title: Zirconia implant abutments: microstructural analysis.
abstract: OBJECTIVE
  Yttria-stabilized zirconia (ZrO₂-Y₂O₃) ceramics have received increasing attention in recent years because of their stress-induced tetragonal-to-monoclinic (martensitic) transformation. This unique process acts as a toughening mechanism, imparting strength and toughness to the ceramic alloy. This property, along with well-documented biocompatibility, is now being exploited in an increasing number of medical applications, including implant dentistry. To prevent clinical problems and predict their behavior and physical limitations, a characterization of the ceramic elements used in dental restorations is essential. The aim of the present study is to characterize the crystal structure, elemental composition, and micr ostructure of asreceived ZiReal Post (Biomet 3i) zirconium oxide abutments, as well as specimens coated with a first layer of a low-fusing fluoroapatite ceramic.
  
  
  METHODS
  Zirconium oxide abutments, both as-received and porcelain-coated, were studied using the following techniques: x-ray diffraction, x-ray fluorescence, energy dispersive x-ray spectroscopy, optical microscopy, and scanning and transmission electron microscopy.
  
  
  RESULTS
  X-ray analyses detected only the presence of Zr, O, Y, and hafnium (Hf), in an amount of 3% to 4% molecular weight Y₂O₃-ZrO₂. X-ray diffraction measurements showed that the ceramic abutment crystallizes mainly in the tetragonal phase, with some residual monoclinic phase. The microstructure is characterized by a rather homogenous grain distribution, formed by equiaxed and fine grains with a mean size of 0.30 Μm.
  
  
  CONCLUSIONS
  Compositional and diffraction results are consistent with polycrystalline yttria-stabilized tetragonal zirconia. The material is susceptible to undergoing the stress-induced transformation toughening mechanism because of the very fine grain size. Except for machining ring marks, the surfaces exhibit an excellent finishing quality. No structural modifications were observed in the fluoroapatite ceramic-coated abutments because of the relatively low temperatures used for ceramization compared with the phase transformation temperatures used for zirconia.
authors: Department of Condensed Matter Physics, University of Seville, Spain.
authors: Cristina
authors: C
authors: Vaquero-Aguilar
authors: Manuel
authors: M
authors: Jiménez-Melendo
authors: Daniel
authors: D
authors: Torres-Lagares
authors: Oriol
authors: O
authors: Llena-Blasco
authors: August
authors: A
authors: Bruguera
authors: Jaime
authors: J
authors: Llena-Blasco
authors: Manuel
authors: M
authors: García-Calderón
authors: Rocío
authors: R
authors: Velázquez-Cayón
authors: José-Luis
authors: JL
authors: Gutiérrez-Pérez
mesh_terms: D001031:Apatites; D002516:Ceramics / Q000737:chemistry*; D020099:Coated Materials, Biocompatible / Q000737:chemistry*; D018360:Crystallography, X-Ray / Q000379:methods; D000044:Dental Abutments; D003776:Dental Porcelain / Q000737:chemistry; D003799:Dental Stress Analysis; D008853:Microscopy / Q000379:methods; D013052:Spectrometry, X-Ray Emission / Q000379:methods; D015019:Yttrium / Q000032:analysis / Q000737:chemistry*; D015040:Zirconium / Q000032:analysis / Q000737:chemistry*
chemical_list: D001031:Apatites; D020099:Coated Materials, Biocompatible; C499362:yttria stabilized tetragonal zirconia; D003776:Dental Porcelain; D015019:Yttrium; D015040:Zirconium; C025105:fluorapatite; C028541:zirconium oxide; C091417:yttria