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.
1 And Beijing ranks as the second largest city of China with a population of 19,959,563 (data based on the result on January 1st 2011).2  China's third largest city is Guangzhou with a population of 13,510,651 (data based on the result on January 1st 2011).ccording to the urban population data of each city, Shanghai ranks as the largest city of China. The 2010 census put Shanghai's total population at 23,019,148, a growth of 37.53% from 16,737,734 in 2000.