Electron Microscopy of Enamel Caries

Abstract

4 successive zones are distinguished in the enamel caries cone through the electron microscopic observation from the outermost zone to the deep zone : 1) a zone of remarkable destruction, containing abundant bacteria and debris, 2) a zone of partial destruction which is poor of bacteria, 3) a zone of incomplete demineralization and finally, 4) a zone of apparently normal enamel.
Carious defects of apatite crystals are the first manifestation of carious destruction detected by electron microscopy. The zone of incomplete demineralization is thus formed. Even at this earliest stage of carious destruction, the dissolution of organic components seems to break out more or less with the subsequent appearance of crystal defects. At the more advanced stage, the appearance of bacterial invasion is brought about and the zone of incomplete demineralization changes into the zone of partial destruction poor of bacteria that is situated directly above the former. Bacterial invasion is not found in any special structures of the enamel but appears in the rod, rod sheath and interrod substance contemporaneously. Bacteria seem to destroy the enamel to a limited degree that they can invade there. Following this stage, bacteria remarkably increase altogether with the heavier progress of carious alterations, and frequent portions of the carious enamel are mostly filled with a large number of microorganisms. The enamel is most heavily destroyed and, at a glance, represents itself in the homogeneous state, in which enamel ruins are barely detected. At this stage, the zone of partial destruction which is poor of becteria turns into the zone of remarkable destruction containing rich bacteria and debris, located immediately above the former as the outermost zone of caries cone.