I was sitting in a doctor's office earlier this morning leafing through a recent TIME Magazine when a small article appeared indicating Mountain Dew is the worse soda pop for your teeth enamel while A&W root beer has virtually no effect on your enamel because it has few preservatives.
Here is the study they were citing I think, not the article itself. Interesting reading in this thread!!
http://www.dentalgentlecare.com/diet_soda.htm
Cowperson