Remineralization of Artificial and Natural Carious Dentin Lesions

Remineralization of carious dentin should lead to a recovery of the mechanical properties of the tissue. Objective: To measure changes in hydrated mechanical properties due to remineralization of artificial and natural carious dentin lesions. Methods: Artificial and natural carious dentin lesions were studied. Artificial lesions were prepared in polished dentin slabs from non-carious third molars by immersion in 0.05M acetate buffer with 2.2 mM Ca²⁺/PO₄^3- at pH 5.0 for 8 hours. Carious lesions with large demineralized zones were also studied. Occlusal carious surfaces (n=3) were characterized by AFM based nanoindentation to obtain elastic moduli (E) at baseline and 7 time points between 1 and 28 days of remineralization. Artificial lesions (n=3 per solution) were placed in one of 6 supersaturated metastable remineralizing solutions. The solutions contained either 2.2 or 1.5 mM Ca²⁺, 1.45 or 0.9 PO₄^3- with 150 mM KCl. In addition 22 mM CO₃^2- (pH 5.5-8.5) were added; and the effect of fluoride was studied. Natural lesions were immersed in the solution that showed the best results on artificial lesions. Results: For the artificial lesions, in the groups without fluoride, the hydrated E increased from below 0.2 GPa to about 3 GPa. Solutions that contained 2 ppm fluoride resulted in remineralized dentin with significantly increased moduli of up to 13 GPa. For the natural carious dentin lesions, hydrated E increased to only 2.9 GPa. Conclusions: Both artificial and natural carious dentin lesions had hydrated mechanical properties partially restored and the addition of fluoride enhanced this effect. Artificial lesions regained more of the mechanical properties lost due to demineralization. Additional study is needed to determine differences between the artificial and natural lesions. Supported by NIH/NIDCR Grant R01-DE16849.