A method for continuous in vivo measurement of fluoride ion activity of human oral fluid is described. An electrochemical fluoride sensor and short range radiotelemetry were employed to study clearance of salivary fluoride after use of fluoride-containing tablets and dentifrices. A miniature transmitter including power supply and reference electrode was mounted on a removable partial denture. The fluoride sensor, a modified Ionalizer fluoride ion activity electrode, was fixed to the denture so that it replaced the buccal surface of a lower first molar. Dissolution of a sodium fluoride tablet (0.7 mg F) placed in the vestibular fold on the electrode side resulted in an increase of fluoride ion activity to a maximum of 150 ppm F within 12 min and in a gradual decrease to the original activity level in 40 min. The same procedure with the tablet placed in the vestibular fold on the opposite side was followed by a small rise only in the range of single ppm F units. Regular toothbrushing with dentifrices containing aminefluoride, sodium fluoride or monofluorophosphate was followed by fluoride activity increases of different magnitudes. © 1969.
