400 avulsed and replanted permanent teeth were examined for periodontal ligament (PDL) healing, using standardized radiographic and clinical examination procedures (i.e. percussion test and mobility test). The effect of various clinical factors was examined, such as age and sex of the patient, type of tooth replanted, presence of crown fracture or bone fracture, stage of root development (including apical diameter and length of the pulp), type and length of extra-alveolar storage, clinical contamination of the root surface, type of root surface cleansing procedure, type and length of splinting period and antibiotic therapy. Surface resorption was generally diagnosed after 12 months; while inflammatory resorption and replacement resorption (ankylosis) were usually observed after 1 month and 1-2 months respectively. Most resorptive processes were diagnosed within the first 2-3 years. However, although rarely, even after 5 and 10 years new resorptive processes could be diagnosed. A univariate statistical analysis of 272 teeth revealed 9 factors significantly related to PDL healing. A subsequent multivariate analysis revealed that the following 4 factors had the strongest impact upon PDL healing, in descending order of significance: Stage of root development; length of the dry extra-alveolar storage period; immediate replantation and length of the wet period (saliva or saline storage). Nonphysiological storage, such as homemade saline and sterilizing solutions (chloramine and alcohol) always led to root resorption. Storage in tap water for more than 20 minutes usually led to root resorption. The common denominator for all these factors related to PDL healing appears to be survival of the PDL cells along the root surface. Based on these findings, immediate replantation is recommended irrespective of stage of root development.

A material of 322 patients with 400 avulsed and replanted permanent teeth were followed prospectively in the period from 1965 to 1988 (mean observation period = 5.1 yrs). The age of the patients at the time of replantation ranged from 5 to 52 yrs (mean = 13.7 yrs and median = 11.0 yrs). Standardized patient records were used through the entire period in order to obtain valid data concerning the extent of injury and treatment provided. At the follow-up period, pulpal and periodontal healing were monitored by clinical examination, mobility testing and standardized radiographic controls. Thirty-two of the replanted teeth (8%) showed pulpal healing. When related to teeth with incomplete root formation, where pulpal revascularization was anticipated (n = 94) the frequency of pulpal healing was 34%. Periodontal ligament healing (i.e. with no evidence of external root resorption) was found in 96 teeth (24%). Gingival healing was found in 371 teeth (93%). During the observation period, 119 teeth (30%) were extracted. Tooth loss was slightly more frequent in teeth with incomplete root formation at the time of replantation than in teeth with completed root formation.

Four hundred avulsed and replanted permanent teeth were examined for pulpal healing. In 110 teeth, the apical foramen was either open or half-open. In 16 teeth, the pulps were extirpated prophylactically. Thus, pulpal revascularization was considered possible in 94 teeth. Revascularization occurred in 32 teeth (34%). Pulp necrosis could usually be demonstrated after 3 weeks. Positive pulpal sensibility and radiographis signs of pulp canal obliteration were usually observed after 6 months. The effect of various clinical factors was examined, such as sex, age, type of tooth replanted, stage of root formation, type and length of extra-alveolar storage, clinical contamination of the root surface, type of cleansing procedure of the root surface, type and length of splinting and the use of antibiotics. Finally, the width of the apical foramen and the length of the root canal were measured on radiographs taken at the time of injury. A multivariate statistical analysis revealed that pulpal revascularization was more frequent in teeth with shorter distances from the apical foramen to the pulp horns. Furthermore, that wet storage (saliva and/or saline) for more than 5 min decreased the chance of pulpal revascularization; whereas dry extraalveolar storage had a monotonous effect on pulpal revascularization, i.e. decreasing chance of revasculatization with increasing length of the extraalveolar dry storage. Based on these findings, immediate replantation after brief cleansing in either tap water or saline is recommended.