How to avoid the rhubarb teeth effect?
Peel the rhubarb before cooking - you can strip off the outer skin from the stalks quite easily.  That helps.

EDIT: My wife told me to explain why.  

In Yorkshire, the rhubarb capital of the world, you can buy "forced rhubarb", which has a tender pink skin because it is forced to grow up through dark tubes towards the light. Because "garden Rhubarb" is not forced, the "gritty teeth sensation" components accumulate in the skin, and an authority on the subject (my mother) told me many (>50) years ago that it was a good idea to peel it. She also taught me that it was a good way to divert children - show them how to pick a tender stem and dip it in sugar, then eat it raw -and that the sugar sticks to the stem easier if you peel the skin off first.

My grandmother had a lot of mysterious ways with rhubarb, including using it in ginger beer instead of the usual lemon. These are lost in time, but she always peeled it, whatever it was being used for, to avoid that sensation.