Mechanical behavior of glass ionomer cements affected by long-term storage in water.
OBJECTIVE
The early strength of glass ionomer cements was investigated previously (Cattani et al., 1993). Using the same set of glass ionomer cements, this study was designed to determine if mechanical property degradation occurred after an extended period of storage in water.


METHODS
In the present study, the effect of aging in water on the compressive, tensile and flexural strengths of twelve commercial glass ionomer cements was evaluated at different time intervals after the beginning of the setting reaction. The aging periods varied from 24 h to 12 mon.


RESULTS
The results show that the mechanical properties of the tested materials are in some cases affected by long-term aging in water. The evolution of strength follows distinct patterns of change. It has been established that the glass ionomer cements are neither characterized by a continuous increase nor a continuous decrease in strength. Most of the materials tested maintained a constant strength. However, several of them first display an improvement of the mechanical strength followed by a reduction. In this case, the 24h and the 12 mon strengths are usually similar.


CONCLUSIONS
The aging mechanisms of glass ionomers are complex. Strengthening probably results from additional crosslinking and build-up of a silica gel phase, whereas weakening may result from erosion and plasticizing effect of water.
Cattani-Lorente
M A
MA
Laboratory of Dental Materials, School of Dentistry, University of Geneva, Switzerland.
Godin
C
C
Meyer
J M
JM
D000180:Acrylic Resins / Q000737:chemistry; D017607:Aluminum Compounds / Q000737:chemistry; D000704:Analysis of Variance; D017610:Calcium Compounds / Q000737:chemistry; D016722:Cermet Cements / Q000737:chemistry; D003188:Composite Resins / Q000737:chemistry; D003736:Dental Cavity Lining; D005899:Glass Ionomer Cements / Q000737:chemistry*; D007101:Immersion; D008277:Magnesium Oxide / Q000737:chemistry; D008298:Maleates / Q000737:chemistry; D008422:Materials Testing; D018583:Pliability; D011076:Polycarboxylate Cement / Q000737:chemistry; D019279:Resin Cements; D012117:Resins, Synthetic / Q000737:chemistry; D012823:Silicate Cement / Q000737:chemistry; D013718:Tensile Strength; D014867:Water / Q000737:chemistry*; D015034:Zinc Oxide / Q000737:chemistry
D000180:Acrylic Resins; D017607:Aluminum Compounds; D017610:Calcium Compounds; D016722:Cermet Cements; D003188:Composite Resins; C079765:Fuji II LC cement; D005899:Glass Ionomer Cements; D008298:Maleates; D011076:Polycarboxylate Cement; D019279:Resin Cements; D012117:Resins, Synthetic; D014867:Water; C054101:ChemFil II; C045751:Aqua-cem; C061499:Ketac-Bond; C090915:GC Fuji III; C035219:calcium aluminate; C074807:BaseLine dental cement; C090914:GC Altect; C073466:Prisma APH; C084541:Fuji glass-ionomer lining cement; D012823:Silicate Cement; D008277:Magnesium Oxide; C029881:Poly F cement; C040235:Ketac-cem; C040964:Ketac-Fil; D015034:Zinc Oxide