Which of the following is the primary mechanism of action of fluoride on topical application?
Forming a reservoir in saliva
Inhibition of plaque bacteria
Improvement in tooth morphology
Conversion of hydroxyapatite to fluorapatite by replacing the OH- ions
The presence of fluoride reduces the solubility of enamel by promoting the precipitation of hydroxyapatite and phosphate mineral. Ca10(P04)6(OH)2 +2F- -> Ca10(PO4)6F2 + 2OH (OH ions are replaced) (hydroxy-apatite) (fluro-apatite) Ref: Essentials of Pedodontics By Tilakraj, Pages 182-3 ; A Textbook of Public Health Dentistry By Marya, Page 348