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 (Urban) 18,590,000/// Area: 16,410 (sq)km /// Density 1,132/(sq)km. Tokyo (Urban) 13,617,445 /// Area: 2,190 (sq)km /// Density: 6,218/(sq)km. So itâs clear that Beijingâs city area is much larger than Tokyoâs but the population density in the two cities is the most important thing to pay attention to. Tokyo is almost 6 times more dense than Beijing, when looking at the urban area (and not the metropolitan area).