Abedin F, Ye Q, Parthasarathy R, Misra A, Spencer P
Bioengineering Research Center, University of Kansas, Lawrence, KS, USA Bioengineering Graduate Program, University of Kansas, Lawrence, KS, USA.
Bioengineering Research Center, University of Kansas, Lawrence, KS, USA
J Dent Res. 2015 Mar;94(3):500-7. doi: 10.1177/0022034514565646. Epub 2015 Jan 9.
The 2-fold objectives of this study were 1) to understand whether model hydrophobic- and hydrophilic-rich phase mimics of dentin adhesive polymerize similarly and 2) to determine which factor, the dimethacrylate component, bisphenol A glycerolate dimethacrylate (BisGMA) or photoinitiator concentration, has greater influence on the polymerization of the hydrophilic-rich phase mimic. Current dentin adhesives are sensitive to moisture, as evidenced by nanoleakage in the hybrid layer and phase separation into hydrophobic- and hydrophilic-rich phases. Phase separation leads to limited availability of the cross-linkable dimethacrylate monomer and hydrophobic photoinitiators within the hydrophilic-rich phase. Model hydrophobic-rich phase was prepared as a single-phase solution by adding maximum wt% deuterium oxide (D2O) to HEMA/BisGMA neat resins containing 45 wt% 2-hydroxyethyl methacrylate (HEMA). Mimics of the hydrophilic-rich phase were prepared similarly but using HEMA/BisGMA neat resins containing 95, 99, 99.5, and 100 wt% HEMA. The hydrophilic-rich mimics were prepared with standard or reduced photoinitiator content. The photoinitiator systems were camphorquinone (CQ)/ethyl 4-(dimethylamino)benzoate (EDMAB) with or without [3-(3, 4-dimethyl-9-oxo-9H-thioxanthen-2-yloxy)-2-hydroxypropyl]trimethylammonium chloride (QTX). The polymerization kinetics was monitored using a Fourier transform infrared spectrophotometer with a time-resolved collection mode. The hydrophobic-rich phase exhibited a significantly higher polymerization rate compared with the hydrophilic-rich phase. Postpolymerization resulting in the secondary rate maxima was observed for the hydrophilic-rich mimic. The hydrophilic-rich mimics with standard photoinitiator concentration but varying cross-linker (BisGMA) content showed postpolymerization and a substantial degree of conversion. In contrast, the corresponding formulations with reduced photoinitiator concentrations exhibited lower polymerization and inhibition/delay of postpolymerization within 2 h. Under conditions relevant to the wet, oral environment, photoinitiator content plays an important role in the polymerization of the hydrophilic-rich phase mimic. Since the hydrophilic-rich phase is primarily water and monomethacrylate monomer (e.g., HEMA as determined previously), substantial polymerization is important to limit the potential toxic response from HEMA leaching into the surrounding tissues.
1）了解牙本质粘合剂中富含疏水相和亲水相的模型类似物的聚合方式是否相似；2）确定双甲基丙烯酸酯成分、双酚A甘油醚二甲基丙烯酸酯（BisGMA）或光引发剂浓度这一因素，对富含亲水相的模型类似物的聚合反应影响更大。目前的牙本质粘合剂对水分敏感，混合层中的纳米渗漏以及相分离成富含疏水相和亲水相的情况就证明了这一点。相分离导致富含亲水相内可交联的双甲基丙烯酸酯单体和疏水性光引发剂的可用性有限。通过向含有45 wt%甲基丙烯酸2-羟乙酯（HEMA）的HEMA/BisGMA纯树脂中添加最大重量百分比的氧化氘（D2O），制备了富含疏水相的单相溶液模型。以类似方式制备了富含亲水相的模型类似物，但使用的是含有95、99、99.5和100 wt% HEMA的HEMA/BisGMA纯树脂。富含亲水相的模型类似物制备时采用标准或降低的光引发剂含量。光引发体系为樟脑醌（CQ）/4-（二甲基氨基）苯甲酸乙酯（EDMAB），有或没有[3-（3,4-二甲基-9-氧代-9H-噻吨-2-基氧基）-2-羟丙基]三甲基氯化铵（QTX）。使用具有时间分辨采集模式的傅里叶变换红外光谱仪监测聚合动力学。与富含亲水相相比，富含疏水相的聚合速率明显更高。在富含亲水相的模型类似物中观察到了聚合后出现二次速率最大值的情况。具有标准光引发剂浓度但双交联剂（BisGMA）含量不同的富含亲水相的模型类似物显示出聚合后情况以及相当程度的转化率。相比之下，光引发剂浓度降低的相应配方在2小时内表现出较低的聚合反应以及聚合后反应的抑制/延迟。在与潮湿口腔环境相关的条件下，光引发剂含量在富含亲水相的模型类似物的聚合反应中起重要作用。由于富含亲水相主要是水和单甲基丙烯酸酯单体（例如，如先前确定的HEMA），充分的聚合反应对于限制HEMA渗入周围组织可能产生的毒性反应很重要。
