應用於牙科修復之可見光聚合新多官能基壓克力單體/二氧化矽混成材料

Abstract

本研究利用二異氰酸鹽(diisocyanate)和甲基丙烯酸-2-羥基乙酯(2-hydroxyethyl methacrylate, HEMA)以2:1當量比反應，形成前驅物，以前驅物中剩下一當量的氰酸酯基與環氧丙烯酸酯(epoxy acrylate, EA)側鏈上的氫氧基反應，形成新多官能基壓克力單體。所選用的二異氰酸鹽為2,4-二異氰酸甲苯(toluene 2,4-diisocyanate, TDI)，六亞甲基二異氰酸鹽(1,6-diisocyanatohexane, HDI)和二異氰酸異佛爾酮(isophorone diisocyanate, IPDI)。藉由調整三種EA側鏈上的氫氧基和二異氰酸鹽的氰酸酯基莫耳比例，可得三種不同官能度的新多官能基壓克力單體。此親核反應會使得新單體的分子量變大，且產生較強的分子間氫鍵，因此黏度會增加。利用三丙稀乙二醇雙丙稀酸酯(tripropylene glycol diacrylate, TPGDA)的不同添加量可調整樹脂基質(matrix)的黏度。此新多官能基壓克力單體照光聚合後可形成交聯網狀結構，因此其聚合收縮應變量(polymerization shrinkage)較小。 在無機填料部份，本研究利用溶膠-凝膠法能有效合成均一粒徑二氧化矽膠體，並藉由調整以下之參數可得不同之粒徑大小：(1)反應溫度、(2)氨水濃度、(3)水對四乙氧基矽烷(tetraethoxysilane, TEOS)的莫耳比例(R值)和(4)四乙氧基矽烷的濃度。本研究利用此方法所合成之均一粒徑二氧化矽膠體的平均粒徑介於0.082到 1.16微米(μm)。甲基丙烯酸酯基三甲氧基矽(3-(trimethoxy silyl) propyl methacrylate, MSMA)可成功地對二氧化矽膠體表面進行改質，使其表面帶有壓克力官能基，以增進有機和無機相介面的相容性。傅立葉轉換紅外線光譜儀(FT-IR)、掃描式電子顯微鏡(SEM)和動態雷射光散射粒徑儀(DLS)為此判斷的依據。 以新多官能基壓克力單體、TPGDA、DL-樟腦醌(DL-camphoroquinone, CQ)、三級胺化合物以及市售之燻矽(fumed silica)或改質之二氧化矽膠體組成一可操作之均勻糊狀物，經可見光(λ=400-520nm)照射30秒後，即得產物。測試由新多官能基壓克力單體組成的複合或混成材料之聚合收縮程度(polymerization shrinkage)、硬度(hardness)、膨潤比(swelling ratio)和丙酮溶解度(acetone solubility)，以bis-GMA(bisphenol A glycerolate dimethacrylate)為樹脂基質之材料為對照組，並與已上市產品做一比較，藉此評估新多官能基壓克力單體和改質之二氧化矽膠體應用於牙科填補材料之可行性。在本研究中，燻矽的最大添加量為50wt%，而改質之二氧化矽膠體可添加至70wt%，因此使得材料的硬度大幅提升。改質之二氧化矽膠體和新多官能基壓克力單體所組成的混成材料之最大硬度為61.1Hv，可達商品化產品標準(Estilite的硬度為53.6Hv)，其聚合收縮程度比以bis-GMA為樹脂基質的混成材料減少4倍，且小於已上市產品Estilite 10倍。因此，多官能基壓克力單體和改質之二氧化矽膠體有應用於牙科修復材料之潛力。

The novel multifunctional methacrylates were prepared by the reaction between the hydroxyl groups of the epoxy-acrylate resin (EA) and the isocyanate groups of the diisocyanate, such as toluene-2, 4-diisocyanate (TDI), 1,6-Diisocyanatohexane (HDI) or isophorone diisocyanate (IPDI) , which were pre-reacted with 2-hydroxyethyl- methacrylate (HEMA) with 2:1 equivalent ratio, and utilized as the dental monomers. By varying the molar ratios between the hydroxyl groups of EA and the isocyanate groups of diisocyanate, the methacrylaes with three types of different functionalities were obtained. As the reaction proceeded, the reaction underwent the nucleophilic addition and the stronger hydrogen bonding raised, resulted in the increase of molecular weights and viscosity. By adding the different amounts of tripropylene glycol diacrylate (TPGDA), the viscosity of the resin matrix could be reduced and adjusted. The mono-dispersed silica spheres were synthesized by the sol-gel process. By varying the reaction temperature, the concentration of ammonium hydroxide, the molar ratio of water to TEOS (R value), and the concentration of tetraethoxysilane (TEOS), the size of mono-dispersed silica spheres could be controlled. In this study, the size of silica spheres ranged from 0.082 to 1.16μm. The silica spheres were successfully modified by 3-(trimethoxy silyl) propyl methacrylate (MSMA), and the acrylate functional groups were chemically bonded to the surface of silica spheres, in order to enhance the compatibility of organic and inorganic interface. FT-IR, DLS and SEM were employed to characterize the modification of the silica spheres. The pastes were composed of the novel multifunctional methacrylate resin, TPGDA, DL-camphoroquinone (CQ), the compound of tertiary amine, and the modified silica spheres or fumed silica (digussa®202). After visible light curing (400-520nm) in 30sec, the hybrids or composites were formed. The shrinkage, hardness, swelling ratio and the acetone solubility of the hybrids or composites obtained from the multimethacrylate resins were analyzed. Those data obtained from the analysis of multimethacrylate-containing materials were compared with the control 2,2-bis[4-(2’-hydroxy-3’-methacryloyloxypropoxy)phenyl] propane (bis-GMA) based materials and the commercialized products in order to evaluate the application of the multimethacrylates as the dental resins and the modified mono-dispersed silica spheres as dental fillers. In this study, the maximum loading of fumed silica was 50wt%, but the modified mono-dispersed silica could reach 70wt%. Hence, the materials composed of modified mono-dispersed silica others than fumed silica could obtain the higher hardness. The maximum hardness of the hybrids composed of the modified mono-dispersed silica spheres and the multifunctional methacrylates was 61.1Hv which was higher than the Estilite (53.6Hv). And its shrinkage was much lower in comparison with the bis-GMA hybrids (lowered by about 4 times) and the commercialized products (lowered by about 10 times). Therefore, it is the potential dental restorative material.