I think if you find somebody to be an expert witness it's going to have to be through a good lawyer.
Two reasons, No money in it unless you had a lawyer hire him to prove your case, and dentist have lost their licence with the ADA for going against traditional practices of the ADA.
Dr. Huggins [who recently died] is a good example. In fact I think he was on the ADA board when he took a stand against Mercury amalgam fillings.
You might have your lawyer call his office http://tinyurl.com/k8t9534 to see if they would, or know of somebody.