Preparation Of Mesocrystal As Inorganic Filler And Its Effect On Properties Of Dental Resin Composites

Dental resin composites possess distinguished esthetics,biocompatibility and convenient clinical manipulation compared with conventional amalgam alloys.Due to the polymerization shrinkage of the composite,it is easy to cause bacteria breeding and secondary caries,which influence the interfacial bonding between filler and resin matrix and the service life of composite.With regard to composites,inorganic fillers are used as reinforcing phase which components,morphology and surface silanization have effects on the resin composites.By adding inorganic particles with specific functions,the physical-mechanical properties of dental composites can be further enhanced.In order to further improve the properties of the resin composites,the preparation of inorganic fillers with hierarchical structure was studied in this paper,the main points are listed as follows:(1)Globular yttria-stabilized zirconia mesocrystals prepared by a hydro-thermal process.The as-synthesized particles were round 800?nm in diameter and each particle was self-assembled from nanocrystallites of(3?5?nm in size).The amorphous silica with a thickness of2?3 nm was uniformly coated on the surface of Zr O₂via a microfluidc process to solve the difficulty in silanization.Zr O₂@Si O₂was added to Bis-GMA based resin as co-filler,and Si O₂nanoparticles were also used as the fundamental filler to prepare dental resin composites by light-curing.The results of mechanical properties showed that the composite Zr5Si65(Zr O₂@Si O₂:Si O₂=5:65,wt/wt,total filler loading 70 wt%)demonstrated the best flexural strength,flexural modulus and compression strength,which were increased by 30.9,22.5 and 11.5%,respectively,in comparison with the composite Zr0Si70 without Zr O₂@Si O₂.The composites with Zr O₂@Si O₂also exhibited acceptable radiopacity and the radiopatcity value of the composite Zr7Si63 is(1.07±0.06)mm Al.(2)In order to improve the mechanical properties of dental resin composites while providing antibacterial properties,Zn O mesocrystals with porous and hierarchical structure was achieved by a thermal hydrolysis method using gum arabic as structure-directing agent.The thickness and diameter of the synthesized Zn O mesocrystals were both about 1.0±0.2?m.The amorphous silica with a thickness of 4?6 nm was uniformly coated on the surface of Zn O mesocrystals via the microfluidc process.Then Zn O@Si O₂was added to Bis-GMA based resin as co-filler,and Si O₂nanoparticles were used as the fundamental filler to make dental resin composites by light-curing.Results showed that the lower loading of Zn O@Si O₂(?5 wt%)could improve the mechanical properties of resin composites effectively.The composite Z3S72(Zn O@Si O₂:Si O₂=3:72,wt/wt,total filler loading 75 wt%)demonstrated the excellent flexural strength,flexural modulus,and compression strength,which was increased by 12.9,6.6 and 3.7%,respectively,in comparison with the composite Z0S75 without Zn O@Si O₂.The composite with Zn O@Si O₂also exhibited superior antimicrobial activity and the antibacterial rate was 98.7%.(3)Hierarchical Zn O mesocrystals with alignment architecture mimicking the natural tooth was achieved by a hydrothermal method using gelatin as structure-directing agent.Thickness and diameter of the Zn O mesocrystals were 1?m and 3?m respectively.Zn O was added to Bis-GMA based resin as co-filler,and Si O₂nanoparticles were used as the fundamental filler to make dental resin composites by light-curing.The results of mechanical properties showed that the composite Zn5Si69(Zn O:Si O₂=5:69,wt/wt,total filler loading 74 wt%)demonstrated the best flexural strength,flexural modulus and compression strength,which were increased by 15.7,19.8 and 4.2%,respectively,in comparison with the composite Zn0Si74 without Zn O.The composite Zn10Si64 also exhibited radiopacity and superior antimicrobial activity,the radiopatcity value of the composite Zn10Si64 is(1.13±0.07)mm Al,ang its antibacterial rate was as high as of 99.0%.