What is the concentration of RX fluoride rinse (Sodium Fluoride)?

• A. 200-1000 ppm
• B. 1000-1500 ppm
• C. 12,300 ppm
• D. 900 ppm

Answer: (D)

Fluoride rinse concentrations are given as the amount of fluoride ion in parts per million (ppm), essentially mg of fluoride per liter of solution. A common RX fluoride rinse uses sodium fluoride at 0.2% w/v. Converting that to ppm: 0.2 g NaF per 100 mL equals 2 g per liter. The fluoride ion fraction in NaF is about 19/41.99, so fluoride per liter is roughly 2,000 mg × 0.452 ≈ 904 mg F− per liter, which is about 900 ppm. This is the typical concentration used for caries prevention with sodium fluoride rinses.

Very high values like 12,300 ppm would be far more concentrated than a rinse; values around 1000–1500 ppm exceed the standard RX rinse level; and 200–1000 ppm is in the same general range, but the established RX rinse concentration is about 900 ppm. So the correct concentration is about 900 ppm.