Irreversible Pulpitis vs. Cracked Tooth in a Heavily Restored Molar
A 45-year-old woman presents with a 3-week history of sharp pain in the upper left first molar (tooth 26) triggered by cold drinks, lasting 10–20 seconds after the stimulus is removed. Over the past 4 days the pain has become spontaneous and wakes her at night; she now avoids chewing on that side. The tooth has a large MOD amalgam with a visible marginal ditching and a hairline crack line on the mesiobuccal cusp. Probing depths are 3–4 mm generally, but 6 mm on the mesiobuccal aspect with bleeding on probing; the crack line appears to extend toward that pocket. Percussion is mildly tender; biting on a cotton roll reproduces a sharp pain that lingers. Cold test: intense pain lasting >30 seconds. Electric pulp test: response at low threshold. Radiograph: widened PDL at the mesiobuccal root apex; no periapical radiolucency. Adjacent teeth respond normally to cold and are non-tender to percussion.
1. Differentiate between irreversible pulpitis, symptomatic apical periodontitis, and a cracked tooth syndrome in this case, and state which is the most likely primary diagnosis.
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Findings mapped to diagnoses
- Lingering cold pain (>30 s) + spontaneous/nocturnal pain → strongly suggests irreversible pulpitis.
- Mild percussion tenderness + widened PDL → symptomatic apical periodontitis (early), consistent with pulpal inflammation extending apically.
- Pain on biting a cotton roll, crack line, marginal ditching → raises concern for cracked tooth.
Most likely primary diagnosis: Irreversible pulpitis with symptomatic apical periodontitis in tooth 26, with a possible cracked tooth that must be excluded before/alongside endodontic treatment.
Why not just cracked tooth syndrome?
- Cracked tooth syndrome classically gives sharp pain on release of biting and often normal or only transient cold response; here the cold response lingers and there is spontaneous nocturnal pain - features of pulpal disease.
- The 6 mm mesiobuccal pocket and crack line extending toward it are a red flag for a vertical root fracture or crack extending subgingivally, which changes prognosis drastically.
Next step to discriminate:
- Transillumination, bite test with a tooth slooth, and careful probing of the crack to see if it extends subgingivally.
- If the crack extends below the alveolar crest or communicates with the pocket, the tooth may be non-restorable and extraction considered.
2. Outline your treatment plan and explain how the crack affects the choice between endodontic treatment and extraction.
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If the crack is confined to the crown (supracrestal)
- Remove the existing amalgam and evaluate the crack extent under magnification; place a provisional restoration or orthodontic band to stabilize.
- Endodontic treatment of tooth 26 (irreversible pulpitis).
- Cuspal coverage restoration (full-coverage crown or onlay) after endodontics to protect against propagation.
- Reassess the 6 mm pocket; periodontal treatment and monitoring.
If the crack extends subgingivally toward/below the crest or communicates with the pocket
- Prognosis is poor; extraction is usually indicated because:
- The crack provides a pathway for bacterial contamination and cannot be sealed.
- Even with endodontics and crown, the tooth will likely fail and may cause recurrent infection or abscess.
- In that case: extraction, then plan for a fixed partial denture or implant after healing.
Key decision rule:
- Supracrestal crack → endodontics + cuspal coverage is reasonable.
- Subcrestal/communicating crack or vertical root fracture → extraction.
Communication: Explain to the patient that the crack determines prognosis and that the final decision may only be made after removing the restoration and directly visualizing/probing the crack.
3. What would change if the cold test had produced a normal, non-lingering response and the pulp tested vital with a normal response?
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Reinterpretation of findings
- A normal, non-lingering cold response would argue against irreversible pulpitis.
- The pain on biting and crack line would then point more toward cracked tooth syndrome (or a reversible pulpitis if symptoms are provoked only).
Revised plan
- Do not start endodontics based on pulpal diagnosis alone.
- Stabilize and evaluate the crack: remove the amalgam, transilluminate, bite test, and consider an orthodontic band or provisional crown to see if symptoms resolve.
- If symptoms resolve with stabilization, consider a cuspal coverage restoration without endodontics, with follow-up.
- If symptoms persist or pulp becomes non-vital, proceed to endodontics.
Why this matters
- Overtreating a vital, reversibly inflamed pulp with endodontics is avoidable; the crack is the driver, and stabilization is the test.
- The 6 mm pocket still needs periodontal evaluation regardless.
Bottom line: The pulpal diagnosis hinges on the lingering cold response; without it, the case shifts to a cracked-tooth management pathway rather than endodontic treatment.