Cementum

Hard tissue covering the tooth root

Basic anatomy of a tooth, showing the location of cementum.

Diagram of a human tooth, illustrating the layers including cementum.

Diagram of the periodontium, highlighting the role of cementum.

Cementum is a specialized calcified substance covering the root of a tooth. It is part of the periodontium, which also includes the gingiva, periodontal ligament, and alveolar bone. Cementum plays a crucial role in tooth support and stability by anchoring the periodontal ligament fibers to the tooth.

Structure

Cementum is a mineralized tissue similar to bone but is avascular, meaning it lacks blood vessels. It is composed primarily of hydroxyapatite, collagen fibers, and water. Cementum is classified into two types based on the presence of cells:

• Acellular cementum: This type covers the cervical two-thirds of the root and is primarily responsible for anchoring the tooth in the socket. It does not contain cells within its structure.
• Cellular cementum: Found mainly in the apical third of the root, this type contains cementocytes within lacunae. It is involved in the adaptive and reparative processes of the tooth.

Function

Cementum serves several important functions:

• Attachment: It provides a medium for the attachment of the periodontal ligament fibers, which connect the tooth to the alveolar bone.
• Protection: Cementum protects the root dentin from resorption and external stimuli.
• Repair: It plays a role in the repair of root surfaces following damage or resorption.

Development

Cementum formation begins during tooth development, after the formation of the root dentin. The process is initiated by the Hertwig's epithelial root sheath, which induces the differentiation of dental follicle cells into cementoblasts. These cementoblasts secrete the organic matrix of cementum, which subsequently mineralizes.

Clinical Significance

Cementum is essential for maintaining tooth stability and health. Loss or damage to cementum can lead to tooth mobility and periodontal disease. Conditions such as cemental tears and hypercementosis can affect the integrity of cementum and require clinical attention.

Also see

• Periodontal ligament
• Alveolar bone
• Dentin
• Enamel
• Periodontal disease