Study On The Influence Of Nano-sifver Base Inorganic Antibacteiral Agents On Antimicrobial Activity And Prolonged Effect Of Room Curing Polymethyl Methacrylate Material

Polymethyl methacrylate material is widely used in clinical dentistry.The specificproperties of PMMA like porosity,irregularity and water absorption,as well as differentmethods of prosthodontics,which change the oral environment,promote deposition ofpathogenic bacteria on its surface,cause diseases like denture stomatitis,dental caries,gingivitis and periodontitis.To prevent the occurrence of these diseases,in recent years,scholars both at home and abroad try to develop new PMMA materials with antimicrobialproperties,and its long-standing exist in oral requires long-term inhibitory effect.Nano-silverbase inorganic antibacterial agents have excellent antibacterial properties,safety and thermalstability.It has become a research focus incorporating it into materials to develop newantibacterial compound materials,researchers have succeeded in adding it into heat curingPMMA,which yielded antimicrobial properties on several oral pathogenic bacteria.But untilnow there was few report on the influence of adding nano-silver base inorganic antibacterialagents into room curing PMMA material on its antimicrobial properties and long terminhibitory effect.This experiment aims at determination of in vitro antimicrobial activity andprolonged effect of room curing PMMA with one kind of nano-silver base antibacterialagents,providing theoretical basis for its long term clinical applications.In this experiment,nano-silver zirconium phosphate inorganic antimicrobial agent(RHA-1) was incorporated into room curing PMMA denture base resin power withball-grinding method,at concentration of1.0%,1.5%,2.0%,2.5%,3.0%.Candida albicans(C.albicans) and Streptococcus mutans (S.mutans) are the main pathogenic bacteria for denturestomatitis and dental caries separately. Therefore this experiment selected the two species forevaluation the antibacterial effect.Agar plate diffusion test was used for antibacterialqualitative detection,and the pellicle-sticking method was used for quantitative determinationof antimicrobial rate.The PMMA resin base samples with the antimicrobial agent RHA-1underwent accelerated aging process for evaluation of long term antibacterial activity.Onegroup was immersed in artificial saliva at57℃for14days,the other group was irradiated byultraviolet UVA-340for8hours.Then the antimicrobial rates of the two aging groups and newly made group against C.albicans and S.mutans were tested in vitro.The main experimental results are as follows:1. There were no inhibition zone around room curing PMMA specimens with differentconcentration of nano-silver antibacterial agent.This result consistent with the fact thatnano-silver zirconium phosphate antimicrobial agent belongs to non-releasing antimicrobialagents.It exhibit antibacterial effect only to those bacteria closely contacted with thematerial,thus the antimicrobial denture base may not affect the surrounding oral environmentand normal flora.2. Compared with the normal room curing PMMA, newly made nano-silver base roomcuring PMMA demonstrated significant antimicrobial effect against C.albicans andS.mutans.The antimicrobial rate was higher for C.albicans,this result consistent with themain aim of developing antimicrobial denture base resin—preventing the occurrence ofdenture stomatitis.3. Compared with newly made nano-silver base room curing PMMA,after UVA-340exposure for8hours,antimicrobial rate of high-concentration groups(above2.5%forC.albicans,above2.0%for S.mutans) remained unchanged,exhibited long term antimicrobialactivity,while antimicrobial rate of low-concentration groups decreased markedly.In practicaluse,in order to maintain its antibacterial activity,nano-silver base dentures should be kept indark place when not used.4. Compared with newly made nano-silver base room curing PMMA, after immersionin artificial saliva at57℃for14days,antimicrobial rate of all concentration groupsdecreased markedly, equivalent to the antibacterial properties decline after storing at roomtemperature for one year. In practical use,whether the antibacterial effect of nano-silver baseroom curing PMMA can meet clinical requirements for long-term antibacterial effect stillneed further experiments.