One goal of modern dentistry is early intervention against dental caries to preserve enamel hydroxyapatite (HAP) crystals. An alternate soaking process using aqueous calcium (Ca) and phosphate (PO₄³⁻) solutions has been developed to form HAP on bone. However, its effect on enamel subsurface lesions has not been investigated. Therefore, this study evaluated the remineralisation potential of an alternate soaking treatment using calcium and phosphate solutions on enamel lesions in vitro.
Bovine enamel slabs (n = 64) with subsurface artificial lesions were randomly allocated into four groups: (1) Alternate soaking with CaCl₂ and Na₂HPO₄; (2) Toothpaste slurry (1450 ppm F); (3) Artificial day-time saliva (positive control); and (4) Tris-HCl (negative control). Treatments were applied twice daily for 6 minutes, and slabs were stored in artificial night-time saliva at 37 °C. After 21 days, lesions were assessed using Quantitative Light-induced Fluorescence (QLF), Micro-Computed Tomography (Micro-CT), and Energy-Dispersive X-ray spectroscopy (EDX). Data were analysed using SPSS version 29, with significance set at p < 0.05.
Significant reductions in lesion depth (ΔF) were observed for the alternate soaking process, toothpaste slurry, and day-time artificial saliva (Diff ± SE: 2.69 ± 1.09%, 4.57 ± 0.86%, and 0.69 ± 0.12%, respectively; p < 0.05). ΔF, lesion volume (ΔQ), and area indicated significantly greater remineralisation for the alternate soaking process and toothpaste slurry compared with other groups (p < 0.05). The results of micro-CT showed an increase in mineralisation in Ca/P, 1450 ppm F, and day-time artificial saliva (Diff ± SE) (2.00 ± 0.10; 2.30 ± 0.17; 0.90 ± 0.26, respectively) compared to Tris-HCL which showed no statistical significance. EDX confirmed increased mineral content, with statistical significance observed only for the Ca/P and toothpaste slurry (1450 ppm F) groups (p < 0.05).
