title: Polymerization kinetics of resin cements after light activation through fibre posts: an in vitro study.
abstract: OBJECTIVE
  To measure the polymerization of light-cured (Variolink Veneer, VLV) and dual-cured (Variolink II, VLII) resin luting cements after light activation through different lengths of fibre post ex vivo.
  
  
  METHODS
  Degree of conversion after prolonged direct light activation (PLA) [12 min after LED light activation for 3 min] was determined using ATR-FTIR. Models were then produced to allow samples of VLV and VLII (n = 5 each group) to be light-activated through 3, 6 and 9 mm lengths of fibre post (Fiber Lux). Degree of conversion was assessed by ATR-FTIR and expressed as a percentage of the degree of conversion achieved after PLA. Data were analysed using anova and Tukey's test (P < 0.05).
  
  
  RESULTS
  Mean [SD] degree of conversion for VLV and VLII after PLA was 57.97% [1.51] and 54.71% [3.77], respectively. Light activation of VLV through a 3 mm post produced 81.62% of the PLA value, compared with 71.03% for the 6 mm and 46.04% for the 9 mm post. Conversion after activation through 9 mm posts was significantly less than through 3 mm and 6 mm posts (P < 0.05). For VLII, activation through a 3 mm post produced 66.51% of the PLA value, compared with 54.38% for the 6 mm and 41.56% for the 9 mm post. A significant decrease in degree of conversion was noted for VLII as post length increased (P < 0.05).
  
  
  CONCLUSIONS
  The degree of conversion for VLV reduced after light activation through 9 mm posts when compared to 3 mm and 6 mm posts, whilst the degree of conversion for VLII decreased with every increase in post length.
authors.affiliation: Department of Restorative Dental Sciences, College of Dentistry, University of Dammam, Dammam, Saudi Arabia.
authors.forename: A
authors.initials: A
authors.lastname: Khabeer
authors.forename: J
authors.initials: J
authors.lastname: Whitworth
authors.forename: S
authors.initials: S
authors.lastname: Rolland
mesh_terms: D006244:Hardness; D055115:Light-Curing of Dental Adhesives; D008422:Materials Testing; D058105:Polymerization; D011176:Post and Core Technique / Q000295:instrumentation*; D019279:Resin Cements / Q000737:chemistry*
chemical_list: C092621:Ivoclar Universal Cement; D019279:Resin Cements; C103502:Variolink
keywords: FTIR; degree of conversion; dual cured; fibre post; light cured; light transmission