A comment I left on A Home for Darya.
My 6 year old birth daughter with Down syndrome goes thru periods of teeth grinding. She has gone thru these cycles ever since she had enough teeth to grind together. It will start out occasional, then build up to a point where I think I'm going to lose my mind. And then one day I'll realize she has totally stopped.
Her speech therapist has said it could be related to wanting oral stimulation. I wonder if it's related to her teeth coming in/oral development since it's cyclical. Anyway, she's old enough now that we can tell her 'make your teeth quiet' and she'll stop for a minute or two anyway.
Also, for better or worse, we've let her keep using a pacifier at night time to fall asleep. We've come very close to making her give it up, but then change our minds. Because when she's in one of those non-stop grinding modes, it's the only thing to give US any relief.