Why does tooth decay start when the pH of mouth is lower than 5.5
pH of mouth decreases than 5.5,due to eating food, various bacteria present in our mouth acts on it and our mouth becomes acidic. When these acids like lactic acid acts with our tooth enamel made up of calcium phosphate gets corroded due to which tooth decay starts. Hence, we can say that tooth enamel start decaying when pH is lower than 5.5.