Instituto de Ciências Ambientais, Químicas e Farmacêuticas, Universidade Federal de São Paulo, Diadema, SP, Brazil.
Universidade Anhanguera de São Paulo (UNIAN), São Paulo, SP, Brazil.
Biomed Res Int. 2018 May 22;2018:7921247. doi: 10.1155/2018/7921247. eCollection 2018.
The aim of this study was to evaluate the effect of camphorquinone concentration in physical-mechanical properties of experimental flowable composites in order to find the concentration that results in maximum conversion, balanced mechanical strength, and minimum shrinkage stress. Model composites based on BISGMA/TEGDMA with 70% wt filler loading were prepared containing different concentrations of camphorquinone (CQ) on resin matrix (0.25%, 0.50%, 1%, 1.50%, and 2% by weight). Degree of conversion was determined by FTIR. Surface hardness was assessed before and after 24 h ethanol storage and softening rate was determined. Depth of cure was determined by Knoop hardness evaluation at different depths. Color was assessed by reflectance spectrophotometer, employing the CIE-Lab system. Flexural strength and elastic modulus were determined by a three-point bending test. Shrinkage stress was determined in a Universal Testing Machine in a high compliance system. Data were submitted to ANOVA and Tukey's test ( = 0.05). The increase in CQ concentration caused a significant increase on flexural strength and luminosity of composites. Surface hardness was not affected by the concentration of CQ. Composite containing 0.25% wt CQ showed lower elastic modulus and shrinkage stress when compared to others. Depth of cure was 3 mm for composite containing 1% CQ and 2 mm for the other tested composites. Degree of conversion was inversely correlated with softening rate and directly correlated with elastic modulus and shrinkage stress. In conclusion, CQ concentration affects polymerization characteristics and mechanical strength of composites. The concentration of CQ in flowable composite for optimized polymerization and properties was 1% wt of the resin matrix, which allows adequate balance among degree of conversion, depth of cure, mechanical properties, and color characteristics of these materials.
本研究旨在评估樟脑醌浓度对实验性可流动复合树脂物理力学性能的影响，以期找到转化率最高、机械强度平衡且收缩应力最小的浓度。以 BISGMA/TEGDMA 为基质，填充 70%重量比的填料，制备了含有不同浓度樟脑醌（CQ）的模型复合材料（树脂基质重量比为 0.25%、0.50%、1%、1.50%和 2%）。通过傅里叶变换红外光谱（FTIR）测定转化率。评估了 24 小时乙醇储存前后的表面硬度和软化率，并通过 Knoop 硬度评估测定了固化深度。采用 CIE-Lab 系统的反射分光光度计评估了颜色。采用三点弯曲试验测定了弯曲强度和弹性模量。在高顺应性系统的万能试验机中测定了收缩应力。数据采用方差分析和 Tukey 检验（ = 0.05）。CQ 浓度的增加显著提高了复合材料的弯曲强度和明度。CQ 浓度对表面硬度没有影响。与其他复合材料相比，含 0.25%wt CQ 的复合材料表现出较低的弹性模量和收缩应力。含 1%CQ 的复合材料的固化深度为 3mm，其他测试复合材料的固化深度为 2mm。转化率与软化率呈负相关，与弹性模量和收缩应力呈正相关。综上所述，CQ 浓度影响复合树脂的聚合特性和机械强度。可流动复合树脂中 CQ 的最佳浓度为树脂基质的 1%wt，这使得这些材料的转化率、固化深度、机械性能和颜色特性之间达到了良好的平衡。
