In the Triumph motor-racing fraternity, where the gudgeon pins where retained by circlips which mounted in a recess within the piston, it was common practice to replace the circlips with PTFE buttons.
Being self lubricating, they never seemed to wear out and they never damaged anything, unlike the circlips which had an unpleasant habit of popping out at high revs and thereby scrapping the engine. I assume nothing so sensible is allowed in the world of certified aero engines?