Department of Conservative Dentistry and Periodontology, University Hospital, LMU, Germany.
Department of Conservative Dentistry and Periodontology, University Hospital, LMU, Germany.
J Mech Behav Biomed Mater. 2021 Dec;124:104810. doi: 10.1016/j.jmbbm.2021.104810. Epub 2021 Sep 3.
The aim of the study was to determine the effects of ultra-fast (3 s) light-curing on the viscoelastic behaviour at clinically relevant frequencies, and cell toxicity, in a resin-based composite (RBC) with reversible addition-fragmentation-chain transfer (RAFT) mediated polymerization.
Three different protocols were used to cure cylindrical samples (height = 4 mm, ϴ = 5 mm), including ultra-fast (3s) cure with high radiant emittance, 10 s and 20 s cure with moderate radiant emittance. The properties of the light curing device were evaluated in all curing protocols by spectrophotometry up to an exposure distance of 10 mm. The light transmission through the samples was determined in real-time with the same spectrophotometer. Absorbance was calculated as a function of wavelength. The quasi-static (indentation hardness/H, indentation modulus/E) and viscoelastic (storage modulus/E', loss modulus/E″, loss factor/tan δ) material behavior was determined in an instrumented indentation test with a DMA (Dynamic Mechanical Analysis) module for 10 frequencies (0.5-5 Hz) by profiling the center of the samples in 330 μm steps from top to bottom. Cellular toxicity on human gingival fibroblast (HGF-1) was assessed using a WST-1 colorimetric assay after incubation time of up to 3 months. One and multiple-way analysis of variance (ANOVA) with Tukey honestly significant difference (HSD) post-hoc tests (α = 0.05) were applied.
The irradiance transmitted through a 4 mm high sample was less than 7% of the incident irradiance, and the absorbance was similar for all curing protocols, showing a decrease with wavelength. Similar quasi-static and viscoelastic parameters were observed regardless of the curing protocol. H increased slightly and E, E', E″ and tan δ decreased with frequency. Occasionally, slightly higher confidence intervals were observed for the ultra-fast curing group, which were related to a potential accumulation of stress. The curing protocol had no effect on cell viability (p = 0.326) but the eluate age (p < 0.001, η = 0.879) did. None of the groups showed cell toxicity at any point in time with respect to the corresponding negative control.
The ultra-fast curing with high irradiance induced no cell toxicity and an equivalent viscoelastic behavior as with conventional curing protocols in a RAFT-modified RBC.
本研究旨在确定在具有可逆加成-断裂链转移（RAFT）聚合的树脂基复合材料（RBC）中，临床相关频率下的超快速（3 秒）光固化对粘弹性行为的影响，以及细胞毒性。
使用三种不同的方案来固化圆柱形样品（高度= 4mm，ϴ= 5mm），包括使用高辐射发射率进行超快速（3 秒）固化、使用中等辐射发射率进行 10 秒和 20 秒固化。通过分光光度法评估所有固化方案中的光固化设备性能，直至 10mm 的曝光距离。使用相同的分光光度计实时测定样品的透光率。吸光度作为波长的函数进行计算。通过动态机械分析（DMA）模块的仪器化压痕试验，在 10 个频率（0.5-5Hz）下确定准静态（压痕硬度/H、压痕模量/E）和粘弹性（储能模量/E'、损耗模量/E"、损耗因子/tanδ）材料性能，通过从顶部到底部以 330μm 的步长对样品的中心进行轮廓分析。使用 WST-1 比色法评估人类牙龈成纤维细胞（HGF-1）的细胞毒性，孵育时间长达 3 个月。应用单因素和多因素方差分析（ANOVA）和 Tukey 诚实显着差异（HSD）事后检验（α= 0.05）。
通过 4mm 高的样品传输的光辐照度小于入射光辐照度的 7%，并且所有固化方案的吸光度相似，随波长减小。无论固化方案如何，均观察到相似的准静态和粘弹性参数。H 略有增加，E、E'、E"和 tanδ随频率降低。偶尔，超快固化组观察到稍微高的置信区间，这与潜在的应力积累有关。固化方案对细胞活力没有影响（p=0.326），但洗脱液年龄有影响（p<0.001，η=0.879）。在任何时间点，与相应的阴性对照相比，任何组均未显示出细胞毒性。
在具有 RAFT 改性 RBC 的情况下，高辐射强度的超快速固化不会引起细胞毒性，并且粘弹性行为与传统固化方案相当。
