A study shows that people have more gum diseases today than they did 2，000 years ago. The study， from London’s King’s College， is now in the British Dental Journal. Researchers looked at the teeth of 303 people who lived 2，200-2，400 years ago. They were from skulls （颅骨） found at an old burial （葬，掩埋） site in England. The researchers said only 5 per cent of the skulls had gum disease. Up to 30 per cent of people today have gum disease. Professor Francis Hughes was surprised because people did not have toothbrushes or toothpaste back then. They also did not visit dentists， like we do today.
　　Smoking is the main reason why people have gum disease today. The study shows that our oral health has become worse over the past 2，000 years. Gum disease can start going down if more people stop smoking. A researcher said： “As smoking becomes weaker， we should see a smaller number of people with the disease.” Gum disease is caused by bacteria （細菌） build up in your mouth. The bacteria do bad to your gums and can make your teeth fall out. People can lower the risk of gum disease by regular brushing， using mouthwash and not smoking.
　　阅读选择
　　1. You can read the study in
　　A. a magazine.
　　B. a library.
　　C. a bookstore.
　　2. How many persons’ teeth were looked at in the article？
　　A. More than 200.
　　B. More than 300.
　　C. More than 400.
　　3. What is the main cause of gum disease today？
　　A. Eating too much.
　　B. Smoking.
　　C. No brushing.