Ugh....NO dentist is going to remove your fillings and leave your tooth wide open and susceptible to getting new decay, causing pain, and eventually needing a root canal. Those temporary filling materials you can buy at stores are for emergencies - for example....its the weekend and filling pops out and its sensitive and you cant see your dentist for a day or two. They are meant for VERY short term use.
Obviously the person who commented above me is NOT a dental professional but rather someone who has very strong opinions about mercury. I have been in the field for 14 years. I have silver fillings. I am not planning on replacing them until they break down and require it as anytime you drill on a tooth you risk damaging the nerve. However, when I do replace them, I will do white fillings.
I heard about a study recently that found it would take about 250 silver fillings to do any damage to a human. I think the prob with mercury is that the small amounts released from fillings combine with all the other things we consume such as fish that contain highers amounts and are taken directly into our bodies. I even read last month in a health magazine that mercury was found in high fructose corn syrup. Go figure.
Also, if you have dental insurance and your fsilver fillings werent done that recently, they should cover a large portion of the new fillings. the "porcelain" you talk about are called onlays or inlays - they are very expensive and ins only covers half. Unless your fillings are huge, composite, which is what they use to fill front teeth it, can be used.
hopefully this was a little more helpful to you
Lauren