Division of Biomaterials and Tissue Engineering, UCL Eastman Dental Institute, London, United Kingdom.
Centro de Investigação Interdisciplinar Egas Moniz (CiiEM), Instituto Universitário Egas Moniz, Monte de Caparica, Portugal.
PLoS One. 2021 Jun 9;16(6):e0252999. doi: 10.1371/journal.pone.0252999. eCollection 2021.
Investigation of polymerisation kinetics using ATR-FTIR systems is common in many dental studies. However, peak selection methods to calculate monomer-polymer conversion can vary, consequently affecting final results. Thus, the aim of this study is to experimentally confirm which method is less prone to systematic errors. Three commercial restorative materials were tested-Vertise Flow (VF), Constic and Activa Bioactive Restorative Kids. Firstly, Attenuated Total Reflectance Fourier Transform Infra-Red (ATR-FTIR) (Spectrum One, Perkin-Elmer, UK) spectra of monomers were acquired-10-methacryloyloxy decyl dihydrogen phosphate (10-MDP), bisphenol-A glycidyl dimethacrylate (Bis-GMA), 2-hydroxyethyl methacrylate (HEMA), triethyelene glycol dimethacrylate (TEGDMA) and urethane dimethacrylate (UDMA) to investigate proportionality of methacrylate peak heights versus concentration. Spectral changes upon light exposure of 2 mm discs of the restorative materials (irradiated for 20 s, LED curing unit 1100-1330 mW/cm2) were assessed to study polymerisation kinetics (n = 3), with continuous acquisition of spectra, before, during and after light exposure. Peak differences and degrees of conversion (DC %) were calculated using 1320/1336, 1320/1350 and 1636/1648 cm-1 as reaction/reference peaks. Inferential statistics included a MANOVA and within-subjects repeated measures ANOVA design (5% significance level). Proportionality of methacrylate peak height to concentration was confirmed, with the 1320/1352 cm-1 peak combination showing the lowest coefficient of variation (8%). Difference spectra of the polymerisation reaction showed noise interference around the 1500-1800 cm-1 region. Across the different materials, DC % results are highly dependent upon peak selection (p<0.001), with higher variability associated to the 1636 cm-1. Significant differences in the materials were only detected when the 1320 cm-1 peak was used (p<0.05). Within the same materials, methods were significantly different for Constic and Activa (p<0.05). It is possible to conclude that the 1320 cm-1 peak is more adequate to assess polymerisation of methacrylates and is therefore recommended.
使用衰减全反射傅里叶变换红外（ATR-FTIR）系统研究聚合动力学在许多牙科研究中很常见。然而，用于计算单体-聚合物转化率的峰选择方法可能会有所不同，从而影响最终结果。因此，本研究的目的是通过实验证实哪种方法不易产生系统误差。测试了三种商业修复材料-Vertise Flow（VF）、Constic 和 Activa Bioactive Restorative Kids。首先，获取单体的衰减全反射傅里叶变换红外（ATR-FTIR）（Spectrum One，Perkin-Elmer，英国）光谱-10-甲氧基癸基二氢磷酸（10-MDP）、双酚 A 缩水甘油二甲基丙烯酸酯（Bis-GMA）、2-羟乙基甲基丙烯酸酯（HEMA）、三乙二醇二甲基丙烯酸酯（TEGDMA）和尿烷二甲基丙烯酸酯（UDMA），以研究甲基丙烯酸酯峰高与浓度的比例关系。评估修复材料 2mm 圆盘在光照射下的光谱变化（LED 固化单元 1100-1330mW/cm2，照射 20s），以研究聚合动力学（n=3），在光照射之前、期间和之后连续采集光谱。使用 1320/1336、1320/1350 和 1636/1648cm-1 作为反应/参考峰计算峰差异和转化率（DC%）。推断统计包括多变量分析和受试者内重复测量方差分析设计（5%显着性水平）。甲基丙烯酸酯峰高与浓度的比例关系得到证实，1320/1352cm-1 峰组合的变异系数最低（8%）。聚合反应的差谱在 1500-1800cm-1 区域显示出噪声干扰。在不同的材料中，DC%结果高度依赖于峰选择（p<0.001），与 1636cm-1 相关的变异性更高。仅当使用 1320cm-1 峰时才检测到材料之间的显着差异（p<0.05）。在相同的材料中，Constic 和 Activa 的方法差异显着（p<0.05）。可以得出结论，1320cm-1 峰更适合评估甲基丙烯酸盐的聚合，因此建议使用。
