Time-Dependent Adhesion and Fluoride Release of Resin-Modified Glass Ionomer Cements on Demineralized Enamel, Sound Enamel and Dentine

<b>Background:</b> The treatment of cavitated lesions has evolved with minimally invasive dentistry (MID), whereby we can leave demineralized enamel that could potentially be remineralizable with the use of materials such as resin-modified glass ionomer cements (RMGICs) that allow these lesions to be repaired and remineralized while removing less tooth tissue. The aim of our study was to compare the influence of aging on adhesion to sound enamel, demineralized enamel, and the healthy dentin of five RMGICs (Vitremer^®, ACTIVA BioACTIVE Restorative, Riva LC, Ionolux^®, and GC Fuji II LC) and fluoride release. There are currently no studies on adhesion in demineralized enamel. <b>Method</b>: A total of 1035 bovine incisors were analyzed in 45 groups of 23 teeth each. The groups were established based on three factors: time (24 h, 1 month, and 3 months); substrate (sound enamel, demineralized enamel, and healthy dentin); and type of material. In each group, 20 samples underwent shear bond strength (SBS) and fracture type analysis. Adhesive interfaces were observed in three samples from each group using field emission scanning electron microscopy (FESEM). Daily and cumulative fluoride release rates were calculated. <b>Results</b>: Adhesion improved over time on both demineralized and sound enamel. ACTIVA BioACTIVE Restorative had the highest SBS values (33.63 ± 10.69 MPa), and Vitremer^® had the lowest (4.10 ± 4.63). Most fractures were adhesive. Vitremer^® and Ionolux^® showed the highest daily and cumulative fluoride release rates (Vitremer daily (24 h): 225.30 ± 26.28 ppm/g; Vitremer cumulative (30 days): 635.99 ± 305.38 ppm/g; Ionolux daily (24 h): 207.59 ± 48.43 ppm/g; Ionolux cumulative (30 days): 501.21 ± 138.71 ppm/g) and ACTIVA BioACTIVE Restorative showed the lowest (ACTIVA daily (24 h): 10.50 ± 0.85; ACTIVA cumulative (30 days): 39.10 ± 2.16). <b>Conclusions</b>: ACTIVA BioACTIVE Restorative was the material with the best adhesion values on all substrates and at all times, but it showed the lowest fluoride release rates.