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 The population of China is estimated at 1,393,783,836 as of July 1 2014. 2  China's population is equivalent to 19.24% of the total world population. 3  China ranks number 1 in the list of countries by population.4  The population density in China is 145 people per Km2. The population density in China is 145 people per Km2. 2  54% of the population is urban (756,300,115 people in 2014). 3  The median age in China is 35.7 years.