Comparative pharmacokinetics of fluoride secretion by major and labial minor salivary glands after oral fluoride intake.

OBJECTIVES

To evaluate whether fluoride secretion by labial minor salivary glands exhibits a pharmacokinetic pattern comparable to that of major salivary glands after oral fluoride intake.

DESIGN

In a randomized, blind and crossover study, eight healthy adult participants ingested aqueous NaF solutions containing 5, 10, or 20 mg of fluoride after overnight fasting. Saliva samples were collected at baseline (time 0) and at 5, 15, 30, 60, and 120 min post-ingestion from four sources: labial minor glands (LG), parotid glands (PG), floor of the mouth (FS), and whole saliva (WS). LG saliva and FS were collected using pipette tips under gentle suction, while PG saliva was obtained using the Carlson-Crittenden device and WS was obtained by asking participants to expectorate directly into a 1.5 mL microtube. Fluoride concentrations were determined using a validated micro-method with an inverted fluoride ion-selective electrode. Pharmacokinetic parameters - maximum concentration (Cmax) and area under the curve (AUC) - were calculated. Data were analyzed by two-way ANOVA and linear regression (α=0.05).

RESULTS

Fluoride secretion from LG demonstrated a dose-dependent response, with Cmax values of 0.37 ± 0.04, 0.45 ± 0.04, and 0.76 ± 0.19 µg/mL, and AUC values of 29.0 ± 6.2, 33.6 ± 3.4, and 52.7 ± 11.5 µg F/mL ×  min for 5, 10, and 20 mg doses, respectively. These parameters did not differ significantly from those obtained from other salivary glands. A significant linear correlation was observed between the ingested fluoride dose and LG fluoride secretion (R² = 0.6469, p < 0.0001).

CONCLUSION

The pharmacokinetic profile of fluoride secretion in labial minor salivary glands is quantitatively comparable to that of major salivary glands. Their use as an alternative source in fluoride pharmacokinetic studies appears valid, offering a non-invasive and practical sampling method.