Tooth decay !! Tooth decay !! Oh my god ! Oh my god ! Enamel (hydroxyapatite) = Ca 10 (PO 4 ) 6 (OH) 2 (insoluble ionic compound) Ca 10 (PO 4 ) 6 (OH) 2 10Ca 2+ (aq) + 6PO 4 3- (aq) + 2OH - (aq) Demineralization Remineralization Cause tooth decay d e f e n s e a g a i n s t t o o t h d e c a y + food (Yummy) metabolism (acetic acid Lactic acid) bacteria in mouth Organic acid OH - (aq) + H 3 O + (aq) → 2H 2 O(l) PO 4 3- (aq) + H 3 O + (aq) → HPO 4 3- (aq) + H 2 O(l) Ca 10 (PO 4 ) 6 (OH) 2 10Ca 2+ (aq) + 6PO 4 3- (aq) + 2OH - (aq) Ca 10 (PO 4 ) 6 (OH) 2 10Ca 2+ (aq) + 6PO 4 3- (aq) + 2OH - (aq) SOS !!! Solution Fluor Eat low sugar NaF SnF2 F- replaces OH- in enamel : F- replaces OH- in enamel : Ca10(PO4)6(F)2(s) 10Ca2+(aq) + 6PO43-(aq) + 2F-(aq) Why floridation ? fluorapatite -Fluorapatite : less solube than hydroxyapatite. - F- : weaker base than OH- more resistant to acid attack fight tooth decay!!! . Tooth decay !! Tooth decay !! Oh my god ! Oh my god ! Enamel (hydroxyapatite) = Ca 10. (aq) + 6PO 4 3- (aq) + 2OH - (aq) Demineralization Remineralization Cause tooth decay d e f e n s e a g a i n s t t o o t h d e c a y + food (Yummy) metabolism