High-Resolution Electron Microscopy of Mineral Deposits on a Thin Layer of Pellicle Adhering to Intact Enamel Surface

Human third molars were used to investigate the ultrastructure of mineral deposits formed over an enamel surface. A small amount of mineral deposits were observed on a thin pellicle containing a few bacteria. High-resolution transmission electron microscopy (HRTEM) and selected-area electron diffraction (SAED) revealed that plate-like crystals were composed of whitlockite and amorphous deposits consisted of an aggregation of fine hydroxyapatite (OH-AP) crystallites. These findings indicate that the present observed deposits are on a free-floating condition without relation to the enamel surface, and that whitlockite and OH-AP can exist independently and stably in vivo.