"Acids attack the enamel layer of the teeth and soften it for a certain amount of time," says Hirschfeld. This strips out some of the key components of the enamel – calcium and phosphate – though these are replaced over a period of hours by minerals in the saliva. "So the process is self-repairing. But if you don"t wait for that self-repair to happen, then this eroded surface will become very susceptible to just being brushed off."