Caementum

Caementum, a term often encountered in older anatomical literature, refers to the mineralized connective tissue that covers the tooth root. In modern usage the term cementum is preferred. It forms a thin but integral layer between dentin and the surrounding periodontal ligament, and it helps secure the tooth within the socket through collagen fibers of the ligament that insert into the cementum (Sharpey fibers).

Cementum can be classified by its cellularity and fiber content. Acellular extrinsic fiber cementum forms a thin, uniform layer at the cervical and middle portions of the root and contains bundled Sharpey fibers. Cellular intrinsic fiber cementum, which can appear in the apical regions, contains cementocytes within lacunae. A third form, cellular mixed stratified cementum, includes both intrinsic and extrinsic components. Cementum is periodontally derived, relatively avascular, and receives nutrients mainly from the periodontal ligament.

Formation begins with cementoblasts derived from the dental follicle or dental sac. These cells secrete an organic matrix that mineralizes to become cementum. Cementum continues to form slowly throughout life, particularly at the root apex, and cementocytes can become embedded within cellular cementum as development proceeds.

Function and clinical relevance include providing anchorage for the periodontal ligament, safeguarding the dentin of the root, and participating in reparative processes following root injury. Cementum is less prone to resorption than alveolar bone, but abnormalities such as hypercementosis (excessive cementum formation) or resorptive processes can occur. Calculus and biofilm can mineralize on cementum surfaces, contributing to dental disease if not managed.