Extent Of Root Resorption Research Articles

Rapid orthodontic extrusion of crown root and cervical root fractured teeth

This study concerns the relapse tendency and extent of root resorption in 33 extruded non-vital crown root fractured or cervical root fractured teeth in 32 patients 10-20 years old. They constitute all orthodontically extruded teeth at the Orthodontic or Pedodontic Departments, Eastman Institutet, Stockholm (1982-1987). A simple extrusion mechanism exerted a force of 60-70 p along the root axis of the tooth. An extrusion of 2-3 mm was obtained in most patients; the most extreme effect was 6 mm. In 16 patients the extrusion was achieved within 3 weeks, in 12 it lasted for 4-6 weeks and in 5, 7-9 weeks. The treatment was more complicated in the lower jaw. After the extrusion, a fibrotomy was done and in most patients also a gingival recontouring to create an optimal relation between the gingiva and the margin of the restoration. Periodically identical radiographs were taken immediately before and after the extrusion, after 3 months and after 1 year. A minor relapse, about 0.5 mm, was observed in 3 patients. Limited root resorption was found in 6 teeth and severe in only 1. The resorptions did not progress in the following 2 years of observation.

Experimental dental traumatology: development of a model for external root resorption.

Abstract Intentional replantation of teeth appears to be a suitable model for examining the etiology and pathogenesis of root resorption elicited after traumatic dental injury. A histomorphometric analysis of root resorption developed with this model is described. An analysis of the accuracy and precision of the method in replanted monkey incisors has demonstrated that the method is usually reliable in revealing the extent and type of root resorption. In some experimental circumstances, however, where the pulp status was not controlled by endodontic therapy, a large intra‐ and interanimal variation was found in the extent of root resorption. Apart from a relation to tooth maturation and tooth type (incisors versus molars), this variation was primarily caused by haphazard occurrence and extent of inflammatory resorption. Based on an analysis of a series of experimental replantation studies, the following guidelines for experimental design seem appropriate: 1) selection of teeth according to identical tooth development and pulp status (i.e. intact, extirpated or root‐canal‐treated); 2) use of a standardized extraction procedure; 3) consideration of the type of teeth included (i.e. molars vs. incisors), unless paired experiments are planned or the experimental design includes an equal number of incisors and molars allotted to the different experimental groups; 4) side differences (right vs. left side) are apparently of no or minor importance; 5) sex differences are apparently of no or minor importance; 6) an individual proneness to resorption is apparently of no or minor importance, which means that more than one tooth can be used in each animal. The experimental design thus does not dictate the use of paired (i.e. homologous) teeth. However, as a matter of safety, when small differences in healing are expected, paired observations should be used.

Interrelation between alveolar bone and periodontal ligament repair after replantation of mature permanent incisors in monkeys.

Interrelation between alveolar bone and periodontal ligament repair was studied in green Vervet monkeys. Maxillary central incisors were extracted. The storage medium for the extracted teeth was saline in an 18 min. extra‐alveolar group and dry storage in a 120 min. extra‐alveolar group. In the experimental groups, the labial bone plate was removed surgically and the teeth replanted. In the control groups, teeth with similar extra‐alveolar periods were replanted into sockets with intact labial bone, The animals were sacrificed 8 weeks after replantation and the replanted teeth examined histometrically. Root resorplion and the position of the labial bone in relation to the cemento‐enamel junction were registered for each tooth. A significant relationship was found between the extent of labial bone repair and the extra‐alveolar period. Thus, teeth with I8 min. extra‐alveolar period showed almost complete repair of the labial bone plate, whereas teeth with an extra‐alveolar period of 120 min. showed a mean position of labial bone 3.7 mm from the pocket epithelium. The extent of root resorption was influenced by the extra‐alveolar period alone and not by the presence or absence of alveolar bone. It is concluded that a vital periodontal ligament upon replanted mature teeth is able to induce the formation of new alveolar bone.