The Effect Of Room Curing Polymethyl Methacrylate With Nano-silver Base Inorganic Antibacterial Agent On Tissue And DNA Damage Of Liver In Mice

Polymethyl methacrylate is the common material in stomatology,and the room curing polymethyl methacrylate has the advantages of ease of fabrication and adjustment,low cost and time saving.However,oral pathogenic bacteria are prone to adhere and aggregate owing to the porous surface structure of it,leading to occurrence of oral infectious diseases.Therefore,it has been paid attention to develop a room-temperature curing type PMMA with antibacterial properties.Nano-inorganic antibacterial materials have a broad antimicrobial spectrum and can inhibit the growth of germ and fungus.Additionally,it also has the advantages of resisting high temperature and inhibiting microorganism for the long term.As a new type of antibacterial agent,it has been widely used in medical products such as toothpaste,medical implants and wound dressings,etc.In the field of stomatology,to prevent or treat oral infections such as denture stomatitis and peri-implantitis,different types of nano-silver base inorganic antibacterial agent have also been applied in dental materials.The primary constituent of nano-silver base inorganic anti-microbial agent used in this experiment is silver-zirconium phosphate,where the silver ion is combined steadily and it has the extensive antibacterial spectrum.The studies have shown that it can effectively kill common pathogenic bacteria in the mouth such as Streptococcus mutans,Lactobacillus,Staphylococcus aureus and the main pathogen of denture stomatitis,Candida albicans.Previous experimental studies of our research group have demonstrated that adding this kind of nano-inorganic antibacterial agent to room curing PMMA can significantly enhance the antimicrobial activity against Streptococcus mutans and Candida albicans.The room curing polymethyl methacrylate,which was under the immersion of saliva,acts in the complicated oral environment,and released silver ion can enter the body through the digestive tract after that be transported to other tissues or organs through the blood circulation.,causing health damage by excess silver ions.Being a new type of nanometer antibacterial agent,the potential hazard of nano-silver base inorganic antibacterial agent is not well understood and the potential toxicity and mechanism should be concentrated on.The liver is a chemical plant for metabolism of human body and it is also one of the target organs that toxic substances attack and aggregate.Nanoparticles can penetrate the cell membrane and enter the cells,causing liver damage through lipid peroxidation or reactive oxygen species and impact the normal physiological function of the liver.The previous research has made a preliminary assessment of the biocompatibility of the material through some tests,such as cytotoxicity test and hemolytic test and so on,however toxicity of this novel material to the liver has not been involved.In this study,further evaluation of the biocompatibility of the material were conducted by studying damage to tissue and detecting genotoxicity of liver.Comet assay is a common method to detect the genotoxicity of silver nanoparticle,being fast,cost-effective and sensitive,which can detect DNA single-strand breaks,DNA double-strand breaks,alkali-labile sites and other types of DNA damages at the single cell level.In this experiment,the male mice were administered orally with extract liquid of room temperature-curing PMMA and room curing PMMA with nano-silver base inorganic antibacterial agent for 3 days,calculating the organ coefficient of liver,measuring blood bio-chemical index and conducting in vivo comet assay to evaluate the damage of liver tissue and DNA.The experimental results showed that the liver organ coefficient was within the normal range,and there was no increase in the levels of alanine aminotransferase and aspartate aminotransferase,indicating that the material did not cause damage to the liver tissue of mice.The results of comet assay showed that % tail DNA,tail length,and Olive tail moment did not increase and there was no significant difference from the negative control group,indicating that the material did not cause DNA damage of liver.In summary,room curing PMMA with nano-silver base inorganic antibacterial agent has good biocompatibility to liver of mice and it is promising for clinical application in the future.