Well, I know that most dentists not only don't think root canals are bad, but also are defensive against the idea. If they have heard of it, they might say it is pseudoscience or a myth. So, when your dentist tries to talk you out of your "fear", you should be aware of where he is coming from and take his lecture with a big block of salt.
I too wonder what best to do instead, though for me it is academic, because I got my root canals years ago, and am now in the position of deciding what priority getting them removed should have (I just had one removed last Thursday, and it is still healing as I write this.)
I know that even Shelton did not think fasting was indicated for everything, there were some cases that he thought needed proper nutrition rather than fasting (physiological rest). I do not know where he believes cavities fit. You should ask on one of the fasting forums.
Weston Price had some things to say about arresting cavities and perhaps even healing them by proper nutrition. I think most of the remineralization stuff is coming from people influenced by him. I've heard a lot of talk that remineralization has its limits, but I don't know what those limits are, and from which school of thought that talk is coming from. (I really like both Price and Shelton, even though they disagree with each other, since Shelton is a militant vegetarian, and Price supports eating meat.)
My feeling is that you would regret it if you allow the dentist to pressure you into getting a root canal, If you want some dental advice from a dentist who shares your concern, you might check with DAMS (Dental Amalgam Mercury Solutions), who keeps a list of mercury free/biologic dentists. Google them, and you can request that they mail you their list.
(minor edit)

So Sarahlzbthz,

Sorry I wasn't able to respond when you asked for advice although I'm not sure that I would have been much help. My father warned me about root canals after his bad experience from many decades ago. When I had a choice to make with one of my back molars, I took the extraction option without hesitation. That was before I got into natural healing so I could only choose between the options the dentist gave me.

I've heard of fasting helping with teeth and gum problems but others have said that they lost teeth while fasting. I get the impression that the body decides what is the best option! However, other than a few anecdotes, I've not encountered any direct advice from the experts on this subject.

As a believer in Natural Hygiene, I personally would trust my body to manage these issues and even if I did give in to a dentists advice, I would fast in conjunction as I expect that it would reduce pain and speed healing.

Whatever you decided to do, I hope it worked out well for you.

NH...

Hey, thanks for the responses, I appreciate it.. I found a holistic dentist. He said the tooth needs to come out, and that it's too far gone even for a root canal (which he doesn't do anyway)... I like this holistic dentist FAR better than any other "regular" dentist I've gone to :) ...Such a better experience going to him!