title: High-strength CAD/CAM-fabricated veneering material sintered to zirconia copings--a new fabrication mode for all-ceramic restorations.
abstract: OBJECTIVE
  With this in vitro study the fracture strength of zirconia-based crown copings being veneered with a CAD/CAM generated high-strength ceramic cap by sintering is compared with anatomically identical zirconia-based crowns, which were either overpressed or veneered by the layering technique for completion.
  
  
  METHODS
  A 1.2mm, 360 degrees chamfer preparation was performed on a second maxillary molar and was dublicated 15 times in a cobalt-chromium-alloy. A sample of 45 zirconia copings was produced and divided into three groups. In the first group (VT) zirconia copings received conventional veneering in layering technique, in the second group the veneering porcelain was pressed over the zirconia coping (PT), and for the third group (ST) a CAD/CAM-fabricated high-strength anatomically shaped veneering cap was sintered onto the zirconia coping. All crowns were cemented conventionally onto their dies and tested in the universal testing machine until clinical failure. The fracture load data were compared by a one-way analysis of variance and a multiple comparison posthoc test (alpha<0.05).
  
  
  RESULTS
  Specimens from group VT showed a mean (S.D.) fracture load of 3700.39 (1238.72) N, group OT 3523.73 (1181.11) N and group ST 6262.67 (2257.42) N. The difference between groups VT/OT and ST were statistically significant (P<0.001).
  
  
  CONCLUSIONS
  The new CAD/CAM-fabricated bilayered restorations (ST) were superior to the present techniques (VT and OT) in terms of fracture load and offer the possibility to produce cost-effective crowns and fixed partial dentures with a potential lower risk of chippings.
authors.affiliation: Department of Prosthodontics, Ludwig-Maximilians-University, Munich, Germany. florian.beuer@med.uni-muenchen.de
authors.forename: Florian
authors.initials: F
authors.lastname: Beuer
authors.forename: Josef
authors.initials: J
authors.lastname: Schweiger
authors.forename: Marlis
authors.initials: M
authors.lastname: Eichberger
authors.forename: Heinrich F
authors.initials: HF
authors.lastname: Kappert
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Gernet
authors.forename: Daniel
authors.initials: D
authors.lastname: Edelhoff
mesh_terms: D001031:Apatites / Q000737:chemistry; D002484:Cementation; D002516:Ceramics / Q000737:chemistry; D002858:Chromium Alloys / Q000737:chemistry; D017076:Computer-Aided Design; D003442:Crowns; D000044:Dental Abutments; D003764:Dental Materials / Q000737:chemistry*; D003776:Dental Porcelain / Q000737:chemistry*; D017267:Dental Prosthesis Design; D019232:Dental Restoration Failure; D003799:Dental Stress Analysis / Q000295:instrumentation; D003801:Dental Veneers; D006358:Hot Temperature; D006801:Humans; D008422:Materials Testing; D008963:Molar; D013314:Stress, Mechanical; D019231:Tooth Preparation, Prosthodontic; D015040:Zirconium / Q000737:chemistry*
chemical_list: D001031:Apatites; D002858:Chromium Alloys; D003764:Dental Materials; C520133:IPS e.max CAD LT; C508050:IPS e.max Press; C493120:lithia disilicate; D003776:Dental Porcelain; C023506:Glass ceramics; D015040:Zirconium; C025105:fluorapatite; C028541:zirconium oxide