External cervical resorption (ECR) is a specific type of tooth damage that originates on the outer surface of a tooth, typically near the gum line. This condition involves the gradual loss of hard dental tissue, such as cementum and dentin, due to the action of specialized cells. ECR is progressive, meaning it can worsen over time if left unaddressed. It is a pathological process that can affect any permanent tooth.
Understanding External Cervical Resorption
External cervical resorption describes a process where tooth structure is “eaten away” from its external surface, specifically in the cervical region near the gum line. This destructive process begins immediately below the epithelial attachment, where the gum tissue connects to the tooth root. The damage then progresses inward, moving through the cementum (the outer layer of the tooth root) and into the underlying dentin, the softer tissue that makes up the bulk of the tooth.
The cellular activity behind ECR involves specialized cells called osteoclasts or odontoclasts, which are responsible for breaking down hard tissues. These cells create small channels as they invade the tooth structure, often infiltrating the resorptive areas with highly vascular granulation tissue. While ECR can extend deeply, it often spares the pulp chamber (the innermost part of the tooth containing nerves and blood vessels) by leaving a thin, protective layer of predentin. This characteristic differentiates ECR from internal resorption, which originates within the pulp chamber, or from typical cavities caused by bacterial acid erosion.
What Causes External Cervical Resorption
The precise causes of external cervical resorption are not fully understood, but several factors contribute to its development. Dental trauma, such as impact injuries or concussion, is frequently associated with ECR, often being considered a primary cause. Orthodontic treatment, involving tooth movement, is another predisposing factor.
Certain dental procedures can also trigger ECR, including internal tooth bleaching, especially when high concentrations of hydrogen peroxide (over 30%) or heat are used. Periodontal surgery or other restorative procedures may also contribute. Localized inflammation or infection near the tooth’s root surface can play a role in initiating or perpetuating the resorptive process.
Genetic predisposition is also a possible factor. Despite these identified factors, some cases of ECR are considered idiopathic, meaning the exact cause remains unknown.
How External Cervical Resorption Is Found
External cervical resorption is often asymptomatic in its early stages, making early detection challenging. When symptoms do appear, they can be subtle, such as mild tooth sensitivity or a slight pinkish discoloration of the tooth crown, which occurs due to the highly vascular granulation tissue infiltrating the lesion. Gum inflammation or a localized periodontal pocket near the affected tooth, which might bleed on probing or feel spongy, can also be clinical indicators. Pain typically arises in later stages, when the resorptive lesion has progressed and involved the pulp.
During a clinical examination, a dentist might identify irregularities in the gingival contour or a cavitation that feels hard to probe, unlike the softer texture of dental caries. Radiographic imaging is the primary diagnostic tool for ECR. Traditional two-dimensional X-rays, such as periapical and bitewing radiographs, can show ECR as an irregular, asymmetrical radiolucency. However, these 2D images often underestimate the true extent and depth of the lesion, as they may not reveal the full spread of the defect within the root.
Cone Beam Computed Tomography (CBCT) is more accurate for diagnosing ECR due to its three-dimensional imaging capabilities. CBCT allows dentists to precisely assess the size, location, and extent of the lesion, including narrow resorptive channels that may extend into the dentin, which are often missed on conventional X-rays. This advanced imaging also helps differentiate ECR from other conditions like internal resorption or dental caries, which is crucial for appropriate treatment planning.
Treating External Cervical Resorption
Treatment for external cervical resorption depends on the stage, location, and extent of the resorptive lesion. For early, superficial lesions, careful monitoring or simple restorative procedures may be considered.
When the lesion is more advanced or accessible, surgical intervention is a common approach. This typically involves surgically exposing the affected area by raising a mucoperiosteal flap, followed by the removal of the resorptive tissue. After the tissue is removed, the defect is restored with a suitable material. Materials such as resin-modified glass ionomer cement, composite resin, or bioceramic materials like Mineral Trioxide Aggregate (MTA) or Biodentine are often used, as they offer good biocompatibility and sealing properties.
If the ECR lesion has progressed to involve or expose the pulp, root canal treatment is necessary. This procedure may be performed before, during, or in conjunction with the surgical repair to eliminate pulpal infection. In severe, extensive, or untreatable cases where the tooth structure is too compromised, extraction of the affected tooth may be the only option. Following extraction, prosthetic replacement options like dental implants or bridges can be considered. Long-term follow-up is important to monitor for recurrence.