title: Degree of conversion of two dual-cured resin cements light-irradiated through zirconia ceramic disks.
abstract: OBJECTIVE
  The aim of this Fourier transform infrared (FTIR) spectroscopic study was to measure the degree of conversion (DC) of dual-cured resin cements light-irradiated through zirconia ceramic disks with different thicknesses using various light-curing methods.
  
  
  METHODS
  Zirconia ceramic disks (KT12) with three different thicknesses (1.0, 2.0, and 4.0 mm) were prepared. The light transmittance of the disks was measured using ultraviolet visible near-infrared spectroscopy. Four different light-curing protocols were used by combining two curing light modes (Elipar TriLight (standard mode) and bluephase G2 (high power mode)) with light-exposure times of 40 and 120 seconds. The DCs of the two dual-cured resin cements (Duo-Link and Panavia F2.0) light-irradiated through the disks was analyzed at three time intervals (3, 7, and 10 minutes) by FTIR spectroscopy. The data was analyzed using repeated measures ANOVA (α=.05).Two-way ANOVA and Tukey post hoc test were used to analyze the 10 minute DC results.
  
  
  RESULTS
  The 1.0 mm thick disk exhibited low light transmittance (<25%), and the transmittance decreased considerably with increasing disk thickness. All groups exhibited significantly higher 10 minute DC values than the 3 or 7 minute values (P<.05), but some exceptions were observed in Duo-Link. Two-way ANOVA revealed that the influence of the zirconia disk thickness on the 10 minute DC was dependent on the light-curing methods (P<.001). This finding was still valid even at 4.0 mm thickness, where substantial light attenuation took place.
  
  
  CONCLUSIONS
  The curing of the dual-cured resin cements was affected significantly by the light-curing technique, even though the additional chemical polymerization mechanism worked effectively.
authors.affiliation: Department of Medical & Biological Engineering, Graduate School, Kyungpook National University, Daegu, Republic of Korea.
authors.forename: Min-Jeong
authors.initials: MJ
authors.lastname: Kim
authors.affiliation: Department of Dental Biomaterials, School of Dentistry, and Institute for Biomaterials Research & Development, Kyungpook National University, Daegu, Republic of Korea.
authors.forename: Kyo-Han
authors.initials: KH
authors.lastname: Kim
authors.affiliation: Department of Conservative Dentistry, School of Dentistry, Kyungpook National University, Daegu, Republic of Korea.
authors.forename: Young-Kyung
authors.initials: YK
authors.lastname: Kim
authors.affiliation: Department of Dental Biomaterials, School of Dentistry, and Institute for Biomaterials Research & Development, Kyungpook National University, Daegu, Republic of Korea.
authors.forename: Tae-Yub
authors.initials: TY
authors.lastname: Kwon
keywords: Degree of conversion; Resin cement; Zirconia ceramic