Further study of mineral deposits at the occlusal fissure of human enamel.

The large mineral deposits at the macroscopically occluded fissure was investigated using a high-resolution electron microscope. The large polygonal crystals at the bottom third of the fissure consisting of single crystals were mainly whitlockite. The contact between the large crystals was formed in some interfaces where the incoherent tilt boundary was formed. The plate-like crystals at the middle third of the fissure corresponded with whitlockite and consisted of the aggregation of small crystallites positioned in different directions at the appositional levels, where the lattice fringes were distorted. These findings suggested that two types of large crystals provide a structure which is favorable for natural occlusion to occur at the intact fissure.