Effect of Mechanical Loading and Simulated Aging on the Microleakage of Metal-Reinforced and Experimental Glass Ionomer Cements

Marginal microleakage is commonly used as an in vitro indicator of restorative materials' sealing performance, although it does not directly predict clinical longevity. Glass-ionomer cements (GICs) chemically interact with tooth mineral and are used where adhesion and fluoride release are advantageous. This study compared dye penetration around a metal-reinforced GIC (Hi-Dense) and an experimental high powder-to-liquid ratio GIC (EXPT), before and after mechanical load cycling. We received 80 freshly extracted, non-carious human molars, prepared Class II, and restored with one of the two GICs. For each material, specimens were allocated to an unloaded control or to load cycling intended to represent one day, one week, or one month. Specimens were coated with nail varnish except for a 1-mm perimeter around the restoration, immersed in 0.1% neutral red for 24 h at 37°C, sectioned, and examined at ×15 magnification. Dye penetration was scored separately at cervical and occlusal margins. Group comparisons were analysed using the Mann–Whitney test with a 95% confidence level. Dye penetration was generally limited, and no section received a score greater than 2. At the occlusal margin after one month of cycling, EXPT showed greater leakage than Hi-Dense (reported p ≤ 0.002). At cervical margins, EXPT showed greater penetration than Hi-Dense at the reported one-day (p ≤ 0.002) and one-month (p ≤ 0.03) loading periods. No significant material difference was reported in unloaded specimens. The authors reported no major overall influence of cycling duration on leakage patterns, although occlusal leakage in Hi-Dense was lower after the one-month condition. Under the conditions of this in vitro experiment, the metal-reinforced Hi-Dense material exhibited less dye penetration than EXPT at both margins, particularly under selected loading conditions. These findings support a comparative laboratory advantage for Hi-Dense, but clinical effectiveness cannot be inferred from dye penetration alone.