2008 年 28 巻 3 号 p. 150-154
Previously, a slit-shaped enamel defect had been observed in a premolar with enamel hypoplasia in the innermost enamel adjacent to the DEJ, where an abnormal step-shaped appearance was seen. In these observations, we happened to find the abnormal tubule- or elongated club-shaped defects in the ground enamel sections of 2 human permanent teeth containing an upper incisor and a third molar when observed the ground sections of 252 human teeth. The defects arose as the thicker club-edges from the innermost enamel adjacent to the dentin-enamel junction (DEJ) and the club-tips gradually thinner towards the enamel surfaces. The maximum length was about 500 μm and the thick club-edge defects were up to about 50 μm in width and contained minute granular deposits, which might be identified as whitlockite. The similar defects which showed many circular defects of the innermost enamel running along the DEJ were also observed in a third molar. Their enamel defects might be caused by the entire disappearance of the initially formed ameloblast groups or the partial break in the ameloblast activity during short or longer time of enamel formation.
