title: Zirconia implant abutment fracture: clinical case reports and precautions for use.
abstract: OBJECTIVE
  Zirconia was recently introduced as a ceramic implant abutment due to its superior mechanical properties and white color. Nevertheless, it requires careful handling to avoid unexpected failure. The aim of this study was to examine five clinically broken zirconia implant abutments using fractography principles.
  
  
  METHODS
  Five clinically fractured zirconia abutments were retrieved for fractographic analysis. The specimens were cleaned, sterilized, and reassembled to allow reconstruction of the broken abutments. Each fragment was gold sputter-coated and individually examined using scanning electron microscopy. The location of the crack origin was identified and the stress at failure was estimated using fracture marks observed on the broken surfaces.
  
  
  RESULTS
  For three abutments, the critical crack was located at the internal ring where the abutments met the internal metallic component. The estimated stress at failure ranged between 978 and 1,228 MPa. Friction landmarks were observed on the surface of the fixation screw, which could be responsible for the generation of high internal stresses. Two abutments broke due to overpreparation and thinning of the lateral walls.
  
  
  CONCLUSIONS
  A confirmatory radiograph is recommended before the final zirconia abutments are screwed into place to prevent improper seating and the generation of damaging internal stresses.
authors.affiliation: Dental Biomaterials Department, Faculty of Dentistry, Alexandria University, Alexandria, Egypt. info@aboushelib.org
authors.forename: Moustafa N
authors.initials: MN
authors.lastname: Aboushelib
authors.forename: Ziad
authors.initials: Z
authors.lastname: Salameh
mesh_terms: D000328:Adult; D000044:Dental Abutments; D015921:Dental Implants; D003776:Dental Porcelain; D019232:Dental Restoration Failure; D003799:Dental Stress Analysis; D019544:Equipment Failure Analysis; D005260:Female; D006801:Humans; D008297:Male; D008855:Microscopy, Electron, Scanning; D008875:Middle Aged; D015040:Zirconium
chemical_list: D015921:Dental Implants; D003776:Dental Porcelain; D015040:Zirconium; C028541:zirconium oxide