Here’s another theory — fluoridation of water is very widespread in the U.S. but is very limited in England. (About 10 percent of drinking water in England is fluoridated.) And, according to the Centers for Disease Control, fluoridation of drinking water “has been credited with reducing tooth decay by 50%-60% in the United States since World War II.”
In the U.S., check out people 50 + — before fluoridation was widely used in drinking water — and compare them with the 45 and under. I know some 40-year-olds who have never had a cavity.