Dental trauma and avulsed teeth — branching viva

Stage 1 — The knocked-out permanent incisor

Examiner: An eight-year-old boy has fallen on the playground and knocked out his upper left permanent central incisor about five minutes ago. The teacher has brought him holding the tooth wrapped in a tissue. What should have been done at the scene, and what do you do now? ^[1]

Candidate: The first-aid should have been to find the tooth, pick it up by the crown only and never the root, rinse a dirty root gently under running water for about ten seconds, and replant the permanent tooth immediately into its socket the right way up, then have the child bite gently on a clean handkerchief or gauze to hold it in place. If it could not be replanted it should have gone into cold milk or Hank's balanced salt solution. Now that the tooth is sitting dry in a tissue, the clock is running, so I replant it immediately after a brief rinse, or if I cannot I get it into milk at once and call the dentist. I never scrub the root, never store it in plain water, and never let it dry. ^{[1] [9]}

Examiner: Why milk, and why not water? ^[9]

Candidate: Because the survival of the tooth depends entirely on the periodontal-ligament cells clinging to the root. Milk and Hank's balanced salt solution are physiologically balanced media that keep those cells alive far longer than dry air. Plain water is hypotonic, so it drives water into the cells and ruptures them by osmosis, destroying the very cells that must re-form the attachment. That is why water is contraindicated as a storage medium even though it is fine for a brief rinse. ^[9]