1996 年 16 巻 4 号 p. 337-344
The inner enamel of human permanent teeth has been reported to be divided into three zones : I, II, and III. In this study, we observed the inner enamel in the lingual side of deciduous incisor teeth with a scanning electron microscope. All transverse ground sections were treated with chromium sulfate. The about 10-μm-thick innermost enamel consisting of prism-like structures was deeply and almost entirely etched. This zone, which was similar to Zone I in permanent teeth, was suggested to contain a smaller amount of organic material and to show a lower calcification. The inner enamel except for the innermost zone may be divided into Zone II and III, because the prisms in the inner enamel adjacent to the innermost zone, about 30 to 40 μm in thickness, contained a larger amount of organic material than the outer-side inner enamel. However, the inner enamel can not be divided into two zones, when the outer-side inner enamel showing an arrangement of Pattern 3 prisms is contained in the middle enamel. Abnormal-shaped prisms were observed in the middle enamel as well as in the inner enamel. The lamella-like stalks of enamel tufts, insoluble with chromium sulfate, ran through the prism bodies surrounded by chromium sulfate-insoluble sheaths for a short or a longer distance towards the enamel surface and then ran together with the prism sheath regions. Many of the tuft stalks appeared discontinuously in the prisms, and some of them had fine branches within prisms. Discontinuous structures of the tuft stalks suggest that the lamella shows a fenestrated membrane.