Ankylosis of experimentally reimplanted teeth related to extra-alveolar period and storage environment

This study was designed to determine if avulsed permanent incisors which have been kept dry for a period and then immersed in an isotonic solution prior to implantation have an increased healing rate. The permanent maxillary incisors of six beagle dogs were grouped by lot in six treatment classes so that each type of incisor was included in each class. After extraction, the teeth of a treatment class were stored either dry, wet, or first dry and then wet. One week after reimplantation, splints were removed and all root canals cleansed and filled with calcium hydroxide. The dogs were sacrificed after three months and the teeth with premaxillas were removed and exposed to routine histologic treatment. Transverse sections were evaluated according to earlier described methods. All root surfaces of a treatment class were regarded as a homogeneous risk mass. The percentage of sites with ankylosis increased with increased dry time. Subsequent wet storage in Hank’s solution decreased the frequency. Storage in just a wet environment for up to 60 minutes resulted in a negligible percentage of ankylosis. It was concluded that avulsed teeth which have been kept dry for 15 minutes or longer should be conditioned in an isotonic solution for about 30 minutes prior to reimplantation. When the dry time exceeds 30 minutes, there is a greatly increased risk of ankylosis after reimplantation. * It is well-known that the risk of ankylosis in reimplanted teeth increases with extension of the extra-alveolar period, particularly if the teeth are stored dry during this period (for review see Andreasenl). In a retrospective clinical study by Cvek et al. 2 the occurrence of ankylosis was analyzed systemically for the first time in relation to extra-alveolar period, with interaction between dry and subsequent wet storage as the modifying factor. Although the statistical evaluation revealed no more than trends, it was concluded that healing might be good after reimplantation of avulsed permanent incisors provided the teeth have been kept dry for not more than 40 minutes, and provided that those which have been kept dry for more than 15 minutes are placed in an isotonic solution for about 30 minutes prior to reimplantation. This presupposes that teeth with necrotic pulp are given adequate endodontic treatment with calcium hydroxide paste as a temporary root-filling material. Under such circumstances complications other than ankylosis need hardly be expected. The material referred to in Table I has been rearranged according to the premises of the present investigation. It consisted of mature as well as immature teeth but did not cover all clinically relevant combinations of dry and wet storage. Therefore, an experimental series was performed in order to confirm or reject the assumptions based on the results from the retrospective study.