Aubrey visits the dentist every six months for a check-up. During her latest appointment, the dentist mentioned that several patients have been switching from manual toothbrushes to electric ones. Aubrey noticed that the waiting room magazine rack was full of advertisements for electric toothbrushes. Based on this, Aubrey claims that switching to an electric toothbrush is the main reason why people who use them get fewer cavities than those who use manual toothbrushes.