Experimental Study Of Dental Resins Modified With Boron Nitride-based Nanocomposite Systems

Composite resins are increasingly used in modern dentistry due to their high similarity to the appearance of teeth and their good physical and mechanical properties.They have developed rapidly,but problems such as failure due to insufficient strength and secondary caries induced by insufficient antimicrobial properties exist.This experiment was guided by molecular dynamics（MD）calculations to achieve the effective construction of a new boron nitride-based nanocomposite system,which was used to modify dental flow resins to enhance the mechanical and antimicrobial properties of the resins,and the mechanical and antimicrobial enhancement mechanisms were further discussed.Details of the work are as follows.1.Preparation and characterization of BNNs/Ti O₂ nanocomposite systems for modified flow resinObjective:This study was guided by MD calculations for the proposed effective construction of two-dimensional boron nitride nanosheets（BNNs）/zero-dimensional titanium dioxide nanoparticles（Ti O₂）nanocomposite system.The nanocomposite system was used to modify flow resins to enhance their mechanical and antimicrobial properties.The mechanism of mechanical and antimicrobial property enhancement was discussed at the microscopic level.Methods:MD modelling analysis was performed using Materials Studio software for BNNs,Ti O₂,and BNN/Ti O₂ nanocomposite systems,respectively,so as to obtain the composite theoretical mechanism of BNNs/Ti O₂ nanocomposite systems.The composite of BNNs and Ti O₂ was realized under the guidance of theoretical calculations.BNNs were prepared by mechanical exfoliation of boron nitride（BN）,and Ti O₂ was grown in situ on BNNs using the hydrothermal method to construct the zero-dimensional-two-dimensional nanocomposite system.The nanocomposite systems were investigated using various analytical tools such as transmission electron microscopy（TEM）,X-ray diffractometer（XRD）,Raman spectra,Fourier infrared spectroscopy（FT-IR）,and ultraviolet-visible spectroscopy（UV）.To obtain different experimental groups,the synthesized nanocomposite systems were added to dental flow resins at 0.4 wt.%,0.8 wt.%,1.2 wt.%,and 1.6 wt.%.The physical properties of the modified flow resins were evaluated,including mechanical properties,depth of cure,double bond conversion rate,water absorption rate,and dissolution rate.The cross-sections were observed by scanning electron microscopy（SEM）and the mechanisms of mechanical property changes were analyzed.The antimicrobial properties of the modified flow resins were evaluated based on the plate counting method in simulated different environments.The biocompatibility of the modified flow resins was evaluated by cytotoxicity experiments.Results:The theoretical calculations showed that the BNNs/Ti O₂ nanocomposite system could be effectively constructed under certain conditions.The microscopic morphology of the synthesized nanocomposite system was that of thin,lamellar BNNs with Ti O₂ nanospheres tightly attached.AFM verified this hypothesis.XRD and Raman also demonstrated the successful compounding of the nanocomposite system.The compressive strength,microhardness,flexural strength,and elastic modulus of the modified flow resin containing 0.8 wt.%of BNNs/Ti O₂ nanocomposite system were improved by 88.23%,58.47%,82.01%,and 55.06%,respectively（P<0.05）.Moreover,the modified flow resin containing 0.8 wt.%of BNNs/Ti O₂ nanoparticles could effectively inhibit the growt.h of Streptococcus mutants（S.mutants）with immediate and aging inhibition rates above 90%,regardless of aging in water（P<0.05）.In addition,the results of scanning electron microscopy tests provided strong evidence for discussing the antibacterial mechanism of the modified flow resins.Significance:In this study,BNNs/Ti O₂ nanocomposite system was successfully synthesized under the guidance of MD theory,and the addition of the composite system significantly enhanced the mechanical properties and antibacterial properties of the flow resin,and the modified resin is expected to be an ideal restorative material for clinical applications.2.Preparation and characterization of BNNTs/n-Zn O nanocomposite systems for modified flow resinObjective:This study was conducted to synthesise and characterise one-dimensional Boron Nitride Nanotubes（BNNTs）/zero-dimensional Nano Zinc oxide（n-Zn O）composite systems under the guidance of MD calculations.The nanocomposite systems were used as nanofillers to modify dental flow resins,and the mechanical,physical,and biological properties of the modified resins were tested.The mechanism of the property changes was explored at the microscopic level.Methods:MD modelling analysis of BNNTs,n-Zn O and BNNTs/n-Zn O nanocomposite systems was carried out using MS software to simulate their compounding processes and discuss their compounding mechanisms.Under the theoretical guidance,BNNTs and n-Zn O were prepared by hydrothermal method,and the two were compounded by in situ growt.h method using electrostatic potential energy,and the composition and structure of the nanosystems were characterized using TEM,SEM,XRD,Raman,and FT-IR.The BNNTs/n-Zn O nanocomposite system modified flow resin was prepared by mechanical stirring,and the physical properties such as compressive strength,microhardness,flexural strength,double bond conversion rate,and curing depth of the modified resin were tested,and the fracture surface morphology of the specimens was observed by SEM to analyze the mechanical property enhancement mechanism.The antibacterial properties and biosafety properties were also tested.Results:TEM,SEM,XRD,Raman,and FT-IR verified the successful compounding of the BNNTs/n-Zn O nanocomposite system.When the addition amount of the composite system was 0.8 wt.%,the compressive strength,microhardness,and flexural strength of the modified resin were 303.34 MPa,54.56 HV,and 144.23 MPa,respectively,which were improved by 68.33%,52.02%,and 30.21%compared with the original samples（P<0.05）,and the antibacterial rate was 73.06%（P<0.05）.Significance:BNNTs/n-Zn O nanocomposite system was successfully synthesized,and the addition of the composite system played a synergistic enhancing effect on the mechanical properties and antibacterial properties of the flow resin,and the BNNTs/n-Zn O nanocomposite system has some application prospects in resin modification.