title: Fatigue resistance of CAD/CAM resin composite molar crowns.
abstract: OBJECTIVE
  To demonstrate the fatigue behavior of CAD/CAM resin composite molar crowns using a mouth-motion step-stress fatigue test. Monolithic leucite-reinforced glass-ceramic crowns were used as a reference.
  
  
  METHODS
  Fully anatomically shaped monolithic resin composite molar crowns (Lava Ultimate, n=24) and leucite reinforced glass-ceramic crowns (IPS Empress CAD, n=24) were fabricated using CAD/CAM systems. Crowns were cemented on aged dentin-like resin composite tooth replicas (Filtek Z100) with resin-based cements (RelyX Ultimate for Lava Ultimate or Multilink Automix for IPS Empress). Three step-stress profiles (aggressive, moderate and mild) were employed for the accelerated sliding-contact mouth-motion fatigue test. Twenty one crowns from each group were randomly distributed among these three profiles (1:2:4). Failure was designated as chip-off or bulk fracture. Optical and electron microscopes were used to examine the occlusal surface and subsurface damages, as well as the material microstructures.
  
  
  RESULTS
  The resin composite crowns showed only minor occlusal damage during mouth-motion step-stress fatigue loading up to 1700N. Cross-sectional views revealed contact-induced cone cracks in all specimens, and flexural radial cracks in 2 crowns. Both cone and radial cracks were relatively small compared to the crown thickness. Extending these cracks to the threshold for catastrophic failure would require much higher indentation loads or more loading cycles. In contrast, all of the glass-ceramic crowns fractured, starting at loads of approximately 450N.
  
  
  CONCLUSIONS
  Monolithic CAD/CAM resin composite crowns endure, with only superficial damage, fatigue loads 3-4 times higher than those causing catastrophic failure in glass-ceramic CAD crowns.
authors.affiliation: Department of Biomaterials and Biomimetics, New York University College of Dentistry, 433 First Avenue, New York, NY 10010, USA.
authors.forename: Fatma A
authors.initials: FA
authors.lastname: Shembish
authors.affiliation: Department of Biomaterials and Biomimetics, New York University College of Dentistry, 433 First Avenue, New York, NY 10010, USA; School of Metallurgy and Environment, Central South University, Changsha, Hunan 410083, PR China.
authors.forename: Hui
authors.initials: H
authors.lastname: Tong
authors.affiliation: Department of Biomaterials and Biomimetics, New York University College of Dentistry, 433 First Avenue, New York, NY 10010, USA; Graduate Program in Dentistry, Federal University of Pelotas, Pelotas, Brazil.
authors.forename: Marina
authors.initials: M
authors.lastname: Kaizer
authors.affiliation: Department of Epidemiology and Health Promotion, New York University College of Dentistry, 380 Second Avenue Suite 301, New York, NY 10010, USA.
authors.forename: Malvin N
authors.initials: MN
authors.lastname: Janal
authors.affiliation: Tissue Engineering and Biophotonics, King's College London Dental Institute, United Kingdom.
authors.forename: Van P
authors.initials: VP
authors.lastname: Thompson
authors.affiliation: Radboud University Nijmegen Medical Centre, College of Dental Sciences, Preventive and Restorative Dentistry, Ph van Leydenlaan 25, PO Box 9101, 6500HB Nijmegen, The Netherlands.
authors.forename: Niek J
authors.initials: NJ
authors.lastname: Opdam
authors.affiliation: Department of Biomaterials and Biomimetics, New York University College of Dentistry, 433 First Avenue, New York, NY 10010, USA. Electronic address: yz21@nyu.edu.
authors.forename: Yu
authors.initials: Y
authors.lastname: Zhang
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry*; D000538:Aluminum Silicates / Q000737:chemistry; D002516:Ceramics / Q000737:chemistry; D003188:Composite Resins / Q000737:chemistry*; D017076:Computer-Aided Design; D003442:Crowns; D003776:Dental Porcelain / Q000737:chemistry; D017267:Dental Prosthesis Design; D019232:Dental Restoration Failure; D003799:Dental Stress Analysis; D005898:Glass / Q000737:chemistry; D006801:Humans; D066298:In Vitro Techniques; D008422:Materials Testing; D008963:Molar; D011140:Polyurethanes / Q000737:chemistry*; D019279:Resin Cements / Q000737:chemistry; D013499:Surface Properties
chemical_list: D000180:Acrylic Resins; D000538:Aluminum Silicates; C029012:Composite Dental Resin; D003188:Composite Resins; C075815:IPS-Empress ceramic; D011140:Polyurethanes; C528569:Rely-X; D019279:Resin Cements; D003776:Dental Porcelain
keywords: CAD/CAM crowns; Fatigue; Fracture; Glass-ceramic; Resin composite; Weibull analysis