Practice question from Dental Admission Exam DAT
What mechanism primarily explains why fluoride in drinking water reduces dental caries when consumed during tooth development? A. Fluoride kills cariogenic bacteria in dental plaque B. Fluoride increases salivary pH and buffering capacity C. Fluorapatite forms in enamel, increasing acid resistance D. Fluoride accelerates remineralization of existing lesions E. Fluoride reduces enamel permeability to organic acids
Answer
C
Explanation
When fluoride is present during tooth development (systemic effect), it substitutes for hydroxyl groups in hydroxyapatite crystal formation, creating fluorapatite. Fluorapatite has a lower critical pH (4.5 vs 5.5), meaning it's more resistant to acid dissolution. Option D describes topical fluoride's post-eruptive effect, which is also important but wasn't asked in this developmental context. Fluoride has minimal direct antibacterial effects (option A) and doesn't significantly alter salivary pH (option B).