Overview

Cementum is a specialized, calcified connective tissue that covers the root portion of a tooth. It is distinct from enamel and is not present on the crown above the gum line; see crown (above the gums). Cementum helps form and maintain the tooth’s attachment apparatus by providing a surface for periodontal ligament fibers to insert.

Structure and types

Microscopically, cementum is less hard than enamel or dentine and contains mineralized matrix produced by cementoblasts. Two broad categories are commonly described: acellular cementum, which contains few or no living cells and is important for fiber attachment, and cellular cementum, which contains cementocytes embedded in lacunae and is often found near the root apex. Variants such as mixed or stratified cementum reflect combinations of these basic types.

Development and origin

Cementum forms after the tooth crown has developed. Cells of the surrounding dental follicle differentiate into cementoblasts that secrete the extracellular matrix which later mineralizes. Cementum continues to be deposited in small amounts throughout life, contributing to repair processes and subtle changes in root contour with age.

Function and clinical importance

  • Attachment: Cementum anchors periodontal ligament fibers that connect the tooth to the alveolar bone, transmitting forces during chewing and stabilizing the tooth. See connection to the periodontal ligament.
  • Protection and repair: It covers and protects root dentine and can participate in limited repair after minor resorption or injury.
  • Clinical relevance: Cemental defects or loss are associated with root sensitivity, periodontal disease, and difficulties in achieving periodontal regeneration.

Clinical issues and notable distinctions

Unlike enamel, cementum is avascular and receives nutrients from the adjacent periodontal tissues. Pathologic conditions include hypercementosis (excess cementum formation), root resorption, and localized defects that expose dentine and cause sensitivity. In dental treatment and surgery, preserving or regenerating cementum is important for re-establishing a healthy attachment to either the maxilla or the mandible. Though thin, cementum plays a key role in the long-term stability and function of teeth.