Sugar in pop combines with bacteria in your mouth to form acid. Diet or "sugar free" pop contains its own acid. Acid in soft drinks, whether they contain sugar or not, is the primary cause of weakening tooth enamel. The acid attacks your teeth. Each acid attack lasts about 20 minutes. The acid attack starts over again with every sip! Ongoing acid attacks weaken your tooth enamel. Bacteria in your mouth cause cavities when tooth enamel is damaged. If you have a receding gum line, acid does more damage below the gum line than above it. This is particularly a concern for adults.
Dr. James L. Johnson