THERAPEUTIC DELIVERY OF CALCITONIN TO INHIBIT EXTERNAL INFLAMMATORY ROOT RESORPTION .1. DIFFUSION KINETICS OF CALCITONIN THROUGH THE DENTALROOT

Insertion of calcitonin into root canals of monkey teeth has been show n to inhibit external inflammatory root resorption and suppress inflam mation. Regulation of this therapeutic event depends upon the rate of arrival (diffusion) of the hormone at sites of resorptive activity. In the present study the diffusion characteristics of calcitonin through the dental root in an extracted human-tooth model are described, and the role of cementum in the diffusion process is also addressed. Root- canals were endodontically prepared to form a reservoir for [I-125]-ca lcitonin, and macerated to remove organic material from dentinal tubul es. In teeth with intact cementum, an initial period of delay (4-5 h) prior to the detection of calcitonin at the external tooth-root surfac e was followed by a rapid release of the calcitonin during the first 1 0.5 h (rate peaks at 6 h). Slower, sustained releases of calcitonin th rough intact cementum were measured for the following 9 days. Removal of cementum, to expose ''smear-free'' dentine, resulted in an earlier efflux of calcitonin (2 h) at external tooth surfaces and increased am ounts of calcitonin release over 9 days. Biphasic delivery of calciton in by such internal diffusion mechanisms suggests that loss of cementu m will enhance therapeutic availability while prolonged delivery to in tact external dental-root surfaces following early intra-canal placeme nt may also be useful for the therapeutic prevention of external infla mmatory root resorption.