title: Fracture rate of monolithic zirconia restorations up to 5 years: A dental laboratory survey.
abstract: BACKGROUND
  The demand for ceramic restorations has increased over the past years because of their esthetic properties and the high cost of noble metals. However, the lack of long-term clinical studies and the difficulty of interpreting in vitro studies have placed the durability of ceramic restorations in doubt.
  
  
  OBJECTIVE
  The purpose of this study was to determine the failure rate of monolithic zirconia restorations due to fracture up to 5 years of clinical performance.
  
  
  METHODS
  Data were collected over 5 years from 2 commercial dental laboratories. Restorations that were returned to the laboratory for remake because of catastrophic 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 a chi-square test (α=.05).
  
  
  RESULTS
  A total of 39827 restoration records were reviewed and included 3731 anterior restorations (1952 SC; 1799 FDP) and 36096 posterior restorations (29808 SC; 6288 FDP). The overall fracture rate of up to 5 years for all restorations (anterior and posterior) was 1.09%. Fracture rates were 2.06% for all anterior restorations and 0.99% for all posterior restorations. Fracture rates were 0.97% for anterior SCs and 0.69% for posterior SCs, and the combined fracture rate (anterior and posterior) was 0.71%. For FDPs, 3.26% restorations fractured anteriorly and 2.42% fractured posteriorly, and the combined fracture rate (anterior and posterior) was 2.60%.
  
  
  CONCLUSIONS
  Within the relative short-term evaluation of 5 years, restorations fabricated from monolithic zirconia material displayed relatively low fracture rates. Anterior restorations fractured at a slightly higher rate than posterior restorations, and FDPs fractured at a rate double that of SCs.
authors.affiliation: Assistant Professor, Department of Operative Dentistry, 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
authors.affiliation: Assistant Professor, Department of Prosthetic Dentistry, University of Turku Institute of Dentistry, Turku, Finland, and Visiting Scholar, 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: Stallings Distinguished Professor, Graduate Program in Prosthodontics, University of North Carolina School of Dentistry, Chapel Hill, NC.
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
mesh_terms: D002516:Ceramics / Q000627:therapeutic use*; D003442:Crowns / Q000009:adverse effects; D019232:Dental Restoration Failure / Q000706:statistics & numerical data*; D003793:Dental Restoration, Permanent / Q000379:methods; D006801:Humans; D011795:Surveys and Questionnaires; D013997:Time Factors; D015040:Zirconium / Q000627:therapeutic use*
chemical_list: D015040:Zirconium; C028541:zirconium oxide