A painful lower molar with a single 7-mm pocket

Diagnosis. Symptomatic irreversible pulpitis with symptomatic apical periodontitis in 36. The spontaneous night pain, lingering cold response and percussion tenderness all point to a pulp that cannot recover, and the 4-mm apical radiolucency confirms apical periodontitis.

Interpreting the pocket. A single 7-mm pocket surrounded by 2–3 mm sites, with bone loss confined to that interproximal area, is far more likely to be a sinus tract draining through the periodontal ligament than a primary periodontal defect. The pocket therefore does not change the pulpal diagnosis, but it changes three things:

1. Sequence. The endodontic lesion is treated first. Scaling and root planing alone will never heal an endodontic pocket, and periodontal surgery on such a site before root canal treatment would be a predictable failure.
2. Restorative feasibility. Caries that extends subgingivally means the final margin, ferrule and isolation must be assessed now, not after obturation. If the margin cannot be sealed and a 1.5–2 mm ferrule created, the tooth is unrestorable even if the canal treatment succeeds - this is the point to discuss with the patient before starting.
3. Documentation. The pocket depth must be charted and re-measured at review, because resolution of the pocket after root canal treatment is the proof that it was of endodontic origin.

Appointment 1. Rubber dam, complete caries removal, access, working length with an apex locator confirmed radiographically, and chemomechanical preparation of all canals. Because she is in pain and has only two visits, I would aim to obturate in the same visit if the canals can be dried and there is no heavy exudate; if the canals remain wet, I place calcium hydroxide, a well-sealed provisional restoration and obturate at visit 2. At the end of the visit I would instrument the isolated 7-mm pocket subgingivally and give oral hygiene instruction.

Appointment 2. Obturation, then a cuspal-coverage provisional or an immediate core build-up designed to provide ferrule.

What decides prognosis:

• Whether the apical radiolucency and the pocket heal - a pocket of endodontic origin should resolve once the canal is clean;
• whether the final restoration seals and retains 1.5–2 mm of ferrule;
• absence of an undetected root fracture or perforation (a persistent pocket with a persistent apical lesion is the classic clue);
• her ability to attend review. She will be abroad for six months, so the review must be planned at 6–12 months with written instructions and a request that she be examined if symptoms recur.

A healed apex with an unchanged 7-mm pocket means the lesion was not purely endodontic - either there was a genuine combined lesion with a periodontal component, or the pocket is a true periodontal defect. The endodontic treatment has done its job; the residual defect is now a periodontal problem.

Next steps:

1. Re-instrument the site subgingivally under local anaesthesia and re-evaluate in 6–8 weeks with full probing chart and bleeding scores.
2. Reinforce interdental cleaning - the distolingual of a lower molar needs an interdental brush of the correct size, not floss alone.
3. If the pocket remains ≥5 mm with bleeding, assess the defect morphology (radiograph, consider CBCT) and decide between a regenerative procedure, a resective approach with osseous contouring, or continued maintenance. Anatomy - a narrow, deep, three-wall defect - favours regeneration; a wide, shallow defect or a furcation involvement favours resection or maintenance.
4. If, instead, the apex had not healed alongside a persistent pocket, I would suspect root fracture, missed canal, or perforation and would image with CBCT before any periodontal surgery.