INHIBITORY EFFECT OF THE TOPICAL ADMINISTRATION OF A BISPHOSPHONATE (RISEDRONATE) ON ROOT RESORPTION INCIDENT TO ORTHODONTIC TOOTH MOVEMENTIN RATS

Root resorption associated with tooth movement is an unsolved problem in orthodontics. If such root resorption could be prevented, it would be an important contribution toward reducing risk factors in orthodont ic treatment. The purpose of this study was to examine the effects of the topical administration of a bisphosphonate, risedronate, which is known to be a potent blocker of bone resorption, on root resorption du ring tooth movement and on the repair of the resorbed root surface aft er tooth movement in rats. In the first experiment, both the right and left upper first molars were moved buccally with a standardized expan sion spring under administration of risedronate. After day 7, extensiv e root resorption had occurred on the control side, and the area of ro ot resorption reached a maximum on day 14. The topical administration of risedronate caused a significant and dose-dependent inhibition of r oot resorption after the orthodontic force was applied. In the second experiment, the right and left upper molars were first moved buccally for 3 weeks. Risedronate treatment began on the day the spring was rem oved. After the force was withdrawn, the resorbed root surfaces on bot h the control and risedronate-treated sides were gradually restored by apposition of repair cementum (cementoid). The topical administration of risedronate did not appear to inhibit the repair process of root r esorption. These results suggest that the topical administration of ri sedronate may be useful in preventing root resorption of teeth during orthodontic treatment.