An avulsed permanent tooth replanted within 15 minutes has approximately what success rate, and what happens by 30 minutes?

Correct answer: B. About 90% success at 15 minutes, falling to roughly 50% by 30 minutes

• A. Immediate replantation carries an excellent prognosis, so figures this low apply only to prolonged dry storage.
• B. CORRECT. Periodontal ligament cell survival collapses rapidly once the root is out of its physiological environment. Replantation within about 15 minutes gives roughly 90% periodontal healing; by 30 minutes this has fallen to around half; and beyond 60 minutes dry, survival of the ligament is negligible. This steep curve is why the single most useful instruction to a parent over the phone is to replant immediately.
• C. This reverses the relationship — success falls with time, it does not rise.
• D. Success is emphatically not uniform; the whole clinical emphasis on speed rests on the fact that it is not.

Note: If replantation on site is not possible: HBSS (Save-A-Tooth) is the best medium, then cold milk, then saliva or saline. Never water — it is hypotonic and lyses the ligament cells.