title: Quality Evaluation of Zirconium Dioxide Frameworks Produced in Five Dental Laboratories from Different Countries.
abstract: OBJECTIVE
  The aim of this study was to assess and compare quality as well as economic aspects of CAD/CAM high strength ceramic three-unit FDP frameworks ordered from dental laboratories located in emerging countries and Switzerland.
  
  
  METHODS
  The master casts of six cases were sent to five dental laboratories located in Thailand (Bangkok), China (Peking and Shenzhen), Turkey (Izmir), and Switzerland (Bern). Each laboratory was using a different CAD/CAM system. The clinical fit of the frameworks was qualitatively assessed, and the thickness of the framework material, the connector height, the width, and the diameter were evaluated using a measuring sensor. The analysis of the internal fit of the frameworks was performed by means of a replica technique, whereas the inner and outer surfaces of the frameworks were evaluated for traces of postprocessing and damage to the intaglio surface with light and electronic microscopes. Groups (dental laboratories and cases) were compared for statistically significant differences using Mann-Whitney U-tests after Bonferroni correction.
  
  
  RESULTS
  An acceptable clinical fit was found at 97.9% of the margins produced in laboratory E, 87.5% in B, 93.7% in C, 79.2% in A, and 62.5% in D. The mean framework thicknesses were not statistically significantly different for the premolar regions; however, for the molar area 4/8 of the evaluated sites were statistically significantly different. Circumference, surface, and width of the connectors produced in the different laboratories were statistically significantly different but not the height. There were great differences in the designs for the pontic and connector regions, and some of the frameworks would not be recommended for clinical use. Traces of heavy postprocessing were found in frameworks from some of the laboratories. The prices per framework ranged from US$177 to US$896.
  
  
  CONCLUSIONS
  By ordering laboratory work in developing countries, a considerable price reduction was obtained compared to the price level in Switzerland. Despite the use of the standardized CAD/CAM chains of production in all laboratories, a large variability in the quality aspects, such as clinical marginal fit, connector and pontic design, as well as postprocessing traces was noted. Recommended sound handling of postprocessing was not applied in all laboratories. Dentists should be aware of the true and factitious advantages of CAD/CAM production chains and not lose control over the process.
authors.affiliation: Department of Reconstructive Dentistry and Gerontology, University of Bern, Switzerland.
authors.forename: Esther
authors.initials: E
authors.lastname: Schneebeli
authors.affiliation: Department of Reconstructive Dentistry and Gerontology, University of Bern, Switzerland.
authors.forename: Urs
authors.initials: U
authors.lastname: Brägger
authors.affiliation: Division of Fixed Prosthodontics and Biomaterials, University Clinics of Dental Medicine, Geneva, Switzerland.
authors.forename: Susanne S
authors.initials: SS
authors.lastname: Scherrer
authors.affiliation: Department of Reconstructive Dentistry and Gerontology, University of Bern, Switzerland.
authors.forename: Andrea
authors.initials: A
authors.lastname: Keller
authors.affiliation: Department of Reconstructive Dentistry and Gerontology, University of Bern, Switzerland.
authors.forename: Julia G
authors.initials: JG
authors.lastname: Wittneben
authors.affiliation: Department of Reconstructive Dentistry and Gerontology, University of Bern, Switzerland.|Division of Fixed Prosthodontics and Biomaterials, University Clinics of Dental Medicine, Geneva, Switzerland.
authors.forename: Stefan P
authors.initials: SP
authors.lastname: Hicklin
mesh_terms: D002681:China; D017076:Computer-Aided Design; D017266:Dental Prosthesis / Q000592:standards*; D017267:Dental Prosthesis Design / Q000592:standards; D003906:Developing Countries; D006801:Humans; D007754:Laboratories, Dental / Q000592:standards; D013557:Switzerland; D013785:Thailand; D014421:Turkey; D015040:Zirconium
chemical_list: D015040:Zirconium; C028541:zirconium oxide
keywords: CAD/CAM; FDP; economics; marginal fit