Sinus tract on a post-retained maxillary molar with a missed canal
A 45-year-old woman attends for a routine check-up. Tooth 26 was root treated nine years ago and restored with a cast post-retained crown. She reports occasional discharge with a salty taste but no pain, no swelling and no fever; she takes no medication and has no relevant medical history. Examination shows an intact crown margin, a 6 mm buccal probing depth with bleeding, no mobility, no tenderness to percussion, and a sinus tract opening on the buccal gingiva that tracks towards the mid-root. A periapical radiograph shows a 5 mm periapical radiolucency, obturation ending 2 mm short of the apex, a palatal post and an untreated, possibly missed, canal. Her general dentist has advised extraction because 'posts make retreatment impossible'. She is keen to keep the tooth and travels abroad in three weeks.
1. Give the diagnosis, explain why nonsurgical retreatment should precede apical surgery, and describe how you would assess restorability.
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Diagnosis: post-treatment apical periodontitis with a sinus tract - that is, a chronic apical abscess - on 26, with a short obturation and an untreated canal. A sinus tract confirms a chronic endodontic infection draining through bone and mucosa; it is typically painless, which fits the absence of symptoms.
Why retreatment first: the cause is intraradicular - biofilm and necrotic tissue in the untreated or missed canal. MB2 is present in the majority of maxillary first molars, so its absence on the radiograph is suspicious rather than reassuring. Apical surgery that leaves this reservoir in place treats the symptom, not the cause, and has a poorer outcome. Nonsurgical retreatment addresses the aetiology, is generally first-line, and keeps surgery in reserve.
Restorability matters as much as the endodontics. The 6 mm buccal pocket must be explained: if it is a draining sinus tract rather than true attachment loss, the periodontal picture may improve after treatment; if it is a narrow defect associated with the post or a vertical root fracture, the tooth is not restorable. Use cone-beam CT to map the post, the canal anatomy, the missed canal and the buccal plate, and to exclude fracture. She is medically fit, which favours retention. If the tooth proves unrestorable, extraction with socket preservation and a planned replacement is the better answer than heroic retreatment.
2. Describe how you would manage the crown and post, and how you would structure treatment around her travel date.
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Assess before drilling. Take a cone-beam CT to map the post, the canal anatomy, the missed canal and the buccal bone, and to look for a fracture.
Crown: remove it only if needed for access, if it is leaking, or if the post lies in a different canal from the one you must negotiate. Where the post is palatal and a separate palatal access is possible, the crown is sometimes retained; more often it must come off to see the canal orifices and to allow a proper coronal seal afterwards.
Post removal: ultrasonic unit under magnification with a post-removal kit. Think about force direction - torque against a post in a thin palatal root is how roots fracture. If the post cannot be removed safely, stop and reassess rather than persist.
Visits and travel: she leaves in three weeks, so plan a two-visit protocol. First visit: access, post removal, canal negotiation, chemomechanical cleaning with sodium hypochlorite and EDTA, calcium hydroxide dressing. Second visit 7–10 days later: obturation, provided the sinus tract has closed or the tooth is asymptomatic. Single-visit treatment is defensible in a fit patient but fits poorly with imminent travel if a flare-up occurs. Give written contingency advice and a contact route abroad. Never leave the tooth open, and do not promise to save the tooth before the post is out and the canals negotiated.
3. Justify your antibiotic and analgesic decisions, state the prognosis, and outline the follow-up you would arrange.
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Antibiotics are not the treatment. There is a draining sinus, no swelling, no fever and no systemic involvement; the infection is localised and draining, so antibiotics would add nothing except selection pressure for resistance. Reserve them for systemic involvement, spreading infection or a compromised host - none of which applies.
Analgesia: advise ibuprofen or paracetamol if pain occurs between visits. True flare-ups are uncommon but she should know how to recognise one and what to do before she travels.
Prognosis: with a missed canal and a short fill, retreatment outcomes in a molar with a post are reasonable but not assured - quote a guarded-to-good prognosis rather than a guarantee. Healing of a 5 mm lesion may take 6–24 months and the radiolucency may reduce rather than disappear completely. Improvement in the patient's symptoms and closure of the sinus tract are the early indicators.
Alternatives and consent: retreatment (preferred), apical surgery if retreatment proves impossible, or extraction with a planned replacement. Each has different costs and time frames; the travel deadline constrains the plan and she should know it.
Follow-up: review at 6 and 12 months with periapical radiographs and clinical examination, ideally with a baseline postoperative film at completion. If healing fails, revisit the diagnosis for a missed canal, perforation or fracture before considering surgery.