title: Light Transmission of Novel CAD/CAM Materials and Their Influence on the Degree of Conversion of a Dual-curing Resin Cement.
abstract: OBJECTIVE
  To evaluate the light transmission characteristics of different types, shades, and thicknesses of novel CAD/CAM materials and their effect on the degree of conversion (DC) of a dual-curing resin cement.
  
  
  METHODS
  Square specimens (12 × 12 mm2) of three CAD/CAM materials - GC Cerasmart, Lava Ultimate, Vita Enamic - of different thicknesses (1.00, 1.50, and 2.00 mm, n = 5 per thickness) were irradiated with an LED unit. The amount of transmitted light was quantified. Thereafter, the DC% of the dual-curing resin cement (RelyX Ultimate) was recorded after 15 min using Fourier transform infrared spectroscopy. Statistical analysis was performed using two-way ANOVA followed by the Tukey's HSD post-hoc test at a significance level of p < 0.05. Regression analysis was performed to investigate the correlation between the DC and radiant energy, and the DC and thickness.
  
  
  RESULTS
  Although the type and shade of CAD/CAM material significantly affect transmitted light irradiation (p < 0.0001), degrees of conversion are similar when the CAD/CAM material or material shade were taken into consideration (p > 0.05). Conversely, material thickness significantly affected light transmission (p < 0.0001) and DC (p < 0.0001). Multiple effects of material, shade, and thickness did not significantly affect the evaluated parameters (p = 0.638 for light irradiation; p = 0.637 for DC). Linear regression analysis showed a correlation between delivered energy and DC% results of the Vita Enamic (R² = 0.4169, p < 0.0001).
  
  
  CONCLUSIONS
  Reduced light transmission in 2-mm-thick specimens of all CAD/CAM materials indicates that proper curing of the cement beneath CAD/CAM materials should be ensured.
authors.forename: Ferhan
authors.initials: F
authors.lastname: Egilmez
authors.forename: Gulfem
authors.initials: G
authors.lastname: Ergun
authors.forename: Isil
authors.initials: I
authors.lastname: Cekic-Nagas
authors.forename: Pekka K
authors.initials: PK
authors.lastname: Vallittu
authors.forename: Lippo V J
authors.initials: LV
authors.lastname: Lassila
mesh_terms: D017076:Computer-Aided Design; D008027:Light; D008422:Materials Testing; D019279:Resin Cements / Q000528:radiation effects*
chemical_list: C095997:DCR cement; D019279:Resin Cements