As to metal in the mouth, I had soft teeth as a child and had to have them all pulled at 12 years old. Believe it or not, I still have the same teeth (dentures) after 53 year, without ever chipping one. They were made well. They have worn down some though and it has always worried me, since learning about the danger of mercury, that I can see metal pins that anchor the teeth, enclosed in the porcelain at the back. I don't know if it is stainless steel or whether it has mercury or not, but Dr. Marshal's statement that "any metal in the mouth is an interference field" worries me. There are probably a lot of people walking around with metal in their mouths that aren't aware that it might affect their health.
And if you're wondering, yes, there have been problems with the dentures being a 12 year old size as I got older, but they were relined a couple of times and I managed to eat ok.