Is it normal that my sister does this?
I have always shared a room with my sister, and for years she has been making this grinding sound with her teeth while she is sleeping. It is a really loud scratching sound that sounds like two rocks scraping together, but it has never affected her teeth. She also can't make the sound when she is awake so I have no idea how she does it, whether it is with her teeth or maybe saliva? IIN?