Internal and external root resorption
- Oral pathology
Resorption is the tooth being eaten away by the body's own cells, from inside the canal or from the root surface. It is often silent and found on a radiograph.
What it is
Root resorption happens when clast cells reach the root, usually after the protective layer of cementum or predentine is damaged and something keeps them active: infection, pressure or inflammation. Internal resorption starts in an inflamed pulp; external resorption starts on the root surface and has several types with different causes and treatments. Most cases have no symptoms until late.
How to recognise it
- Internal: a round, balloon-like widening of the canal outline on the radiograph; driven by inflamed pulp; treated with root canal treatment.
- External inflammatory: after trauma with a necrotic infected pulp; stopped by root canal treatment.
- Replacement resorption (ankylosis): bone replaces the root after severe damage to the ligament, often after avulsion; a high, metallic percussion sound and, in children, a tooth that sinks below its neighbours.
- External cervical (invasive) resorption: starts near the gum line; linked to trauma, orthodontics and internal bleaching; may show a pink spot.
- Pressure resorption: from an impacted canine, a tumour or orthodontic force.
Differential and risks
- Changing the radiograph angle helps: an internal lesion stays with the canal; an external one moves.
- CBCT shows the size and position of resorption and whether it can be repaired.
- Replacement resorption in a growing child can leave a sunken tooth and a bone defect; timing of removal matters.
Next step / Initial management
- Look for resorption on radiographs after dental trauma and during orthodontic treatment.
- Any resorption found: refer to the dentist or endodontist; the type decides between root canal treatment, repair, monitoring or extraction.
- Avulsed and replanted teeth: follow up with radiographs for at least several years.
Test yourself
Think of the answer, then tap the question to see it.
How does internal resorption look on a radiograph?
A round, balloon-like widening continuous with the canal outline.
Which type of resorption follows severe ligament damage after avulsion?
Replacement resorption (ankylosis), in which bone replaces the root.
What is one risk factor for external cervical resorption?
Any of: dental trauma, orthodontic treatment, internal bleaching.
Connections
Educational content; it does not replace assessment by a dentist or doctor and is not a clinical instruction. For facial or neck swelling with difficulty swallowing or breathing, a knocked-out tooth or bleeding that will not stop, go to an emergency department at once.
Sources: Tooth root resorption: A review (Science Progress (PMC open access), 2022); Tooth Resorption, Part 1: The evolvement, rationales and controversies of tooth resorption (Dental Traumatology (PMC open access), 2022); External cervical resorption: Radiological diagnosis and literature (Review) (Experimental and Therapeutic Medicine (PMC open access), 2021).
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Representative model, for educational purposes only.