Here is some info from a Dentist about composites, and I agree 100%:
Excerpt:
Ward Eccles, a Livermore dentist who has been mercury free for 17 years, says in his opinion your best bet is fillings made of "composite," a plastic material that's been around for 25 years. "Composite wears equal to or better than mercury amalgam, it bonds better, it looks like a tooth." The rap on composite, he says, was that it wasn't strong enough to be used to fill teeth in the back of your mouth, where the pressure of chewing is greatest.