Preparation And Performance Evaluation Of Zn-N-TiO₂ Nanoparticles-containing Dental Adhesive

Objective:In recent years,composite resin has become the preferred material for tooth defect repair because of its excellent aesthetics and convenient operation.However,secondary caries at the dentin-resin bonding interface often lead to failure of composite resin repair.Therefore,the development of a new antibacterial dental adhesive to inhibit the growth of bacteria on the dentin-resin bonding interface is an effective method to prevent secondary caries.At present,nano-technology promotes the rapid development of nano-antibacterial materials.Nano-materials have a large specific surface area,which can significantly improve the chemical reactivity of the material surface,open up a new way of inhibiting bacteria.Metal and metal oxide nanoparticles as new effective antibacterial agents have been paid attention by researchers.Among them,titanium dioxide nanoparticles have good biosafety,low cost,abundant yield and superior chemical properties,especially good photocatalytic bactericidal activity.Ti O₂is a chemically stable material,which can play a sustainable antibacterial role under light and is widely used in disinfection,water cleaning,deodorization,pollution control and other aspects.However,due to the wide band gap,Ti O₂can only be excited by UV irradiation.In order to reduce the harm caused by ultraviolet light,many studies have successfully modified Ti O₂by doping technology,so that its absorption wavelength can be expanded to the range of visible light.In this study,zinc and nitrogen doped titanium dioxide nanoparticles were selected to prepare a new dental adhesive.The performance of3%Zn-3%N-Ti O₂NPs-containing dental adhesive was comprehensively evaluated by testing its antibacterial activity,cytotoxicity and observing the changes of microtensile strength,fracture mode,double bond conversion rate and water contact angle,so as to provide reference for the development of new antibacterial adhesives.Methods:1.Synthesis of Zn-N-TiO₂NPs with different doping ratios by sol-hydrothermal method;X-ray diffraction,Raman Spectra,scanning electron microscope,SEM and UV-vis were used to characterize it.2.Observe the inhibition effect of Zn-N-Ti O₂NPs combined with LED light of Streptococcus mutans（S.mutans）,screen out the best antibacterial doping ratio,and preliminarily discuss the antibacterial mechanism of Zn-N-Ti O₂NPs.3.Using the commercial dental adhesive Single Bond Universal as a control group.The silanized Zn-N-Ti O₂NPs were added into Single Bond Universal at the concentration of 1wt%,3wt%,5wt%and 7wt%separately and mixed evenly to prepare the experimental adhesives.The antibacterial activity of the experimental adhesives was observed.The number of S.mutans adhered to adhesive specimens in the experimental group was observed by plate colony counting method,the metabolic activity of S.mutans was analyzed by MTT method,and the state of S.mutans adhered to adhesive specimens in the experimental group was observed by live/dead bacterial staining experiment.4.CCK-8 method was used to determine the cytotoxicity of the adhesive in the experimental groups.5.The microtensile strength,fracture mode,double bond conversion rate and water contact angle of the adhesive in experimental groups were observed to judge the change of adhesive propertiesResults:1.Zn-N-Ti O₂NPs was successfully synthesized and the doping ratio with the best anti-S.mutans effect was selected,that is,Ti O₂NPs with3%Zn and 3%N had the best anti-S.mutans effect.2.New antibacterial adhesives containing different concentrations（1wt%,3wt%,5wt%,7wt%）of 3%Zn-3%N-Ti O₂NPs were synthesized and tested for antibacterial activity and cytotoxicity.The results showed that 5wt%and 7wt%groups had the best antibacterial activity.The cytotoxicity grade of 1wt%group,3wt%group and 5wt%group was 1,and the cytotoxicity grade of 7wt%group was 2.3.Select 1wt%group,3wt%group and 5wt%group to test the bonding performance.Compared with the 0wt%group,the microtensile strength and double bond conversion of the 1wt%,3wt%and 5wt%groups decreased gradually with the increase of 3%Zn-3%N-Ti O₂NPs concentration,but the differences were not statistically significant（P>0.05）.The water contact angle of the 1wt%group,3wt%group and 5wt%group increased gradually,and there was no significant difference between the 1wt%group and the 0wt%group（P>0.05）,while there was significant difference in the 3wt%group and 5wt%group compared with the 0wt%group（P<0.05）.Conclusion:1.Titanium dioxide nanoparticles with 3%zinc and 3%nitrogen doping concentration combined with LED light can effectively inhibit the growth of S.mutans.2.The new adhesive containing 3%Zn-3%N-Ti O₂NPs with the concentration of 5wt%has good antibacterial activity and biocompatibility,and its adhesion performance is not significantly affected.