Which of the following conditions most classically produces pain that MIMICS irreversible pulpitis, leading to unnecessary endodontic treatment?

Correct answer: B. Prodromal herpes zoster of the trigeminal nerve

• A. Incorrect. Cardiac referred pain does occur in the mandible/left jaw, but it is exertional, bilateral or diffuse, relieved by rest/nitroglycerin, and is not reproduced by thermal testing of a tooth — so it mimics a cardiac-origin toothache, not pulpitis specifically.
• B. Correct. In the PRODROMAL phase of herpes zoster (before the vesicles appear), the patient has severe, spontaneous, poorly-localised burning or throbbing pain along a trigeminal branch. Multiple teeth in that dermatome may test as though they are irreversibly inflamed. Endodontic treatment is frequently started before the unilateral vesicular rash appears 2–4 days later and reveals the true diagnosis.
• C. Incorrect. Maxillary sinusitis causes pressure-type pain in several maxillary posterior teeth that worsens on bending forward. It is a classic mimic of periapical pain, but the pain is dull, bilateral-multiple-tooth, and not the sharp lingering thermal response of pulpitis.
• D. Incorrect. Primary HSV presents with fever, malaise, lymphadenopathy and widespread painful vesicles/ulcers on gingiva and mucosa — the diagnosis is obvious on inspection and is not confused with pulpitis.

Note: Rule of thumb: unilateral, severe, multi-tooth pain with NO identifiable dental cause and normal radiographs = think prodromal zoster and wait for the rash.