title: [Effects of different die materials on fracture and failure behaviors of all-ceramic crowns].
abstract: OBJECTIVE
  To investigate the influence of different die materials on fracture strength and failure mode of IPS e.max Press crowns in mechanical test.
  
  
  METHODS
  Thirty-six IPS e.max Press crowns were divided into 3 groups. They were cemented to extracted maxillary first premolars in Group 1, to epoxy dies in Group 2, and to porous NiTi alloy dies in Group 3 respectively. All the crowns were subjected to compressive load in an universal mechanical testing machine. The maximum fracture strength(N) was recorded and fracture modes of the tested crowns were classified. Fractographies of the failed crowns were observed with a stereomicroscope.
  
  
  RESULTS
  Statistical analysis results showed that the mean fracture strength of the IPS e.max Press crowns on extracted natural teeth [(1159.7 +/- 256.0) N] and porous NiTi alloy dies [(1229.6 +/- 326.7) N] were obviously higher than that of epoxy dies [(883.5 +/- 198.1) N, P = 0.016 and 0.003]. Observations of the fractographies of failed crowns showed that the crowns on epoxy die fractured mesio-distally and no plastic deformation and characteristic cracks were observed. However, crowns in the other groups showed cone cracks at the contact area on occlusal surface and radical cracks initiated from the adhesive interfaces.
  
  
  CONCLUSIONS
  Die material has a significant influence on fracture resistance and fracture mode of the IPS e.max Press crowns. The crowns cemented to porous NiTi alloy dies show a similar fracture mode as those on extracted natural teeth.
authors: Department of Prosthodontics, Guanghua School and Hospital of Stomatology & Institute of Stomatological Research, Sun Yat-sen University, Guangzhou 510055, China.
authors: Xiao-Ping
authors: XP
authors: Wu
authors: Da-Sheng
authors: DS
authors: Li
authors: Jun
authors: J
authors: Zhang
authors: Xiao
authors: X
authors: Ma
authors: Ke
authors: K
authors: Zhao
authors: Xin-Ping
authors: XP
authors: Zhang
mesh_terms: D001641:Bicuspid; D002516:Ceramics; D003442:Crowns; D003776:Dental Porcelain; D019232:Dental Restoration Failure; D003799:Dental Stress Analysis / Q000379:methods*; D008422:Materials Testing; D008437:Maxilla; D009532:Nickel; D019279:Resin Cements; D014025:Titanium
chemical_list: C508050:IPS e.max Press; D019279:Resin Cements; D003776:Dental Porcelain; C040654:titanium nickelide; D009532:Nickel; D014025:Titanium