Odds are it is an Amalgam which contain mercury, but you might check with the dentist who put it in.
Yes, I was plesantly surprised to see my TPO numbers drop like they did. Also through diet modification, i.e., gluten elimination and primarily a paleo type diet my thyroglobulin antibodies have dropped as well down to a 1.3, on a target of 0-.99 IU/ml. My endo has me on thyroid meds due to a diagnosis of Hashi's a while back. She started me on pharmaceuticals, Synthroid, but I dashed that in favor of the natural stuff. The pharmaceuticals were making me crazy, literally.
Check out a book/website called Stop The Thyroid Maddness. They have a wealth of information regarding your Thyroid and how to take care of it, talk to your doctor, etc.
Best of luck.