What is Cementum in Teeth? With Classification

When we think about the mouth and its different parts, teeth, tongue, and jaw are what come to mind. But there are several other parts of a mouth, which play an essential role too. One of these parts is the cementum. It is a connective tissue that forms along a tooth’s root and helps solidify it by connecting to fibers that support the tooth’s place in the jawbone.

In some mammals, such as herbivores, cementum may extend over the crown of the tooth. However, in humans, Cementum only surrounds the root of the tooth. In this article, we will get to know more about cementum in detail and its role in the oral cavity.


What is cementum?

Cementum is a bone-like mineralized tissue lining the dentin of the root that protects the root and also serves as an attachment surface to anchor the periodontal ligament to the tooth. It is light yellow in appearance. It is thinner near the tooth neck (about 20-50 microns) and thicker at the root apex (about 150-200 microns). Cementum is very similar to bone but has no blood or nerve supply. Also, cementum moves with the movement of the tooth. (1)

tooth anatomy with labels

Classification of cementum

Cementum may be classified in the following ways –

By location-

  • Radicular cementum – the cementum that is formed on the root surface.
  • Coronal cementum – the cementum that forms on the enamel covering the crown.

By cellularity-

  • Cellular cementum – cementum containing cementocytes in lacunae within the cementum matrix.
  • Acellular cementum – cementum without any cells in its matrix.

By the presence of collagen fibrils in the matrix-

  • Fibrillar cementum – cementum with a matrix that contains well-defined fibrils of type I collagen.
  • Afibrillar cementum – cementum that has a matrix devoid of detectable type I collagen fibrils.

By the origin of the matrix fibers (applies only to Fibrillar forms of collagen)

  • Extrinsic fiber cementum – cementum that contains primarily extrinsic fibers i.e., Sharpey’s fibers.
  • Intrinsic fiber cementum – cementum that contains primarily intrinsic fibers i.e., fibers produced by cementoblasts.

Functions of the cementum

The primary role of cementum is to provide attachments to the collagen fibers present in the periodontal ligament. It helps maintain the integrity of the root and its position in the gums and the bone. Cementum is also deeply involved in the repair and regeneration of teeth.

Clinical significance of cementum

  • Cementum is essential for the normal anchorage of the tooth. It mediates the attachment of the tooth to the gingiva, and also to the periodontal ligament and alveolar bone.
  • Cementum provides a protective function to the tooth itself, as it is less susceptible to resorption than bone. It allows pressure-induced movement of the tooth through bone, as in orthodontics, while minimizing damage to the tooth.
  • Scaling and root planning, aimed at removing calculus and bacterial deposits, also readily removes the relatively thin cementum layer.
  • New cementum formation is a critical process during therapeutic procedures aimed at gaining new attachment. It mediates new attachment of the tooth to the periodontal ligament and bone.
  • Cemental deposition in the apical portion of the root compensates to some degree for the slow eruption that takes place throughout life to compensate for occlusal attrition.
  • Cemental spurs can be found at or near the cementoenamel junction. It results from the irregular deposition of cementum on the root. They can present some clinical problems in differentiation from calculus and may be noted on radiographs. They are not easily removed, and thus may also interfere with periodontal treatment.
  • When gingival recession exposes the cementum, it quickly undergoes abrasion by mechanical friction. The exposure of the dentin can lead to problems such as extrinsic staining and dentin hypersensitivity.
  • The incidence of Cemental caries increases in older adults as gingival decline occurs from either trauma or periodontal illness. It is a chronic condition that forms a large, shallow lesion and slowly invades first the root’s cementum and then dentin to cause a chronic infection of the pulp.

Developmental anomalies of cementum

Several structural dental defects have been described that can be attributed directly or indirectly to errors in the developmental process of the cementum. Some of these developmental anomalies are –

Enamel pearls

Enamel pearls are localized masses of enamel that develop ectopically, typically over the root surface, near the cementoenamel junction.

Enamel projections

If amelogenesis is not turned off after the enamel of the crown has been laid down, the enamel organ may continue to produce enamel over the root dentin. This additional enamel often takes the shape of enamel spurs that project into the furcation of multi-rooted teeth. These projections may favor the onset of periodontal lesions in the affected furcations.


It refers to abnormally large cellular cementum deposits on the apical third of one or more teeth. Such deposits form bulbous enlargements on the roots that may interfere with dental extractions. (2)


Cementicles are small, spherical particles of cementum that may lie free in the periodontal ligament adjacent to the cementum surface. It may be composed of Fibrillar or Afibrillar cementum or a mixture of the two. They are usually acellular.


Over to you

Cementum is one of the key players in keeping your teeth sturdy while protecting them from decay. Cementum loss is one of the main factors leading to sensitive teeth, along with enamel loss and gum recession. Gum disease can cause Cemental loss too. Protecting your teeth by employing a diligent oral care regimen is the best way to avoid potential issues with the loss of cementum or, in the worst case, a tooth.


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