The extra-alveolar dry time before replantation is the most critical factor influencing the prognosis of a replanted avulsed tooth because prolonged dry time causes irreversible damage to the periodontal ligament cells. Once these cells die, the risk of ankylosis and root resorption significantly increases, leading to poor long-term survival. Immediate replantation or storage in an appropriate medium within 15-20 minutes is crucial to preserve cell viability and promote successful healing. While storage medium, age, and root development are important, they have less impact than limiting dry time on the tooth’s prognosis.

Reference: Textbook of Oral and Maxillofacial Surgery, 3rd Edition.