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Calcium hydroxide [Ca(OH)2], when used as a root canal dressing, has been shown to promote periapical healing, induce formation of an apical hard tissue barrier (apexification), and arrest infection-related root resorption. The main mechanism of action is thought to be the high alkalinity of Ca(OH)2 ensuring a bactericidal or bacteriostatic effect upon microorganisms in the root canal and dentinal tubules. Several anatomical factors related to the root canal, such as the coronal access cavity, the apical foramen, the dentinal tubules, and existing resorption cavities on the root surface, all allow leakage of hydroxide ions from the root canal. The purpose of the present clinical study was to analyze pH changes in 63 permanent anterior teeth in which Ca(OH)2 (Calasept®) was used as an initial canal dressing after replantation and subsequent pulp necrosis had developed. The pH changes in the pulp canal were studied with relation to observation period, stage of root formation, healing of any periapical radiolucency, infection-related root resorption, formation of an apical hard tissue barrier, and finally the radiographic appearance of Ca(OH)2 in the canal (i.e. present or not). The study showed that several factors determined the pH level: the observation period (i.e. observation periods exceeding 6 months showed a significant drop in pH level below a pH of 10), an initial active inflammatory root resorption (tendency to be related to a drop in pH), and a subsequent progression of infection-related resorption (the same tendency to be related to a drop in pH to below 10). The size of the apical foramen and the length of the pulp had no relation to pH change. The radiographic disappearance of Ca(OH)2 in the root canal (loss of radiopacity of the canal dressing) was found to be significantly associated with a drop in pH (P=0.001). It was concluded that radiographic monitoring of the Ca(OH)2 presence in the root canal is essential for endodontic treatment planning (i.e. when to replace Ca(OH)2 or perform a permanent root filling). Furthermore, continuous activity of inflammatory root resorption may indicate a drop in pH and should result in replacement of new Ca(OH)2. It should be noted that these findings apply to a Ca(OH)2 product (Calasept®) with no added radiopaque material.

Replanting avulsed teeth with a doubtful long-term prognosis due to unfavorable extra-alveolar conditions has recently been questioned by Kenny and Barrett (1). Many factors, however, still favor replanting such teeth. First of all, reliability of failure predictors has not yet been tested in prospective studies. Secondly, preservation of even resorbing replanted teeth may offer significant long-term advantages in preparation for definitive treatment. Also, for psychological reasons, replantation can significantly reduce the anxiety and despair of both the injured child and the parents. Furthermore, decoronation of a resorbing anterior tooth will allow it to serve as a matrix for alveolar bone formation and preserve an otherwise resorbing alveolar process, thereby leaving an environment of bone and soft tissue that is optimal for both single implant insertion or fixed prosthesis. Finally, replantation and subsequent decoronation, if indicated, appears to be cost-effective in comparison with non-replantation combined with subsequent repeated prosthetic tooth replacements owing to vertical alveolar growth of adjacent ridge areas, with eventual definitive implant placement or a fixed prosthesis.

Decoronation of ankylosed teeth in infraposition was introduced in 1984 by Malmgren and co-workers (1). This method is used all over the world today. It has been clinically shown that the procedure preserves the alveolar width and rebuilds lost vertical bone of the alveolar ridge in growing individuals. The biological explanation is that the decoronated root serves as a matrix for new bone development during resorption of the root and that the lost vertical alveolar bone is rebuilt during eruption of adjacent teeth. First a new periosteum is formed over the decoronated root, allowing vertical alveolar growth. Then the interdental fibers that have been severed by the decoronation procedure are reorganized between adjacent teeth. The continued eruption of these teeth mediates marginal bone apposition via the dental-periosteal fiber complex. The erupting teeth are linked with the periosteum covering the top of the alveolar socket and indirectly via the alveolar gingival fibers, which are inserted in the alveolar crest and in the lamina propria of the interdental papilla. Both structures can generate a traction force resulting in bone apposition on top of the alveolar crest. This theoretical biological explanation is based on known anatomical features, known eruption processes and clinical observations.

Traumatic dental injuries are for the most part unanticipated events that, if not managed appropriately, can have serious consequences for the patient. The purpose of this review is to describe the current concepts in establishing diagnosis descriptive of specific traumatic entities, and to delineate recommended treatment approaches for these injuries based on available evidence.