title: [A comparative study of mechanical experiment and three-dimensional finite element analysis on fracture mode of all-ceramic molar crowns].
abstract: OBJECTIVE
  To investigate the influence of indenter diameter on fracture strength and fracture mode of IPS e. max all-ceramic crowns using mechanical experiments and three-dimensional finite element (3-DFE) method, to validate the 3-DFE model using mechanical experiments, and to provide a guideline for occlusal surface design for IPS e. max all-ceramic crowns.
  
  
  METHODS
  A 3-DFE model of an all-ceramic crown on a molar was established using ANSYS10.0 software. The 3-DFE crown was loaded occlusally at three points to simulate the contact points of a hemispherical indenter loading on the crown. Two indenter diameters (4 mm and 10 mm) were designed by changing loading point, load level and its direction. The stress distribution and the principal stress in the 3-DFE model were calculated. Meanwhile, IPS e. max ceramic crowns were made on a laboratory model and loaded with indenters. The diameters of the indenters were also 4 mm and 10 mm respectively. Fracture mode and fracture-resistance of the crowns were recorded.
  
  
  RESULTS
  The principal stress increased as load increases for both small and large indenters. Stress concentrated in the central fossa of the 3-DFE crown when loaded with the small indenter. Stress concentration appeared in the middle area of the occlusal surface mesio-distally when 3-DFE crown was loaded with large indenter. The fracture-resistance load was 600 N to 700 N for 4 mm diameter indenter, and 2500 N to 2750 N for 10 mm diameter indenter. Mechanical experiments indicated the same results as those from 3-DFE analysis.
  
  
  CONCLUSIONS
  Both the three-dimensional finite element analysis and the mechanical experiment showed the same results. When loaded with 4 mm diameter indenter, fracture occurred in the central fossa of the crown, however, 10 mm diameter indenter usually caused extensive crown damage.
authors.affiliation: Department of Prosthodontics, Guanghua School of Stomatology, Sun Yat-sen University, Guangzhou 510055, China.
authors.forename: Qin-qin
authors.initials: QQ
authors.lastname: Wang
authors.forename: Jun
authors.initials: J
authors.lastname: Zhang
authors.forename: Ke
authors.initials: K
authors.lastname: Zhao
authors.forename: Xin-ping
authors.initials: XP
authors.lastname: Zhang
mesh_terms: D002516:Ceramics; D003776:Dental Porcelain; D003799:Dental Stress Analysis; D020342:Finite Element Analysis; D008422:Materials Testing; D013314:Stress, Mechanical
chemical_list: D003776:Dental Porcelain