Scanning electron microscopic observations were carried out on the fractured etched and unetched surfaces of the dentin of non-attrited third molars and moderaely attrited first and second molars. In the dentin of non-attrited molars, increased solubility of the peritubular but not of the intertubular detnin was demonstrated. However, as the result of the deminerlization a tubular structure was not seen. The tubular structure appeared in many of the dentinal tubules in portions other than close to the pulp cavity in attrited molars. In the dentin of attrited molars, the peritubular zone around the tubular structure was completely dissolved. While the external wall of the tubular structure was rather smooth, the internal surface appeared granular. Based on these observations the etching effect on the peritubular zone was found to be different in non-attrited and attrited molars. The tubular structure seen in the molar with attrition is apparently related to the aging reaction of the dentinal tubules, and its appearance is influenced by the important action of the reprecipitation of the crystal dissolved at the time of etching.
Dental hard tissues have been studied by the use of the scanning electron microscope, but Tomes' fibers which occupy the dentinal tubules have not yet been observed in detail. In the present study, the scanning electron microscope shows Tomes' fibers very clearly.