[Effects of 1-hydroxyethylidene-1, 1-bisphosphonate (HEBP) on the unimpeded eruption rate and the dental hard tissue formation in rat mandibular incisor].

To understand the mechanism of eruption in continuously growing teeth, the relationship between the rate of eruption and formation of dental hard tissues was examined following administration of 1-hydroxyethylidene-1, 1-bisphosphonate (HEBP), an inhibitor of hard tissue formation. Three experimental groups of rats received daily subcutaneous injections of 9, 18 or 36 mg P of HEBP/kg, respectively, for 7 days. Tetracycline was also injected to mark the dentine in some animals. To maintain an unimpeded state, all four incisors in each rat were shortened repeatedly during the experimental period. Eruption rates of the mandibular incisors were measured by a photographic method. Transverse sections of the mandibles were cut and histological, microradiographic and fluorescent micrographic examinations were done. Significant decreases of the eruption rates were found in all experimental groups following the administration of HEBP. However, differences were not marked among the three experimental groups. It was also shown that matrix formation and calcification of the dentine were markedly inhibited following the administration of HEBP. Matrix formation and calcification of the enamel were also inhibited by the drug administration. It is assumed that the eruption of the rat incisor is not closely associated with the formation of dental hard tissues and their calcification.