Surface Integrity of Widely Used Resin-Modified Glass Ionomers: New Findings Amid Limited Scientific Literature.

Abstract

Resin-modified glass ionomer cements are considered bioactive materials due to their sustained fluoride release, which has supported their continued use in clinical practice. Although some of these materials have been available on the market for many years and continue to be widely used in restorative dentistry, the scientific evidence regarding their mechanical properties remains limited and, in many cases, based on older or insufficiently updated studies. This situation highlights the need to generate new and updated scientific evidence to better understand the behavior of these materials under conditions that simulate long-term clinical use. The aim of this study was to evaluate and compare the surface microhardness of three resin-modified glass ionomer cements after an artificial aging process simulating two years of clinical use. Thirty-six discs (10 mm × 2 mm) were fabricated and distributed into three experimental groups (n = 12), corresponding to three commercial resin-modified glass ionomer cements: Gold Label 2 LC, Riva LC, and Vitremer. All specimens were prepared strictly according to the manufacturers' instructions. Surface microhardness was evaluated using the Vickers method with a calibrated microhardness tester, performing three indentations per specimen. Measurements were carried out at three experimental time points: baseline, after 10,000 cycles, and after 20,000 thermocycles. Data were analyzed using descriptive statistics, analysis of variance, and a linear mixed-effects model, considering a significance level of = 0.05. All evaluated materials showed a progressive decrease in surface microhardness after artificial aging. Statistically significant differences were observed among the resin-modified glass ionomer cements (p < 0.05). Gold Label 2 LC exhibited the highest surface microhardness values and the greatest stability throughout the aging process, followed by Riva LC, whereas Vitremer showed the lowest microhardness values after aging. After artificial aging, all resin-modified glass ionomer cements showed a progressive decrease in surface microhardness. Gold Label 2 LC exhibited the highest stability, followed by Riva LC, whereas Vitremer showed the least favorable performance.