Do not go back to him to remove it. First off he openly lied to you. Some people actually do that while smiling. It's called deception. He knew darn well what was in it and openly and knowingly deceived you just to get the business.
As well he is not set up to remove it safely. There is a very stringent protocol used by alternative dentists who understand and apreciate the toxicicity of mercury.
Once bitten...twice shy, especially where heath is concerned.