title: Effect of one-year water storage on the surface microhardness of resin-modified versus conventional glass-ionomer cements.
abstract: OBJECTIVE
  Conventional and resin-modified glass-ionomer cements (GIC, RM-GIC) are available for clinical use as restorative materials or as liners and bases. This study was conducted to compare the effect of a 12-month storage period in water on the surface microhardness, measured in Vickers units (VH), between a GIC and a RM-GIC group and to determine if the addition of resins improved the GIC microhardness.
  
  
  METHODS
  VH microhardness was assessed in three GIC: Ketac-Fil, Ketac-Molar and Ketac-Silver (KF, KM, KS) and three RM-GIC: Photac-Fil, Fuji II LC and Vitremer (PF, FU, VI) stored in distilled water at 37 degrees C for 12 months. Measurements were taken at 1, 7, 15, 30, 90, 180 and 365 days. The statistical evaluation was done by means of one-way analysis of variance (ANOVA) and Tukey's multiple comparison tests.
  
  
  RESULTS
  There are significant VH differences among the materials studied and within each material over storage time. GICs, except for KS, showed a higher VH throughout the study period. Among the RM-GIC, VI showed a significantly higher VH at 12 months than at 1 day. The VH of PF diminished in the final stage of the study, whereas that of FU stabilized.
  
  
  CONCLUSIONS
  The results suggest that the addition of resins to the GIC did not appear to improve the surface microhardness of these materials. Furthermore, the surface microhardness of both the conventional and resin-modified glass-ionomers suffered variations over time. However, these materials should not be deemed inadequate for use in clinical applications. Probably, conventional and resin-modified GICs placed in the oral environment would not be affected to the same extent as in in vitro tests.
authors.affiliation: Department of Stomatology, Faculty of Medicine and Odontology, University of the Basque Country, 48940-Leioa, Vizcaya, Spain. ellakuria@euskalnet.net
authors.forename: J
authors.initials: J
authors.lastname: Ellakuria
authors.forename: R
authors.initials: R
authors.lastname: Triana
authors.forename: N
authors.initials: N
authors.lastname: Mínguez
authors.forename: I
authors.initials: I
authors.lastname: Soler
authors.forename: G
authors.initials: G
authors.lastname: Ibaseta
authors.forename: J
authors.initials: J
authors.lastname: Maza
authors.forename: F
authors.initials: F
authors.lastname: García-Godoy
mesh_terms: D000704:Analysis of Variance; D016722:Cermet Cements; D003188:Composite Resins; D003793:Dental Restoration, Permanent; D004356:Drug Storage; D005899:Glass Ionomer Cements / Q000737:chemistry*; D006244:Hardness; D008298:Maleates; D008422:Materials Testing; D012117:Resins, Synthetic / Q000737:chemistry; D018709:Statistics, Nonparametric; D013499:Surface Properties; D014867:Water
chemical_list: D016722:Cermet Cements; D003188:Composite Resins; C079765:Fuji II LC cement; D005899:Glass Ionomer Cements; D008298:Maleates; C081144:Photac-Fil; D012117:Resins, Synthetic; C084550:Vitremer; C110712:ketac-molar; D014867:Water; C040964:Ketac-Fil