title: Polymerization behavior and thermal characteristics of two new composites at five temperatures: refrigeration to preheating.
abstract: OBJECTIVE
  Heat of composite polymerization (HP) indicates setting efficacy and temperature increase of composite in clinical procedures. The purpose of this in vitro experimental study was to evaluate the effects of 5 temperatures on HP of two new composites.
  
  
  METHODS
  From each material (Core Max II [CM] and King Dental [KD]), 5 groups of 5 specimens each were prepared and their total HPs (J/gr) were measured and recorded, at one of the constant temperatures 0℃, 15℃, 23℃, 37℃ and 60℃ (2 × 5 × 5 specimens) using a differential scanning calorimetry (DSC) analyzer. The data were analyzed using a two-way ANOVA, a Tukey's test, an independent-samples t-test, and a linear regression analysis (α=0.05).
  
  
  RESULTS
  No polymerization reactions occurred at 0℃; then this temperature was excluded from statistical analyses. The mean HP of the remaining 20 KD specimens was 20.5 ± 14.9 J/gr, while it was 40.7 ± 12.9 J/gr for CM. The independent-samples t-test showed that there were significant differences between the HP of the two materials at the temperatures 15℃ (P=.0001), 23℃ (P=.0163), 37℃ (P=.0039), and 60℃ (P=.0106). Linear regression analysis showed statistically significant correlations between environment temperatures and HP of CM (R(2)=0.777).
  
  
  CONCLUSIONS
  Using CM is advantageous over conventional composite because of its better polymerization capacity. However due to its high HP, further studies should assess its temperature increase in vivo. Preheating KD is recommended. Refrigerating composites can negatively affect their polymerization potential.
authors.affiliation: Department of Dental Materials, Faculty of Dentistry, Tehran University of Medical Sciences; Research Center for Medical and Technology in Medical Sciences, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Tahereh Sadat
authors.initials: TS
authors.lastname: Jafarzadeh-Kashi
authors.forename: Marzieh
authors.initials: M
authors.lastname: Mirzaii
authors.forename: Mohmmad
authors.initials: M
authors.lastname: Erfan
authors.forename: Akbar
authors.initials: A
authors.lastname: Fazel
authors.forename: Solmaz
authors.initials: S
authors.lastname: Eskandarion
authors.forename: Vahid
authors.initials: V
authors.lastname: Rakhshan