The physico-mechanical consequences of exposing glass ionomer cements to water during setting.

The effect of exposing glass ionomer cement to water during the first 48 hours after mixing was studied. The strength of the set cement was only reduced if exposure to water occurred within the first hour after mixing. The gel matrix formed during the setting reaction was shown to be the source of fluoride ions released when glass ionomer cement is placed in water. The degree of hydration, rate of fluoride release, and degree of cross-linking of the gel matrix were all shown to be affected by the water ingress during the setting reaction. Finally the fluoride release from the cements was found to cease within six months of exposure to water indicating that only fluoride ions released into the gel matrix during the setting reaction are available to protect surrounding tooth structure.