A crowned, previously root-treated molar with a short obturation
A 46-year-old man is referred with a 5-day history of a dull, poorly localised ache in the lower right first molar (tooth 46). The tooth was root-canal treated and crowned with a metal-ceramic restoration 8 years ago and has been asymptomatic since. He is otherwise healthy apart from hypertension controlled with amlodipine 5 mg daily. There is no swelling and no sinus tract. The tooth is tender to percussion, not mobile, and probing depths are 2 to 3 mm all round with no bleeding on probing. The crown margin is clinically sound. A periapical radiograph shows that the obturation ends 3 mm short of the radiographic apex, there is a 4 by 5 mm periapical radiolucency, and the mesial root shows a widened periodontal ligament space. The canal orifices cannot be seen because the crown is cemented. He has already taken two courses of amoxicillin obtained from a pharmacist, with only temporary relief, and asks whether the tooth is worth saving, because he cannot take more than two days off work.
1. State the most likely diagnosis, the specific findings that support it, and two alternative explanations you must exclude before starting treatment.
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Most likely diagnosis: previously treated tooth 46 with symptomatic apical periodontitis.
The reasoning rests on three observations. First, tenderness to percussion plus a spontaneous dull ache indicates sensitisation of apical nociceptors. Second, the 4 by 5 mm radiolucency and widened periodontal ligament space are the radiographic expression of apical periodontitis. Third, the history of root canal treatment converts this into post-treatment apical periodontitis, and the 3 mm short obturation supplies a plausible cause: the apical canal was never cleaned or sealed.
The two antibiotic courses gave only temporary relief. That is expected, because antibiotics cannot remove an intraradicular biofilm, and it strengthens the case for a dental rather than a purely medical source.
Must be excluded:
- Cracked tooth or fractured cusp. A cemented crown hides the crack. Look for a J-shaped radiolucency, one isolated deep pocket, pain on release after biting, and a history of crunching. Sulcus depths of 2 to 3 mm make a vertical root fracture less likely but do not exclude one.
- A lateral canal or periodontal-endodontic lesion. Widening confined to the mesial root may reflect a lateral canal exit; a narrow deep pocket would support this.
- Referred pain from tooth 47 or from a myofascial trigger point, and sinusitis if the tooth were maxillary.
Record pulp sensibility tests on adjacent and contralateral teeth and a bite test before committing. If a fracture is confirmed, retreatment is contraindicated.
2. The patient wants a decision today: retreatment, extraction, or referral. Give your recommendation with the prognostic factors that drive it, and describe the two most likely technical difficulties.
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Recommendation: orthograde retreatment, provided the tooth is restorable and no fracture is found. Referral is reasonable if magnification, ultrasonic equipment or retreatment files are unavailable, but simple extraction is premature.
Factors favouring retention: a functioning molar with a clinically sound crown margin; no mobility; a healthy periodontium with 2 to 3 mm sulci; a periapical lesion confined to the apex; no sinus tract; a controlled medical history; and a patient who is asking about saving the tooth rather than demanding its removal. The short obturation identifies a correctable cause, which improves the expected outcome.
Factors against: cost and time, a possible vertical root fracture hidden under the crown, and the difficulty of removing a well-cemented restoration. Extraction becomes correct if a fracture or a non-restorable tooth is found.
Technical difficulty 1 - access and the crown. Access through ceramic risks chipping, obscures the orifices and leaves old restorative material in the pulp chamber. Removing the crown gives vision, allows assessment of remaining tooth structure and is justified because a new restoration is needed anyway.
Technical difficulty 2 - removing the existing gutta-percha and sealer without apically extruding infected debris or perforating. Use rotary retreatment files, reserve solvent for the coronal third, confirm patency, and expect a calcified or missed canal such as a middle mesial. Magnification and ultrasonic troughing are needed.
Warn about flare-up and prescribe only if clinically indicated.
3. He asks what will happen to the crown and how soon he can return to work and eat normally. Outline your restorative and postoperative plan with reasoning.
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Coronal seal first. The most important restorative principle in retreatment is an immediate, well-adapted seal, because coronal leakage re-infects the canal system faster than apical leakage. After chemomechanical preparation and obturation, place a bonded composite or amalgam core in the same visit.
Crown decision. If the existing crown is removed for access, a provisional crown is needed; the definitive crown is made once the tooth is asymptomatic and the tissue is stable, usually within a few weeks. If the crown is retained, verify marginal integrity and ferrule. A root-treated molar needs cuspal coverage because the access cavity and loss of marginal ridges reduce stiffness and predispose to cusp fracture.
Time off work. Retreatment is normally one or two appointments of 60 to 90 minutes. He can return to work the next day. Advise ibuprofen 400 mg every 8 hours as needed, with paracetamol as an alternative, and avoidance of heavy biting on the tooth until the core is placed.
Prognosis and review. Explain that a 4 to 5 mm lesion with a corrected cause and a good coronal seal has a favourable but not guaranteed outcome; radiographic healing is expected over 6 to 12 months. Review clinically and radiographically at 12 months. Persistent symptoms, an enlarging lesion or a new sinus tract would prompt consideration of apical surgery or extraction. He should also be told that the antibiotic courses were not curative and that future swellings require dental assessment, not repeated prescriptions.