title: Fracture-resistant monolithic dental crowns.
abstract: OBJECTIVE
  To quantify the splitting resistance of monolithic zirconia, lithium disilicate and nanoparticle-composite dental crowns.
  
  
  METHODS
  Fracture experiments were conducted on anatomically-correct monolithic crown structures cemented to standard dental composite dies, by axial loading of a hard sphere placed between the cusps. The structures were observed in situ during fracture testing, and critical loads to split the structures were measured. Extended finite element modeling (XFEM), with provision for step-by-step extension of embedded cracks, was employed to simulate full failure evolution.
  
  
  RESULTS
  Experimental measurements and XFEM predictions were self-consistent within data scatter. In conjunction with a fracture mechanics equation for critical splitting load, the data were used to predict load-sustaining capacity for crowns on actual dentin substrates and for loading with a sphere of different size. Stages of crack propagation within the crown and support substrate were quantified. Zirconia crowns showed the highest fracture loads, lithium disilicate intermediate, and dental nanocomposite lowest. Dental nanocomposite crowns have comparable fracture resistance to natural enamel.
  
  
  CONCLUSIONS
  The results confirm that monolithic crowns are able to sustain high bite forces. The analysis indicates what material and geometrical properties are important in optimizing crown performance and longevity.
authors.affiliation: Department of Biomaterials and Biomimetics, New York University College of Dentistry, New York, NY 10010, USA. Electronic address: yz21@nyu.edu.
authors.forename: Yu
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Department of Biomaterials and Biomimetics, New York University College of Dentistry, New York, NY 10010, USA.
authors.forename: Zhisong
authors.initials: Z
authors.lastname: Mai
authors.affiliation: School of Mechanical and Chemical Engineering, University of Western Australia, Crawley, WA 6009, Australia.
authors.forename: Amir
authors.initials: A
authors.lastname: Barani
authors.affiliation: School of Mechanical and Chemical Engineering, University of Western Australia, Crawley, WA 6009, Australia.
authors.forename: Mark
authors.initials: M
authors.lastname: Bush
authors.affiliation: Material Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA.
authors.forename: Brian
authors.initials: B
authors.lastname: Lawn
mesh_terms: D001732:Bite Force; D003188:Composite Resins / Q000737:chemistry*; D017076:Computer-Aided Design; D003442:Crowns; D003776:Dental Porcelain / Q000737:chemistry*; D003799:Dental Stress Analysis / Q000379:methods*; D020342:Finite Element Analysis; D008422:Materials Testing; D013314:Stress, Mechanical; D015040:Zirconium / Q000737:chemistry*
chemical_list: D003188:Composite Resins; C520133:IPS e.max CAD LT; C493120:lithia disilicate; D003776:Dental Porcelain; D015040:Zirconium; C028541:zirconium oxide
keywords: Dental composite; Fracture resistance; Lithium disilicate; Monolithic crowns; Splitting; Zirconia