
authors.lastname: Gagliani
authors.forename: Marco
authors.initials: M
authors.lastname: Ferrari
authors.forename: Francesco
authors.initials: F
authors.lastname: Mangani
authors.forename: Laura E
authors.initials: LE
authors.lastname: Depero
authors.forename: Antonio
authors.initials: A
authors.lastname: Cerutti
mesh_terms: D003188:Composite Resins / Q000737:chemistry*; D001840:Dental Bonding / Q000379:methods*; D003799:Dental Stress Analysis; D005898:Glass; D006244:Hardness; D006801:Humans; D055115:Light-Curing of Dental Adhesives / Q000379:methods*; D008422:Materials Testing; D058105:Polymerization; D011176:Post and Core Technique; D019279:Resin Cements
chemical_list: D003188:Composite Resins; D019279:Resin Cements; C009753:fiberglass