I've been using Squigle Tooth Builder (Sensitive), 36% Xylitol.
It has no flavor nor fluoride and for me, does not burn. I checked w/ my dentist and he said I really don't need flouride. For now, however, I'm mixing it w/ a small amount of the original Biotene paste (still have a couple of tubes). http://www.squigle.com/tbingredients.html

If you want/need fluoride try Squigle Enamel Saver, also has 36 % Xylitol + flavor (peppermint).
http://www.squigle.com/squigleingredients.html

I haven't tried the Enamel Saver because I generally do not do well w/ natural flavors.

Check out the links for exact ingredients. No SLS. Per Squigle only "mouth friendly ingredients" which help w/ canker sores/mouth ulcers, dry mouth and other things.

I originally ordered the Tooth Builder on Amazon, but now see the price is outrageous there. Luckyvitamin.com has it for $7.52 Only need to use a small amount.