title: Bending strength of zirconia/porcelain functionally graded materials prepared using spark plasma sintering.
abstract: OBJECTIVE
  The purpose of this study was to fabricate functionally graded materials (FGMs) consisting of yttria-stabilised tetragonal zirconia polycrystal (Y-TZP) and porcelain using spark plasma sintering (SPS) and examine the influence of their microstructures and thermal stress on their bending strengths.
  
  
  METHODS
  Two types of four-layered Y-TZP/porcelain FGMs having a constant layer thickness and a varying layer thickness, Y-TZP/porcelain composite materials having a microstructure corresponding to each layer in FGMs and monolithic materials of Y-TZP and porcelain were fabricated by SPS. The Y-TZP/porcelain volume fraction of each layer in FGMs was varied over 100/0-70/30. Three-point bending test, X-ray diffraction, density measurement, microstructure observation, and thermal stress estimation were performed to characterise the materials.
  
  
  RESULTS
  The bending strength of the Y-TZP/porcelain composite materials decreased with the volume fraction of the porcelain. About FGMs, when the 100%Y-TZP layer was on the tensile stress side during the bending test, the bending strength was almost the same as that of the 100%Y-TZP monolithic material. On the other hand, when the 100%Y-TZP layer was on the compressive stress side, the bending strength of FGM having a constant layer thickness was almost the same as that of the 70%Y-TZP+30%porcelain composite material, while the bending strength of FGM with a varying layer thickness was significantly higher than that of the 70%Y-TZP+30%porcelain composite material.
  
  
  CONCLUSIONS
  The FGMs prepared and analyzed in this research can potentially be used for crowns and bridges as well as for inlays and onlays.
  
  
  CONCLUSIONS
  The SPS method could effectively fabricate the Y-TZP/porcelain FGMs, and the bending strength results revealed that the graded structure was very efficient to raise the bending strength.
authors.affiliation: Department of Restorative Dentistry and Endodontology, Kagoshima University Graduate School of Medical and Dental Sciences, Sakuragaoka, Kagoshima, Japan. Electronic address: tsukada@dent.kagoshima-u.ac.jp.
authors.forename: Gakuji
authors.initials: G
authors.lastname: Tsukada
authors.affiliation: Department of Mechanical Engineering, Graduate School of Science and Engineering, Kagoshima University, Korimoto, Kagoshima, Japan.
authors.forename: Hidekazu
authors.initials: H
authors.lastname: Sueyoshi
authors.affiliation: Department of Mechanical Engineering, Graduate School of Science and Engineering, Kagoshima University, Korimoto, Kagoshima, Japan.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Kamibayashi
authors.affiliation: Department of Restorative Dentistry and Endodontology, Kagoshima University Graduate School of Medical and Dental Sciences, Sakuragaoka, Kagoshima, Japan.
authors.forename: Masayuki
authors.initials: M
authors.lastname: Tokuda
authors.affiliation: Department of Restorative Dentistry and Endodontology, Kagoshima University Graduate School of Medical and Dental Sciences, Sakuragaoka, Kagoshima, Japan.
authors.forename: Mitsuo
authors.initials: M
authors.lastname: Torii
mesh_terms: D000538:Aluminum Silicates / Q000737:chemistry; D002516:Ceramics / Q000737:chemistry*; D003764:Dental Materials / Q000737:chemistry*; D003776:Dental Porcelain / Q000737:chemistry*; D055119:Elastic Modulus; D055664:Electrochemical Techniques; D006801:Humans; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D010316:Particle Size; D058626:Plasma Gases / Q000737:chemistry*; D018583:Pliability; D017680:Potassium Compounds / Q000737:chemistry; D011208:Powders / Q000737:chemistry; D011312:Pressure; D011791:Quartz / Q000737:chemistry; D013314:Stress, Mechanical; D013499:Surface Properties; D013696:Temperature; D014618:Vacuum; D014961:X-Ray Diffraction; D015019:Yttrium / Q000737:chemistry*; D015040:Zirconium / Q000737:chemistry*
chemical_list: D000538:Aluminum Silicates; D003764:Dental Materials; D058626:Plasma Gases; D017680:Potassium Compounds; D011208:Powders; C499362:yttria stabilized tetragonal zirconia; D003776:Dental Porcelain; C016447:feldspar; D011791:Quartz; D015019:Yttrium; D015040:Zirconium
keywords: Bending strength; Functionally graded material; Porcelain; Spark plasma sintering; Thermal stress; Y-TZP