Objective

To investigate the effect of two light-curing protocols on mechanical behavior of three bulk-fill resin composites (BFRC) considering their optical properties.

Methods

One increment of 4 mm thickness of the bulk-fill resin composites Opus Bulk Fill, Tetric N-Ceram and Filtek Bulk Fill Flow were submitted to two different light-curing protocols: Sp - irradiance of 1000 mW/cm² (20 s); Xp - irradiance of 3200 mW/cm² (6 s). To assess the influence on the mechanical behavior it was studied polymerization shrinkage by X-ray microtomography (n = 3), Vickers hardness (n = 10) at the top and bottom surfaces of the samples, irradiance reaching the bottom surface (n = 3) and absorbance spectrum during the light-curing time interval (n = 3). Data were analyzed by two-way ANOVA test for parametric data and Kruskal Wallis test, followed by Wilcoxon or Mann-Whitney U post-test, for non-parametric data.

Results

All BFRCs contracted when light-cured, with greater contraction for Xp. Filltek Bulk Fill Flow showed highest polymerization shrinkage, for both Sp and Xp. All BFRCs showed minor hardness values on the bottom surface, with greater reduction for Xp. All BFRCs exhibited a decrease in irradiance at 4 mm depth. A decrease in absorbance intensity throughout the light-cure was observed, except for Opus Bulk Fill.

Conclusions

Regardless BFRCs composition, the light-curing protocol with lower irradiance and longer exposure time results in lower polymerization shrinkage and higher hardness. The higher irradiance in a shorter time interval compromises the mechanical behavior of the resin composites, which may result in undesirable clinical outcomes.

中文翻译：

---

光固化方案对块状填充树脂复合材料机械性能的影响。

客观的

要研究两种光固化协议对三种填充树脂复合材料（BFRC）的光学性能的力学行为的影响。

方法

将厚度为4 mm的增量填充树脂复合材料Opus批量填充，Tetric N-Ceram和Filtek批量填充流的增量增加到两种不同的光固化方案：Sp-1000 mW / cm ²（20 s）的辐照度；Xp-3200 mW / cm ²（6 s）的辐照度。为了评估对机械性能的影响，通过X射线断层照相术（n = 3），样品顶部和底部的维氏硬度（n = 10），辐照度到达底部表面（n = 3）研究了聚合收缩率。 ）和光固化时间间隔（n = 3）期间的吸收光谱。对于非参数数据，通过双向方差分析（ANOVA）测试和参数Kruskal Wallis测试对数据进行分析，然后通过Wilcoxon或Mann-Whitney U后测试对数据进行分析。

结果

光固化时，所有BFRC都收缩，而Xp的收缩更大。对于Sp和Xp，Filltek本体填充流量均显示出最高的聚合收缩率。所有BFRC的底表面都显示出较小的硬度值，而Xp的降低幅度更大。所有BFRC在4 mm深度处的辐照度均降低。除了Opus Bulk Fill，整个光固化过程中的吸光度都降低了。

结论

不管BFRCs的组成如何，具有较低的辐照度和较长的曝光时间的光固化方案都会导致较低的聚合收缩率和较高的硬度。在较短的时间间隔内较高的辐照度会损害树脂复合材料的机械性能，这可能会导致不良的临床结果。