title: Fracture load of monolithic CAD/CAM lithium disilicate ceramic crowns and veneered zirconia crowns as a posterior implant restoration.
abstract: OBJECTIVE
  To compare the fracture load and failure mode of the monolithic lithium disilicate crown (e.max group) and 2 types of veneered zirconia crowns, hand layer (ZV group) and heat pressed (ZP group), as a posterior implant-supported restoration.
  
  
  METHODS
  A total of 24 all-ceramic crowns for molar tooth were fabricated using the computer-aided design/computer-assisted manufacture (CAD/CAM) system. The e.max group crowns and zirconia copings for ZV and ZP groups were fabricated using a Cerec milling unit. The ZV group was fabricated using a hand-layer veneering method, and the ZP group using a heat-pressing method. All crowns were luted to the abutments, which were connected to implant fixtures, using resin cement. Fracture load was measured using the universal testing machine, and the fracture surface was evaluated by scanning electron microscopy.
  
  
  RESULTS
  The ZP group showed significantly higher fracture load (5229.3 N) compared with the e.max group (3852.1 N) and ZV group (3100.3 N). All fractures in the ZV group occurred in the veneered layer.
  
  
  CONCLUSIONS
  Monolithic CAD/CAM lithium disilicate crowns are applicable to posterior implant-supported restorations because the fracture load was higher than the average occlusal force.
authors.affiliation: Department of Prosthodontics, College of Dentistry, Yonsei University, Seoul, Korea.
authors.forename: Jee Hwan
authors.initials: JH
authors.lastname: Kim
authors.forename: Su-Jeong
authors.initials: SJ
authors.lastname: Lee
authors.forename: Jun Sub
authors.initials: JS
authors.lastname: Park
authors.forename: Jae Jun
authors.initials: JJ
authors.lastname: Ryu
mesh_terms: D002484:Cementation / Q000379:methods; D017076:Computer-Aided Design; D003442:Crowns; D001840:Dental Bonding; D015921:Dental Implants; D003776:Dental Porcelain / Q000737:chemistry*; D017267:Dental Prosthesis Design; D019094:Dental Prosthesis, Implant-Supported; D019232:Dental Restoration Failure; D003799:Dental Stress Analysis / Q000295:instrumentation; D003801:Dental Veneers; D006801:Humans; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D008963:Molar; D019279:Resin Cements / Q000737:chemistry; D013314:Stress, Mechanical; D013499:Surface Properties; D015040:Zirconium / Q000737:chemistry*
chemical_list: D015921:Dental Implants; C520133:IPS e.max CAD LT; D019279:Resin Cements; C493120:lithia disilicate; D003776:Dental Porcelain; D015040:Zirconium; C028541:zirconium oxide