Heavily broken-down first molar with reversible versus irreversible pulpal symptoms
A 38-year-old woman is referred for restoration of the lower left first molar. A large MOD amalgam is present, the distobuccal cusp is fractured and there is visible caries beneath the mesial cavity margin. Cold testing produces an exaggerated response that persists for about 30 seconds after the stimulus is removed; there is no tenderness to percussion, probing depths are 2-3 mm and the furcation is not involved. Radiographs show caries approaching the pulp horn but no periapical radiolucency. There is 2 mm of supragingival dentine on the mesial and 5 mm on the distal. She grinds heavily at night, has a dry mouth from a tricyclic antidepressant and drinks three cans of cola daily. She asks whether the tooth can 'just be filled'.
1. What is your pulpal and periapical diagnosis, and why is 'just filling it' not adequate?
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Diagnosis
- Symptomatic irreversible pulpitis in a mature tooth. The key discriminator is the lingering response - pain continuing 30 seconds after the stimulus is removed indicates a pulp that can no longer recover, not merely a hypersensitive but vital one.
- Normal apical tissues: no tenderness to percussion, normal probing, no periapical radiolucency. This matters because it means the endodontic problem, if treated, is straightforward: no infection has yet established in the canal space beyond the coronal pulp.
- Caries is 'approaching the pulp horn' radiographically, which in a tooth already producing lingering pain makes direct pulp capping unpredictable.
Why not just fill it
- The pulp is already irreversibly inflamed; cutting caries out will expose it and a direct pulp cap in a symptomatic, irreversible pulp in a 38-year-old has a poor and unquantifiable success rate.
- The residual tooth is weak: a fractured distobuccal cusp plus a wide MOD means the cusps are unsupported. A direct or even indirect intracoronal restoration in a heavy bruxist will fracture, and the fracture will likely be catastrophic and subgingival.
- There is nothing wrong with the periodontal support - 2-3 mm pockets, no furcation - so the tooth is worth spending effort on. The prosthodontic problem, not the periodontal one, sets the limit.
So the realistic options are root canal treatment with cuspal coverage, or extraction with a planned replacement. Simply filling it defers the decision to an uncontrolled fracture.
2. Compare the options you would offer and state how you would decide between them.
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Option A - Root canal treatment plus cuspal coverage (core and onlay or full contour crown) Arguments for: the tooth has good bone support and no furcation involvement; the apical tissues are healthy, so the endodontic prognosis is favourable; a cuspal-coverage restoration splints the remaining walls and is the only way to protect a cracked, undermined molar in a bruxist. Arguments against: the mesial wall has only 2 mm of supragingival dentine, so a ferrule/crown-lengthening decision arises; the patient's caries risk is high (frequent cola, xerostomia) and a complex reconstruction may fail by recurrent caries rather than by structural failure; bruxism demands a night guard.
Option B - Extraction and replacement (bridge or implant) Arguments for: removes the risk of an unpredictable fracture and the cost of a restoration with uncertain medium-term survival; a single implant in a periodontally sound site with adequate bone is predictable and avoids preparing the adjacent teeth. Arguments against: loss of a restorable tooth is irreversible; the adjacent teeth appear sound, so a conventional bridge would be destructive; implant placement in a xerostomic patient requires excellent hygiene.
Option C - Extraction with no replacement in a first molar risks mesial drift and tipping of the second molar - a poor default in a 38-year-old.
How to decide The decision turns on restorability and the patient's values, not on a rule. Check the mesial wall after caries removal: if there is a sound supragingival margin to seat a core, Option A is reasonable. Quantify caries risk and address it (diet analysis, fluoride varnish, high-fluoride toothpaste, sugar-free substitute, discussion with her GP about the xerostomia if the tricyclic can be changed). Offer a hard occlusal splint. Then present the honest trade-off between cost, number of visits and the risk of late fracture.
3. She asks what will happen if the tooth fractures later. What structural and occlusal factors would you document now?
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Document the factors that determine the consequences of fracture
- Amount of sound tooth structure: the 2 mm supragingival mesial wall is the weak link. If a fracture line runs there it will be subgingival, and the tooth may become unrestorable even with a crown.
- Cusp support: a fractured distobuccal cusp plus a wide MOD means both marginal ridges are lost; unsupported cusps flex under load. This is the classic precursor to a cracked tooth with symptoms on release of biting.
- Furcation status: currently uninvolved. A vertical root fracture in a molar typically presents with a narrow, isolated pocket and a J-shaped radiolucency; if that develops, the tooth is not salvageable. Note the baseline so a future change is detectable.
- Occlusal scheme and bruxism: note wear facets, any non-working-side contacts, and assess the opposing dentition. Bruxism converts a static load into a repeated fatigue load.
- Restorative material: an unbonded amalgam core will not strengthen the tooth; adhesion does, so plan the core and the coverage as one bonded unit if you restore.
Explaining it honestly Explain that the risk is not a gradual decline but an event: the tooth may break suddenly, often under a normal load, and that the fracture line - not the force - determines whether it can be saved. Give the patient the specific symptoms that should prompt urgent contact (sharp pain on release of biting, a localised deep pocket, mobility) and record the discussion. Then re-examine probing depths at each review rather than waiting for symptoms.