What purpose is the phosphoric acid serving? How much is in there and will it have any effect in demineralizing enamel?
The purpose of the phosphoric acid is to buffer the CPP-ACP. MI Paste is an exceptionally good buffer of acid yet we still need the formulation to be relatively neutral to be able to get the most effective levels of remineralization. The final pH of MI Paste is around 7.8 (slightly alkaline), without the phosphoric acid it would be higher (more alkaline) which is helpful for buffering an acidic mouth but not as effective for the remineralization process. Phosphoric acid is used to adjust the pH of MI Paste to get it close to neutral instead of alkaline (basic). The percentage composition of phosphoric acid is < 00.3% (ie less than .3 of one percent) so it is very small. You can imagine it is more added as a formulation "tweak" to ensure the optimum performance (phosphoric acid is a recognized food additive and antioxidant) balancing between buffering and remineralization benefits. There is absolutely zero chance/potential for demineralization.
