Comparison of natural and artificial root caries lesions using microcomputed tomography and microhardness test.

Background: This study compared natural root caries lesions with artificial root caries lesions prepared with one of the two demineralising solutions.

Methods: Twelve natural root caries lesions on upper incisors and 24 artificial root lesions were prepared on sound root surfaces using 50 mM acetic acid, 1.5 mM CaCl , 0.9 mM KH PO at pH 5.0 or 80 mL/L Noverite K-702 polyacrylate solution, 500 mg/L hydroxyapatite, 0.1 mol/L lactic acid at pH 4.8 (n = 12/group) for 96 hours. Lesions were scanned using micro-CT. Inciso-gingival oriented images were analysed and mineral density calculated at 7.5 μm increments from the surface to 225-μm deep. Sectioned lesions were analysed by Knoop microhardness up to 250 μm from the lesion surface. Data were analysed by the Dunn's test with Bonferroni correction.

Results: Natural and artificial lesion mean mineral densities were not statistically different (P > 0.05). Mineral density from the surface to 75 μm was greater in natural lesions and from 150 to 225 μm was greater in artificial lesions (P < 0.05). Microhardness values were statistically higher in artificial lesions (P < 0.05); no difference was found among artificial lesions produced by the two solutions (P > 0.05). Mineral density and microhardness of natural and artificial root caries are different from each other. A greater mineralized surface layer existed on natural lesions.