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Formation of Cementum
Dentin (A) lies along the right margin of the field, the periodontal region occupies the left side. Note the islands of epithelial cells (B) near the center of the field. These islands are called epithelial rests (of Malassez) and are remnants of the disintegrating epithelial root sheath (of Hertwig). As the epithelial root sheath breaks up, connective tissue of the dental follicle (sac) comes into contact with the dentin. In these regions multipotential cells of the dental follicle differentiate into cementoblasts (C) adjacent to the dentin. They deposit a ground substance around collagen fibers of fibroblast origin. The osteoid-like mixture of ground substance with collagen fibers is called cementoid. Mineralization converts cementoid to cementum.
Cementum (D) in this image contains several basophilic "resting" lines (E) that reflect periods when formation slows down or stops and then starts again. Resting lines are incremental lines formed by fiber-free ground substance. No cells are trapped in this cementum so it is classified as acellular cementum - the first type to be formed. It is also referred to as primary cementum.
Legend
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A - dentin |
D - cementum |
