thumb|Cervical margin of the tooth

In dental anatomy, the cementoenamel junction (CEJ) is the location where the enamel, which covers the anatomical crown of a tooth, and the cementum, which covers the anatomical root of a tooth, meet. Informally it is known as the neck of the tooth. The border created by these two dental tissues has much significance as it is usually the location where the gingiva (gums) attaches to a healthy tooth by fibers called the gingival fibers. It is almost synonymous with the cervical margin, where the crown and root meet, and is also referred to as the tooth's neck or cervical line.

Active recession of the gingiva reveals the cementoenamel junction in the mouth and is usually a sign of an unhealthy condition. The loss of attachment is considered a more reliable indicator of periodontal disease. The CEJ is the site of major tooth resorption. A significant proportion of tooth loss is caused by tooth resorption, which occurs in 5 to 10 percent of the population. The clinical location of CEJ which is a static landmark, serves as a crucial anatomical site for the measurement of probing pocket depth (PPD) and clinical attachment level (CAL). The CEJ varies between subjects, but also between teeth from the same person.

Anatomy

The cervical margin, also known as the cervical line or neck of the tooth, represents the boundary between the enamel covering the crown and the cementum covering the root. The cementum typically overlaps the enamel, although in some cases, it may meet edge-to-edge.

The cervical region includes the residual tooth structure between the gingival margin and the bone crest, encompassing the supragingival tooth area (STA) and gingival sulcus.

The curvature of the CEJ varies and is influenced by the height of the contact area and the crown's buccolingual diameter. Proximal cervical curvatures are more pronounced on mesial surfaces, with central incisors exhibiting the most significant curvature, progressively decreasing toward posterior teeth . However, relationship between CEJ and cervical margin is often suggested as age related factor, as there could be extra gingiva covering the anatomical crown in a 10 - year old child, meanwhile old adults with periodontal disease can reveal their CEJ due to gingival recession. Despite this, gingival margin and CEJ are still consistently on the same or almost same location on a healthy adult. There are three possible relationships at the CEJ: Cementum overlaps enamel (65% of cases), cementum and enamel meet end-to-end (25%), dentin is exposed due to a gap between enamel and cementum (10%) and these variations can occur around different areas of the same tooth.

Types

  • Coronal cementum - where the enamel overlaps the cement.
  • Abutment - It is also known as vis a vis relation, where the cement and enamel meet at the butt joint, occurring in 30% of sections, and the least common, occurring in 10% of sections.
  • Gap between cementum and enamel exposing the dentin.

Curvature

thumb|Comparison of the cementoenamel junction on the mesial surfaces of the maxillary central, first bicuspid, and first molar|172x172px

The shape and location of the cementoenamel junction (CEJ) on each tooth surface should be considered. CEJs differ from tooth to tooth in terms of their anatomy. The curvature of the CEJ is greatest on anterior teeth due to the narrow profile of these teeth. On the anteriors, the distal aspect's curvature is usually one mm lower than the mesial aspect. Posterior teeth have flatter CEJ curvatures on the inter-proximal surfaces in comparison to the anteriors.

Teeth resorption

Root resorption often starts at cementoenamel junction (CEJ) in teeth. Types of tooth resorption include internal resorption and external resorption.

Internal

There are two types of internal resorption - root canal (internal) replacement resorption and internal inflammatory resorption.

thumb|Types of Resorption|180x180px

External

External resorption can be classified into four categories by its clinical and histologic manifestations: external surface resorption, external inflammatory root resorption, replacement resorption, and ankylosis. External inflammatory root resorption can be further categorized into cervical resorption with or without a vital pulp (invasive cervical root resorption) and external apical root resorption.

Importance

Subgingival crown margins can contribute to gingivitis and periodontitis, leading to attachment loss, and improperly placed restoration margins and ill-fitting restorations violate the biological width, impacting periodontal health. Key considerations for subgingival margins include: proper contouring in the gingival third, polishing and rounding of the margin, ensuring an adequate zone of attached gingiva, avoiding biological width violation, regular maintenance and patient compliance to prevent periodontal issues.

Diseases of cervical margin area

Due to the cervical margin area being extremely close to the cervical part of tooth, the diseases related are usually overlapping with other diseases that could happen in the area.

Common treatments

Non-Carious Cervical Lesion (NCCL) Management

Composite restorations commonly restore lost tooth structure, and Glass Ionomer Cement commonly used too due to difficulty in moisture control The Immediate Dentin Sealing (IDS) technique, often performed alongside DME, enhances bond strength, reduces marginal leakage, and minimizes post-operative sensitivity

Clinical relevance

Endodontics

In endodontics, gaining access to the pulp chamber is an essential step to complete procedures such as Root Canal Treatment or Pulpotomy. According to the Law of Centrality in Endodontics, the pulp chamber of the tooth is located at the level of the cementoenamel junction.

The cervical margin area is extremely critical in determining the success of few restorations in dentistry, such as crowns and bridges. A good preparation around the cervical margin area, or the tooth structure near the cervical margin ensures the preparation is able to provide marginal integrity for accurate fit of the crown, reduced overhang between crown and cement to prevent bacteria or plaque accumulation. and providing resistance to occlusal forces to prevent fracture of the restorative material.

References

  • Biology-Online