I have a problem that I cannot seem to find a solution for on the internet, and do not know if a dentist should see it or not. Every once in a while (about every other month), for a few days I get a strange metallic taste in my mouth. My tongue usually swells up and some filmy stuff shows up on it. I cannot get rid of it, it seems like the more I scrub away there is more coming up, too. This usually lasts a couple of days and my mouth is really sore, and then it goes away. I also get a tingling sensation in the gums and on a tooth that was previously root canaled when this happens. There is no bleeding and no pain, just a kind of deep itching feeling. What is this that I have? Is it serious? Does it need to be seen by a professional?