Liang Xiaoxu, Liu Fang, He Jingwei
College of Materials Science and Engineering, South China University of Technology, Guangzhou 510641, China.
College of Materials Science and Engineering, South China University of Technology, Guangzhou 510641, China.
Dent Mater. 2014 Aug;30(8):917-25. doi: 10.1016/j.dental.2014.05.021. Epub 2014 Jun 18.
In this study, new dimethacrylate monomer SiMA without Bisphenol A (BPA) structure was synthesized and used as base resin of dental composite materials with the aim of reducing human exposure to BPA derivatives.
SiMA was synthesized through ring-opening addition reaction between 1,3-bis[2(3,4-epoxycyclohex-1-yl)ethyl]tetra-methyldisiloxane and methacrylic acid, and its structure was confirmed by FT-IR and (1)H NMR spectra. SiMA was mixed with TEGDMA (50/50, wt/wt) and photoinitiation system (0.7 wt% of CQ and 0.7 wt% of DMAEMA) to form resin system. Experimental composite EC was then prepared by SiMA based resin loading with BaAlSiO2 microfillers (72wt%). Double bond conversion (DC) was determined by FT-IR analysis. Volume shrinkage (VS) was measured through variation of density before and after irradiation. Water sorption (WS) and solubility (SL) were obtained until the mass variation of polymer in distilled water kept stable. Flexural strength (FS) and modulus (FM) of the polymer were measured using a three-point bending set up. Extract of composite was used to evaluate its cytotoxic effect on humane dental pulp cells, and relative growth rate (RGR) was obtained by CCK-8 assay. Bis-GMA/TEGDMA (50/50, wt/wt) resin system and universal dental restorative materials 3M ESPE Filtek™ Z250 were used as references for neat resin system and composite material, respectively.
FT-IR and (1)H NMR spectra showed that structure of SiMA was the same as designed. For the neat resin systems: DC of SiMA based resin was higher than that of Bis-GMA based resin (p<0.05); SiMA based resin had lower VS than Bis-GMA based resin; WS of SiMA based resin was lower than that of Bis-GMA based resin (p<0.05), while SL of SiMA based resin was nearly the same as that of Bis-GMA based resin (p>0.05); FS and FM of SiMA based resin were lower than those of Bis-GMA based resin (p<0.05). For the composite materials: DC of EC was higher than that of Z250 (p<0.05); EC and Z250 had same VS; WS of EC was lower than that of Z250 (p<0.05), and SL of EC was higher than that of Z250 (p<0.05); FS and FM of EC were lower than those of Z250 (p<0.05); RGRs of EC were lower than those of Z250 after the cells were incubated with relative extract for 24h and 48h (p<0.05), while after being incubated for 72 h, RGR of EC and Z250 had no obvious difference (p>0.05).
SiMA had potential to replace Bis-GMA as base resin of dental composite materials. However, formulation of SiMA based resin and composite should be optimized in terms of mechanical strength to satisfy the requirements of resin based dental materials for clinical application.
本研究合成了一种不含双酚A（BPA）结构的新型二甲基丙烯酸酯单体SiMA，并将其用作牙科复合材料的基础树脂，以减少人体对BPA衍生物的接触。
通过1,3-双[2-(3,4-环氧环己基-1-基)乙基]四甲基二硅氧烷与甲基丙烯酸之间的开环加成反应合成SiMA，并通过傅里叶变换红外光谱（FT-IR）和核磁共振氢谱（¹H NMR）对其结构进行确证。将SiMA与三乙二醇二甲基丙烯酸酯（TEGDMA，质量比50/50）和光引发体系（质量分数0.7%的樟脑醌（CQ）和0.7%的甲基丙烯酸二甲氨基乙酯（DMAEMA））混合形成树脂体系。然后通过用BaAlSiO₂微填料（质量分数72%）填充基于SiMA的树脂制备实验性复合材料EC。通过FT-IR分析测定双键转化率（DC）。通过测量辐照前后密度的变化来测定体积收缩率（VS）。直至聚合物在蒸馏水中的质量变化保持稳定，从而获得吸水率（WS）和溶解度（SL）。使用三点弯曲装置测量聚合物的弯曲强度（FS）和模量（FM）。用复合材料的提取物评估其对人牙髓细胞的细胞毒性作用，并通过CCK-8法获得相对生长率（RGR）。双酚A双甲基丙烯酸缩水甘油酯/TEGDMA（质量比50/50）树脂体系和通用牙科修复材料3M ESPE Filtek™ Z250分别用作纯树脂体系和复合材料的对照。
FT-IR和¹H NMR光谱表明SiMA的结构与设计的相同。对于纯树脂体系：基于SiMA的树脂的DC高于基于双酚A双甲基丙烯酸缩水甘油酯的树脂（p<0.05）；基于SiMA的树脂的VS低于基于双酚A双甲基丙烯酸缩水甘油酯的树脂；基于SiMA的树脂的WS低于基于双酚A双甲基丙烯酸缩水甘油酯的树脂（p<0.05），而基于SiMA的树脂的SL与基于双酚A双甲基丙烯酸缩水甘油酯的树脂几乎相同（p>0.05）；基于SiMA的树脂的FS和FM低于基于双酚A双甲基丙烯酸缩水甘油酯的树脂（p<0.05）。对于复合材料：EC的DC高于Z250（p<0.05）；EC和Z250的VS相同；EC的WS低于Z250（p<0.05），且EC的SL高于Z250（p<0.05）；EC的FS和FM低于Z250（p<0.05）；在用相对提取物孵育细胞24小时和48小时后，EC的RGR低于Z250（p<0.05），而在孵育72小时后，EC和Z250的RGR没有明显差异（p>0.05）。
SiMA有潜力替代双酚A双甲基丙烯酸缩水甘油酯作为牙科复合材料的基础树脂。然而，基于SiMA的树脂和复合材料的配方应在机械强度方面进行优化，以满足树脂基牙科材料的临床应用要求。
