Why can't I type with my mouth closed? I've tried everything in my power. Once I start typing, my mouth begins to open gradually. It can only stay closed if I put in conscious effort for it to remain closed. When I say my mouth opens, I mean my upper tooth are not touching the lower tooth but my lips remains closed. I was a mouth breather for twenty years because my noses were blocked so I could only breath through my mouth. But now that has been fixed, I find it hard to shut my mouth (teeth)