| Objectives In order to avoid the harm caused by enamel caries white spots,which often high in the orthodontic process,we explore the shear strength and antibacterial properties of the new orthodontic adhesive,two kinds of antibacterial agents were mixed with commercial resin in a certain proportion,one of the antibacterial agents was dimethylaminohexadecyl methacrylate(DMAHDM)that synthesized,the other one was the composite of chlorhexidine diacetate(CHA)encapsulated in mesoporous silica nanoparticles(MSNs),to provide a theoretical basis for clinical application.Methods Experiment 1: DMAHDM was prepared from 2-dimethylaminoethyl methacrylate(DMAEMA)and 1-bromohexadecane(BHD)which were viewed as raw materials,and the synthesis of DMAHDM was analyzed by fourier transform infrared spectroscopy(FTIR).At room temperature,CHA was encapsulated in MSNs(SBA-15)by physical high-speed stirring,which was recorded as CHA@MSNs.The microstructure of the CHA@MSNs was observed by scanning electron microscopy,the conformation of the CHA@MSNs was analyzed by X-ray diffraction(XRD)and fourier transform infrared spectroscopy,and the CHA which encapsulated content of SBA-15 was measured by thermogravimetric analyzer.Experiment 2: The 192 healthy premolars were randomly divided into 16 groups,12 in each group.DMAHDM with weight percentages of 0%,3%,5%,7.5% and CHA(in the form of CHA@MSNs)of 0%,3%,5%,and 6.4% are combined in pairs with the commercial 3M mobile resin to form 16 groups of the new orthodontics bonding resin.The metal premolar brackets and the new bonding resin were used to adhere to the center of the premolar clinical crown and buccal surface.After cold and hot cycling in a hot and cold cycler,the roots of the isolated teeth were embedded with super anhydrite.Finally,the shear strength of each group of brackets was tested on the universal testing machine,and the adhesive residue index on the brackets was calculated.Experiment 3: The 16 groups of the new bonding resins were laid on the bottom of the groove on the cover of a 96-well plate,and the light was cured by a light curing lamp to form a the new bonding resin sheet having a thickness of 0.5mm and a diameter of 8mm.The structure of the resin was observed by scanning electron microscope.1 16 groups of the new bonding resin sheets were cultured in a 24-well plate in order to form a Streptococcus mutans biofilm.The MTT method was used to detect the activity of the biofilm,and the antimicrobial effect of the new adhesive resin sheet was observed by scanning electron microscope.2 The extraction solution of 16 groups of modified adhesive resin tablets was extracted,and cultivate them in 96-well plates to form Streptococcus mutans biofilm culture,and detect the biofilm activity by MTT method.Results Experiment 1: 1 The material DMAHDM was subjected to FT-IR detection and the presence of NR4+group confirmed the successful preparation of quaternary ammonium salt monomer DMAHDM.2 The material CHA@MSNs was subjected to FTIR detection.Compared with the standard CHA infrared spectrum,it was found that CHA was successfully encapsulated on SBA-15.XRD found that loading CHA into SBA-15 did not change its amorphous structure.Scanning electron microscope observation showed that SBA-15 is composed of rod-shaped particles.The edges of CHA@MSNs rod-shaped particles were not obvious,which confirmed that CHA was encapsulated in SBA-15.Thermogravimetric analysis found that the proportion of CHA loaded into SBA-15 was 41.9%.Experiment 2: 1 Comparison of shear strength: The difference in SBS values among 16 groups in CHA was statistically significant(F=82.647,P<0.01).The difference between the group with CHA and the group without CHA was statistically significant(P<0.05).The group with 6.4% CHA had the largest drop in shear strength,suggesting that the addition of 6.4% CHA had the greatest effect on the bonding performance of the bonding resin.There was no statistically significant difference between the groups with 3% and 5% CHA added(P>0.05).The difference in SBS values among groups with DMAHDM was statistically significant(F=2.900,P<0.05).The difference between the addition of 3% DMAHDM and the group without DMAHDM was not statistically significant(P>0.05),but the difference between the addition of 5% and7.5% DMAHDM and the group without DMAHDM was statistically significant(P<0.05),suggesting that a higher proportion of DMAHDM has an influence on the bonding performance of the bonding resin.Adding 5% DMAHDM and 7.5% DMAHDM had no statistically significant difference(P>0.05),indicating that adding 5% and 7.5%DMAHDM had little difference in resin adhesion.CHA@MSNs and DMAHDM interact when physically mixed(F=4.822,P<0.01),suggesting that DMAHDM disperses some CHA@MSNs in the resin.2 Bracket adhesive residue index: The difference between the groups was not statistically significant(c2= 10.099,P>0.05),suggesting that the addition of two antimicrobial agents had little effect on the fracture mode of the bracket.Experiment 3: 1 The new adhesive resin sheet scanning electron microscope found that the addition of DMAHDM had little effect on the resin structure,while the addition of 6.4% CHA caused agglomeration and dense particles due to the large amount of filler.At the same time,the addition of DMAHDM and CHA could be "complementary" to the resin structure.And had little effect on the resin structure.2 The OD value of 16 groups of resin tablets: the difference between DMAHDM weight concentration gradients was statistically significant(F=69.970,P<0.01),7.5%DMAHDM had the best antibacterial effect.In CHA,the difference between 0%,3%,and 5% was statistically significant(F=50.058,P<0.01),and 5% had the best antibacterial effect,while the difference between 6.4% and 5% was not statistically significant(P>0.05).3 Compared with electron microscope scanning of group 5C+7.5D and group 3M,the number of streptococcus mutans decreased,the membrane deformation and even the content flowed out,and the antibacterial effect was better.4There was no statistically significant difference between the weight concentration gradients of DMAHDM(F=0.439,P>0.05),which indirectly indicates that DMAHDM was covalently cross-linked in the resin to exert antibacterial function and cound not release antibacterial.There was a statistically significant difference between the three weight concentration gradients of 0%,3% and 5% in CHA(F=50.058,P<0.01),and the antibacterial effect of 5% was the best,but the difference between 6.4% and 5% was not statistical Significance(P>0.05).Conclusions 1 DMAHDM and CHA@MSNs under the premise of meeting the orthodontic clinical adhesive strength,the maximum amount of antimicrobial agent cound be added was 5% CHA and 7.5% DMAHDM.2 DMAHDM and CHA@MSNs have antibacterial function,and the antibacterial effect was when 5% CHA and 7.5%DMAHDM or 6.4% CHA and 7.5% DMAHDM were added.3 Adding 5% CHA and7.5% DMAHDM was the best combination of antibacterial effect without affecting the shear strength.Figure 17;Table 6;Reference 153... |
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