High resolution electron microscopy of mineral deposits at the human fissure floor.

The mineral deposits at the fissure floor was investigated using a high resolution electron microscope. Three different shapes of crystals were observed at the floor: the fine pavement-like, plate-like and large crystals. A direct contact between two different shapes of crystals was recognized in high resolution images. Selected area electron diffractions indicated that the fine crystals consisted of hydroxyapatite (OH-AP), the plate-like crystals were a mixture of OH-AP and whitlockite, and the large crystals were mainly whitlockite. These findings indicate that a natural occlusion at the fissure floor might occur through mineral deposition although contact boundaries of crystals had an intricate configuration.