I don't know a source for a holistic dentist but you may want to take a look at http://www.uncleharrys.com.
He started his website when he began having tooth problems himself and came across an aryuvedic recipe for a tooth powder. His website is chock-full of information on natural methods for taking care of dental issues. One I read recently involves swishing sesame oil in the mouth for a few seconds after getting up in the morning which indian clinical studies prove removes toxic bacteria from the mouth.
My wife and I use his tooth powder everyday and will never use regular toothpaste
again. Recently my wife went to her dentist for a teeth cleaning and they said there was no point as she had no plaque! Hope this helps.