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White enamel patches on approximal surfaces of human teeth were examined with a scanning electron microscope following the removal of plaque. The affected areas disclosed a honeycomb-like structure constructed of enamel prisms, the cores of which were preferentially dissolved. The defects resembled those due to acid decalcification. [ABSTRACT FROM AUTHOR]

The pressure side of human premolars subjected to experimental movement for 5-76 d were studied in the scanning electron microscope. Sham-operated and untreated premolars were used as controls. In order to study the morphology and occurrence of root resorptions, the organic tissue was removed using 1:2 diamino ethane or sodium hypochlorite and the denuded root surfaces were re-examined in the scanning electron microscope. Areas of compressed soft tissue were regularly present and the size, shape and number of such zones varied in the experimental groups. Initially, tissue affected by pressure was mainly located in the marginal region and subsequently the mid-portion of the roots became generally influenced. Removal of hyalinized tissue started shortly after the formation, and during this soft tissue removal the underlying hard tissue was resorbed. Observation of circumferentially removed, coalesced fibers corresponded with the finding of extensively resorbed lacunae in the mineralized tissue beneath. The resorptive processes of the cementum began after 10 d as round cavities measuring about 6 μm. Further resorption in cementum was characterized by numerous small, thin-walled round lacunae which confluenced into extensive, shallow resorptions after 20 d. Dentin was distinguished by the presence of tubules, and in sites of active resorption removal of mineral crystals had occurred, exhibiting a latticed fiber arrangement. [ABSTRACT FROM AUTHOR]

Sound, demineralized adult guinea pig dentin was observed by means of the scanning electron microscope. The dentinal tubules were fairly regular, some of them containing odontoblastic processes (Tomes fibers). These fibers were smooth surfaced, branching and much smaller than the surrounding tubules. Their small diameters were probably caused by the preparation procedures. The inner tubular walls were rough, probably because of interlacing collagen fibrils. The peritubular dentin was relatively compact and composed of a considerable amount of cross-striated fibrils. Similar fibrils were found in the intertubular zones where they were arranged in fiber-bundles giving the intertubular zones a honeycombed or sponge like appearance. Such a distinct honeycombed appearance was not found in transmission electron microscope studies of dentin. This discrepancy is possibly due to differences in tissue preparation. The relatively poor development of peritubular dentin compared with intertubular dentin is in agreement with other studies in animals with continued tooth growth. [ABSTRACT FROM AUTHOR]