Asians have smaller faces and smaller alveolar bones than Europeans and Americans. One more root will make their teeth wider. With wide teeth and narrow alveolar bones, their teeth will be crowded, so their gums will be stretched thin. When they suffer from periodontal disease or brush their teeth improperly, their gums and periodontal tissues are easily damaged and atrophied. There is another situation. People in the East mainly eat carbohydrates, and they have less food, so it is easier to plug their teeth, so the situation of periodontal disease will be more serious. In other words, Asians have three characteristics of oral cavity: 1, crowded teeth, thin gums and high carbohydrate diet.