Human tooth development the formation of odontoblasts continue from the tips of the cusps, the odontoblasts secrete a substance, an organic matrix, into their immediate surrounding. The organic matrix contains the material needed for dentin formation. As odontoblasts deposit organic matrix termed predentin, they migrate toward the center of the dental papilla. Thus, unlike enamel, dentin starts forming in the surface closest to the outside of the tooth and proceeds inward. Cytoplasmic extensions are left behind as the odontoblasts move inward. The unique, tubular microscopic appearance of dentin is a result of the formation of dentin around these extensions. After dentin formation begins,
Human tooth ligaments include osteoblasts, osteoclasts, fibroblasts, macrophages, cementoblasts, and epithelial cell rests of Malassez. Consisting of mostly Type I and III collagen, the fibers are grouped in bundles and named according to their location. The groups of fibers are named alveolar crest, horizontal, oblique, periapical, and interradicular fibers. The nerve supply generally enters from the bone apical to the tooth and forms a network around the tooth toward the crest of the gingiva. When pressure is exerted on a tooth, such as during chewing or biting, the tooth moves slightly in its socket and puts tension on the periodontal ligaments. The