According to a study in the March/April issue of General Dentistry, root beer is the "safest" soft drink for teeth because it does not contain the acids that are known to harm teeth.
“Drinking any type of soft drink poses risk to the health of your teeth,” says Kenton Ross, DMD, FAGD. “My patients are shocked to hear that many of the soft drinks they consume contain battery acid. For example, one type of cola ranked 2.39 on the acid scale, compared to battery acid which is 1.0.”
Ross recommends that patients consume fewer soft drinks by limiting their intake to meals. He also advises patients to drink with a straw to reduce soda’s contact with teeth.
Researchers conclude that noncolas cause a greater amount of erosion than colas. Citric acid is the predominant acid in noncola drinks and is a major factor in why noncola drinks are especially erosive. There is a significant difference between sugared and diet colas.
“The bottom line,” says Ross, “is that the acidity in all soft drinks is enough to damage your teeth and should be avoided.”
[Academy of General Dentistry, March 20, 2007]