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Cementum

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Dental Anatomy Dental Glossary

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Cementum

Cementum is a specialized, mineralized connective tissue that covers the outer surface of a tooth root, serving as the primary anchor point for fibers of the periodontal ligament. Unlike enamel, which coats the visible crown, cementum is confined to the root and is indispensable for securing the tooth within the alveolar bone.

Structure and Composition

Cementum is composed of roughly 45–50% inorganic mineral content — primarily hydroxyapatite — with the remainder consisting of organic matrix and water. Sharpey’s fibers from the periodontal ligament embed directly into its surface, creating a fibrous bridge between the root and surrounding bone. It is softer than both enamel and dentin, which makes it more susceptible to wear and resorption when exposed to the oral environment.

Two principal types are recognized:

  • Acellular (primary) cementum — Formed during tooth development, it lacks embedded cells and is found mainly in the coronal portion of the root, where it provides a stable attachment surface.
  • Cellular (secondary) cementum — Deposited after eruption, it contains living cementocytes and is concentrated in the apical third of the root, continuing to form throughout life.

Clinical Significance

Cementum is directly involved in several conditions that clinicians encounter regularly:

  • Periodontal disease — Bacterial toxins can infiltrate and degrade cementum, disrupting periodontal ligament attachment and contributing to progressive bone loss.
  • Root scaling and planing — Instrumentation targets contaminated cementum to create a biologically compatible root surface that supports tissue reattachment.
  • Cementum resorption — Excessive orthodontic force, trauma, or periapical pathology can trigger root resorption that is not always self-limiting.
  • Hypercementosis — Abnormal cementum thickening, associated with conditions such as Paget’s disease or chronic periapical inflammation, can complicate extractions.
  • Cementoenamel junction (CEJ) — The landmark where cementum meets enamel guides clinical attachment level measurements and periodontal charting.

Regenerative Potential

A key distinction from enamel is that cementum retains limited regenerative capacity. Cementoblasts remain active throughout life and can deposit new cementum in response to injury or physiological demand — a property that underpins periodontal regeneration procedures, which aim to stimulate simultaneous formation of new cementum, periodontal ligament, and alveolar bone on previously diseased root surfaces.

Maintaining cementum integrity through consistent oral hygiene, timely periodontal intervention, and careful clinical technique is foundational to long-term tooth retention and overall periodontal stability.