title: The influence of water sorption on the development of setting shrinkage stress in traditional and resin-modified glass ionomer cements.
abstract: OBJECTIVE
  The aim of this study was to determine the setting stress development for some traditional and resin-modified glass ionomer cements and to assess the effect of early water exposure to this stress.
  
  
  METHODS
  The development of the setting stress of the glass ionomer cements was determined in a tensilometer set-up as described earlier by Feilzer et al. (1987).
  
  
  RESULTS
  The results of this study show the influence of water sorption on the development of setting shrinkage stress in bonded glass ionomer cements. When curing took place under isolated conditions (no hydration or dehydration), all the traditional glass ionomer cements investigated fractured spontaneously, either adhesively and/or cohesively, due to the developing stress. Early exposure to water led to stress relief and prevented spontaneous fracturing. For the light-cured products, no spontaneous failures were observed under isolated conditions. Stress relief due to water sorption reversed the contraction stress into an expansion stress.
  
  
  CONCLUSIONS
  Exposure of traditional glass ionomer cements to water at an appropriate time by the use of permeable matrix systems is advised. Whether the conversion of contraction stresses into expansion stresses as observed for the resin-modified products, is beneficial for a restoration requires further study.
authors.affiliation: Department of Dental Materials Science, Academic Center for Dentistry Amsterdam (ACTA), Amsterdam, The Netherlands.
authors.forename: A J
authors.initials: AJ
authors.lastname: Feilzer
authors.forename: A I
authors.initials: AI
authors.lastname: Kakaboura
authors.forename: A J
authors.initials: AJ
authors.lastname: de Gee
authors.forename: C L
authors.initials: CL
authors.lastname: Davidson
mesh_terms: D000042:Absorption; D000538:Aluminum Silicates / Q000737:chemistry; D003188:Composite Resins / Q000737:chemistry*; D003799:Dental Stress Analysis; D005899:Glass Ionomer Cements / Q000737:chemistry*; D008027:Light; D008298:Maleates / Q000737:chemistry; D008422:Materials Testing; D012117:Resins, Synthetic / Q000737:chemistry; D013314:Stress, Mechanical; D013997:Time Factors; D014867:Water
chemical_list: D000538:Aluminum Silicates; D003188:Composite Resins; C079765:Fuji II LC cement; D005899:Glass Ionomer Cements; D008298:Maleates; C081144:Photac-Fil; D012117:Resins, Synthetic; D014867:Water; C084541:Fuji glass-ionomer lining cement; C039733:Chemfil; C040964:Ketac-Fil