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.
While some would believe that Shanghai has hit its peak population, this is far from the truth. It's projected that Shanghai, along with Beijing, will have a population of more than 50 million by 2050, which is double the current level because of fast-paced urbanization in the region and strong economic growth.