Long-Term Water Balance Evaluation in Glass Ionomer Restorative Materials

Abstract

The complex role of water in glass ionomer cement (polyalkenoate) dental restorative materials has been studied, but much of the present understanding concerning water balance within these materials is based on very early studies and short-term experiments. This study evaluated the nature of the water species of six conventional and four resin modified glass ionomer restorative materials over 3 years using thermogravimetric analysis techniques. Materials were prepared, placed in crucibles, and stored in physiologic phosphate buffered saline and evaluated at 24 h, 1 week, and then at 1, 3, 6, 9, 12, 18, 24, 30 and 36 months. All materials demonstrated a significant increase in unbound water percentage content but except for the resin modified materials, the enthalpy required to remove the unbound water species did not significantly change over 36 months. Also, bound water content percentage and removal enthalpy was established at 24 h, as no significant increase was noted in both bound water content and removal enthalpy over the course of this evaluation. This study suggests that unbound water species may increase with time and is loosely held except for the resin modified materials. Protective coatings placement and re-evaluation are prudent to prevent unbound water loss.

In vitro Study on Water Absorption of Dental Restorative Materials

“…In vitro studies have shown that glass ionomer cements absorb more water than compo-sites [40]. Resin-modified glass ionomer cements showed higher water absorption than conventional glass ionomer cements due to the hydrophilicity of 2-hydroxyethyl methacrylate (HEMA) [CH₂=C(CH₃)COOCH₂CH₂OH] [41][42][43][44][45][46]. Fillers made of glass ionomers need to be covered with a protective varnish, as indicated by each manufacturer to prevent water absorption in the obturation and subsequently its degradation in the first hours after curing [47][48][49][50][51][52].…”

The influence of hydrothermal fatigue on the clinically relevant functional properties of conventional glass-ionomer cements

“…In the polyacid-salt matrix of the GIC kit, water exists in two forms: free water particles, which can be removed from the matrix by drying, and bound water particles, which are chemically locked in the matrix 80 . Since water plays an important role during cement maturation and ion diffusion 4 , properties of GICs are susceptible to both water uptake, as well as dehydration 81 , 82 .…”

“…For some GICs, with aging, the porosity of the material changes 83 , and the volume fraction of the bound water 83 . However, it was presented that GICs tend to increase the content of unbound water in time 80 . While we observed a great contrast in mechanical and tribological performance between the three tested GICs (Figs.…”

Evaluation of Abfraction Lesions Restored with Three Dental Materials: A Comparative Study

“…Light activation of conventional glass ionomer cements (GICs) permits the formation of supplemental cross-links [34]. The disadvantages include great polymerization contraction and cytotoxicity [35,36]. After Faridi et al [37], the strength of the GICs was raised for the encapsulated form when compared to the manually mixed form.…”