Invasive Cervical Resorption: A Radiographic Perspective
Invasive cervical resorption is often asymptomatic and easily missed on routine imaging. This article explains how to recognize its key radiographic features, distinguish it from internal resorption, and understand why CBCT is often critical for accurate diagnosis and treatment planning.
Invasive cervical resorption (ICR) is one of the most challenging resorptive defects encountered in dental imaging, not because it is rare, but because it is often silent. Frequently asymptomatic and discovered incidentally, ICR can progress significantly before it becomes clinically evident. Accurate radiographic identification plays a critical role in determining prognosis and guiding appropriate management
What Is Invasive Cervical Resorption?
Invasive cervical resorption is an external resorptive process that originates at or just below the cemento-enamel junction (CEJ) and progresses longitudinally along the dentin. Unlike caries or internal resorption, ICR arises from a small, often punctate defect on the external root surface, typically preserving the pulpal space until late in the disease process.
Clinically, the tooth may remain asymptomatic and vital for an extended period, which contributes to delayed detection.
Cropped axial, sagittal, and coronal cross-sectional views of #6 illustrating resorptive changes along the palatal root surface immediately apical to the CEJ.
Etiology and Predisposing Factors
The exact pathogenesis of invasive cervical resorption is still an enigma and not fully understood. A variety of predisposing factors have been proposed, ranging from genetic predisposition to environmental and systemic involvement.
Classifications
Radiographic evaluation is central to the diagnosis of invasive cervical resorption. The appearance can vary widely depending on lesion size, location, and extent.
Heithersay Classification (Based on 2D Imaging)
Heithersay first described invasive cervical resorption based on two-dimensional imaging and classified lesions into four categories:
Class 1: A small lesion located near the cervical area with shallow penetration into the dentine
Class 2: A well-defined lesion that has penetrated close to the coronal pulp chamber but shows little or no extension into the radicular dentine
Class 3: Deeper invasion of dentine involving the coronal dentine and extending into the coronal third of the root
Class 4: A large resorptive process that has extended beyond the coronal third of the root
Patel Classification (Based on CBCT Imaging)
Patel introduced a three-dimensional classification system based on CBCT imaging. This system incorporates:
Lesion height
Circumferential spread
Proximity to the pulp
This classification allows more accurate staging and improves treatment planning by defining lesion extent in three dimensions.
ECR lesion (red arrow); level of the bone crest (yellow dotted line); PR of tooth (a); CBCT sagittal image (b); axial images (c).Source.
Radiographic Presentation
Appearance on 2D Imaging
On periapical or panoramic radiographs, invasive cervical resorption typically appears as an irregular radiolucency in the cervical region of the root.
Key features may include:
Asymmetrical radiolucency superimposed over the root surface
Ill-defined or “moth-eaten” borders
Apparent preservation of the pulpal outline in early and moderate lesions
One of the most important diagnostic clues is that the root canal space remains intact and traceable through the lesion, helping differentiate ICR from internal resorption.
However, due to projection geometry and superimposition, 2D imaging often underestimates lesion size and extent.
CBCT Findings
Video snippet showing ICR in #6 with Patel classification3Bp
Exact lesion location, typically beginning at the cervical region, with a small origin point
Depth and circumferential spread of resorption
Relationship to the pulp chamber and root canal system
A CBCT report frequently reveals that lesions appearing small on periapical radiographs are far more extensive than initially suspected. This information is critical for selecting appropriate surgical or non-surgical treatment approaches and determining restorability.
Differential Diagnosis
Several conditions may mimic invasive cervical resorption, particularly on two-dimensional imaging, where the lesion origin may not be clearly visualized.
Internal Resorption
Internal resorption originates within the pulp space and typically presents as a well-defined, symmetrical enlargement of the canal. In contrast, invasive cervical resorption often shows a traceable root canal outline through the lesion.
Cervical Root Caries
Cervical caries may appear as a radiolucency near the CEJ but typically demonstrates a more diffuse appearance and may correlate with clinical evidence of surface cavitation or gingival recession.
Why Invasive Cervical Resorption Matters
The clinical significance of invasive cervical resorption lies in its potential for progressive and destructive behavior once established.
Treatment options and prognosis depend heavily on:
Lesion size and circumferential involvement
Accessibility for surgical debridement
Proximity to or invasion of the pulp space
Structural integrity of the remaining tooth
Early-stage lesions may be managed conservatively, while advanced cases may be deemed non-restorable. Without accurate imaging, clinicians risk either overtreatment or delayed intervention.
Key Takeaways
Invasive cervical resorption is often asymptomatic and incidentally detected
2D imaging may suggest the diagnosis, but it frequently underestimates severity
CBCT is critical for accurate localization, staging, and treatment planning
Early radiographic identification can significantly improve prognosis
Radiology Pearl:
Preservation of the root canal outline through a cervical radiolucency is a key feature that favors invasive cervical resorption over internal resorption.
When should CBCT be recommended if invasive cervical resorption is suspected on a periapical radiograph?
CBCT is appropriate when a 2D radiograph suggests cervical resorption but does not clearly show lesion depth, circumferential spread, or proximity to the pulp. It is especially useful when treatment planning depends on restorability, surgical access, or differentiation from internal resorption. In many cases, what appears limited on periapical imaging proves substantially more extensive on CBCT.
What imaging features suggest that a tooth with ICR may be difficult or impossible to restore?
Features that worsen prognosis include deep dentinal invasion, broad circumferential spread, extension well into the root, and close pulpal involvement or communication. Loss of remaining sound tooth structure and lesion extension into areas that are difficult to access for complete debridement also reduces the likelihood of predictable treatment. Imaging is critical because restorability is often underestimated clinically.
What should be included in a radiology report when invasive cervical resorption is identified?
A useful radiology report should describe the lesion location, estimated vertical extent, circumferential involvement, depth, and relationship to the pulp and canal system. It should also note whether the root canal outline remains discernible, whether perforation or pulpal communication is suspected, and whether CBCT assessment is recommended or has already clarified the full extent. This gives the referring clinician information that directly supports treatment planning.
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