Out of curiosity...
What exactly do you mean by space-maintainer???
I had the spacers that go in between the molars, at the gum-line, so that there is room to put the metal bands on to put the braces on.
Those did hurt!
Ibuprofen is my pain reliever of choice.
But, if something is rubbing and abrasive....
That is something that I would look into.
I don't see how these could be abrasive.
I also had a palatal expander... a contraption that goes on your upper palate, across the roof of your mouth, and actually widens the upper palate. There is a seam down the middle of the bone in your upper mouth that can be widened in children and young teens. That wasn't painful in the same way that the spacers were. But, it was still just awful!