APF Gel Composition — NDEB AFK MCQ
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Correct answer: A — Sodium fluoride in phosphoric acid buffer (1.23% fluoride, pH 3.0-3.5)
APF gel contains 1.23% fluoride ion (12,300 ppm F⁻) derived from sodium fluoride in an acidulated phosphoric acid buffer (pH 3.0-3.5). The acidic pH enhances fluoride uptake into enamel by promoting dissolution of surface enamel and subsequent formation of fluorapatite. APF should NOT be used on porcelain/composite restorations (the acid etches and roughens these materials) or on teeth with exposed dentin/cementum (risk of hypersensitivity). Neutral sodium fluoride (1.1% NaF, pH 7.0, 5,000 ppm) is the alternative for these patients.
Reference: CDA – Fluoride Position Statement; Fejerskov & Kidd – Dental Caries, 3rd ed., 2015