title: Mechanical properties of dental resin/composite containing urchin-like hydroxyapatite.
abstract: OBJECTIVE
  To investigate the reinforcing effect of urchin-like hydroxyapatite (UHA) in bisphenol A glycidyl methacrylate (Bis-GMA)/triethylene glycol dimethacrylate (TEGDMA) dental resin (without silica nanoparticles) and dental composites (with silica nanoparticles), and explore the effect of HA filler morphologies and loadings on the mechanical properties.
  
  
  METHODS
  UHA was synthesized by a facile method of microwave irradiation and studied by X-ray diffraction (XRD), scanning electron microscope (SEM), and thermogravimetric analysis (TGA). Mechanical properties of the dental resin composites containing silanized UHA were tested by a universal mechanical testing machine. Analysis of variance was used for the statistical analysis of the acquired data. The fracture morphologies of tested composites were observed by SEM. Composites with silanized irregular particulate hydroxyapatite (IPHA) and hydroxyapatite whisker (HW) were prepared for comparative studies.
  
  
  RESULTS
  Impregnation of lower loadings (5 wt% and 10 wt%) of silanized UHA into dental resin (without silica nanoparticles) substantially improved the mechanical properties; higher UHA loadings (20 wt% and 30 wt%) of impregnation continuously improved the flexural modulus and microhardness, while the strength would no longer be increased. Compared with silanized IPHA and HW, silanized UHA consisting of rods extending radially from center were embedded into the matrix closely and well dispersed in the composite, increasing filler-matrix interfacial contact area and combination. At higher filler loadings, UHA interlaced together tightly without affecting the mobility of monomer inside, which might bear higher loads during fracture of the composite, leading to higher strengths than those of dental resins with IPHA and HW. Besides, impregnation of silanized UHA into dental composites (with silica nanoparticles) significantly improved the strength and modulus.
  
  
  CONCLUSIONS
  UHA could serve as novel reinforcing HA filler to improve the mechanical properties of dental resin and dental composite.
authors.affiliation: State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, College of Material Science and Engineering, Donghua University, Shanghai, 201620, PR China.
authors.forename: Fengwei
authors.initials: F
authors.lastname: Liu
authors.forename: Bin
authors.initials: B
authors.lastname: Sun
authors.forename: Xiaoze
authors.initials: X
authors.lastname: Jiang
authors.forename: Sultan S
authors.initials: SS
authors.lastname: Aldeyab
authors.forename: Qinghong
authors.initials: Q
authors.lastname: Zhang
authors.forename: Meifang
authors.initials: M
authors.lastname: Zhu
mesh_terms: D000818:Animals; D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry*; D003188:Composite Resins / Q000737:chemistry*; D019245:Compressive Strength; D003764:Dental Materials / Q000737:chemistry*; D003799:Dental Stress Analysis / Q000295:instrumentation; D017886:Durapatite / Q000737:chemistry*; D055119:Elastic Modulus; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D008872:Microwaves; D053758:Nanoparticles / Q000737:chemistry; D010316:Particle Size; D018583:Pliability; D011092:Polyethylene Glycols / Q000737:chemistry*; D011109:Polymethacrylic Acids / Q000737:chemistry*; D012617:Sea Urchins; D012821:Silanes / Q000737:chemistry; D012822:Silicon Dioxide / Q000737:chemistry; D017550:Spectroscopy, Fourier Transform Infrared; D013314:Stress, Mechanical; D013718:Tensile Strength; D013818:Thermogravimetry; D014961:X-Ray Diffraction
chemical_list: D003188:Composite Resins; D003764:Dental Materials; D011109:Polymethacrylic Acids; D012821:Silanes; C020946:triethylene glycol dimethacrylate; D011092:Polyethylene Glycols; D017438:Bisphenol A-Glycidyl Methacrylate; D012822:Silicon Dioxide; D017886:Durapatite