A deep isolated pocket on a non-vital molar in a diabetic smoker

Most probable diagnosis: a primary endodontic lesion with secondary periodontal involvement (endo-perio lesion) on 36.

Reasoning:

• Pulp sensibility testing is negative on both cold and electric testing, so the pulp is necrotic. A purely periodontal lesion does not make a tooth unresponsive to sensibility testing unless the pulp is also involved.
• The defect is a single narrow deep pocket on a tooth with no caries and no restoration. Periodontitis is a plaque-driven, broadly distributed disease; the adjacent teeth have 2-3 mm pockets, so generalised periodontitis of that severity is not present.
• The periapical radiolucency and the pocket both track to the apex on the same roots: the classic pattern of an endodontic lesion draining through the periodontal ligament.
• Mobility alone is not diagnostic; it is explained by the localized attachment loss plus possible occlusal trauma.

Alternative that must be excluded: a vertical root fracture (or cracked tooth). This is the key judgement, because a fracture changes the plan from endodontics to extraction.

Features that would point to fracture: a narrow, isolated, deep pocket on one aspect only - which he has - a J-shaped or halo radiolucency, pain on biting, and a history of heavy occlusal loading, large restoration or previous root canal treatment. His tooth is unrestored, so a fracture is less likely but not excluded. Examine under magnification for a crack line, test individual cusps, and check the occlusion for a premature contact on 36. If a fracture is confirmed or strongly suspected, do not start root canal treatment.

Sequence:

1. Confirm the diagnosis - sensibility testing repeated, transillumination/magnification, bite test, percussion with the tooth and adjacent teeth, periodontal chart of the full mouth, and a periapical film of 36. Exclude fracture and check the occlusion.
2. Root canal treatment first, before any periodontal surgery. The endodontic component is the treatable cause of the pocket; the periodontal defect may partly resolve once the apical inflammation is removed. Doing periodontal surgery first would be treating a defect whose cause is still present.
3. Non-surgical periodontal therapy for the whole mouth (oral hygiene instruction, scaling) delivered in parallel - the patient's general periodontal status must be controlled whatever happens to 36.
4. Reassess at 3 months: probing depths, mobility, symptoms, periapical radiograph. Reduction of the 8 mm pocket to 4-5 mm with radiographic healing indicates a healed endo-perio lesion.
5. Restore 36 with cuspal coverage once healing is confirmed, since a root-treated molar needs protection.
6. Risk factor management: smoking cessation advice (refer to a cessation service) and liaison with his diabetes team. Healing and prognosis are materially worse with HbA1c near 9% and 20 cigarettes a day; these are not optional extras but part of the treatment plan.

Antibiotics: not indicated. There is no systemic involvement, no swelling and no sinus tract; a chronic periapical lesion is treated by removing the source. Prescribing would give the patient false reassurance, does not improve healing, and adds to resistance.

Splinting: not indicated as routine. A splint does not treat the cause and complicates hygiene. Reserve it for a tooth that is symptomatic or functionally unusable because of mobility, and then only as a temporary measure.

Interpretation: the symptom has resolved but the defect has not. Persistence of an 8 mm pocket with bleeding at 3 months after adequate root canal treatment means the periodontal component is now the dominant, self-sustaining problem - the lesion is no longer purely endodontic.

Reasons the pocket may persist:

• The endodontic treatment may be incomplete (missed canal, short fill, unfilled isthmus in the mesial root) - re-check the quality of the obturation and the coronal seal radiographically before blaming the periodontium.
• A vertical root fracture may have been missed; reconsider this, especially if the pocket is narrow and isolated.
• True combined disease with attachment loss that will not regenerate spontaneously.
• Continuing smoking and poor glycaemic control, both of which blunt the response to any therapy.

Prognosis: guarded. A molar with a residual 8 mm pocket, grade II mobility, furcation involvement and uncontrolled diabetes/smoking has a high risk of loss. It is not, however, automatically hopeless.

Plan:

1. Re-examine the endodontic result and the restoration for leakage; retreat if deficient.
2. Confirm fracture is absent.
3. Periodontal re-treatment: subgingival instrumentation of the site, reinforced hygiene, and review of occlusion.
4. If the pocket remains ≥6 mm with bleeding after further non-surgical therapy, offer periodontal surgery (open debridement, with or without regenerative techniques) with realistic expectations, or discuss extraction.
5. Have an honest conversation about the tooth's expected survival and the alternatives (extraction with implant or bridge), and record that the risks of retention - including acute abscess and further bone loss - were explained. Give the patient the choice rather than drifting into repeated reviews.