[Observation on structural features and characteristics of occlusal fissures and pits in human permanent molars].

In a series of studies to investigate the structural features and the characteristics of the tooth, a detailed observation was made on the enamel surface and the enamel composing the fissure and pit of the freshly extracted human permanent molars, using scanning electron microscopy and transmission electron microscopy. The materials employed in this observation were taken from the noncarious surface of molars. The following results were obtained: The hypocalcified zone was observed more or less in the enamel composing the fissure and pit. In many cases, the dental cuticle can be seen on the enamel surface. A rodless enamel was present, in greater or lesser degree, in the enamel surface layer. Retzius's line was observed clearly in the enamel composing the fissure and pit. In many cases, perikyamata was found on the enamel surface. In some cases, tubular pits invaginated secondarily from the fissure and pit were observed. In some, a dental calculus can be observed in the fissure and pit. By the observation of the inner structure of the dental calculus, mineralization occurred around and within the bacteria and in the interbacterial matrix composing the dental caluculus. Bacteria of the same degree of calcification appear in the microcolonies.