Abstract
The forming enamel surfaces of deciduous molar teeth germs of human fetuses aged from 7 to 9 months were observed by a scanning electron microscopy.
Smooth calcified surfaces and circle-like pits of various diameter (3-5 μm) were seen at the cervical area of the enamel.
The shapes of the pits were divided into three types at the area between the cuspal summit and the cervical area of the enamel. These are; Type I: hexagonal shape (diameter: 5-6 μm), Type II: longitudinal spindle shape (major axis: about 6 μm, minor axis: about 4μm), Type III: mixed type of ovoid, spindle, and rod shape etc.(major axis: 2-6 μm, minor axis: 1-5 μm). Furthermore, a relationship between the arrangement and the shape of these pits was established. The arrangement pattern of the hexagonal and the spindle pits were respectively type HI and type II as described by Boyde, and the irregular pattern was observed in the mixed type. Longitudinal partition (l. p.) which bounded the right and the left pits was well developed but transverse partition (t. p.) which bounded superior and inferior pits did not form well. The concave surface of a pit was composed of two faces, a flat surface (S face) which formed an enamel rod and a curved surface (N face) at which Tomes' process slided.
These two faces were cuspally and cervically directed respectively.
There were few shallow grooves at the cuspal summit area. The pits composing them assumed ellipsoidal shape and had relatively large diameters (6-7μm). The cavity of pit was shallow because of improper development of l.p. and t.p. Consequently, it was not easy to distinguish S from N face.
The relationship between the morphology of enamel surface and the enamel formation was explained based upon these findings.
