A material of 637 concussed, subluxated, extruded, laterally luxated and intruded permanent incisors was analyzed with respect to factors influencing the development of pulp canal obliteration (PCO) after injury. A total of 96 (15%) developed partial PCO; 9 of these (1% of the total material) went on to develop total PCO. Only 2 teeth exhibited yellow discoloration of the clinical crown and 1 showed grey discoloration. Sensibility to electrometric pulp testing of the teeth with PCO was not significantly different from sensibility of contralateral homologues at the final examination (except for after lateral luxation, where the teeth with PCO had a significantly lower perception threshold). PCO was significantly more frequent among teeth with incomplete root formation than in teeth where root formation was completed. Extrusion, lateral luxation and intrusion showed more frequent occurrence of PCO than did concussion and subluxation. Moreover, the use of orthodontic band/resin splints significantly increased the occurrence of PCO, presumably due to the additional trauma of forceful placement and cementation of orthodontic bands in contrast to the relatively passive placement of an acid‐etch/resin splint. Based on previous and present clinical and radiographic findings concerning pulp response to luxation injuries, it is suggested that PCO is a sequel to revascularization and/or reinnervation of a damaged pulp after injury.

A relationship between type of luxation injury, stage of root development and development of pulp necrosis after injury has been demonstrated. It was therefore decided to delve more deeply into the relationship between stage of root development and the later development of pulp necrosis after injury in a material of luxated permanent teeth. In this context, the diameter of the apical foramen and the distance from the apical foramen to the pulp horn, as measured on radiographs taken at the time of injury, were used as indicators of root development. In order to justify this approach, the precision of the measuring technique and the accuracy of the radiographic technique were studied. Regarding precision of the measuring technique, it was found that there was a 1% to 4.3% error of the means of all measurements for the various parameters and exposure techniques employed. With respect to accuracy of the radiographic technique, it was found that there was a systematic error in the radio‐graphic technique which resulted in a median relative distortion of between 3.5% and 8% image magnification for the various parameters and the exposure techniques employed. These findings indicated that the measuring technique employed in the present investigation was reliable for studying the parameters in question. In a material of 226 extruded, intruded and laterally luxated maxillary permanent incisors, observed for up to 10 years, it was found that the development of pulp necrosis after injury was significantly related to the diameter of the apical foramen. For extruded and laterally luxated teeth, the smaller the diameter, the greater the probability of pulp necrosis. Intruded teeth with incomplete root development (i.e. radiographic diameters ≥1.2 mm) were associated with a much higher probability of pulp survival than teeth with complete root development (i.e. radiographic diameters ≤0.7 mm). The distance from the apical foramen to the pulp horn did not appear to be of importance in predicting pulp survival when diameter of the apical foramen was taken into account. Pulp survival after luxation injuries with displacement thus appears to be dependent upon the size of apical contact between the pulp and the periodontium.