Biting pain on release in a heavily restored mandibular molar
A 52-year-old man complains of sharp pain in the lower left first molar (tooth 46) when eating, particularly at the moment he releases his bite. Episodes have occurred for four months and are brief; he cannot localise which tooth is responsible and has no spontaneous or night pain. The tooth has a large amalgam with a distal marginal ridge that has visibly flexed. Cold testing produces a sharp response that resolves within a few seconds, and the adjacent premolar and second molar respond similarly. Percussion is mildly tender. Probing reveals a single 8 mm pocket on the distobuccal aspect with bleeding, not present on the adjacent teeth. A bite test with a wooden stick reproduces the pain sharply on release. The periapical radiograph shows no apical radiolucency but a widened distal periodontal ligament space and a subtle J-shaped halo extending to the distal crest. Transillumination reveals a mesiodistal line in the distal cusp that disappears at the gingival margin.
1. Establish the most likely diagnosis and justify it against the alternatives using the findings described.
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Most likely diagnosis: a cracked tooth (cracked posterior tooth) with reversible pulpal inflammation and early distal periodontal involvement.
Supporting features. Pain on release of biting is the classic signature - the cusps separate on loading and the crack springs open, firing pulpal nociceptors. Sharp, brief, well-localised pain with a normal, non-lingering cold response supports reversible rather than irreversible pulpitis. The isolated 8 mm pocket on the distobuccal aspect of a cracked tooth reflects a localised vertical defect, not generalized periodontitis, and is a recognised warning sign. The transilluminated line and the widened distal PDL with a J-shaped halo are consistent with a crack; a halo is an early sign of a developing lateral lesion.
Alternatives considered. Irreversible pulpitis is excluded by the absence of spontaneous or night pain and by the normal cold response duration. Periodontal abscess would usually present with a vital or non-vital tooth, a deep pocket and often systemic signs, but would not explain the pain on release or the crack line. Occlusal trauma can cause widened PDL and biting discomfort but does not produce a linear transillumination defect or a narrow isolated pocket. Vertical root fracture must be actively excluded: a deep narrow pocket on one aspect, a J-shaped radiolucency and a crack reaching the gingival margin raise this possibility, and if the crack can be traced below the crest the tooth is unrestorable.
Next step. The decisive question is the depth and extent of the crack. If it reaches or passes the gingival margin on the distal aspect, prognosis falls sharply and extraction with implant or bridge replacement should be discussed; if it remains supragingival and the pulp is only reversibly inflamed, cuspal coverage is viable.
2. Compare the treatment options for this tooth and justify your recommended plan, including what you would tell the patient about prognosis.
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Option 1 - Bonded cuspal coverage without root canal treatment. Appropriate when the pulp is reversibly inflamed and the crack is supragingival. The cusp is removed, the crack is sealed with a dentine-bonding resin, and the tooth is restored with an adhesive overlay or a crown with a bevelled, ferrule-like margin engaging 1.5–2 mm of sound axial wall. Advantage: pulp preserved. Risk: the crack propagates, and later root canal treatment or loss may follow.
Option 2 - Root canal treatment followed by cuspal coverage. Justified if the pulp becomes irreversibly inflamed, if sensibility testing changes, or if the crack is close to the pulp. Root canal treatment does not heal a crack; it only removes pulpal pain. The tooth must then be protected with cuspal coverage, and a post should be avoided unless retention demands it, because posts wedge cracks open. Advantage: retains the tooth. Risk: a crack that propagates to the furcation or root will still require extraction.
Option 3 - Extraction and replacement (implant, bridge or denture). Indicated if the crack extends below the crest, if a vertical root fracture is confirmed, or if the isolated 8 mm pocket does not resolve. An implant in the 46 position is predictable but commits the patient to a surgical procedure and maintenance.
Recommendation. Given the supragingival transilluminated line, reversible pulpitis and a single narrow pocket, I would explain the guarded but reasonable prognosis and offer bonded cuspal coverage with the crack sealed, with a clear review at 6 and 12 months. The patient must be told that roughly a third to a half of cracked teeth eventually need root canal treatment or extraction, and that biting on hard objects on that side should be avoided. If the crack extends under the gingiva at the time of preparation, the plan converts to extraction.
3. Eighteen months later, after root canal treatment and a crown, the patient returns with a discharging sinus and a deep narrow pocket on the distal aspect. How do you reason through the decision, and what would you do?
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Interpret the new findings. A sinus and a deep narrow isolated pocket on the same aspect as the original crack, in a tooth that has already had root canal treatment and cuspal coverage, strongly suggests crack propagation or a vertical root fracture rather than failure of the root canal treatment itself. The differential includes a missed canal or inadequate coronal seal, but these usually produce a periapical lesion without an isolated deep pocket on one aspect.
What to do next. Take a periapical radiograph; a J-shaped or halo radiolucency alongside the root supports fracture. Remove the crown - the crack is often visible after restoration removal or under magnification with transillumination and dye. If the fracture line runs vertically down the root, or extends below the alveolar crest on the distal, the tooth is unrestorable and extraction is indicated. If the fracture is confined to a coronal cusp and the root is intact, re-treatment and a new restoration remain possible, though this is the less likely scenario given the narrow pocket.
Communicate honestly. The patient should be told that the crack was the original problem and that despite treatment it has progressed; this is a known outcome rather than a failure of care. Discuss replacement options with a clear comparison: implant (surgical, high survival, requires adequate bone and no uncontrolled systemic contraindications), resin-bonded or conventional bridge (prepares the adjacent 45 and 47, which currently sound), or a removable partial denture. Note that 45 and 47 have reasonably sized restorations, which lowers the biological cost of a bridge. Record the discussion and the patient's choice.