Fractured distolingual cusp in a bruxer who refuses root canal treatment
A 38-year-old man attends complaining of sharp pain in the lower right first molar (46) on drinking cold fluids for the past three weeks. The pain lasts a few seconds and never occurs spontaneously or at night. He is a night-time bruxer and wears a hard acrylic splint. Tooth 46 carries a twelve-year-old MOD amalgam; the distolingual cusp is fractured and the fracture line runs about 2 mm subgingivally on the lingual aspect. Probing depths are 2–3 mm, there is no mobility and no tenderness to percussion. A periapical radiograph shows normal periapical tissues, no visible marginal caries, and a large restoration close to the pulp. A bite test with a wooden stick reproduces the sharp pain on release over the distolingual cusp. Tooth 47 carries an intact similar amalgam. The patient asks for a tooth-coloured restoration and states firmly that he does not want root canal treatment under any circumstances.
1. State the pulpal and structural diagnoses and explain which clinical or radiographic findings would change each of them.
Read the worked answer
Structural diagnosis: cracked cusp (incomplete cusp fracture) of 46. Pulpal diagnosis: reversible pulpitis.
Reasoning: pain that is provoked only by cold and lasts seconds, with no spontaneous or nocturnal pain, points to a vital pulp that is still capable of recovery. The bite test is decisive here: pain reproduced on release of pressure on the distolingual cusp means the fragment moves when loaded and the split dentine springs apart - the classic sign of a cracked cusp. Normal percussion, no mobility, 2–3 mm pockets and a normal periapex all support a localised, non-infected process.
Findings that would change the pulpal diagnosis to irreversible pulpitis: a cold response lingering beyond about 30 seconds, spontaneous or night pain, or tenderness to percussion. Findings that would change the structural diagnosis: the crack reaching the pulp chamber floor, extending below the gingival attachment, or an isolated narrow pocket along the fracture line - any of these make the tooth unrestorable and extraction becomes the honest option. Caries encountered directly over the pulp during excavation also changes the plan.
Record the test results before treatment begins, because the picture often shifts once the restoration is removed and the crack can be seen directly.
2. Compare a direct composite with bonded cuspal coverage for this tooth, and explain how you would manage the 2 mm subgingival lingual margin.
Read the worked answer
Both options must be judged against the fact that this is a heavily restored molar in a bruxer with a fractured cusp - the dominant failure mode is fracture, not wear.
Direct composite: conservative, inexpensive, and preserves the remaining cusp, but it does not cover the weakened distolingual wall. Replacing a large MOD amalgam with composite without cuspal coverage in a bruxer risks the cusp breaking further, possibly subgingivally and unrestorably.
Bonded cuspal coverage (onlay, ceramic or composite): covers the cusps, splints the cracked wall and is the more defensible choice, provided there is enough sound enamel at the margin and the crack does not reach the pulp floor.
The 2 mm subgingival lingual margin: do not simply force a matrix subgingivally. Options in order of preference: (1) trough the sulcus with electrosurgery or a diode laser under local anaesthetic to expose the margin - quick, no bone removed; (2) deep margin elevation, raising the margin with flowable composite under rubber dam after caries removal; (3) surgical crown lengthening, which removes bone and risks the furcation on a lower molar - usually avoided here; (4) orthodontic extrusion, slow and rarely justified. If the margin cannot be made supragingival without unacceptable bone loss, discuss extraction and replacement instead.
3. How would you address his refusal of root canal treatment, and what would you say about prognosis and long-term maintenance?
Read the worked answer
His refusal is not a reason to hide the options; it is a reason to document precisely what was explained and what he chose.
Explain the natural history: the pulp is currently reversible, but a crack plus a deep restoration are the two common routes to irreversible pulpitis and apical periodontitis. If the pulp is exposed or becomes symptomatic during treatment, the realistic choices are root canal treatment or extraction - not 'just fill it and hope'. Direct pulp capping of a deep carious exposure in a mature, symptomatic molar has a lower success rate than in a young tooth with a traumatic exposure, and I would not present it as a reliable alternative.
Respect autonomy by presenting three pathways: cuspal-coverage restoration with root canal treatment held ready if the pulp declares itself; extraction with bridge or implant replacement; or temporisation with review. He may decline root canal treatment, but he cannot decline its consequences, and the consent discussion should say so plainly.
Prognosis: a well-bonded cuspal-coverage restoration in an occlusally stable tooth with controlled bruxism has a good medium-term outlook; without coverage, or if the crack propagates, failure is likely. Emphasise the splint, an occlusal review, and short recall intervals. If he declines both definitive options, removing the tooth is better than leaving a symptomatic, unrestorable cracked molar in function.