title: Failure analysis of fractured dental zirconia implants.
abstract: OBJECTIVE
  The purpose of the present study was the macroscopic and microscopic failure analysis of fractured zirconia dental implants.
  
  
  METHODS
  Thirteen fractured one-piece zirconia implants (Z-Look3) out of 170 inserted implants with an average in situ period of 36.75±5.34 months (range from 20 to 56 months, median 38 months) were prepared for macroscopic and microscopic (scanning electron microscopy [SEM]) failure analysis. These 170 implants were inserted in 79 patients. The patient histories were compared with fracture incidences to identify the reasons for the failure of the implants.
  
  
  RESULTS
  Twelve of these fractured implants had a diameter of 3.25 mm and one implant had a diameter of 4 mm. All fractured implants were located in the anterior side of the maxilla and mandibula. The patient with the fracture of the 4 mm diameter implant was adversely affected by strong bruxism. By failure analysis (SEM), it could be demonstrated that in all cases, mechanical overloading caused the fracture of the implants. Inhomogeneities and internal defects of the ceramic material could be excluded, but notches and scratches due to sandblasting of the surface led to local stress concentrations that led to the mentioned mechanical overloading by bending loads.
  
  
  CONCLUSIONS
  The present study identified a fracture rate of nearly 10% within a follow-up period of 36.75 months after prosthetic loading. Ninety-two per cent of the fractured implants were so-called diameter reduced implants (diameter 3.25 mm). These diameter reduced implants cannot be recommended for further clinical use. Improvement of the ceramic material and modification of the implant geometry has to be carried out to reduce the failure rate of small-sized ceramic implants. Nevertheless, due to the lack of appropriate laboratory testing, only clinical studies will demonstrate clearly whether and how far the failure rate can be reduced.
authors.affiliation: m.gahlert@knihagahlert.de
authors.forename: M
authors.initials: M
authors.lastname: Gahlert
authors.forename: D
authors.initials: D
authors.lastname: Burtscher
authors.forename: I
authors.initials: I
authors.lastname: Grunert
authors.forename: H
authors.initials: H
authors.lastname: Kniha
authors.forename: E
authors.initials: E
authors.lastname: Steinhauser
mesh_terms: D015921:Dental Implants; D017267:Dental Prosthesis Design; D019232:Dental Restoration Failure; D019544:Equipment Failure Analysis; D006801:Humans; D008855:Microscopy, Electron, Scanning; D013499:Surface Properties; D015040:Zirconium
chemical_list: D015921:Dental Implants; D015040:Zirconium; C028541:zirconium oxide