ULTIMATE TENSILE-STRENGTH OF PDL OF MOLARS IN RATS AFTER 1-HYDROXYETHYLIDENE-1,1-BISPHOSPHONATE INJECTIONS

Objectives and methods: Administration during root formation of a bisp hosphonate, 1-hydroxyethylidene-1,1-bisphosphonate (HEBP), at a dose c orresponding to 10 mg P/kg body weight, has been found to interfere wi th the formation of acellular cementum in rats. The purpose of this st udy was to measure the force required to extract a tooth lacking norma l acellular cementum, and to correlate this force and the ultimate per iodontal strength with the morphology of the periodontal tissues at di fferent time intervals after single or multiple injections of HEBP. Re sults: A single injection of HEBP given during root formation inhibite d the formation of acellular cementum and resulted in a temporary redu ction of the extraction force and the ultimate tensile strength. Ninet y days after the injection of HEBP, both parameters were the same as i n the controls. The increase in extraction force and ultimate tensile strength was associated with the onset of occlusal contact of the teet h. The organization of periodontal ligaments was improved after the te eth reached the occlusal level. After daily injections of HEBP for 3 d ays, there was a permanent reduction in root length and dento-alveolar ankylosis developed in the furcation area. Conclusion: (1) A single o r three injections of HEBP changed the formation of acellular cementum to that of an atypical hyperplastic cementum which increased the reso rption risk at this site. (2) The ultimate tensile strength was marked ly reduced in teeth lacking acellular cementum. (C) 1997 Elsevier Scie nce Ltd.