title: The Impact of In Vitro Accelerated Aging, Approximating 30 and 60 Years In Vivo, on Commercially Available Zirconia Dental Implants.
abstract: BACKGROUND
  Despite increased popularity of Zirconia dental implants, concerns have been raised regarding low temperature degradation (LTD) and its effect on micro-structural integrity.
  
  
  OBJECTIVE
  This study evaluated the effect of LTD on four types of Zirconia dental implants at 0, 30, and 60 years of artificial aging. The impact of aging on t-m transformation and micro crack formation was measured.
  
  
  METHODS
  Accelerated aging at 15 and 30 hours, approximating 30 and 60 years in vivo, aged 36 Zirconia dental implants: Z systems®(A), Straumann®(B), Ceraroot®(C), and Zeramex®(D). Focused ion beam-scanning electron microscopic analysis determined the micro structural features, phase transformation, and the formation of micro cracks.
  
  
  RESULTS
  At 15 hours, type A implant presented with micro cracks and t-m transformation of 0.9 µm and 3.1 µm, respectively. At 30 hours, micro cracks remained shallow (1 µm). At 15 hours, type B implant presented micro cracks (0.7 µm) and grain transformation (1.2 µm). At 30 hours, these features remained superficial at 0.6 and 1.5 µm, respectively. Type C implant presented surface micro cracks of 0.3 µm at 15 hours. The depth of t-m transformation slightly increased to 1.4 µm. At 30 hours, number of micro cracks increased at the surface to an average depth of 1.5 µm. Depth of t-m transformation increased to an average of 2.5 µm. At 15 hours, micro cracks remained superficial (0.8 µm) for type D implant and depth of t-m transformation increased to 2.3 µm. At 30 hours, the depth of micro cracks increased to an average of 1.3 µm followed by increased t-m transformation to a depth of 4.1 µm.
  
  
  CONCLUSIONS
  Depth of grain transformation remained within 1-4 µm from the surface. The effect of aging was minimal for all Zirconia implants.
authors.affiliation: Private practice, 120 South Spalding Drive, Suite 201, Beverly Hills, CA, 90212, USA.
authors.forename: Mona
authors.initials: M
authors.lastname: Monzavi
authors.affiliation: Private practice, 801 Wayne Ave, Suite G200, Silver Spring, MD, 20910, USA.
authors.forename: Sammy
authors.initials: S
authors.lastname: Noumbissi
authors.affiliation: Private practice, 120 South Spalding Drive, Suite 201, Beverly Hills, CA, 90212, USA.
authors.forename: Hessam
authors.initials: H
authors.lastname: Nowzari
mesh_terms: D000375:Aging; D003080:Cold Temperature; D015921:Dental Implants; D003764:Dental Materials / Q000737:chemistry*; D003799:Dental Stress Analysis; D006801:Humans; D066298:In Vitro Techniques; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D015040:Zirconium / Q000737:chemistry*
chemical_list: D015921:Dental Implants; D003764:Dental Materials; D015040:Zirconium
keywords: Zirconia dental implant; accelerated aging; low temperature degradation; micro cracks; t-m transformation