Preparation And Property Study Of Glass Ionomer Cements With TiO₂ Nanoparticles

Glass ionomer cements（GICs）are widely used clinically as adhesive materials（for temporary crown,PFM,orthodontic banding,bracket,etc.）,because of the low thermal expansion coefficient,releasing fluoride to prevent caries,using easily without etching the tooth surface and the color similar to the tooth.But due to the shortcomings of poor mechanical strength and unclear explainment for releasing fluoride to prevent caries etc. This study tried to add different mass content of Ti O₂ nanoparticles to the conventional GICs,and dicuss the changes of the mechanical and antimicrobial properties of the composites,to provide experiment evidences for follow-up clinical application.Objective: Prepare the conventional glass ionomer cement with Ti O₂ nanoparticles and evaluate the mechanical property,adhesive property,friction and wear property and antibacterial property of the nanoparticle Ti O₂-GIC.Materials and methods:（1） characterized the crystal phase, particle morphology and structure Ti O₂ nanoparticles with X Ray Diffraction（XRD）and scanning electron microscope（SEM）.（2）Manually grinding and ultrasonic vibration to combine Ti O₂ nanoparticles with glass powder according to different weight percentage（0%,2%,5%,7%,10%）.Then mixed the powder and liquid with the ratio of 2:1（mass ratio）to the dough stage.（3）Set the paste in the stain steel mold with 2MPa to prepare the samples,and stored them in distilled water 37℃ for 24 hours.（4）Use universal testing machine to test the compressive strength of five groups,and record the highest during loading process.Test the microhardness of five groups with micro hardness tester with 50 g loading for 10 s.Test the coefficient of friction of five groups on the UMT-2MT instrument with 1N loading,distance 5mm,frequency 1Hz,and on the LSR-2M instrument with 10 N loading,distance 5mm,frequency 1Hz.Then test the depth of the wear scar.Test the adhesive strength of the three groups（0%wt%,2%wt%,5%wt%）.Prepare the human molar crowns with the same size.Then embed them in the epoxy resin,heat and set.Use universal testing machine to test the highest as adhesive strength before the GIC composite materials out.（5）Test the antibacterial property of the GIC and composites with direct contact method for Streptococcus mutans and Lactobacillus by recording the absorbance values（OD values） with a microplate reader.Set A group in UVA-light and B group in dark.Both A and B group were divided into 6 groups（blank,0%wt%,2%wt%,5%wt%,7%wt%,and 10%wt%）.The resulting data were analyzed through ANOVA statistical analysis.Result and conclusion:1. The XRD pattern of Ti O₂ Nanoparticles showed 2θ = 25.3 °, showing crystal Ti O₂ nanoparticles of anatase phase. SEM image showed Ti O₂ particles pellets were nano. Compared with glass ionomer cements,Nano-Ti O₂ glass ionomer cements were more smooth,and uniformly distributed in the GIC matrix.2. According to the microhardness from strong to weak,the order was 2%wt%（average 47.8N/mm2）、0%wt%（average 37.95N/mm2）、5%wt%（average 33N/mm2）、7%wt%（average 27.1N/mm2）和10%wt%（average 22.35N/mm2）.Compared with 0%wt%,the microhardness of 2%wt% increased significantly.3. According to the microhardness from strong to weak,the order was 2%wt%（average 119.8MPa）、5%wt%（average 117.7MPa）、0%wt%（average 100.7MPa）、7%wt%（average 100.4MPa）和10%wt%（average 99.4MPa）.The results showed compared with the control group,the compressive strength of 2%wt% increased significantly（p <0.05）.4. With 10 N loading,the friction coefficients according to the descending order were 0%wt%（0.68）,2%wt%（0.33）,5%wt%（0.32）,7%wt%（0.29） and 10%wt%（0.28）.The wear scar depths according to the descending order were 0%wt%（0.45mm）,2%wt%（0.41mm）, 5%wt%（0.4mm）, 10%wt%（0.37mm） and7%wt%（0.36mm）.With 1N loading, the friction coefficients according to the descending order were 0%wt%（1.16）,2%wt%（0.53）,5%wt%（0.5）,7%wt%（0.45） and 10%wt%（0.43）. The wear scar depths according to the descending order were 0%wt%（77.73μm）,2%wt%（66.09μm）,5%wt%（54.41μm）, 7%wt%（54.02μm） and10%wt%（53.28μm）.But the difference between 0%wt% and 2%wt% of the friction coefficient was significant as well as the wear scar depth（p<0.05）.5.Adhesive strength:The average of 0%wt% was 520.498 MPa. The average of 2%wt% was 785.906 MPa.The average of 5%wt% was 626.644 MPa.Compare 0%wt% with 2%wt%. The adhesive strength increased by 18.83% with statistical significance.Compared with 2%wt%,the adhesive strength decreased slightly without statistical significance.6.The OD values of the blank of UVA-light and black were not significant.With the addition ratio of Ti O₂ nanoparticles（0%wt%,2%wt%,5%wt%,7%wt%and 10%wt%）,the antibacterial properties for Lactobacillus of the UVA-light were improved,and the OD values were decreased,which were respectively 0.876,0.807,0.112,0.103,0.07,0.038. With the addition ratio of Ti O₂ nanoparticles（0%wt%,2%wt%,5%wt%,7%wt%and 10%wt%）,the antibacterial properties for Streptococcus mutans of the UVA-light were improved gradually,and the 2%wt% was the most significant, which were respectively 0.452,0.43,0.15,0.12,0.099,0.096.There was an increasing trend of antibacterial property of the black group for Lactobacillus,which was 0.951、0.798、0.594、0.579、0.54、0.469 respectively.The increasing trend of antibacterial property occurred in the black group for Streptococcus mutans,which was respectively0.415、0.405、0.197、0.103、0.079、0.048.Conclusion:According to the results above,it could be concluded that the group of 2%wt% Ti O₂-GIC had the best complex behavior about mechanical,wear and friction,adhesive and antibacterial.