-_- you do realize sugar is in plant based foods, bread... pretty much in most foods without us having to artificially add it. And our saliva breaks down many complex carbohydrates into more simple sugars, and that even if that wasn't the case, the bacteria that cause the increase in tooth decay relating to sugar can break down more complex carbohydrates into sugar, so your point is completely unsound. It isn't the sugar itself that increases tooth decay, but the bacteria in your mouth, many of which are also symbiotic. Furthermore, even if you were to propose instead that these bacteria were not present, our teeth still wear down from just use alone, to the point that my post still stands. This is why even people that brush their teeth and don't eat foods high in simple sugars can still get cavities. And let's not forget the acidity of food, that also plays a role.