title: In vitro fracture resistance of three commercially available zirconia crowns for primary molars.
abstract: OBJECTIVE
  The purpose of this study was to measure the fracture resistance of primary mandibular first molar zirconia crowns from three different manufacturers-EZ Pedo (EZP), NuSmile (NSZ), and Kinder Krowns (KK)-and compare it with the thickness of the zirconia crowns and the measured fracture resistance of preveneered stainless steel crowns (SSCs).
  
  
  METHODS
  The thickness of 20 zirconia crowns from three manufacturers were measured. The mean force required to fracture the crowns was determined. Preveneered NuSmile (NSW) SSCs were tested as a control.
  
  
  RESULTS
  EZP crowns were significantly thicker in three of the six measured locations. The force required to fracture the EZP crown was significantly higher than that required for NSZ and KK. There was a positive correlation between fracture resistance and crown thickness in the mesial, distal, mesioocclusal, and distoocclusal dimensions. None of the zirconia crowns proved to be as resistant to fracture as the preveneered SSCs.
  
  
  CONCLUSIONS
  Statistically significant differences were found among the forces required to fracture zirconia crowns by three different manufacturers. The increase in force correlated with crown thickness. The forces required to fracture the preveneered stainless steel crowns were greater than the forces required to fracture all manufacturers' zirconia crowns.
authors.affiliation: Department of Pediatric Dentistry, School of Dentistry, School of Public Health, Louisiana State University Health Sciences Center, New Orleans, La., USA. jtown2@lsuhsc.edu.
authors.forename: Janice A
authors.initials: JA
authors.lastname: Townsend
authors.affiliation: Private practice, Lawrenceburg, Tenn., USA.
authors.forename: Patrick
authors.initials: P
authors.lastname: Knoell
authors.affiliation: School of Public Health, Louisiana State University Health Sciences Center, New Orleans, La., USA.
authors.forename: Qingzhao
authors.initials: Q
authors.lastname: Yu
authors.affiliation: School of Dentistry, School of Public Health, Louisiana State University Health Sciences Center, New Orleans, La., USA.
authors.forename: Jian-Feng
authors.initials: JF
authors.lastname: Zhang
authors.affiliation: School of Dentistry, School of Public Health, Louisiana State University Health Sciences Center, New Orleans, La., USA.
authors.forename: Yapin
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Biostatistics Program, School of Public Health, Louisiana State University Health Sciences Center, New Orleans, La., USA.
authors.forename: Han
authors.initials: H
authors.lastname: Zhu
authors.affiliation: Private practice, London, Ontario, Canada.
authors.forename: Sean
authors.initials: S
authors.lastname: Beattie
authors.affiliation: Department of Comprehensive Dentistry and Biomaterials, School of Dentistry, School of Public Health, Louisiana State University Health Sciences Center, New Orleans, La., USA.
authors.forename: Xiaoming
authors.initials: X
authors.lastname: Xu
mesh_terms: D003442:Crowns; D003722:Dental Alloys / Q000737:chemistry; D003764:Dental Materials / Q000737:chemistry*; D017267:Dental Prosthesis Design; D019232:Dental Restoration Failure; D003799:Dental Stress Analysis / Q000295:instrumentation; D003801:Dental Veneers; D006801:Humans; D008422:Materials Testing; D008963:Molar / Q000473:pathology*; D013193:Stainless Steel / Q000737:chemistry; D013314:Stress, Mechanical; D013499:Surface Properties; D014094:Tooth, Deciduous / Q000473:pathology*; D015040:Zirconium / Q000737:chemistry*
chemical_list: D003722:Dental Alloys; D003764:Dental Materials; D013193:Stainless Steel; D015040:Zirconium; C028541:zirconium oxide