Dentifricium Mouthwash was a wizarding brand of mouthwash, made from 100% pure african red pepper. The label promised "clean teeth, healthy feeling gums and magical taste" and attested that it was free of preservatives and dyes. Ronald Weasley kept a bottle of this mouthwash on his nightstand at Gryffindor Tower in the 1990s.
Dentifricium is Latin for tooth powder, an ancient method of cleaning teeth that has been mostly supplanted by toothpaste in modern times. The English term "dentifrice" refers to tooth powder and other agents used to clean the teeth, including mouthwash.