I think it can be a symptom of poisoning because of relation to depression. I wasn't shy until I got fillings - quite the contrary. I was very outgoing, wanted to be in everything at school, play the lead, really be noticed - but once I started to get amalgams, I got very withdrawn and couldn't even face reading in class. I don't know if that is coincidence, but it happened. I am still very introvert today and don't do well in social situations.