Biogenic nanohydroxyapatite dentifrice for remineralization of erosively softened enamel: An in vitro comparative study of surface roughness and microhardness

Abstract Background: Dental erosion from frequent acidic beverage consumption increases enamel surface roughness and reduces hardness, predisposing teeth to wear and hypersensitivity. This in vitro study compared the remineralizing efficacy of biogenic nanohydroxyapatite (nHAp), herbal, fluoride, and casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) dentifrices on eroded enamel using surface roughness, microhardness, and scanning electron microscopy (SEM). Materials and Methods: Fifty extracted premolars with standardized 2 mm × 2 mm enamel windows were prepared. Baseline surface roughness (Ra) and Vickers microhardness (VHN) were recorded. Specimens underwent a 10-min daily erosive challenge in a carbonated beverage for 7 days, with intermittent storage in artificial saliva. Samples were randomized into five groups (n = 10): nHAp, herbal, fluoride, CPP-ACP, and saliva control. Treatment groups were brushed twice daily for 30 days using a standardized 2:1 toothpaste-to-saliva slurry; the control group remained in artificial saliva. Ra and VHN were reassessed posterosion and posttreatment. SEM evaluated surface morphology in two specimens per group. Data were analyzed using repeated-measures analysis of variance (ANOVA), one-way ANOVA, and the Kruskal–Wallis test (α = 0.05). Results: Erosion significantly elevated Ra and reduced VHN across all groups (P < 0.05). After 30 days, all treatment groups demonstrated improved roughness and hardness relative to the eroded state. The nHAp group recovered Ra and VHN to baseline levels, achieving significantly higher VHN than all other groups ( P = 0.001), with SEM confirming superior mineral surface coverage. Conclusion: Biogenic nHAp toothpaste demonstrated the greatest remineralization potential, providing superior surface smoothing, hardness recovery, and mineral deposition compared with herbal, fluoride, and CPP-ACP dentifrices.