My son is 11 months and has been doing it for the last week. It's awful isn't it?! Sets my own teeth on edge. I think it's fine though, my friend's daughter did it for about a month when her top teeth came through. Just a sensory thing
My daughter also did this and does when a new tooth comes through, doesn’t last long! I just ignore it! They’re probably just getting used to the strange new feeling
My daughter did this for a few weeks at that age and then stopped. Just ignore it lol