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.
Beijing is located in northeastern China at the northern tip of the North China Plain, near the meeting point of the Xishan and Yanshan mountain ranges. The city itself lies on flat land (elevation 20 to 60 m (66 to 200 ft)) that opens to the east and south.ast Lingshan (elevation 2,303 metres (7,556 ft)), a Xishan peak on the border with Hebei, is the highest point in Beijing Municipality. It is located 122 km (76 mi) from the city. Xishan is also known for high mountain meadows and scenic river gorges, including Shidu. Foothills of Xishan reach the city itself.