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.
The city's name was also switched from Beijing to Beiping (meaning Northern Peace) twice in its history. After the founding of the People's Republic of China however, its name officially became Beijing. 2) It is believed that Beijing has been inhabited by modern humans for about 27,000 years.) Beijing is located at the tip of the North China Plain (map) and it is surrounded by mountains to the north, northwest and west. The Great Wall of China is located in the northern part of the municipality. Mount Dongling is Beijing's highest point at 7,555 feet (2,303 m).