Toothache during fasting

Has anyone experienced toothache during fasting? I'm on day 3 of a (so far) successful water/juice fast, and for some reason my teeth have started to ache on one side, even though I'm cleaning them as usual. My teeth are in good shape, and toothache is something I never get (or only when the anaesthetic is wearing off after having had a filling). I have a mixture of old mercury fillings and new white fillings in my mouth (replacing the old ones with white ones when they wear out or I need new ones), and funnily enough, the aching is in the place where I have the white fillings only! Has anyone any ideas, also is it OK to rub teething gel or clove oil on my gums to relieve some of the pain?