Replantation of 400 avulsed permanent incisors. 3. Factors related to root growth.

Four hundred avulsed and replanted permanent incisors were examined for pulpal and periodontal healing. In 30 teeth, root formation was incomplete at the time of injury. Two teeth were excluded from the study due to nonphysiological extraalveolar storage (i.e. homemade saline). Of the 28 remaining replanted incisors, 7 showed subsequently completed root development, 8 partially completed root development and 13 arrested root development. Completed root development subsequent to replantation was found to be significantly related to pulpal revascularization, being rare in cases with pulp necrosis (5 of 15 teeth) and frequent after pulpal healing (11 of 13 teeth) (p = 0.01). Root development was not found to be significantly related to the extraalveolar storage period; but occurred slightly more frequently when the dry storage period was less than 45 min. (p = 0.13). Ingrowth of bone and formation of an internal periodontal ligament (PDL) was found in 6 teeth and was related to arrested root formation in cases with pulpal healing. The explanatory factor for these findings appeared to be damage to the Hertwig's epithelial root sheath.