Interesting. For a few years I was extremely bad about brushing my teeth. I wonder if not doing that is why my consumption of coffee, carbonated drinks, and sugary snacks/desserts did nothing to the teeth themselves other than maybe a little extra staining. The first dentist visit I had after that stretch of 3 years required nothing but a cleaning! (Of course it's still bad to not brush consistently because the plaque turns to tartar along the gums which causes them to recede)
Similar situation, he was surprised by how white they were too. I drink almost everything that isn't water through a straw and never swish it around. He said that's probably why the only reason he had to do any work was due to the very back edge of my teeth where even when drinking through a straw the liquid touches.
