Without Calcium pre-rinsing, NaF Does Not Form CaF₂ in Plaque

Plaque fluid F released from bioavailable plaque F deposits is an important factor in the cariostatic effect of this ion. These reservoirs can be delineated as biological/bacterial (bio-Ca-F), which appears to be a relatively labile oral F source and “calcium-fluoride-like” (oral-CaF₂), which appears to be a more persistent oral F source. Objectives: To quantify these reservoirs after a NaF rinse. Methods: Fasted plaque was recovered from 11 subjects 0.5h after rinsing with a 228 ppm F (NaF) rinse. The plaque was homogenized and split into two ≈2 mg aliquots. The fluid from these samples was recovered, combined and analyzed (Caries Res 2007p421). One plaque aliquot was repeatedly equilibrated with a 500 µl of PO4 free solution having the same pH, Ca and F as the fluid recovered from these samples. Since this plaque-fluid-like solution is undersaturated with respect to oral-CaF₂, this equilibration extracts all of this type of plaque F deposit without changing the amount of F in the bio-Ca-F reservoir. The total F in both aliquots was then determined by strong acid extraction. Results: The F recovered (average±SE, µg/g) in the plaque aliquots extracted with the plaque-fluid-like solution (49.1±17.6) was not significantly different (p>0.05, paired difference test) from the amount in the unextracted aliquots (47.5±16.3), suggesting that no oral-CaF2 was formed in plaque after a NaF rinse. In contrast a recent preliminary (N=5) study employing the same extraction technique, (Abst. 0506, 2007 IADR), suggests that a Ca pre-rinse given before a NaF rinse formed substantial amounts of oral-CaF₂. Conclusion: Without a Ca pre-rinse, the NaF rinse does not form oral-CaF₂. This may partially account for the large amounts of plaque/plaque fluid F found with the Ca pre-rinse/NaF rinse compared to the NaF rinse alone. (Vogel JDR, in press). Supported by NIDCR grants DE16416, 14707,ADAF, and NIST.