Although metal toxicity may not be the only cause for these conditions, replacing all metal fillings with composites certainly assists your immune system in its effort to protect your body against disease. A composite filling is one that is primarily non-metallic. There are a large variety of materials used in composite fillings, but some metals may be present. Ordinary composites are not suitable for large cavities. If used for large cavities they tend to last no more than five or six years. Indirect composites, on the other hand, can be placed in large cavities. They can even be used in place of gold crowns. They look like a real tooth and last as long as gold. If selected properly, indirect composites are quite non-allergenic and non-toxic. They are fairly new and can be as expensive as gold fillings, but they can save you a lot of trouble and money in the long-term. Since many dentists don't know how to place them properly, you may need to do a bit of research to find an experienced mercury-free dentist who also works with indirect composites. The fillings should be replaced cautiously and gradually, one or two (if small ones) at a time. Donít replace fillings more often than once every two months, although some dentists use special safety procedures that allow them to replace a number of fillings at a time.