High resolution electron microscopy in the dentino-enamel junction.

The direct crystal connection at the dentino-enamel junction was investigated using high resolution electron microscope. High resolution electron microscopy revealed that lattice fringes of dentine crystals entered into and directly contacted with those of enamel crystals. In such junction, intricate and irregular tilt boundaries were located in fusion levels. Dentine crystals were closely joined at the outermost dentine surface where fusions occurred. At the fusion level, dislocation appeared to form tilt boundaries. The tilt boundaries at the fusion levels in dentine crystals had more regular curvature than those at the dentino-enamel junction. These findings suggest that growth of dentine crystals brings direct connection with enamel crystals. Furthermore, it is suspected that dentino-enamel junction is weak in mechanical and/or chemical attacks.