Abstract
The aim of this study was to evaluate the compressive strength of resin-modified glass ionomer cement Fuji II LC and Vitremer, in powder/liquid ratios of 1:1, 1:2 and 1:3, at three periods (24 hours, 7 and 28 days) of storage in distilled water at 37ºC. For each material, P/L ratio and storage time, 5 cylindrical specimens were prepared, with 4mm diameter and 6mm height, in silicon moulds. Specimens were light-cured for 40 seconds at each extremity, removed from the moulds and laterally light-cured (perpendicular to long axis) for 40 seconds, protected as recommended by the manufacturers and immersed for the time tested. The specimens were submitted to compressive strength testing in an Instron machine at a crosshead speed of 1.0mm/min until failure. Data were submitted to ANOVA and Tukey's test (5%), and showed that the compressive strength of resin-modified glass ionomer cement was reduced when P/L ratio was reduced and that the storage in water had little influence on compressive strength.
Highlights
Mechanical properties of glass ionomer cements have been investigated since their development, and concerns have remained even after the development of resin-modified versions
Retention of glass ionomer cement pit and fissure sealants seems to be related to adhesion to enamel and the mechanical strength of the material[24,26], which is lower when fluoride release is higher[29]
No statistically significant difference in compressive strength was observed between the storage times for all P/L ratios studied (p>0.05)
Summary
Mechanical properties of glass ionomer cements have been investigated since their development, and concerns have remained even after the development of resin-modified versions. The powder/liquid ratio is reduced to improve flow properties[10,14,19,20] and results in higher solubility[23], compromising the durability of the fragments that remain in the fissure, responsible for protection of the occlusal surface[16]. For this reason, improvement of retention rates is desirable to avoid caries development on occlusal surfaces for extended periods
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