hi there, here are some thoughts on reading your message-
1. fasting is a great idea. Jump in and see how it helps you.
2. I forget who the quote is from but "If it can be cured, fasting will cure it". I don't see why the constipation shouldn't be cured by fasting. Do you know what caused it? I would have thought it would clear up on a high-raw diet.
3. I haven't found fruit damaging to my teeth personally. I've read that citrus fruits, eaten to excess can cause problems. I've never had trouble with sweet tropical fruits like mangoes or bananas even on very painful sensitive areas of tooth.
4. after completion of a fast there can be constipation, probably due to a general state of dehydration on a fast. Don't let this panic you, it's normal and passes after a couple of days if not sooner.
4. fasting helps with Acne (though it can become worse during the fast) and rosacea. It will help combat infections too.
5. fasting is good for the health of teeth and gums, but to the best of my knowledge will not reverse decay that is already present. I wish it did!
6. I would recommend a short fast to start with, and see how you feel after. Get used to the different feelings that arise in the body, and the process of breaking the fast, which is important, and easy to do badly.