The aim of the study was to determine the pharmacokinetics of a new hydroxyapatite-Eudragit RS100 diffusion-controlled fluoride-releasing system designed for intra-oral use with a 0.15 mg F-/day release for a 1-month period. Matrix tablets, each containing 18 mg of sodium fluoride, were bonded to the buccal surface of the first maxillary molar teeth of 20 subjects (age 20-23 years). Morning and evening salivary and urinary samples were collected 5 days before the study and every day for the 1st week, then once a week for 1 month. Fluoride ion measurements were done using the microdiffusion method. The salivary and urinary fluoride concentrations were significantly raised during the treatment period (p < 0.05). Morning salivary fluoride levels were higher than evening salivary fluoride levels (p < 0.05) whereas evening urinary fluoride levels were higher than morning urinary fluoride levels (p < 0.05). The statistically significant increase in salivary fluoride levels indicates a caries preventive role for this device. Copyright (C) 2005 S. Karger AG, Basel.