title: Alumina-reinforced zirconia implants: survival rate and fracture strength in a masticatory simulation trial.
abstract: BACKGROUND
  Alumina-toughened zirconia (ATZ) is a possible alternative material to titanium for oral implants. No data are available on the fracture strength of ATZ oral implants.
  
  
  OBJECTIVE
  The purpose of this study was to examine one-piece implants made of ATZ ceramic under artificial loading conditions and to compare the fracture strength of these implants with implants fabricated from tetragonal zirconium dioxide poylcrystal (TZP)-A.
  
  
  METHODS
  A total of 72 implants, 48 ATZ implants (groups A and B) and 24 TZP-A implants (group C), were investigated. A chamfer preparation at the implant heads was performed on all implants of groups B and C. Eight implants of each group underwent 1.2 or five million thermomechanical loading cycles in the chewing simulator (load value: 98 N). Further eight implants of each group were not cyclic loaded. Finally, the fracture strength of all implants was determined using a universal testing machine.
  
  
  RESULTS
  No implant fractured during loading in the chewing simulator. All implants were placed in the universal testing machine to evaluate fracture strength. The mean fracture strength values±standard deviations for the implants without artificial loading were 1734±165 N (ATZ, no preparation), 1220±85 N (ATZ, with preparation), and 578±49 N (TZP-A, with preparation); 1489±190 N (ATZ, no preparation), 1064±121 N (ATZ, with preparation), and 607±57 N (TZP-A, with preparation) with 1.2 million loading cycles; and 1358±187 N (ATZ, no preparation), 1098±97 N (ATZ, with preparation), and 516±45 N (TZP-A, with preparation) with five million cycles. The ATZ implants showed significantly higher mean fracture strengths compared with the TZP-A implants. Modification of the implant head using diamond burs and increased loading time also led to a significant decrease in fracture strength.
  
  
  CONCLUSIONS
  The ATZ implants showed an increased mechanical stability compared with the TZP-A. Modification of the implant head resulted in a decrease in fracture strength. However, within the limits of this in vitro investigation it can be concluded that ATZ implants will withstand functional loading over an estimated period of 20 years.
authors.affiliation: Department of Prosthodontics, School of Dentistry, Albert-Ludwigs-University, Freiburg, Germany. ralf.kohal@uniklinik-freiburg.de
authors.forename: Ralf-J
authors.initials: RJ
authors.lastname: Kohal
authors.forename: Martin
authors.initials: M
authors.lastname: Wolkewitz
authors.forename: Constanze
authors.initials: C
authors.lastname: Mueller
mesh_terms: D000537:Aluminum Oxide / Q000737:chemistry*; D000704:Analysis of Variance; D003198:Computer Simulation; D003722:Dental Alloys / Q000737:chemistry; D015921:Dental Implants; D003764:Dental Materials / Q000737:chemistry; D017267:Dental Prosthesis Design; D019232:Dental Restoration Failure; D003799:Dental Stress Analysis; D006801:Humans; D008409:Mastication; D008422:Materials Testing; D013499:Surface Properties; D015040:Zirconium / Q000737:chemistry*
chemical_list: D003722:Dental Alloys; D015921:Dental Implants; D003764:Dental Materials; D015040:Zirconium; D000537:Aluminum Oxide; C028541:zirconium oxide