If a permanent tooth is completely knocked out, hold it by the crown, gently rinse it, reinsert it into the socket immediately if possible, or submerge it in milk and seek immediate dental emergency care; never reinsert a baby tooth

Handle the knocked-out tooth strictly by its white crown and never touch the root surface. If dirty, rinse gently with milk or sterile saline; if possible, reinsert it immediately into its socket and gently bite down on a clean cloth. If reinsertion fails, submerge the tooth in a cup of cold milk and see a dentist immediately; never wrap it in dry tissue paper. Immediate replantation carries only a ~17% long-term root ankylosis rate, whereas teeth left dry for over an hour suffer over 85% ankylosis. Baby teeth must never be replanted.

Zero financial cost for first-aid preservation; subsequent dental repositioning, splinting, and endodontic care incur clinical fees. Whole milk or sterile saline is readily available in homes or nearby convenience stores. The psychological barrier is overcoming squeamishness to push an avulsed tooth back into an open bleeding socket, and correctly distinguishing an adult permanent tooth from a deciduous baby tooth.

NHS emergency guidance for a knocked-out tooth dictates: hold the tooth strictly by the crown (the white portion visible above the gumline) without contacting the root surface. If contaminated, rinse gently in milk, saline, or saliva. Attempt to reinsert the tooth back into its socket; if successful, bite gently on a clean tissue or handkerchief to hold it steady and visit an emergency dentist immediately. If reinsertion is impossible, transport the tooth submerged in milk or buccal saliva. Baby teeth (deciduous teeth) must never be replanted as reinsertion damages the underlying developing permanent tooth bud. The International Association of Dental Traumatology (IADT) "Save a Tooth" protocols outline identical steps: retrieve tooth, handle only by crown, rinse briefly under cold tap water if dirty, and choose one of three storage methods: (1) immediate replantation into socket; (2) immersion in a glass of cold milk or physiological saline; or (3) transport held between cheek and gum (buccal sulcus), followed by immediate dental transit. A long-term clinical database study from Copenhagen University Hospital tracking 145 avulsed permanent teeth in 116 patients followed for 7 months to 23 years evaluated the risk of replacement resorption (ankylosis, where root cementum fuses to alveolar bone and is gradually resorbed): teeth replanted immediately showed a 17.2% ankylosis rate; teeth stored in physiological wet media (saliva/saline) prior to replantation showed 55.3%; and teeth left in dry storage for >=60 minutes exhibited an 85.7% ankylosis rate. An earlier cohort of 400 avulsed teeth re-evaluated in 2020 revealed that for immature teeth with open apices, dry storage <20 minutes carried a 33.9% ankylosis risk, rising to 60.0% past 60 minutes; for mature teeth with closed apices, ankylosis escalated from 59.4% to 86.4% at 900 days. Tap water storage for >20 minutes caused widespread periodontal ligament necrosis and root resorption. Overall, 30% of avulsed teeth eventually required extraction during long-term follow-up.

Graded Evidence Grade B because statistics stem from longitudinal specialized dental hospital trauma registries without prospective randomized arms. Benefit is categorized as Moderate because tooth preservation preserves dentition aesthetics and masticatory function rather than preventing mortality. Researchers emphasize that even teeth experiencing prolonged dry storage (>60 min) should not be discarded, as specialized endodontic splinting and chemical treatments still salvage a proportion of teeth or maintain alveolar ridge volume for future implants. Tap water should only be used for a brief 10-second rinse; never transport teeth immersed in tap water due to hypotonic cell lysis. Primary beneficiaries are active children and adults prone to sports impacts, falls, and cycling collisions. In cases of unrecoverable tooth loss, removable partial dentures can bridge the gap during childhood until definitive adult dental bridges or endosseous implants are placed (see Chapter 24, Rule 12 for dental implant bundled pricing).

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