title: Investigation of the dry and wet fatigue properties of three all-ceramic crown systems.
abstract: OBJECTIVE
  The aim of this study was to investigate the influence of fatigue on the fracture strength of In-Ceram (Vita Zahnfabrik), Optimal Pressable Ceramic (Opc, Jeneric Pentron), and IPS Empress (Ivoclar-Vivadent) in both wet and dry environments.
  
  
  METHODS
  Twenty-six crown shapes measuring 8.0 mm in diameter and 8.5 mm in height were fabricated for each ceramic system. For each ceramic system, 10 specimens were tested for fracture strength without fatiguing. A second group (8 specimens) was submitted to a fatigue and fracture test in dry conditions, and a third group (8 specimens) was fatigued and fractured in a wet environment using a mechanical testing machine (Instron). The results were statistically analyzed using a Mann-Whitney test.
  
  
  RESULTS
  The results indicated that: (1) The facture strength for In-Ceram was significantly stronger than IPS Empress. No difference was found between In-Ceram and Opc, and Opc and IPS Empress. (2) The strength of the three ceramic systems decreased significantly after fatiguing in both dry and wet environments compared with the nonfatigued specimens. No difference was found between fatiguing in dry and wet environments. (3) For the three systems fatigued in a dry environment and then fracture tested, In-Ceram and Opc were significantly stronger than IPS Empress, but no difference was found between the three systems fatigued in a wet environment.
  
  
  CONCLUSIONS
  Significant differences in the fracture strengths of the different systems investigated may be seen that result from both the nature of the system and the environment in which the specimens were fatigued.
authors.affiliation: Department of Biomaterials, Piracicaba Dental School (UNICAMP), Brazil.
authors.forename: L C
authors.initials: LC
authors.lastname: Sobrinho
authors.forename: M J
authors.initials: MJ
authors.lastname: Cattell
authors.forename: R H
authors.initials: RH
authors.lastname: Glover
authors.forename: J C
authors.initials: JC
authors.lastname: Knowles
mesh_terms: D000537:Aluminum Oxide / Q000737:chemistry; D000538:Aluminum Silicates / Q000737:chemistry; D002516:Ceramics / Q000737:chemistry; D019245:Compressive Strength; D003442:Crowns; D003776:Dental Porcelain / Q000737:chemistry; D019232:Dental Restoration Failure; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D018709:Statistics, Nonparametric; D014867:Water / Q000737:chemistry
chemical_list: D000538:Aluminum Silicates; C075815:IPS-Empress ceramic; C105911:Optimal Pressed Ceramic; D014867:Water; D003776:Dental Porcelain; C070870:In-Ceram; D000537:Aluminum Oxide