title: Chipping behaviour of all-ceramic crowns with zirconia framework and CAD/CAM manufactured veneer.
abstract: OBJECTIVE
  The aim of this in vitro study was to assess the ultimate load to failure of zirconia based crowns veneered with CAD/CAM manufactured ceramic.
  
  
  METHODS
  32 identical, anatoform zirconia (Sirona inCoris ZI, mono L F1) frameworks (thickness 0.6mm) were constructed (Sirona inLab 3.80). Afterwards, 16 crowns were completed using a CAD/CAM manufactured lithium disilicate ceramic veneer (IPS e.max CAD, Ivoclar Vivadent). The remaining 16 frames were veneered using conventional manual layering technique. For the CAD/CAM manufactured veneers, the connection between framework and veneer was accomplished via a glass fusion ceramics. Before fracture tests, half of the specimens underwent thermocycling and chewing simulation (1.2 million chewing cycles, force magnitude F(max)=108 N). To further investigate the new technique, finite element computations were carried out on the basis of the original geometry.
  
  
  RESULTS
  Nearly all (87.5%) conventionally veneered crowns failed already during chewing simulation, whereas crowns with CAD/CAM manufactured veneers were non-sensitive to artificial ageing. Crowns veneered with lithium disilicate ceramic displayed ultimate loads to failure of about 1600 N.
  
  
  CONCLUSIONS
  The CAD/CAM production of veneers for restorations with zirconia framework is a promising way to reduce failures originating from material fatigue.
authors.affiliation: Department of Prosthodontics, Section for Biomaterial Research, University of Heidelberg, 69120 Heidelberg, Germany. Marc_Schmitter@med.uni-heidelberg.de
authors.forename: M
authors.initials: M
authors.lastname: Schmitter
authors.forename: D
authors.initials: D
authors.lastname: Mueller
authors.forename: S
authors.initials: S
authors.lastname: Rues
mesh_terms: D001696:Biomechanical Phenomena; D001732:Bite Force; D002516:Ceramics / Q000737:chemistry; D003198:Computer Simulation; D017076:Computer-Aided Design; D003442:Crowns; D003764:Dental Materials / Q000737:chemistry*; D003776:Dental Porcelain / Q000737:chemistry*; D019232:Dental Restoration Failure; D003801:Dental Veneers; D055119:Elastic Modulus; D020342:Finite Element Analysis; D006801:Humans; D008422:Materials Testing; D013314:Stress, Mechanical; D013499:Surface Properties; D013696:Temperature; D013997:Time Factors; D015040:Zirconium / Q000737:chemistry*
chemical_list: D003764:Dental Materials; C520133:IPS e.max CAD LT; C493120:lithia disilicate; D003776:Dental Porcelain; C023506:Glass ceramics; D015040:Zirconium; C028541:zirconium oxide