Two weeks after a luxation injury, a tooth gives no response to electric pulp testing. What is the most likely explanation?

Correct answer: D. Transient disruption of the sensory nerve supply

• A. A single negative test this early does not establish necrosis. Diagnosis requires a combination of findings over time: persistent non-response, periapical change, discolouration and tenderness.
• B. Ankylosis is diagnosed by a high metallic percussion note, absent mobility and loss of the periodontal ligament space — not by pulp testing.
• C. Internal resorption is a radiographic diagnosis showing a balloon-like expansion of the canal, and the pulp typically remains partially vital.
• D. CORRECT. Trauma produces a temporary sensory paresis. The A-delta fibres that mediate the electric pulp test response are more vulnerable than the blood supply, so a tooth may be entirely VITAL — with intact circulation — yet give no reading for weeks or even months. Basing a decision to open the tooth on a single negative reading soon after trauma is a classic error.

Note: After trauma, record a baseline and retest at 2, 4, 8 and 12 weeks and at 6 months and 1 year. Compare against contralateral teeth. Never intervene on the basis of one reading.