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Fluoride concentrations were determined in saliva from children and young adults by means of a fluoride ion electrode (Orion Research Inc.). Children who consumed drinking water containing 1 ppm fluoride (Group 1) showed a mean fluoride concentration of 0.009 ppm in parotid saliva. Children residing in a community with less than 0.1 ppm fluoride in the drinking water (Group 2) showed a mean concentration of 0.007 ppm. The comparable mean concentration was 0.008 ppm in children from the same community receiving a daily supplement of 1 mg fluoride (Group 3) while adults from a non-fluoridated community who refrained from the use of fluoride dentifrices for one week (Group 4) had a mean concentration of 0.010 ppm in parotid saliva. It was further found that simultaneously collected stimulated parotid and submaxillary saliva had identical concentrations on an individual basis. Fluoride concentrations were higher in whole saliva than in duct saliva from the same individual. The mean fluoride concentration in whole saliva in Group 1 was 0.033 ppm compared to 0.011, 0.015 and 0.017 ppm respectively in Groups 2, 3 and 4. The increased fluoride concentrations in whole saliva were attributed to inclusion of cellular debris and mucus since the concentrations decreased when whole saliva was ‘cleared’ by centrifugation. Also the fluoride concentration tended to decrease in a series of successively collected samples of whole saliva. Dental plaque and material scraped from the tongue contained significant amounts of fluoride.

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No abstract

Hydroxyapatite was exposed to solutions of monofluorophosphate (MFP) at pH 5 and pH 7, for periods up to 48 h, and fluoride (F^––) and F as MFP were measured in solution and solid. The exposed solid was dissolved in 0.5 m HC104 at 2 °C and F^–– measured immediately, and after hydrolysis had been completed 24 h later, employing a fluoride electrode. Solutions were analyzed in a similar manner. Solution F^–– (3% of total F) decreased rapidly and then gradually increased to concentrations above the original level. Solution MFP decreased continuously, the rate decreasing with time. The corresponding deposition of F on the solid was in the forms of both F^–– and MFP. The fraction of deposited F^–– increased with increased time of exposure while the fraction of F as MFP decreased. MFP was removed more readily by washing than F^––. MFP in MFP exposed apatite decreased while forming F^–– under humid conditions, but remained constant under dry conditions. Only small amounts of F were deposited from MFP in intact enamel. MFP retained in the mouth after a MFP rinse was subjected to rapid hydrolysis. The findings showed that the uptake of F from MFP was greater at pH 5 than at pH 7 and that MFP is hydrolyzed by two mechanisms, one operating at the solid solution interface of the apatite and the other in saliva and/or plaque. It is concluded that the caries-reducing effect of MFP is due to F^–– released by hydrolysis.