Influence of Nanocoats on the Physicomechanical Properties and Microleakage of Bulk-fill and Resin-modified Glass Ionomer Cements: An In Vitro Study

Abstract

To analyze the impact of two nanocoating materials, EQUIA Forte nanocoat and universal adhesive, on flexural strength, color changes, surface roughness, and microleakage of bulk-fill and resin-modified glass ionomer cements (RM-GICs). A total of 45 specimens were prepared for each group, bulk-fill (EQUIA Forte Fil) and RM-GI (Fuji II LC) cements, according to manufacturer's instructions for flexural strength, color change, and surface roughness tests. Each group was equally subdivided into three subgroups according to coating materials used; either without a coat (negative control) or covered with EQUIA Forte coat or universal adhesive. For the flexural strength test, 15 bar-shaped specimens were prepared using a rectangular-split Teflon mold (25 × 2 × 2 mm), then the test was conducted using a universal testing machine. Thirty disk-shaped specimens were prepared for color change and surface roughness tests using cylindrical-split Teflon mold (10 mm diameter and 2 mm height). The color change was measured using a spectrophotometer after immersion in tea infusion for seven days at room temperature. Surface roughness was examined using a profilometer after exposure to 2400 brushing cycles. Moreover, a microleakage test was conducted in 30 teeth restored with the same restorative protocols and evaluated using a stereomicroscope. Finally, the data were statistically analyzed. EQUIA Forte nanocoat subgroups exhibited the highest flexural strength in both tested GICs compared to other subgroups (91.07 ± 7.12 MPa for RM-GIC and 51.61 ± 4.42 MPa for bulk-fill GIC). For the color change, the lowest ΔE values for bulk-fill and RM-GICs were recorded in EQUIA Forte nanocoat subgroups (2.37 ± 0.25 and 2.97 ± 0.39, respectively) with no significant difference between both groups. The surface roughness of both GICs was significantly decreased in the coated subgroups either with EQUIA Forte coat or universal adhesive, with no significant difference between both coating agents. Also, microleakage was significantly decreased in the coated subgroups with no significant difference between the coating materials. Nanocoats, especially the EQUIA Forte nanocoat, positively impact the physicomechanical properties and adaptation of bulk-fill GICs and RM-GICs. The application of nanocoats on GI restorations is highly recommended.