1. If you are worried that you are reacting to your filling materials, find out what they are (ring the dentist) and then get tested for them. Get tested for all dental materials so you know what you are allergic or sensitive to. It is a simple blood test. If you are in Australia I can tell you where to get it done but I am sure if you are in the US there are many places that will do it- goolge search it. Ask on the dental forums.
2. If you can't find anywhere or don't have the money ask your dentist to give you samples of the materials of what you have in your mouth and/or what you wnat to change to and muscle test it. GO to a good kinesiologist and find out. Or have NAET done. It is allergy testing and also elimination. It is called something different here in australia but has been very helpful to me and accurate.
3. Or you can put the dental materials in your mouth and see if you get a reaction!! I did this with denture materials for a replacment tooth. I took the samples home with me and each day placed a sample in my mouth. You will know soon enough if it doesn't agree.