title: Hertzian load-bearing capacity of a ceramic-reinforced glass ionomer cement stored wet and dry.
abstract: OBJECTIVE
  To investigate the development of the load-bearing capacity of a ceramic-reinforced glass ionomer cement (GIC), stored dry or wet, using Hertzian indentation.
  
  
  METHODS
  GIC discs 2mm thick and 10mm in diameter were made (Amalgomer CR, Advanced Healthcare, Tonbridge, Kent, UK), randomly divided into 8 groups and stored at 37 degrees C in air or artificial saliva (AS) for 1, 7, 30 and 90 days. Discs were tested by loading centrally using a 20mm diameter hard steel ball while resting freely on a filled-nylon substrate (E: 10GPa), at 23 degrees C in air. The failure load at the first bottom-initiated radial crack was detected acoustically.
  
  
  RESULTS
  All the failure loads of air-stored specimens were higher than those of AS-stored specimens. The failure load was relatively stable for air-stored specimens but showed a significant decreasing tendency for AS-stored specimens.
  
  
  CONCLUSIONS
  Zirconia-reinforced GIC is sensitive to moisture. Artificial saliva storage has a detrimental effect on the failure load of ceramic-reinforced GIC that may indicate long-term deterioration in service.
authors.affiliation: Department of Prosthodontics, Guanghua School of Stomatology, Sun Yat-sen University, Guang Zhou, China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Wang
authors.forename: B W
authors.initials: BW
authors.lastname: Darvell