Fluoride in gingival crevicular fluid and a new method for evaporative water loss correction

The concentrations of fluoride in the gingival crevicular fluid (GCF) of dog canines and carnassials were determined as a function of plasma fluoride levels using the filter paper strip technique. These were compared to the simultaneous concentrations of ¹³¹I or (99m)Tc which were assumed to be markers for evaporative water loss of GCF. Plasma fluoride levels ranged from 15 to 300 μmol/l. The GCF to plasma fluoride concentration ratios at all plasma fluoride levels were consistently greater than unity. This was also true for the ¹³¹I and (99m)Tc GCF to plasma ratios. When the GCF to plasma fluoride ratios were factored by the radiotracer ratios, the values closely approximated unity. Thus, ¹³¹I and (99m)Tc appear to be valid markers for evaporative water loss of GCF. It is concluded that GCF fluoride levels are nearly identical to those of plasma over a wide range of plasma fluoride concentrations and that GCF is a source of fluoride for the oral environment.