I read on the net that dental fillings (silver-mercury based) are toxic. could they be removed safely?

Yes, they can..: But you've read a lot of gibberish. Silver fillings have been used for over 150 years on millions if not billions of patients. You'd think by 2013 we would know if they were dangerous to our health.. Makes sense, right? It would be best to replace them with white fillings as they break down over time, one by one. However, it's your mouth, do what you feel is best.

You can remove: However, amalgam is a safe and durable choice. Most research finds no relationship between fillings and symptoms of mercury poisoning or other side effects. Advances in modern dental technology allow to place tooth colored composite fillings instead of amalgam fillings to restore the natural appearance of the tooth.

Can be removed, but: Once an amalgam (mercury containing) filling has set, it can not leach out mercury. The mercury is chemically bound up with the other components of the filling material and can not get free. Mercury toxicity from fillings is fear-mongering, not fact. You can also cause damage to the tooth removing the old filling. If you have a broken filling that needs replacing then go ahead otherwise leave it.

Mixed opinions: The amalgam (silver) filling and its safety has been debated for decades. It often depends on whom or what organization is saying the fillings are unsafe. Most fillings these days are acrylic or porcelain, with no silver/mercury. But to remove all existing silver fillings to cure an ailment is not necessarily true, and removal may create more problems- sensitive teeth, root canals, etc.