At a family gathering during the holidays, your uncle, age 78, discusses his last dental visit with you. He says the dentist told him he needed to brush with a new type of toothpaste with a much higher concentration of fluoride. "He told me I have exposed roots and that worries me. I don't know what that means, or why I have to change toothpastes all of a sudden. My teeth don't hurt." How do you respond?