Light irradiance through novel CAD–CAM block materials and degree of conversion of composite cements

Diogo Pedrollo Lise, Annelies Van Ende, Jan De Munck, Kumiko Yoshihara, Noriyuki Nagaoka, Luiz Clovis Cardoso Vieira, Bart Van Meerbeek

Research output: Contribution to journalArticle

5 Citations (Scopus)

Abstract

Objective: To assess light irradiance (LI) delivered by two light-curing units (LCU's) and to measure the degree of conversion (DC) of three composite cements, when cured through different thicknesses of two novel CAD–CAM block materials. Methods: 100-μm-thick films of a dual-curable composite cement (G-CEM LinkAce, GC), a light-curable flowable resin-based composite (RBC) (G-ænial Universal Flo, GC) and a micro-hybrid RBC (G-ænial Posterior, GC) were investigated as luting agents. Two ‘polymer–ceramic’ CAD–CAM blocks (Cerasmart, GC; Enamic, Vita Zahnfabrik) were sectioned in slabs with different thicknesses (1, 3 and 5 mm). LI at the bottom of the specimens was measured using a calibrated spectrometer, while being light-cured through the CAD–CAM block slabs for 40 s with a low- (±500 mW/cm2) or high- (±1,600 mW/cm2) irradiance LCU (n = 5). After light-curing, micro-Raman spectra of the composite films were acquired to determine DC at 5 min, 10 min, 1 h and 24 h. LI data were statistically analyzed by Kruskal–Wallis followed by post-hoc comparisons, while a linear mixed-effect model was applied for the DC analysis. In addition, the CAD–CAM blocks ultrastructure was characterized upon argon-ion slicing using scanning transmission electron microscopy (STEM). Finally, light transmission (LT) through each CAD–CAM block material was assessed using a spectrophotometer. Results: Curing-light attenuation and DC were significantly influenced by thickness and type of the overlying material. LCU only had a significant effect on DC of the micro-hybrid RBC. DC significantly increased over time for all composite cements. CAD–CAM block structural analysis revealed a relatively small and homogenous filler configuration (mean filler size of 0.2–0.5 μm) for Cerasmart, while Enamic contained ceramic grains varying in shape and size (1–10 μm), which were interconnected by the polymer-based network. LT was much higher at a wavelength range of 300–800 nm for Cerasmart than for Enamic. Significance: Light-curable composite cements can be cured through a restoration up to 2.7-mm thickness, depending on the kind of CAD–CAM material. A high-irradiance LCU only has a limited effect on the maximum thickness of the polymer–ceramic CAD–CAM material that can be cured through.

Original languageEnglish
Pages (from-to)296-305
Number of pages10
JournalDental Materials
Volume34
Issue number2
DOIs
Publication statusPublished - Feb 1 2018

Keywords

  • CAD–CAM
  • Composite cement
  • Degree of conversion
  • Light spectrometer
  • Micro-Raman
  • STEM

ASJC Scopus subject areas

  • Materials Science(all)
  • Dentistry(all)
  • Mechanics of Materials

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    Lise, D. P., Van Ende, A., De Munck, J., Yoshihara, K., Nagaoka, N., Cardoso Vieira, L. C., & Van Meerbeek, B. (2018). Light irradiance through novel CAD–CAM block materials and degree of conversion of composite cements. Dental Materials, 34(2), 296-305. https://doi.org/10.1016/j.dental.2017.11.008