Adding Nanometer Ag - Tio < Sub > 2 < / Sub > Antibacterial Agent Of Resin Base Supporting Research On The Effects Of Antimicrobial Properties And Mechanical Properties

BackgroundWith the gradually coming of aging society, more and more people wear the removablepartial dentures（RPD） or complete dentures. The original oral microbial flora has beendestroyed after wearing dentures, especially the number of oral conditional pathogenicbacterium increased obviously. The special physical and chemical properties of artifical teethand denture resin base materials are likely to adhere bacteria and fungi. Furthemore, it isdifficult to remove the bacterial plaque adhered on the surface of dentures, which results in aseries of oral diseases, for instance, secondary dental caries, gingivitis, paradentosis and denturestomatitis. Therefore, it is a central point how to improve the antibacterial property of denturesand reduce dental incidence after wearing dentures at home and abroad.There are many ways in improving antibacterial effect of dentures, such as mechanicalcleaning, chemical soaking, surface modifying and organic antibacterial agent adding. However,the treatments mentioned above have the disadvantages including destroying the surfacemorphology of plate, shorter antibiosis time, inferior heat resistance, so they are far from theclinical demands.Recently, inorganic antibacterial agent has generally been the hot point in the field ofantibiosis materials by right of wider antibacterial spectrum, longer antibiosis efficacy, betterthermal stability and good biocompatibility. There are tow kinds of inorganic antibacterial agent.One of them are antibacterial metal ions, such as Ag+, Cu+, Zn+, which are loaded on zeolites orsilica gels by means of physical adsorption or ion exchange. Ag is the best one. Other one is thephotocatalytic material, which generates reactive oxygen species（ROS） by photocatalysis thatshows antibacterial effect, such as titanium dioxide（TiO₂）. There have been considerable studiesin researching the effects of inorganic antibacterial agent on antibiosis improvement of resinsplicing agent, soft lining materials and denture resin base. Nevertheless, applications ofNano.Ag-TiO₂antibacterial agent adding in denture base resin have few been reported so far.Objective The objective of this study is to explore the feasibility of Nano.Ag-TiO₂antibacterial agent as oral rehabilitation materials, in order to improve the self-antibiosisproperty of denture resin base. Firstly, study antibacterial activity of the Nano.Ag-TiO₂ antibacterial agent on two kinds of oral common pathogens in vitro. Then, the denture resin baseadding Nano.Ag-TiO₂antibacterial agent with self-antibiosis properties and mechanicalproperties are testified with following experiments, antibiosis efficacy evaluation; durability ofantibacterial effect evaluation and mechanics experiments, in order to offer the theoretical andexperimental foundations for clinical application in future.Methods1. Test the antibacterial activity of Nano.Ag-TiO₂antibacterial agent on Streptococcusmutans and Candida albicans in vitro. Minimum inhibitory concentration（MIC） and Minimalbactericidal concentration（MBC） were determined by Liquid dilution method.2. Different qualities of Nano.Ag-TiO₂antibacterial agent were added into resin base inorder to prepare antibacterial resin base. In vitro analysis of antibacterial effect of the baseagainst Streptococcus mutans, Staphylococcus aureus, Candida albicans was assayed with thepellicle-sticking method. Furthermore, the growth of Streptococcus mutans and Candidaalbicans bacterial plaque on the antibacterial resin base were examined by SEM.3.2.5%（w/w%） qualities of Nano.Ag-TiO₂antibacterial agent were added into resin base.Then, they were dealt by natural olding processa, ccelerated olding process respectively. In vitroanalysis of the antibacterial prolonged effect of the resin base against Streptococcus mutans,Candida albicans was assayed with the pellicle-sticking method.4. Test the mechanical properties of denture resin base with different qualities of Nano. Ag-TiO₂antibacterial agent by following experiments: impact strength experiment, bendingstrength experiment and elastic modulus test.Results1. Compared with the control group, the MIC, MBC of Nano.Ag-TiO₂antibacterial agentagainst Streptococcus mutans were0.625mg/ml,1.25mg/ml; Candida albicans were1.25mg/ml,5.0mg/ml.2. Compared with the control group, the antibacterial ratio （R%） for Staphylococcus aureuswas93%by antibacterial resin base with0.7%Nano.Ag-TiO₂antibacterial agent; forStreptococcus mutans90%with1.5%; for Candida albicans91%with2.5%. Furthemore, theirbacterial plaque were also inhibited effectively within a period of48h. 3. Compared with the control group, the antibacterial ratio （R%） for Staphylococcusmutans was98.1%,97.1%,96.3%; for Candida albicans90.3%,89.4%,88.7%by the newprepared group, the natural olding process group and the accelerated olding process group.There are no differences in antibacterial ratio（R%） of the three groups.4. Compared with the control group, the impact strength, bending strength and elasticmodulus of the antibacterial denture base rise following the number of Nano.Ag-TiO₂increaseat first. However, more Nano.Ag-TiO₂lower mechanical properties. Therefore,theincorporation ratio of Nano.Ag-TiO₂should be controlled in range of2%-3%in this study.Conclusion According to the above results of this study, it can be concluded thatNano.Ag-TiO₂antibacterial agent can inhibit oral pathogenic bacterium effectively; theantibacterial denture base adding Nano.Ag-TiO₂show better and permanent antibacterialproperties; the right incorporation ratio of Nano.Ag-TiO₂adding into denture resin base is2%-3%.