Fractured Cusp in a Bruxer: Direct or Indirect Cuspal Coverage
A 38-year-old woman attends with discomfort in the lower right first molar (46) after biting on crusty bread two days ago. 46 has a large MOD amalgam placed 12 years ago. The distobuccal cusp has fractured off: buccally the fracture is at the level of the gingival margin, lingually it sits about 3 mm above the gingival margin. The exposed dentine is sensitive to cold; Endo-Ice produces a response that resolves within about 3 seconds of removal. There is no spontaneous pain, no tenderness to percussion and no periapical radiolucency. The bitewing shows the amalgam approaching the pulp to within about 1 mm at the mesial horn, with no radiographic secondary caries.
She grinds her teeth at night - her partner reports it - and has generalised enamel wear with a large palatal composite on 16. She drinks two coffees a day, does not smoke and has no relevant medical history. She asks whether she can "just have a white filling", because she is a bridesmaid in four weeks.
1. Recommend a restoration for 46 and justify it against the alternatives, including whether elective root canal treatment is indicated.
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Diagnosis: fracture of the distobuccal cusp of 46 in a patient with probable sleep bruxism, with reversible pulpal symptoms - provoked, sharp, resolving in seconds, no spontaneous pain, no percussion tenderness, no apical pathosis.
Recommendation: an indirect bonded cuspal-coverage restoration (lithium disilicate or composite onlay, or full-coverage crown if the remaining walls will not support an onlay), placed after stabilising the tooth.
The reasoning is about remaining structure and load, not about material preference. A cusp is gone, roughly 1 mm of dentine remains over the mesial horn, and the patient has parafunction. A large direct composite would be a deep, high-configuration-factor restoration in a patient who loads it heavily - the predictable failure modes are debonding, marginal staining, wear and post-operative sensitivity. Amalgam would also require cuspal coverage and gives no adhesive benefit. Gold has excellent longevity but cost and appearance count here. A full crown removes more sound tissue than an onlay; keep it as the fallback if the walls are too thin after preparation.
Elective root canal treatment is not indicated. There is no irreversible pulpitis. Root canal treatment does not prevent post-restorative pain, it removes the tooth's vitality and proprioception, and it adds cost and a failure mode to a pulp that may never cause a problem. Manage the pulp on its merits if it is exposed.
2. Describe how you would remove the existing restoration and manage the remaining tooth structure, including what you would do if you exposed the pulp.
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Work under rubber dam with magnification and good light. Remove the amalgam and any caries methodically - a slow handpiece and round burs, checking with a caries detector - working from the periphery towards the pulp and stopping when the dentine is hard and leathery. Preserve the enamel periphery and every millimetre of the remaining cusps; the buccal and lingual walls give the onlay its bond and its ferrule effect.
If the pulp is exposed:
- Small (under about 2 mm), healthy exposure with controllable bleeding in a vital, asymptomatic tooth → partial pulpotomy: remove 2–3 mm of pulp tissue with a sterile bur, irrigate with sodium hypochlorite, achieve haemostasis, place MTA or Biodentine and seal immediately. This preserves vitality with good evidence and avoids a root canal.
- Uncontrollable bleeding, symptoms of irreversible pulpitis, or necrotic tissue → complete root canal treatment before the definitive restoration, ideally in the same treatment sequence.
Build the missing dentine with composite, seal the dentine adhesively at the time of preparation, and either scan/impress for the onlay or place a well-bonded composite provisional. If the buccal margin sits at the gingival level, consider deep margin elevation with composite so the final margin is cleanable rather than subgingival. Avoid leaving calcium hydroxide as a long-term base under a bonded restoration.
3. What would you tell her about the four-week timeline and expected longevity, and how would you design the occlusion to protect the restoration?
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Four weeks is achievable with a local laboratory but leaves no slack. The tooth must be protected regardless: either place a well-bonded composite cuspal-coverage provisional now and the definitive onlay after the wedding, or complete the onlay within two weeks as a rush case. What I would not do is place a large direct composite as a "temporary" that then stays in place for five years.
Longevity conversation: an indirect bonded onlay has a reasonable evidence base - roughly 80–90% survival at five years depending on material and operator - but the number that matters to her is that bruxism is the main threat to any restoration, and none of this cures the grinding. Be explicit that this is stabilisation and that she should expect maintenance, possible repair and, eventually, replacement. Record that discussion.
Occlusal design: keep contacts on tooth structure or on the restoration near the margins where possible; avoid heavy centric stops and excursive contacts concentrated on the ceramic; check the envelope of function and adjust any premature contacts. Review the 16 palatal composite and the worn anterior guidance, and prescribe a hard, full-coverage maxillary occlusal splint. If she declines the splint, document that you recommended it and why - it is the single most useful thing she can do for the restoration.