The other defense against acid is fluoride. As the active ingredient in many toothpastes and rinses, topical fluoride lowers the susceptible pH of enamel from 5.5 to 4.5, meaning any acid must be ...

Acids have a sour taste, like vinegar, which contains ethanoic acid, and lemons, which contain citric acid ... This is measured using the pH scale, which runs from pH 0 to pH 14.