Early and long-term wear of 'fast-set' conventional glass-ionomer cements.

OBJECTIVE: Fast setting high viscous glass-ionomer cements have been introduced to reach the set state sooner and to improve early mechanical properties. The aim of this study was to investigate whether 'fast-set' cements have improved the early three-body wear. METHOD: The three-body wear of four glass-ionomer cements was measured after 1, 4, 7, 30, 90, and 365 days. The chemical composition of the cements was determined with EDAX. The particle size of the powders was determined with a Mastersizer 2000. RESULTS: The three-body wear of Fuji IX Fast was only slightly less than that of 'regular-set' Fuji IX, but Ketac Molar Quick showed a higher wear compared to the regular-set Ketac Molar. The wear rate of all four glass-ionomer cements decreased over a period of 1 year and could be described by second order reaction kinetics and depended on polyalkenoic acid content, chemical composition, and the size of the glass particles. SIGNIFICANCE: Based on the results of this laboratory study on long-term wear, the glass-ionomer cements investigated may compete with composites, but the early wear characteristics should be further improved. Furthermore, a better understanding of the wear and reaction behavior of glass-ionomer cements is obtained.

In situ transformation of glass-ionomer into an enamel-like material.

PURPOSE: To assess the nature of clinically detectable alterations in glass-ionomer after long-term clinical service. METHODS: In addition to clinical macro pictures, SEM was carried out on replicas and on two sectioned primary molars SEM-EDAX analysis was performed to determine chemical transformation in the glass-ionomer. Also with SEM-EDAX, the composition was determined of a partially removed half-year old sealant. RESULTS: The clinically observed altered optical aspect and increased hardness could be related with surface structure changes as identified by SEM. The changed glass-ionomer showed a continuous integration with the adjacent enamel. The SEM-EDAX analysis revealed an increase of calcium and phosphorus in the surface layer, tentatively suggesting a sort of additional "mineralization" of the material. This phenomenon was only observed for restorations that had minimally 2-3 years in vivo dwell time.

Mechanical properties of glass ionomer cements affected by curing methods.

OBJECTIVE: The primary objective of the study was to assess the influence of externally applied 'command' set applications on the mechanical properties of several commercially available conventional glass ionomer cement (GIC). METHODS: Four different restorative GICs cements (Fuji IX FAST, Fuji IX, Ketac Molar Quick, Ketac Molar) were cured using three different methods, e.g. standard curing conditions (SC), ultrasonic excitation (UC) and by an external heat source (HC). The compressive strength of these samples was measured and the groups were compared using one-way ANOVA. A standard thermocouple (K-type) measured the temperature in GIC during curing. RESULTS: In general all experiments showed an increase in strength going from SC, UC to HC. Especially, the compressive strength of Fuji IX FAST and Ketac Molar increased by UC and HC compared to the SC values. The compressive strength of Fuji IX FAST as a function of time showed an increase in strength during 28d. There was a clear relationship between the temperature in the sample (SC