Design And Preparation Of Nanocomposite Hydrogels Forapplication In Canalfilling Materials

Root canal therapy is considered to be an effective means of treating deep caries，pulpalnecrosis and periapical lesions, where root canal filling materials as important part of the rootcanal filling step, have attracted much attention. Ideal root canal filling materials should possessgood biocompatibility, mobility, X-ray radiopacity, antibacterial ability, stability and ability to sealthe cavity completely, however, current root canal filling materials do not comply with all of theabove characteristics and have microleakage problems. Hydrogels, due to its excellentbiocompatibility, swelling property and stability, can prevent apical or coronal microleakage, havethe potential as root canal sealers, but still need to have certain degree of X-ray radiopacity andantibacterial ability.Based on the current commercialized zirconia nanoparticles without X-ray radiopacity and itsX-ray radiopacity stemming from crystalline structures, and long-lasting antibacterial function，thedispersion, stability issues of water-soluble silver nanoparticle, in this paper, ZrO2, Agnanoparticles were synthesized and diffused in the hydrogels to prepare ZrO2, Ag and ZrO2/Agnanocomposite hydrogels, and the X-ray radiopacity and antimicrobial properties of ZrO2, Ag andZrO2/Ag nanocomposite hydrogels were systematically investigated. The X-ray radiopacity ofZrO2nanocomposite hydrogels were equivalent to3～4mm Al, could meet the requirements ofISO standards. After swelling in simulated oral conditions for30d, the antibacterial efficiency ofAg nanocomposite hydrogels were more than90%. In addition, the X-ray radiopacity andantimicrobial properties of bicomponent ZrO2/Ag composite hydrogels were nearsingle-component composite hydrogels. The results showed that X-ray radiopacity and antimicrobial properties of the two-component composite hydrogels could meet the requirementsof the root canal filling materials.ZrO2, Ag nanoparticles were synthesized by hydrothermal method, and nanocompositehydrogels were synthesized by in situ radical polymerization. The morphology, structure andX-ray radiopacity properties of prepared nanocomposite hydrogels were characterized by fieldemission scanning electron microscopy (FESEM), Fourier transform infrared (FTIR), X-raydiffraction (XRD) and dental ray machines. In addition, antimicrobial properties of nanocompositehydrogels were studied by shaking flask method and the service behavior of the nanocompositehydrogels in simulated oral cavity were investigated. The research results were as follows:1. ZrO2nanocomposite hydrogels: The characteristic peaks around670cm-1on theFT-IR,peaks at28.2°,31.6°of the XRD patterns and scanning electron micrographs showed thesuccessful synthesis of ZrO2nanocomposite hydrogels. Scanning electron microscopy showed thatthe particle size of prepared zirconia nanoparticles were about50nm and well dispersed, XRDpatterns indicated that the zirconia prepared by the hydrothermal method had tetragonal crystal;X-ray radiopacity performance experiments showed that ZrO2nanocomposite hydrogels hadX-ray radiopacity performance, with the increasing of zirconia content, the X-ray radiopacityincreased. When the content of zirconia nanoparticles were10%, the X-ray radiopacity of ZrO2nanocomposite hydrogels were to3～4mm Al, could meet the radiopacity performancerequirements for the root canal filling materials.2. Ag nanocomposite hydrogels: Peaks at37.8o,43.8o,64.2o,77.2oand81.8oof the XRDdiffraction patterns and TEM photographs confirmed the successful synthesis of Ag nanoparticleswith good crystallization and uniform dispersion. Particle size analysis showed that the mean sizeof silver nanoparticles was about100nm.Peaks near450nm of UV-Visible spectra provedsuccessful introduction of the silver nanoparticles into hydrogel. SEM images showed that silvernanoparticles dispersed well in the surface and cross section of the hydrogels. Shaking flaskmethod experiments showed that with the addition of silver nanoparticles nanocompositehydrogels possessed excellent antimicrobial performance and after swelling in simulated oralenvironment for7d,30d still had excellent antibacterial properties, antibacterial efficiency ofnanocomposite hydrogels were about90%and had long-lasting antibacterial function.3. ZrO2/Ag nanocomposite hydrogels: SEM images showed that inorganic particles wereuniformly dispersed in the hydrogels. Shaking flask method experiments confirmed that zirconiananoparticles did not affect the antibacterial properties of silver nanoparticles, the antibacterialefficiency of ZrO2/Ag nanocomposite hydrogels were still more than90%, moreover, afterswelling in a simulated oral environment for7d,30d, ZrO2/Ag nanocomposite hydrogels still hadgood antibacterial properties. Its X-ray radiopacity experiments showed that ZrO2/Ag nanocomposite hydrogels possessed good X-ray radiopacity, which were equivalent to3～4mmAl. And ZrO2/Ag nanocomposite hydrogels had stable swelling rate (80%) in the normal range oftemperature, pH changes of oral environment, could be applied into root canal filling materials.