The recent use in biology of the Scanning Electron Microscope allows a new vision of the sample, completing the previous ones: the Optical Microscope (OM) and the Conventional Electron Microscope--CEM. The object is observed in space, in a direct way and, due to a system of variable sizes, the passage from a general image to the detailed tissue and cell study is permitted. The outer enamel surface with its perikymaties, its flaws and its changes caused by usage as well as by the internal enamel structure on the fractured area have been studied. On the occlusal surface of the decayed teeth, focal holes have been found; they resulted probably from creation disturbances due to some amelogenetic disorders that damage the ameloblast, matrix creation or its mineralization. These lacunar flaws are the favourite zones for the microbe plate accumulation and propitious to carious lesions initiation. The same clinical aspect, of profound enamel creation defects with an anfractuous crevass network aspect, having a variable expansion and depth, can be found in microscope with some healthy teeth. Regrouping in fascicles of the different prism directions can be found after structural analysis of the prismatic morphology of the parodontotic tooth enamel. An aspect of a more compact structure is thus obtained sectionally. This explains partially the increased resistance to decay of these teeth. In a comparative study of the fractioned area of some decayed and ruined temporary teeth, significant differences in prism arrangement can be found. The decayed teeth show expansions of the intraprismatic spaces, accusing reduced resistance against decay attack.