Oral Hygiene
You gotta keep those teeth clean. No way around it. Some airlines even supply their passengers with a small toothbrush and an accordingly small tube of toothpaste, for exactly this reason. They know that after a long flight, some people might feel the need to have a fresh mouth. That’s perfectly normal and encouraged.
So, what’s wrong with this photo, you ask? Well, you can excuse yourself to the toilet and brush your teeth in there, in privacy. Not in your seat, next to the other passengers. You can also wait until you get to the airport, and brush your teeth there. That’s what most people do. Just a suggestion, for next time.