Research On Preparation Of The Antimicrobial PMMA Restorative Material And Its Related Properties

With the aging of the population,more and more patients have suffered dental problems such as tooth loss.Removable denture has been widely used in clinical practice by virtue of its low cost,good repair effect and high acceptability.Polymethyl methacrylate(PMMA)has become one of the most commonly used materials for this type of restoration due to its good biocompatibility and mechanical properties.However,the long-term use of removable denture will increase the attachment of plaque on the surface of the prosthesis because of the complex oral environment and the rough surface of removable denture,which will give rise to a series of dental problem among which the incidence of denture stomatitis accounts for70% Therefore,the critical factor to improve the quality of medical treatment for these patients is to increase the antibacterial ability of the prosthesis and reduce plaque attachment.For the purpose of reducing the occurrence of oral complications,our research group developed the nano-Cu-ZnO antibacterial agent(Cu-ZnO)and innovatively added nano-Cu-ZnO composite material which was independently developed by our group to PMMA bases,in order to reduce bacterial adhesion.Objective: In order to investigate the feasibility of inorganic nano-Cu-ZnO antibacterial materials used in oral prosthesis materials.Objective to determine the effects of adding different doses of nano-Cu-ZnO antibacterial agents on the antibacterial,biocompatibility and mechanical properties of PMMA base,so as to provide experimental reference for the clinical feasibility of the new antimicrobial PMMA base.Methods:1.The antibacterial effect of Cu-ZnO antibacterial agents with different concentrations on Staphylococcus aureus(S.aureus)and Candida albicans(C.albicans)was evaluated by the method of oscillating contact culture.2.Nano-Cu-ZnO antibacterial agent was added into the PMMA base powder by ball milling method to prepare the antibacterial resin base powder which was observed by scanning electron microscope(SEM)to figure out its the internal structure.The film adhesion method was utilized to detect the resin base with different concentrations of antibacterial agent in vitro antibacterial effect on C.albicans.3.The antimicrobial PMMA bases with different concentrations were co-cultured with mouse fibroblasts(L929)for 1 day,3 days and 7 days,respectively.The cytotoxicity of the corresponding extracts to L929 was determined by cytometry(Cell Counting Kit-8,CCK8)method,and the biological safety of the extracts was preliminarily confirmed.4.The universal mechanical material testing machine was used to evaluate the bending strength and elastic modulus of the antimicrobial PMMA base,and to explore whether the addition of inorganic antimicrobial materials had influence on its mechanical properties.Results:1.The higher the concentration of nano-Cu-ZnO antibacterial agent was,the better the antibacterial effect against S.aureus and C.albicans became.When the concentration of nano-Cu-ZnO antibacterial agent reached 10.0 mg/ml,the antibacterial rate against C.albicans reached 97.99%,showing a strong antibacterial effect.When the concentration of nano-Cu-ZnO antibacterial agent reached 20.0 mg /ml,its antibacterial rate against S.aureus reached 98.58%,which had strong antibacterial effect.2.SEM results showed that the nano-Cu-ZnO particles were uniformly dispersed in the antibacterial PMMA base,and the microscopic morphology was consistent with that of the nano-Cu-ZnO antibacterial agent,which means nano-Cu-ZnO particles in the antibacterial PMMA substrate has good stability.When the concentration of nano-Cu-ZnO antibacterial agent reached 0.50%(wt%),the antibacterial rate against C.albicans reached 91.98%,showing a good antibacterial effect;when its concentration reached 5.00%(wt%),the antibacterial rate against C.albicans can reach 99.9%.3.By calculating the relative growth rate(RGR)of L929 cells,it was found that when the concentration of the added antibacterial agent was ≤2%(wt%),the RGR value was ≤80%,and the grade of cytotoxicity was ≤1,which had good biological safety.4.With the increase of nano-Cu-ZnO antibacterial agent concentration,the flexural strength and elastic modulus of the antibacterial resin base increased firstly and then decreased.When the nano-Cu-ZnO antibacterial agent concentration reached1.00%(wt%),the flexural strength reached the maximum which was(123.58 ± 9.79)MPa.When the concentration of the antimicrobial agent reached 0.50%(wt%),the elastic modulus reached the maximum value which was(3.79 ± 0.37)GPa.Then,the two mechanical properties gradually decreased.Conclusion: The structure of nano-Cu-ZnO antibacterial agent has good stability and good antibacterial effect on S.aureus and C.albicans.When the concentration of antibacterial agent was 0.50% ～1.00%(wt%),the antimicrobial PMMA base modified by nano-Cu-ZnO has excellent antibacterial ability and good biological safety and mechanical properties.The new PMMA base can provide a new idea for reducing the occurrence of denture stomatitis.