Can docs please explain are cracked mercury amalgam fillings dangerous?

Only got new decay: The real danger from cracks in a silver filling is that bacteria and oral fluids can seep underneath them and cause new decay under the old silver amalgam filling. If the cracked filling isn't replace, then the danger is a toothache and possibly more complex dental work to treat what could be a simple fix. Don't wait, see your dentist.

Definitely no: Amalgam is a safe and durable choice. Most research finds no relationship between fillings and symptoms of mercury poisoning or other side effects. Eventually, any cavity if not treated, can lead to pain, infection, root canal and even tooth loss. See your dentist for evaluation, x-rays and treatment.