If a permanent tooth is knocked out whole, hold it by the crown and rinse it; put it back if possible, otherwise store it in milk and see a dentist immediately; do not reinsert a baby tooth

No monetary cost for these steps. Milk or saline can be found at home or a convenience store; dental care costs are separate. The hard part is having the confidence to put the tooth back yourself, and identifying on the spot whether it is a baby or permanent tooth.

The UK's NHS dental injury page says to hold the crown, the white part normally visible above the gum, without touching the root. If dirty, gently rinse with milk, saline, or saliva. Try to put it back in its original socket. If it fits, gently bite on a clean cloth to hold it in place and see a dentist as soon as possible. If not, store it in milk or saliva. Do not reinsert baby teeth, as this can damage the developing permanent tooth underneath. Even if the knocked-out tooth cannot be found, arrange an emergency dental appointment. The International Association of Dental Traumatology's “Save Your Tooth” poster gives similar steps: find the tooth, hold the crown, plug the sink, and briefly rinse under cold tap water. Then either reinsert it, place it in a cup of milk or saline, or hold it between cheek and gum. Finally, see a dentist immediately. A dental trauma database at Copenhagen University Hospital in Denmark included 145 avulsed and replanted permanent teeth in 116 people, followed for 7 months to 23 years. The outcome was fusion of the tooth root to the socket bone, called ankylosis, after which the root is gradually resorbed. This occurred in 17.2% of teeth replanted immediately, 55.3% stored in saliva or saline before replantation, and 85.7% left dry for more than 1 hour. An earlier cohort of 400 teeth from the same hospital was reanalyzed in 2020. In children's teeth with incompletely developed roots, estimated ankylosis risk was 33.9% after less than 20 minutes dry and 60.0% after more than 60 minutes. In teeth with fully developed roots, it rose from 59.4% to 86.4%. Both sets of estimates were at 900 days after replantation. A 1995 study of the same 400 teeth also found that storage in tap water for more than 20 minutes was usually followed by root resorption. During follow-up, 30% of these 400 teeth were eventually extracted.

NHS. Knocked-out tooth（2025-02-06 审核）：「Hold the tooth by the white bit that sticks out of the gum (the crown) – do not touch the root」「If the tooth is dirty, rinse it gently in milk, saline or saliva」「Do not put a baby tooth back in as it could damage the tooth growing underneath」「If you cannot put the tooth back in, you can put it in either milk or saliva」. https://www.nhs.uk/conditions/knocked-out-tooth/；International Association of Dental Traumatology. Save your tooth（海报）. https://iadt-dentaltrauma.org/guidelines-and-resources/save-a-tooth-poster/；Gul A 等 (2024). Risk of ankylosis of avulsed teeth immediately replanted or stored under favorable storage conditions before replantation: A long-term clinical study. Dental Traumatology. https://doi.org/10.1111/edt.12898；Lauridsen E 等 (2020). Risk of ankylosis of 400 avulsed and replanted human teeth in relation to length of dry storage: A re-evaluation of a long-term clinical study. Dental Traumatology. https://doi.org/10.1111/edt.12520；Andreasen JO 等 (1995). Replantation of 400 avulsed permanent incisors. 1. Diagnosis of healing complications. Endodontics & Dental Traumatology. https://doi.org/10.1111/j.1600-9657.1995.tb00461.x；Andreasen JO 等 (1995). Replantation of 400 avulsed permanent incisors. 4. Factors related to periodontal ligament healing. Endodontics & Dental Traumatology. https://doi.org/10.1111/j.1600-9657.1995.tb00464.x

The evidence grade is B because the figures come from observational follow-up at one hospital, without randomized controlled groups. The benefit is judged medium: this preserves teeth rather than life, and the endpoint is root ankylosis rather than direct tooth loss. The researchers also say some teeth left dry for more than an hour still did not develop ankylosis, so do not discard a tooth because time has passed; take it to the dentist anyway. Use tap water only for a quick rinse, not to store the tooth during transport. The main beneficiaries are your children, but the same approach applies to adults injured in falls, ball sports, or cycling accidents. The NHS says a tooth that cannot be saved can initially be replaced with a removable denture, with a bridge or implant considered after healing. For asking about implant costs, see Section 24, Item 12 (ask for the complete package price before a dental implant).