How bad is diet pop for your teeth?

Not like regular: Diet soda may have other health issues, but not bad for teeth. Regular soda has lots of sugar: sucrose (a mixture of glucose and fructose) or high fructose corn syrup (a cheaper version of glucose and fructose). It leads to increase in plaque (bacteria) and increases tooth decay. Neither give good nutritional value. Milk (or soy milk) gives protein, calcium, vits. Water or seltzer refesh, no cals.

Not good: Regular soda, filled with sugars, feed bacteria that turn the sugars into acids which harm the tooth enamel. Both diet and regular soda are made with carbonic acid (carbonated water) that gives soda it's bubbles. No matter the source, acids destroy enamel. If you're going to drink soda, clear the acids by drinking some tap water afterward.