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.

中文翻译：

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新型CAD–CAM块材料的光辐照度和复合水泥的转化度

客观的

评估通过两种厚度不同的两种新型CAD-CAM块状材料固化时，两个光固化单元（LCU）传递的光辐照度（LI）并测量三种复合水泥的转化率（DC）。

方法

100微米厚的双固化复合水泥（G-CEM LinkAce，GC），可光固化的可流动树脂基复合材料（RBC）（G-ænialUniversal Flo，GC）和微混合RBC（研究了G-ænialPosterior（GC）作为诱剂。将两个“聚合物-陶瓷” CAD-CAM块（Cerasmart，GC； Enamic，Vita Zahnfabrik）切成不同厚度（1、3和5 mm）的平板。使用校准的光谱仪测量样品底部的LI，同时以低（±500 mW / cm ²）或高（±1600 mW / cm）的强度通过CAD–CAM块平板将其光固化40 s。^2个）辐照度LCU（n = 5）。光固化后，获得复合膜的显微拉曼光谱，以测定5分钟，10分钟，1小时和24小时的DC。LI数据通过Kruskal–Wallis进行统计学分析，然后进行事后比较，而线性混合效应模型用于DC分析。此外，使用扫描透射电子显微镜（STEM）进行氩离子切片，对CAD-CAM块的超微结构进行了表征。最后，使用分光光度计评估通过每种CAD–CAM块材料的透光率（LT）。

结果

固化光的衰减和DC受到上覆材料的厚度和类型的显着影响。LCU仅对微混合RBC的DC有显着影响。所有复合水泥的DC随时间显着增加。CAD–CAM块结构分析显示Cerasmart的填充物构型相对较小且均质（平均填充物尺寸为0.2–0.5μm），而Enamic包含形状和尺寸（1–10μm）不同的陶瓷颗粒，这些颗粒通过聚合物相互连接基于网络。Cerasmart在300–800 nm波长范围内的LT比Enamic高得多。

意义

根据CAD-CAM材料的种类，光固化复合水泥可以通过厚度最大为2.7 mm的修复体进行固化。高辐照度的LCU仅对可固化的聚合物-陶瓷CAD-CAM材料的最大厚度产生有限的影响。