Effect of Ultrasonic Excitation on the Microtensile Bond Strength of Glass Ionomer Cements to Dentin After Different Water Storage Times

The application of ultrasound waves on glass ionomer cement (GIC) surface can accelerate the early setting reaction and improve the mechanical properties of the material, resulting in higher resistance to masticatory forces within a short period of time and thus increasing the clinical longevity of the GIC restoration. In this study, the microtensile bond strength (μTBS) of two high-viscosity GICs (Fuji IX GP and Ketac Molar Easymix) and one resin-modified GIC (RMGIC-Vitremer) to dentin was tested after ultrasonic excitation and water storage. GIC blocks were built up on coronal dentin either receiving or not receiving a 30-s ultrasound application during the material initial setting. After storage in water for either 24 h or 30 d, beam-shaped specimens with a cross-sectional area of approximately 1.0 mm2 were cut perpendicular to GIC/dentin interface and tested to failure. At 24 h, the ultrasonically set Ketac Molar had significantly higher (p < 0.05) μTBS than the cement set conventionally. Chemically set Ketac Molar presented significantly higher μTBS after the longer water storage (p < 0.05). The RMGIC presented the highest μTBS regardless of ultrasonic excitation and storage period. In conclusion, ultrasound application to Ketac Molar improved its adhesion to dentin, particularly within the first 24 h after setting. Clinically, it seems that ultrasonic excitation can contribute to prevent retention loss of restoration at early stages of GIC setting reaction.