The acid in lemons is not good for teeth at all. If you keep doing this sooner or later it will eat into your enamel. I am having trouble with it now from eating so many grapefruits and not brushing my teeth right after eating them.

Blueduck

As a suggestion...you should take a spoon and scrape off the "furry white" stuff off of your tongue. It's toxins from your body and it's good practice to get to do this everyday.