As someone with the same habits as the poster, I would say negative reinforcement. Every time I brush my teeth -- EVERY TIME! -- they hurt for about two days,

As someone with the same habits as the poster, I would say negative reinforcement. Every time I brush my teeth -- EVERY TIME! -- they hurt for about two days, and I get nasty bad breath. But if I go without brushing for weeks on end, things are fine. I brush anyway, when I want to look nice for something, but usually I skip it. I've always wondered if, when I brush, I wipe out whatever bacteria are taking up the niche the teeth-eating bad-breath-causing ones usually fill. I haven't thought of a test for that, but my continued experience with teeth that only don't hurt if I haven't brushed for a while doesn't seem to align with the conventional idea of how it works...