Potato starch is hardly likely to hurt your teeth, though I've often managed to assault my gums with sharp crispy edges. If bits of crisp stick in your teeth, salivary amylase will slowly convert some of it to a disaccharide sugar but one which will be very diluted and far less harmful than the sudden rush of sucrose provided by a sweet drink feeding the acid-producing bacteria in your mouth, the ones that do the real damage. There's data that reveals a very sudden drop in pH in the mouth when a sugary drink, or just syrup, is consumed. It doesn't take long, and the argument that sugary liquids are less harmful because they're soon gone doesn't hold up. It doesn't help that almost all sugary drinks are also markedly acidic to begin with. Stick to dry wine is my advice. ;-)