title: [Cyclic fatigue of Vita mark II machinable ceramics under Hertzian's contact].
abstract: OBJECTIVE
  To investigate the cyclic fatigue modes of Vita mark II machinable ceramics under Hertzian's contact.
  
  
  METHODS
  Hertzian's contact technique (WC spheres r = 3.18 mm) was used to investigate the cyclic fatigue of Vita mark II machinable ceramic. All specimens were fatigued by cyclic loading in moist environment, furthermore, surviving strength was examined by three point test and morphology damage observation.
  
  
  RESULTS
  In homogeneous Vita mark II machinable ceramics, two fatigue damage modes existed after cyclic loading with spheres under moist environment, including conventional tensile-driven cone cracking (brittle mode) and shear-driven microdamage accumulation (quasi-plastic mode). The latter generated radial cracks and deeply penetrating secondary cone crack. Initial strength degradation were caused by the cone cracks, subsequent and much more deleterious loss was caused by radial cracks.
  
  
  CONCLUSIONS
  Cyclic fatigue modes of Vita mark II machinable ceramics includes brittle and quasi-plastic mode.
authors.affiliation: Dept. of Prosthodontics, School of Stomatology, Tongji University, Shanghai 200072, China.
authors.forename: Wei-Cai
authors.initials: WC
authors.lastname: Liu
authors.forename: Zhi-Shen
authors.initials: ZS
authors.lastname: Zhang
authors.forename: Cheng-Min
authors.initials: CM
authors.lastname: Huang
authors.forename: Yong-Lie
authors.initials: YL
authors.lastname: Chao
authors.forename: Qian-Bing
authors.initials: QB
authors.lastname: Wan
mesh_terms: D002516:Ceramics; D003776:Dental Porcelain; D006801:Humans; D008422:Materials Testing; D013499:Surface Properties
chemical_list: C082340:Vita Mark II; D003776:Dental Porcelain