Crown or extraction on a heavily restored first molar in a bruxist
A 42-year-old man attends with a cracked 16. The tooth has a large existing MOD amalgam, a distal cusp fracture extending subgingivally on the palatal aspect, and is tender to percussion but vital and not mobile. Probing depths are 3 mm or less except distopalatally, where the probe reaches 5 mm at the fracture line. Radiographs show the fracture line approaching but not clearly involving the pulp, and the roots are sound with adequate bone support. He grinds heavily at night (worn incisal edges, masseter hypertrophy) and does not wear a splint. He asks what will last longest. He is 42, systemically well, and a non-smoker.
1. How would you decide between crown and extraction, and what would you tell him about prognosis?
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The decision hinges on restorability, not just tooth presence.
- Subgingival extent: a fracture reaching 5 mm distopalatally with a 5 mm probing depth means the fracture margin is at or below the crestal bone level. This is the key negative prognostic feature - a crown cannot seal a margin that cannot be kept dry and clean, and the periodontal defect will persist.
- Vitality and symptoms: the tooth is vital and tender to percussion without a clear pulpal exposure, so the pulp may be salvageable, but the tenderness suggests some inflammation and a crown would likely need root canal treatment if the pulp is exposed during preparation.
- Bruxism: heavy grinding without a splint markedly increases the risk of fracture of any restoration and of the remaining cusps; any crown must be planned with this in mind.
Tell him: a crown is possible but the subgingival margin worsens the prognosis; combined with bruxism, the medium- to long-term risk of failure is significant. Extraction with a planned replacement (implant or bridge) is a legitimate option, particularly if the fracture proves to extend further once the restoration is removed. The honest answer is that the prognosis is guarded either way and depends on what is found when the old amalgam comes out.
2. What would you do at the first visit, and what would make you change course?
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First visit:
- Remove the existing restoration and explore the fracture directly - this is the single most informative step and should be done before committing to a crown.
- If the fracture margin can be brought supragingivally (e.g. by crown lengthening or by the preparation itself), proceed with a core and a provisional crown, warn about the guarded prognosis, and plan a splint.
- If the fracture extends to or below the bone crest and cannot be sealed, extract.
Change course if:
- The fracture involves the pulp and cannot be predictably restored - root canal treatment plus a post-core may be needed, which further reduces prognosis in a bruxist.
- The distopalatal defect cannot be kept dry and clean.
- The patient is unwilling to wear a splint, which materially changes the risk of failure.
Also:
- Discuss and arrange a night splint regardless of the choice, to protect the remaining dentition.
- Obtain informed consent for either outcome before starting, since the decision may only be clear once the tooth is opened.