cervical margins

The cervical margins of teeth are the surfaces where the crown and root meet, and is also referred to as the tooth's neck or cervical line.

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.

Periodontal consideration

Biological width

The biological width is a crucial factor in maintaining periodontal health. It refers to the soft tissue dimensions coronal to the alveolar bone, consisting of junctional epithelium and supracrestal connective tissue attachment. However, by violating the biological width during restorative procedures can lead to periodontal breakdown, inflammation, gingival recession, and bone loss. Gargiulo et al. (1961) established that the biological width is approximately 2.04 mm, composed of epithelial and connective tissue components.

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.

Relationship with Cemento-enamel junction

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.

Histology

Histologically, the cervical margin area can be appreciated by the gingiva histology surrounding the curvature, or cemento-enamel junction that aligns on the same location on a healthy tooth individual. However, due to pathological reasons such as gingival recession, the gingival margin may get located below CEJ, hence histologically it is difficult to have a precise sample to study on.

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.

Carious lesions

Caries occurring at the cervical region of the tooth are often linked to carious cervical lesions (CCLs), which are commonly found in patients with poor oral hygiene or exposed root surfaces due to improper brushing technique.

Non Cervical carious lesions (NCCL)

* Abfraction: Caused by occlusal forces leading to microfractures in the enamel and dentin
* Abrasion: Mechanical wear due to habits like aggressive tooth brushing
* Erosion: Chemical dissolution from acidic foods, beverages, or gastric reflux

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

Deep Margin Elevation (DME)

As proposed by Diestschi and Spreafico, this technique involves coronally repositioning sub-gingival margins using composite resin. It aids in dental dam isolation, impression-taking, restoration placement, and finishing. It is a conservative alternative to crown lengthening, which requires the removal of bone and gingival tissue. Moreover, DME improves bonding strength and marginal integrity, especially in cases where indirect restorations are planned. 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

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Dental anatomy