Study On The Properties Of Dental Restorative Resin Incorporated With Polymerizable Gemini Quaternary Ammonium Salts

Since the concept "polymeric antimicrobial agent" was introduced to the field of dental materials, the antimicrobial agent and antimicrobial modified materials have been studied by many chemists worldwide. In this article, based on the contact antibacterial mechanism of antibacterial modification of polymer materials and the general single-chain quaternary ammonium are not sensitive to Gram-negative bacteria, six kind of polymerizable Gemini quaternary ammonium salts (QAS) MEBU-TMEDA-MEBU、MEBU-TMHDA-MEBU、 MEBU-TMEDA-C12、 MEBU-TMEDA-C14、MEBU-TMHDA-C12、MEBU-TMHDA-C14were designed and synthesized. All the QAS monomers were characterized by’H-NMR and IR spectra to determine the structure and purity.To investigate the added of antimicrobial monomer’s influence on dental composite resin system, the six kinds of QAS monomers were bonded to the resin system by light curing method which is a common method of clinical dental restoration. The degree of polymerization, hardness and rate of up and down surface hardness of the resin system incorporated with monomer MEBU-TMEDA-C12were74.18%,32.8MPa and12.3%, the result showed that quaternary ammonium salts promotes the polymerization and mechanical properties. The surface contact angle decreased when the composite resin incorporated with QAS monomers, the results showed that hydrophilic of composites incorporated with quaternary ammonium salt became better and can prevent bacterial adhesion onto the surface. The TG results showed that the adding of QAS monomer did not have an effect on the thermal stability of the resin system.To evaluate the bactericidal activity of these QAS compounds against E. coli, S. aureus and S. mutans, the minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) were tested by using broth dilution test, The monomer MEBU-TMEDA-C12showed strong antibacterial activity, the MIC values against these bacteria were1.48×10-5,0.809×10-5,0.402×10-5mol/L. The inhibitory effect of composite resin incorporated with quaternary ammonium salts against the growth of S. aureus on its surface was determined by counting the number of viable cells, the result showed that the antibacterial activities of cured experimental composite resins were increased with the concentration of QAS monomers increased, and the structure of the carbon chain length and positive charge density of compounds affect antimicrobial activity. Bacterial adhesion of the antimicrobial modified composite resin incorporated with monomer MEBU-TMEDA-C12 were observed by scanning electron microscope (SEM), It can be seen that the number of bacteria generated on the surface of antimicrobial modified composite resins were fewer than that of blank group, it showed that the added of monomer inhibited the reproduction and growth of bacteria. When the amount of monomer was5%, some bacteria were found deformation and fracture.