Abstract
It seems that conventional heat-curing resins for crown and bridge are not necessarily satisfactory in respect to their thermal and mechanical properties. In order to improve these properties, not a few attempts have already been made for many years. But the results are not so successful so far as polymethylmethacrylate is used as the initiating polymer powder for further polymerization with a suitable monomer liquid. In this study, therefore, other polymer powders than polymethylmethacrylate were used to improve the inferior properties of the conventional heat-curing resins. Eight polyfunctional methacrylates, namely, ethyleneglycol dimethacrylate (EDMA), diethyleneglycol dimethacrylate (Di-EDMA), triethyleneglycol dimethacrylate (Tri-EDMA), neopenthylglycol dimethacrylate (NPG), trimethylol propane trimethacrylate (TMPT), bisphenol-A dimethacrylate (BPDMA), 2, 2-bis (4-methacryloxyethoxyphenyl) propane (Bis-MEPP), and bisphenol-A diglycidylmethacrylate (Bis-GMA), were selected and polymerized by the powder-liquid method as in dental use. Then the physical and mechanical properties of the polymers obtained, such as polymerization shrinkage, knoop hardness, abrasion loss, coefficient of thermal expansion, and others were measured as well as their cytotoxicity to Hela cells. The properties of the eight experimental resins were compared with those of a commercial resin, SR-pyroplast. From the results, four polyfunctional methacrylates (EDMA, NPG, BPDMA, Bis-MEPP) were selected as hopeful out of eight ones. Then four kinds of polymer powder were prepared out of the selected four methacrylate monomers, respectively, and these were further polymerized with each one out of the selected four monomers or all the combinations of two-component copolymers of them. The kinds of resulting polymers numbered (_4II_4+4_4C_2=) 40. From these forty combinations the most superior ones were selected in view of the properties mentioned above. At the same time, the most preferable mol fraction (%) of components of the comonomer was also determined. As the conclusion, it was found that the copolymer which was prepared by polymerization of NPG (60mol%)-Bis-MEPP (40mol%) comonomer with Bis-MEPP polymer, possessed many excellent physical and mechanical properties, such as high resistance to water sorption, high values of Knoop hardness number and abrasion resistance. These were highest among those of the specimens prepared in this study and higher than those of a commercial 'hard type' resin, SR-pyroplast.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
