Internal Root Resorption

Internal root resorption is loss of dentine from the wall of the root canal by odontoclasts, driven by chronic inflammation of the pulp, and it enlarges the canal from within. It is uncommon, found in under 1% of teeth, and the incisors and molars are the usual teeth.

When it reaches the crown it shows as a pink spot (the pink tooth of Mummery), and it can perforate the root wall to reach the periodontal ligament.

Pathophysiology. Resorption needs a vital pulp coronal to the lesion to supply clastic cells and an infected, necrotic pulp apical to it that provides the stimulus, plus loss of the predentine barrier from trauma or inflammation.

Triggers include trauma, chronic pulpitis, pulpotomy, heat from restorative work, orthodontic movement, cracked teeth and, rarely, viral infection. Transient and replacement forms have also been reported.

Usually no symptoms, found on a routine radiograph. A pink discolouration of the crown, pulp polyp, or pain with pulp inflammation or when the lesion perforates.

Sensibility tests are positive in early disease because the apical pulp is vital, and become negative later. Swelling, a sinus or periodontal defect at the site of perforation suggests an infected or perforated lesion.

• Periapical radiograph: a symmetrical, oval or round enlargement of the canal with smooth outlines and continuity with the canal. The lesion stays centred on the canal when the beam angle is changed, which separates it from external resorption.
• Cone beam CT: confirms the position, extent, perforation and remaining dentine thickness, and guides treatment planning.
• Pulp sensibility tests and percussion.
• Periodontal probing for a perforation or defect.
• Exclude external cervical resorption, which may have a similar appearance.

Differential diagnosis.

• External cervical resorption
• External inflammatory resorption with a canal overlay
• Dens invaginatus and other anatomical variants
• Caries involving the pulp
• Replacement resorption
• Pulp canal obliteration (a narrowing and not an enlargement of the canal)
• Cyst or tumour involving the root

• Root canal treatment as soon as the lesion is found, to remove the pulp tissue that feeds the resorption. The prognosis is good in early, non-perforating lesions.
• Irrigation with sodium hypochlorite 2.5 to 5.25% with ultrasonic activation to dissolve the granulation tissue in the irregular defect, because instruments cannot reach all of it, with 17% EDTA at the end.
• Intracanal calcium hydroxide dressing for 2 to 4 weeks, repeated if bleeding persists, and obturation with warmed gutta percha or a bioceramic sealer technique to fill the defect.
• Perforating lesions: repair of the perforation with a calcium silicate cement through an orthograde or surgical approach. The prognosis depends on the size and location.
• Extraction when the tooth is non-restorable because of weakened root walls, a large perforation or fracture.
• No antibiotics, unless there is infection with spread.

Monitoring. Radiographic review at 6 and 12 months and annually for up to 4 years. Assess healing of any perforation and lesion stability.

Referral and escalation. Refer to an endodontist for all cases, particularly with perforation, because treatment is technically demanding. Refer to oral surgery for surgical repair or extraction.