This research investigated, under in vitro conditions, the protective capability of two enamel-repairing formulations: a varnish composed of β-tricalcium phosphate combined with sodium fluoride (β-TCP-F), and a paste containing casein phosphopeptide–amorphous calcium phosphate supplemented with sodium fluoride (CPP-ACP-F). Enamel samples (n = 120) obtained from extracted human third molars were divided into four experimental sets (30 specimens per group): Group I—sound enamel (control), Group II—artificially demineralized enamel, Group III—demineralized enamel treated with β-TCP-F, and Group IV—demineralized enamel treated with CPP-ACP-F. For 15 consecutive days, Groups II–IV underwent daily pH cycling consisting of 21 h in a demineralizing medium (pH 4.4) and 3 h in a remineralizing medium (pH 7.0). Before each cycle, the treated groups received their respective materials. Fluoride ion release was recorded after every cycle. Surface hardness, surface roughness, contact angle, and Streptococcus mutans biofilm accumulation were determined on days 5, 10, and 15. CPP-ACP-F application resulted in a greater increase in surface microhardness (515.2 ± 10.7) compared to β-TCP-F (473.6 ± 12.8). Both agents lowered surface irregularity relative to untreated demineralized enamel; however, after 15 days, β-TCP-F-treated samples retained a roughness of 1.193 μm—still significantly higher than intact enamel—whereas CPP-ACP-F-treated enamel achieved 0.76 μm, matching that of healthy enamel. Contact angle analysis showed enhanced wettability in both experimental groups (β-TCP-F: 71.01°, CPP-ACP-F: 65.24°), approaching or slightly surpassing that of normal enamel. Both β-TCP-F and CPP-ACP-F demonstrated remineralizing and protective potential against enamel demineralization. Nevertheless, CPP-ACP-F provided superior recovery of hardness and smoother surfaces under controlled in vitro conditions. These materials effectively prevented the detrimental surface changes caused by acid challenge on human enamel.
