A new study shows that people today have more gum disease than people living 2,000 years ago. The study is from the university King's College in London and is published in the 'British Dental Journal'. Researchers looked at the teeth in the skulls of 303 people who lived between 200-400 AD (2,200-2,400 years ago). The skulls were found at an old burial site in the west of England. The researchers found that only 5 per cent of the skulls showed signs of gum disease. Up to 30 per cent of people in England today have gum disease. Professor Francis Hughes was surprised by what he found. He said people did not have toothbrushes or toothpaste back then and did not visit dentists, like we do today. The main reason why modern people have more gum disease is smoking. Theya Molleson, co-author of the report, said the study shows that people's oral health has become much worse over the past 2,000 years. She added that she thinks gum disease could start going down from now as more people stop smoking. She said: "As smoking declines in the population, we should see a decline in the [numbers of people with] the disease." Gum disease happens when bacteria build up in your mouth. The bacteria eat away at your gums and can make your teeth fall out. People can reduce the risk of gum disease by regular brushing, using mouthwash and not smoking.