title: Fracture of layered zirconia restorations at 5 years: A dental laboratory survey.
abstract: BACKGROUND
  The use of ceramic restorations has significantly increased in recent years because of their esthetic properties and the high cost of noble metals. However, given the lack of long-term clinical trials and the limitations of in vitro studies, the durability of ceramic restorations is still questionable.
  
  
  OBJECTIVE
  The purpose of this retrospective study was to determine the fracture rate of layered zirconia restorations at up to 5 years of clinical performance by using a dental laboratory survey model.
  
  
  METHODS
  Data up to 5 years were collected from 2 commercial dental laboratories. Layered zirconia restorations returned to the laboratory for remaking because of failure (fracture) were identified and included. Restorations were categorized as anterior or posterior. Each category was further divided into complete coverage single crowns (SCs) and multiple unit fixed dental prostheses (FDPs). Fracture rates were compared and analyzed using the chi-square test (α=.05).
  
  
  RESULTS
  A total of 31594 restoration records were reviewed and included 13419 anterior restorations (10134 SCs and 3285 FDPs) and 18175 posterior restorations (12810 SCs and 5365 FDPs). The overall fracture rate up to 5 years for all restorations (anterior and posterior) was 3.31%. The fracture rates for anterior restorations were less than for posterior restorations. The fracture rates for anterior SCs were approximately half those of the posterior SC fracture rate, and the combined fracture rate (anterior and posterior) was 3.25%. For FDPs, anterior FDPs fractured at a rate similar to that of posterior FDPs. The combined fracture rate (anterior and posterior FDPs) was 3.47%.
  
  
  CONCLUSIONS
  Layered zirconia restorations displayed relatively low fracture rates in the relatively short term of 5 years.
authors.affiliation: Assistant Professor, Department of General Practice, School of Dentistry, Virginia Commonwealth University, Richmond, Va; and Adjunct Assistant Professor, Department of Prosthodontics, University of North Carolina School of Dentistry, Chapel Hill, NC.
authors.forename: Aous A
authors.initials: AA
authors.lastname: Abdulmajeed
authors.affiliation: Professor and Section Head, Biomaterials Sciences, Department of Operative Dentistry, University of North Carolina School of Dentistry, Chapel Hill, NC.
authors.forename: Terence E
authors.initials: TE
authors.lastname: Donovan
authors.affiliation: Associate Dean for Research and Department Head, Oral Biology, University of Illinois at Chicago, College of Dentistry, Chicago, Ill.
authors.forename: Lyndon F
authors.initials: LF
authors.lastname: Cooper
authors.affiliation: Clinical Associate Professor, Department of Operative Dentistry, University of North Carolina School of Dentistry, Chapel Hill, NC.
authors.forename: Ricardo
authors.initials: R
authors.lastname: Walter
authors.affiliation: Assistant Professor, Department of Operative Dentistry, Director of Biomaterials and Biomimetics, University of North Carolina School of Dentistry, Chapel Hill, NC. Electronic address: sulaiman@unc.edu.
authors.forename: Taiseer A
authors.initials: TA
authors.lastname: Sulaiman
mesh_terms: D003442:Crowns; D003722:Dental Alloys; D017266:Dental Prosthesis; D019232:Dental Restoration Failure / Q000706:statistics & numerical data*; D006801:Humans; D012189:Retrospective Studies; D014481:United States; D015040:Zirconium
chemical_list: D003722:Dental Alloys; D015040:Zirconium; C028541:zirconium oxide