When a reader posed this question my first response was, “Yes, if it's appropriate to the restroom.”
In the dining seminars I lead, I remind participants (and will again when dining together becomes commonplace once more), “If you find yourself with something between your teeth, quietly excuse yourself to the restroom.” Excusing yourself from the shared common space of a dinner or reception to solve a personal issue in private is what is called for.
You opt for this because you couldn’t imagine yourself picking your teeth in the company of others. And, of course, you typically brush your teeth in private.
We all consider restrooms to be, as Miss Manners has said, “backstage areas, in which one prepares oneself to go on public view . . . Many routines that are performed in order to increase human attractiveness are themselves unattractive.”
Though, hypothetically you are tending to private needs in a carved out personal area (the sink of the bathroom), others are also tending to their private needs. And there you are – sometimes several of you – sharing common space to handle these private needs. (Readers, I can sense you pausing to contemplate this.)
In public restrooms, courtesy calls upon you to allow the appearance of privacy in that shared space. The smaller the restroom, the less ideal it is to brush your teeth.
The person who wrote to me explained that she always brushes her teeth after each meal and sometimes wants to floss her teeth as well. This is a commendable hygiene practice, but understandably can make you and others feel awkward when strangers are present, especially during recent times of social distancing.
In an attempt to remain completely private, she has tried brushing in the restroom stall. But dropped items in the stall pose sanitary, if not physically awkward challenges.
The bottom line is: it is appropriate to brush your teeth at the sink in a public restroom. However, be mindful and courteous as others will be using the sink area after you. Posted restroom rules may eliminate the possibility of brushing your teeth.
You’ve probably seen off-putting scenarios in airports involving strangers using basin and counter areas with loud flourishing and messy spitting. Of course that would never be you, and you probably envision traveling again when people are more constrained in their possible invasion of shared spaces.
Tending to personal needs should balance with hygiene and intimate space concerns for others.
Generally, restrooms rank along with kitchens as shared spaces where annoyances register strongly. Again, public restrooms call for courtesy:
These courtesies build on your personal and public good etiquette habits.
Adam Smith, the famous moral philosopher/economist, emphasized that through built-in empathy with others, we learn which emotions distress others and we learn how to recognize and handle situations by managing our actions to the point where any average dis-interested person or stranger would go along with (in some sense approve of) our actions.
Regardless of the culture we are in, the mannerly principle that we tend to ourselves while simultaneously respecting the space of others may well bring a pause to the question of brushing your teeth in a public restroom.