title: [The influence of thickness ratios on the fatigue behaviors of two kinds of dental ceramic].
abstract: OBJECTIVE
  To investigate the intensity changes of different thickness ratios of Empress II glass ceramic and GI- II glass-infiltrated alumina ceramic before and after Hertzian contact cyclic fatigue.
  
  
  METHODS
  Disk-shaped specimens of different thickness ratios of Empress II glass ceramic and GI-II glass-infiltrated alumina ceramic were respectively fabricated. Hertzian contact technique was imposed on the specimens. Critical loads of the specimens before and after 10(5) cycles loading were recorded.
  
  
  RESULTS
  The average values of critical loads of all specimens reduced significantly after cycles loading (P < 0.05), and critical loads declined with diminishing thickness of the core ceramic. The critical load of GI-II glass-infiltrated alumina ceramic was significantly higher than Empress II glass ceramic before and after cycle loading(P < 0.05).
  
  
  CONCLUSIONS
  Cycle loading can reduce the strengths of the two kinds of dental ceramic, and the latter is better than the former in the resistance to fracture and cyclic fatigue. Critical loads of the two kinds of dental ceramic are mainly influenced by the core ceramic's strength and thickness.
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: Ling-Yun
authors.initials: LY
authors.lastname: Guo
authors.forename: Hai-Bo
authors.initials: HB
authors.lastname: Wang
authors.forename: Jun-Hua
authors.initials: JH
authors.lastname: Wu
authors.forename: Jian-Sheng
authors.initials: JS
authors.lastname: Su