Extra Canal Invasive Resorption (ECIR)
Extra Canal Invasive Resorption (ECIR)
ECIR Definition:​
ECIR is a form of external root resorption that typically begins in the cervical area, just beneath the epithelial attachment of a permanent tooth. This topic is particularly fascinating to me, as our practice has managed a notable number of cases involving this condition in recent years. While it remains relatively uncommon in the general population (affecting less than 1% overall), it stands out as the most frequently encountered type of resorption in our endodontic work.
Figure 1 is a cartoon of the periodontal tissues for reference.​
Etiology:
The exact cause of ECIR remains unclear, but evidence suggests that a flaw in the cementum is a necessary precursor—whether due to a developmental abnormality (see Figure 2) or injury-related damage. This flaw permits direct exposure of the dentin to certain resorptive cells within the surrounding periodontal tissues, leading to infiltration by highly vascularized tissue and progressive loss of tooth structure.
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In a pivotal study by Heithersay (2004), data from 222 patients involving 257 affected teeth was examined, revealing several potential risk factors. The most frequently identified were orthodontic treatment, trauma, internal bleaching, and prior surgical procedures near the cementoenamel junction. Of these, orthodontics (24.1% of cases) and trauma (15.1%) were the most common standalone contributors. This trend aligns closely with what we observe in the majority of ECIR cases at our practice.
That said, if you’ve had braces and later developed a resorptive lesion, don’t rush to blame your orthodontist—chances are, you’re part of the 24.1% of a condition that affects under 1% of the population. The good news is that when ECIR is diagnosed early, outcomes are typically favorable. I’ll cover treatment approaches in next week’s blog post.
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Classifications:
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Heithersay (2004) developed a useful classification system for ECIR lesions that is defined in the Figure 3 below.
Clinical Presentation:
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A major challenge with ECIR lesions is they are typically asymptomatic and difficult to discover unless they are at a class III or IV. If clinically detectable, a tooth may take on a pinkish hue near the gingival margin, due to the highly vascular inflammatory tissue that is replacing the tooth structure. There may be a cavitation that is detectible with an explorer. The tooth structure is usually hard, not sticky as is the case when detecting a carious lesion, however large lesions may also have secondary decay as a result of the defect creating a hygiene issue. Localized periodontal inflammation may also be observed for this reason as well. (Figures 5 and 6)
Radiographic Presentation:
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ECIR lesions are usually missed until they have reached a class III or IV status, appearing as a moth eaten radiolucency with ragged borders (Figure 7). The communication with the periodontal tissues may be pinpoint or cavernous. Larger lesions may also contain hard tissue and have a trabecular bone type appearance. The pattern of resorption is unique as it typically progresses vertically alongside the pulp without penetration(Figure 8). A thin layer of dentin and predentin usually remains intact and walls off the pulp from the invasive fibrovascualar tissue. As a result most teeth with ECIR lesions contain vital pulp tissue and periapical tissues appear normal. Again the resorption process is due to rogue clastic periodontal host cells and does not inherently involve acute or chronic inflammatory cells unless microorganisms have secondarily invaded the space.
Cone Bean Computed Tomography (CBCT) Presentation:
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ECIR lesions can be difficult to appreciate in 2 dimensional radiographs so we usually take a cone beam CT scan of almost every ECIR case we encounter. The CBCT is invaluable as it allows for the most accurate 3 dimensional representation of the lesion and leads to more accurate assessment, diagnosis, and treatment planning (See Figure 9). Additionally, the scan provides an excellent visual aid for patient communication and education. We spend a lot of time getting to know every patient and we make sure they understand as much as possible. This is extremely important as many times ECIR lesions are asymptomatic and it may be difficult for a patient to understand the need for treatment when there is no pain. The truth is radiographic and CBCT images are invaluable for treatment planning however they are of very little value when it comes to predicting a patient’s discomfort.
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Now is a good time to conclude part one. Next week in part 2, I will review treatment options, clinical procedures, and prognosis. I will also post a few recent cases from our office. Thank you for reading and see you again next week!
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