That dentist suggested that you get another root canal, so I wouldn't take his advice about anything including the Easy Graft.
A quick search says it's some kind of plastic. Called Alloplastic which requires a hardner to get it to set up.
Is it bad for you? Who knows, but I wouldn't let them install it to find out later it was.
When I had my amalgams replaced, I was sent to a lab to see which amalgam product was compatible with my system. It cost me $300, but I felt it was worth it. You have no idea what this stuff is let alone know if it is suitable for your system.