Abstract
The purpose of this research was to evaluate the effect of the salivary flow rate on fluoride retention in the mouth and to measure the site specificity of oral fluoride clearance when six healthy adults were awake and when they had been sleeping.
In the first experiment, the subjects rinsed their mouth with a 450 ppm fluoride solution at 2 pm and 0:00 am immediately prior to sleeping. The unstimulated salivary flow rate and salivary fluoride concentration were measured 15, 30, 60, 120 and 150 minutes after rinsing, while the same measurements were made at 6:30 am after the subjects had awakened. In the second experiment, ten mg of Naf and 5 ml of distilled water were mixed with 0.15 g of agarose which was heated until the agarose dissolved. Aliquots were pipetted into holders and these were bonded onto mouthguards produced from the plaster casts of each subject. The bonding sites were on the labial of maxillary incisors (UAB), the buccal of right and left maxillary molars (UPB-L-R) and the lingual of lower incisors (LAL). When the subjects were awake, the upper and lower mouthguards were fixed in the mouth and exposed to saliva for 10, 20, 60 and 100 minutes. The agarose was taken out of the holder and put into 2 ml of distilled water for 90 minutes and the fluoride concentration was 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.
At 30 minutes in the first experiment, the fluoride concentration in the saliva of each examinee had decreased to 1 ppm or less. There were significant negative correlations at 15, 30 and 60 minutes after moth-rinsing between the fluoride concentration and the salivary flow rate. The mean fluoride concentration in the saliva at 6:30 am corresponded with the concentration at 30 minute after the mouthrinsing at 2 pm.
In the second experiment, The half-times (the time for the initial F concentration to decreased by half) were lowest in LAL and highest in UAB. When the subjects had slept, the half-times in UAB were also highest.
The retention of fluoride in the mouth is affected by salivary flow rate and in order to keep a high fluoride level in the saliva for a long time, one possibility is to use a fluoride rinse before going to bed. The site-specificity of fluoride clearance from various sites in the mouth advantageous for UAB.
