The Initial Research On The Antimicrobial Activitives Of Polymethylmethacrylate Denture Base With Ag-embedded Nano-TiO₂ In Vitro

Polymethyl methacrylate(PMMA)is the most useful material to manufacture the removable denture currently,which has been applied extensively to mouth rehabilitation in clinical dentistry for many years because of its good physical,chemical and biological character.It also exists the shortages such as dental caries and denture stomatitides usually at the abutment tooth which are induced by wearing the artificial removable denture made of PMMA.In order to solve the medical puzzle of reducing the opportunity of complications including caries with abutment tooth of removable denture and denture stomatitis,we attempt to do the preliminary test in which we put Ag-embedded nano-TiO₂ into the artificial removable denture made of PMMA,and observe the antimicrobial activity in vitro then to provide the scientific evidence for its wide-spread applicationThe materials of Ag-embedded nano-TiO₂ were invented by School of Metallurgical Science and Engineering of Central South University.The preparation of the complex Ag-embedded nano-TiO₂ is follow:precursor of nano-TiO₂ was prepared from industrial H₂TiO₃ and 98%sulfuric acid in continuous acid dissolution and pyro-hydrolysis.The precursor was embedded with silver in the form of Ag₃PO₄.The optimum parameters for the preparation was the ratio of H₂TiO₃ to H₂SO₄ in dissolving process 3,time about 150～180 min and hydrolysis time about 100～120 min.After dried with a sprayer and thermal treated at 450℃,500℃and 550℃, the TiO₂ present in the product was in anatase phase and without simple silver saline phase based on the analyses of X-ray diffraction(XRD).The particle size of product Ag-embedded nano-TiO₂ was in the range of 20～80 nm.The minimum inhibitor concentration(MIC)of the product was 100 ppm and the efficiency of sterilization was 99.99%to bacterium coli.The Ag-embedded nano-TiO₂ posses the characteristic such as stronger antimicrobial activity,broadly antibacterial spectrum,longer duration,more safety and lowerprice etc.But there is no report of the Ag-embedded nano-TiO₂ applied in the PMMA in the literature report retrieved by Academy of Medical Sciences of Zhejiang province.This study is to observe the antimicrobial activity of denture resins substrates with the Ag-embedded nano-TiO₂ and find out whether the Ag-embedded nano-TiO₂ can help demolishing the formation of dental plaque.It can provide more experiment data for the further application of the Ag-embedded nano-TiO₂ in the prosthodontics field.The main results of the study are as followly:At first,The minimal inhibitory concentration(MIC)and minimal bactericidal concentration(MBC)of the Ag-embedded nano-TiO₂ against Streptococcus mutans(S.mutans)was 0.5mg/ml and 2.5mg/ml respectively in vitro.The denture base with Ag-embedded nano-TiO₂ has good antimicrobial activities against S.mutans,which can be used in the denture base for antimicrobial activities.Secondly,When put the Ag-embedded nano-TiO₂ at 2.5mg/ml into PMMA,the inhibition ratios of the base against to S.mutans was 89.9%,against to Actinomycetes viscosus was 94.2%and against to Candida albicans was 31.5% respectively. The artificial Ag-embedded nano-TiO₂ into removable denture made of PMMA can be able to satisfy the fundamental antimicrobial request in the normal oral environment.Thirdly,Under the same culturing environment,The bacterial adherence growth of streptococcus mutans and actinomycetes viscosus on the surface of the samples of denture resins substrates with Ag-embedded nano-TiO₂ are obviously less than that of the control(P＜0.05)by scanning electron microscope(SEM).The adherence growth of candida albicans on the surface of the samples of denture resins substrates with Ag-embedded nano-TiO2 is also less than that of the controlbut the difference is not significant(P＞0.05)by SEM.This preliminary test shows that the artificial Ag-embedded nano-TiO₂ into removable denture made of PMMA can be able to satisfy the fundamental antimicrobial request in the normal oral environment by reducing the opportunity of complications including caries with abutment tooth of removable denture and denture stomatitis,and can help demolishing the formation of dental plaque.and can provide the scientific evidence which is valuable of further application of the Ag-embedded nano-TiO₂ in the prosthodontics field.