As adults, people often isolate themselves in a special room to brush their teeth in privacy. Even so, toothbrushing is a profoundly social act, relying on shared knowledge and observance of social norms for hygiene and health.
Brushing our teeth is a very unique action that humans take for hygiene because not many, if any, other animals brush their teeth. But we heavily rely on it every day to keep us keep and use it in our routines.