Long-term mechanical characteristics of resin-modified glass ionomer restorative materials.
OBJECTIVE
The purpose of this study was to compare the effects of long-term water storage on the mechanical characteristics of four resin-modified glass ionomer restorative materials with those of a conventional glass ionomer cement and a resin composite material.


METHODS
Cylindrical specimens were prepared and stored in water for 1 h, 24 h, 1 wk, 1 mon, 3 mon and 6 mon prior to determination of diametral tensile strength (DTS) and depth of surface indentation both under 1 N load and after removal of the load.


RESULTS
Diametral tensile strength was lowest for the conventional glass ionomer cement and highest for the composite; the resin-modified glass ionomer cements were intermediate between the reference materials. Water storage reduced DTS between 24 h and 1 wk or 1 mon but then remained unaffected until the final measurements after 6 mon. The materials showed a trend toward a slight increase in the depth of indentation both under load and after removal of the load with increasing storage time. These mechanical properties indicate the position of four resin-modified glass ionomer cements on a continuum with conventional glass ionomer cement and resin composite as the end points.


CONCLUSIONS
The mechanical properties of resin-modified glass ionomers show that this group of materials is weaker than resin composite but stronger than conventional glass ionomer cement. Water storage for 6 mon has little adverse effect on the mechanical properties.
Uno
S
S
Department of Operative Dentistry, Hokkaido University, Sapporo, Japan.
Finger
W J
WJ
Fritz
U
U
D000704:Analysis of Variance; D020770:Compomers; D003188:Composite Resins / Q000737:chemistry*; D001840:Dental Bonding; D003793:Dental Restoration, Permanent; D005899:Glass Ionomer Cements / Q000737:chemistry*; D008298:Maleates / Q000737:chemistry; D008422:Materials Testing; D008689:Methacrylates / Q000737:chemistry; D012044:Regression Analysis; D012117:Resins, Synthetic / Q000737:chemistry; D017640:Silicates / Q000737:chemistry; D013718:Tensile Strength; D014867:Water / Q000737:chemistry
D020770:Compomers; D003188:Composite Resins; C088486:Dyract; C079765:Fuji II LC cement; D005899:Glass Ionomer Cements; D008298:Maleates; D008689:Methacrylates; C084019:Pekafill; C081144:Photac-Fil; D012117:Resins, Synthetic; D017640:Silicates; C084550:Vitremer; D014867:Water; C040964:Ketac-Fil