Effects of Remineralizing Products Containing NaF, CPP-ACPF, and NovaMin on Enamel Microhardness and Bond Strength

This in vitro study evaluated the effects of remineralizing products on enamel microhardness and the shear bond strength (SBS) of composite resin to enamel. A total of 110 human premolars were allocated to five groups, with 100 teeth allocated for microhardness and SBS testing (n = 20 per group) and 10 for scanning electron microscopy (SEM; n = 2 per group). The groups were sound enamel, demineralized enamel, casein phosphopeptide–amorphous calcium phosphate with fluoride (CPP-ACPF), 5% sodium fluoride (NaF), and NovaMin. Enamel demineralization was induced using 0.5% citric acid twice daily for three days. NaF varnish was applied once for 5 min, whereas CPP-ACPF- and NovaMin-containing products were applied twice daily for seven days. Composite bonding was performed using Clearfil S3 Bond Universal. Enamel microhardness, SBS, and failure modes were assessed using Vickers hardness testing, a universal testing machine, and stereomicroscopy, respectively. Demineralized enamel exhibited the lowest microhardness (202.61 ± 15.77 VHN) and SBS (11.81 ± 3.69 MPa). All remineralizing products significantly increased both parameters compared with demineralized enamel (p < 0.05). However, microhardness remained significantly lower than that of sound enamel (p < 0.001). SBS in the NaF group did not differ significantly from that of sound enamel (p = 0.175), whereas the CPP-ACPF and NovaMin groups exhibited significantly lower values (p < 0.05). No significant SBS differences were observed among the remineralizing product groups (p > 0.05). Adhesive failure was most frequent in the demineralized enamel group (50%), although the overall distribution of failure modes did not differ significantly among the groups (p > 0.05). The tested remineralizing products improved enamel microhardness and immediate composite bond strength compared with demineralized enamel, without significant differences in SBS among the products.