Biomimetic Enamel-like Crystals: A Versatile Platform for Unraveling the Basic Mechanisms of Demineralization and Remineralization.

Enamel is a cellular, nonregenerative, highly mineralized tissue essential for the mechanical durability and wear resistance of human teeth. Combating its degradation necessitates effective remineralization strategies, with hydroxyapatite (HAp) playing a central role in both natural and synthetic enamel restoration. Fluoride incorporation enhances HAp stability, forming fluoridated hydroxyapatite (FHAp), which is widely used to prevent or resist dental caries and improve remineralization. However, a mechanistic understanding of demineralization and remineralization remains incomplete due to the limitations of conventional ex situ techniques, which fail to capture real-time crystal dissolution and growth dynamics. In this study, we developed and applied a facile synthesis method for oriented FHAp nanocrystals under ambient pressure and at body temperature. This unlocks the possibility of direct in situ liquid imaging using atomic force microscopy (AFM) that serves as a platform for direct observation of demineralization and remineralization processes at the nanoscale. Investigation of the morphology, spectroscopy, and mechanical properties of nanocrystals grown in different conditions elucidated the effect of the substitution rate of fluorine through both in situ and ex situ studies. The findings presented offer a generic approach for understanding the re/demineralization mechanisms in enamel and demonstrate the potential for charting biomimetic enamel restoration pathways.