The Site-specificity of Fluoride Clearance in the Mouth

Objectives: The purpose of this study was to evaluate the effect of salivary flow rate on fluoride retention in the mouth and also to measure the site-specificity of them when six healthy adults were awake and when they had been sleeping. Methods: NaF (10,20,40 mg) and 5 ml distilled water were mixed with 0.15 g of agarose which was heated until the agarose dissolved. Aliquots were pipetted into holders (diameter 4 mm, depth 1 mm) and there were bonded onto mouthguards produced from each subject. The bonding sites were on the upper anterior buccal (UAB), the upper posterial buccal (UPB), and the lower anterior lingual (LAL). When the subjects were awake, the mouthguards were fixed in the mouth and exposed to saliva for 15, 45 minutes. The agarose was taken out of the holder and put into 2 ml of distilled water for 90 minutes and the fluoride concentration were measured by a fluoride ion meter. To examine the retention of fluoride in the mouth during sleep, the mouthguards were placed before going to bed (0:00 am) and removed at 6:30 am and the fluoride concentration measured as above. Results: The fluoride clearance from various sites in the mouth was extremely lower when subjects were asleep than when they were awake. The half-times (the time for the initial F concentration to decrease by half) were highest in UAB and lowest in LAL. When the subjects had slept, the clearance rates of F from the gel were also showed the same results of the above. Conclusion: The retention of fluoride in the mouth is affected by salivary flow rate.