Fluoride Toxicity Calculation — NDEB AFK MCQ
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Correct answer: A — 1.25 mg/kg
0.05% NaF = 0.5 mg NaF per mL. NaF is approximately 45% fluoride by weight, so 0.5 mg NaF × 0.45 = 0.226 mg F⁻ per mL. For 50 mL: 0.226 × 50 = 11.3 mg F⁻. Wait — let me recalculate: 0.05% NaF = 0.5 mg/mL NaF. Fluoride content of NaF = 45.25%, so F⁻ = 0.5 × 0.4525 = 0.226 mg/mL. Total F⁻ = 0.226 × 50 = 11.3 mg. Dose = 11.3/20 = 0.565 mg/kg. However, 0.05% NaF contains 226 ppm F⁻. Alternatively, 0.05% NaF = 500 ppm NaF = 226 ppm F⁻. 226 ppm = 0.226 mg/mL. 50 mL × 0.226 = 11.3 mg F⁻. Dose = 11.3 mg / 20 kg = 0.565 mg/kg. This is below the probable toxic dose (5 mg/kg) but monitoring is recommended. Selecting the closest answer — but given the options, let me reconsider: 0.05% NaF means 0.5 mg NaF/mL. In 50 mL = 25 mg NaF = 25 × 0.45 = 11.25 mg F. Dose = 11.25/20 = 0.5625 mg/kg. Closest answer is 0.5 mg/kg. The probably toxic dose (PTD) of fluoride is 5 mg/kg.
Reference: Dean – McDonald and Avery's Dentistry for the Child and Adolescent, 11th ed., 2021