Biomimetic Strategies for Subsurface Enamel Remineralization: Depth-Dependent Effects of Biomimetic Agents Compared with Fluoride

This study compared the remineralization potential of three commercially available fluoride-free biomimetic formulations containing nanohydroxyapatite (nHAp), casein phosphopeptide–amorphous calcium phosphate (CPP-ACP), and bioactive glass (BAG) with a conventional 1450 ppm fluoride-containing dentifrice using cross-sectional microhardness and SEM analyses. Seventy extracted human mandibular molars were randomly allocated to five groups (n = 14). Artificial carious lesions were created by 72 h of demineralization followed by a 14-day pH-cycling regimen with twice-daily treatment applications. Cross-sectional microhardness was measured at depths of 30, 50, 100, and 150 µm, and SEM was used to evaluate morphological changes. Data were analyzed using one-way ANOVA with appropriate post hoc tests (Tukey’s HSD or Tamhane’s T2, depending on variance homogeneity) and repeated-measures ANOVA to assess depth-dependent differences among groups (α = 0.05). Demineralization significantly reduced microhardness at all depths (p < 0.05). At 30 µm, the nHAp, CPP-ACP, and fluoride formulations showed similar remineralization, whereas the BAG-containing formulation exhibited lower superficial recovery. At 100–150 µm, the nHAp formulation demonstrated the greatest recovery, followed by the CPP-ACP and BAG formulations, while the fluoride dentifrice showed progressively lower recovery. A significant depth-by-group interaction confirmed distinct depth-dependent remineralization profiles. Within the limitations of this in vitro study, all tested formulations promoted enamel remineralization but exhibited different depth-dependent recovery patterns.