Dental decay, also known as dental caries, begins first inside the tooth. A white spot appears on the enamel where the tooth has started to weaken inside. At this stage, the tooth can repair the weakened area with the help of fluoride and minerals in saliva.
Beijing, also Peking, is the capital of the People's Republic of China and one of the most populous cities in the world. Its population in 2013 was 21,150,000. The city proper is the 3rd largest in the world.
As of July, 2014, China's population is estimated at 1,355,692,576. In 2011, the urban population in China was down to 50.6 percent with a 2.85 percent average annual growth rate from 2010 to 2015. The most densely populated cities in China include Shanghai, Beijing, Guangzhou and Shenzhen.Learn more about East Asia.