title: Low temperature degradation and reliability of one-piece ceramic oral implants with a porous surface.
abstract: Low temperature degradation of zirconia (3Y-TZP) oral implants and its effect on fatigue reliability is poorly documented.
  
  
  OBJECTIVE
  The aim of this investigation was to follow the aging process occurring at the surface of implants exhibiting a porous coating and to assess its influence on their mechanical (fatigue) properties.
  
  
  METHODS
  Tetragonal to monoclinic transformation (t-m) was evaluated during accelerated aging tests up to 100h in autoclave (134°C, 2 bars) by X-ray diffraction (XRD) and focused ion beam (FIB). A series of implants were steam-aged for 20h before fatigue testing. Such temperature-time conditions would correspond roughly to 40 years in vivo. The aged specimens and a non-aged control group were step-stress fatigued until failure or survival.
  
  
  RESULTS
  The evolution of XRD surface monoclinic content was slow, i.e. 16% and 35% for 20 and 100h respectively. However, FIB revealed a significant transformation, initiated at the interface between the porous layer and the bulk, preferentially growing towards the bulk. FIB is therefore better indicated than XRD to follow aging in such implants. Higher average fatigue strength (aged 1235N versus non-aged 826N) and reliability levels were observed for the 20h aged group.
  
  
  CONCLUSIONS
  After aging for durations compatible with clinical use, 3Y-TZP with porous surface presented higher fatigue performance. This is in contrast to previous studies where loss of strength due to aging was often reported. Generalizations must therefore be avoided when considering aging of zirconia dental products and every new material/process combination should be tested before drawing conclusions.
authors: INSA-Lyon, UMR CNRS 5510 (MATEIS), 7 avenue Jean Capelle, 21 Villeurbanne Cedex, France.
authors: Clarisse
authors: C
authors: Sanon
authors: Jérôme
authors: J
authors: Chevalier
authors: Thierry
authors: T
authors: Douillard
authors: Ralf J
authors: RJ
authors: Kohal
authors: Paulo G
authors: PG
authors: Coelho
authors: Jenni
authors: J
authors: Hjerppe
authors: Nelson R F A
authors: NR
authors: Silva
mesh_terms: D000537:Aluminum Oxide / Q000737:chemistry*; D020099:Coated Materials, Biocompatible / Q000737:chemistry*; D015921:Dental Implants; D003799:Dental Stress Analysis; D019544:Equipment Failure Analysis; D008855:Microscopy, Electron, Scanning / Q000379:methods; D016062:Porosity; D013499:Surface Properties; D013696:Temperature; D014961:X-Ray Diffraction; D015019:Yttrium / Q000737:chemistry*; D015040:Zirconium / Q000737:chemistry*
chemical_list: D020099:Coated Materials, Biocompatible; D015921:Dental Implants; C499362:yttria stabilized tetragonal zirconia; D015019:Yttrium; D015040:Zirconium; D000537:Aluminum Oxide