Synthesis Of New Methacrylate Monomers And Their Applications In Root Canal Sealer

The methacrylate resin-based root canal sealers have attracted wide attention with superior aesthetic qualities, good mechanical properties, excellent adhesion ability with dentin, and good biocompatibility. However, their main drawback is large volumetric shrinkage during their polymerization, which can forms marginal gaps between dentin and sealer to lead microleakage and clinical failure. Therefore, at the base of endowing methacrylate monomer with excellent adhesion property and biocompatibility, it has significant academic value for the studies of synthesis of original methacrylate monomers with low polymerization shrinkage and the relationship between structure of monomer and properties of its polymer. Once the original methacrylate monomers were applied in the field of dental materials, both people's health level and life quality will be greatly improvement which causes a huge social and economic benefits. Moreover, it also has great practical significance in developing the application of methacryalte monomers in the fields of biomaterials, coating, adhesives, ink, special films, and holographic technology.In the dissertation, the intermediate products with epoxy groups, 9,9'-bis(4-oxiranyl- methoxyphenyl)fluorine (2a), 4,4'-(?-Methylbenzylidene)bis(oxiranylmethoxy)benzene (2b), 4,4'-(1,4-phenylenediisopropylidene)bis(oxiranylmethoxy)benzene (2c), 4,4'-(1,3-phenylene- diisopropylidene)bis(oxiranylmethoxy)benzene (2d),?,?,?'-tri[4-(oxiranylmethoxy) phenyl]- 1-ethyl-4-isopropyl-benzene (?,?,?'-TOPEIB) and 5,5'-bis[4-(oxiranymethoxy)-phenyl]-hexa- hydro-4,7-methanoindan (5,5'-BOMPHM) were synthesized by the reaction of 9,9'-di(4- hydroxyphenyl)flourene, 4,4'-(?-methylbenzylidene)bisphenol, 4,4'-(1,4-phenylene-diiso- propylidene)-bisphenol, 4,4'-(1,4-phenylenediisopropylidene)bisphenol,?,?,?'-tri(4-hydroxyl phenyl)-1-ethyl-4-isopropylbenzene and 5,5'-bis(4-hydroxylphenyl)-hexahydro-4,7-methan- oindan with epichlorohydrin, respectively. Then the six original methacrylate monomers with high molecular weight and big molecular volume, 9,9'-bis[4-(2'-hydroxy-3'-methacryl- oyloxy-propoxy)phenyl]fluorine (3a), 4,4'-(?-Methyl-benzylidene)-bis(2'-hydroxy-3'-meth- acryloyl-oxypropoxy)benzene (3b), 4,4'- (1,4-phenylene-diisopropylidene)-bis(2'-hydroxy-3'- methacryloyl-oxypropoxy)benzene (3c), 4,4'-(1,3-phenylene-diisopropylidene)-bis(2'-hydroxy -3'-methacryloyl-oxypropoxy)benzene (3d),?,?,?'-tri[4-(2'-hydroxy-3'-methacryloyloxy- propoxy)phenyl]-1-ethyl-4-isopropyl-benzene (?,?,?'-THMPEIB) and 5,5'-bis[4-(2'-hydroxy- 3'-methacryloyloxy-propoxy)-phenyl]-hexahydro-4,7-methanoindan (5,5'-BHMPHM) were synthesized by the ring-opening additional reaction of 2a~2d,?,?,?'-TOPEIB and 5,5'-BOMPHM with methacrylic acid (MA), respectively. The final yields for two steps were 51.5% for 3a, 47.0% for 3b, 57.2% for 3c, 57.9% for 3d, 58.2% for?,?,?'-THMPEIB, 46.2% for 5,5'-BHMPHM, respectively. Structures of the intermediate products with epoxy groups (2a~2d,?,?,?'-TOPEIB and 5,5'-BOMPHM) and the original methacrylate monomers (3a~3d,?,?,?'-THMPEIB and 5,5'-BHMPHM) were characterized and confirmed by FTIR, 1HNMR, elemental analysis, and mass spectrometry.The influences of reaction temperature, molar ratio of reactant, content of catalyst and kinds of catalyst on the reaction of the intermediate products with epoxy groups (2a~2d) and methacrylic acid (MA) were investigated by FTIR. The results showed that the conversion rate of epoxy groups increased with increasing reaction temperature. Their reactivity order was 2b > 2c?2d >2a. The optimal molar ratio of (2a~2d)/MA is 1:4. The optimal molar ratio of (2a~2d)/catalyst is 1:0.0255. The catalytic efficiency order of three catalysts used is DMAP> DMBA>TEA.2,2-bis[4-(2-hydroxy-3-methacryloyloxypropoxy)phenyl]propane (Bis-GMA), 3a, 3b, 3c, and 3d were copolymerized with tri(ethyleneglycol) dimethacrylate (TEGDMA), respectively. Their polymerization behaviors and properties of these copolymers were studied. The results showed that their polymerization behaviors were the same, but the double bond conversion of each system was different because of the difference between their structures. The final double bond conversion order is Bis-GMA/TEGDMA system>3b/TEGDMA system>3c/TEGDMA system?3d/TEGDMA system >3a/TEGDMA system. The polymerization shrinkage of four original methacrylate monomers (3a~3d) is lower than that of Bis-GMA obviously. The properties of these copolymers, such as medium resistance, mechanical properties, thermal stability, and toxicity to periodontal cell, are meet the requirement of dental materials. The 3b/TEGDMA copolymer has the best overall properties.New resin-based root canal sealer (NRS) was prepared using 3b as base resin. The mass ratio of organic resins in NRS is 3b/TEGDMA/CQ/DMAEMA=50/50/2/4. The optimal mass ratio of inorganic fillers in NRS is BaSO4/ZnO/HA=9/3/2. The optimal mass ratio of inorganic fillers to organic resins in NRS was 50:50. Properties of NRS prepared by the optimal formula , such as polymerization shrinkage (1.83%), water sorption ( (3.57±0.05)% ), solubility ( (0.68±0.07)% ), shear bond strength between NRS and root canal wall ( (15.68±2.29)MPa ), push out strength between NRS and root canal wall ( (1.94±0.82) MPa ), and microleakage in root tip ( (4.46±1.99)mm ), were all better than that of clinical root canal sealer Epiphany. Especially, flowability ((23.7±0.3)mm) and solubility ((0.68±0.07)%) of NRS are meet the ISO 6876 standard (?20mm,?3%).Cytotoxicity test, acute systemic toxicity test, dermal sensitization test, and hemolytic test were used to evaluate the biocompatibility of NRS. The results showed that NRS has low cytotoxicity to periodontal cell, no acute systemic toxicity, no sensitization and no hemolytic activity. It implied that NRS had excellent biocompatibility.