Abstract
The arrangement of the matrix fiber, the fiber component and the crystal deposition of the secondary cementum in the human incisor and premolar were studied by light microscopy and electron microscopy.
The results are as follows:
1 . Between the incremental lines in the secondary cementum, there are observed many fine lamellar structures (cementum lamellae) which are parallel to the incremental lines and the mean diameter of the lamellae is about 2. 5. μm.
2. The collagen fibrils, which compose the principal fiber of the cementum lamella form fibril bundles, and the mean diameter of these fibril bundles is about 0. 3. 0. 7. μm. The mean diameter of each collagen fibril is about 90. Em.
3. There are observed bundles of collagen fibrils which are arranged in parallel in the direction which cross the principal fibers composing the cementum lamella almost at a right angle cross fibers) .
4. Fundamentally, the cross fibers are arranged in the direction which cross the cementum lamella almost at a right angle and as a whole it may be considered that the cross fibers run in the direction inward and outward of the cementum.
5. With the collagen fibrils in which the crystals are deposited quite densely, it seems that the changes in the structure of the collagen fibrils due to the crystal deposition are remarked compared to the collagen fibrils with less deposition of crystals.
