Dissertation Research: Secular Change of Japanese Occlusion: The Frequency of the Overbite and its Association with Food Preparation Techniques and Eating Habits

直到200多年前，人类正常的咬合都是边对边的。也就是说，当磨牙咬合在一起时，上门牙和下门牙的切割边缘彼此相遇，而不是像现在认为的那样重叠。这一变化发生在18世纪晚期，随着餐叉的采用和饮食习惯的改变，欧洲发生了变化。由于美国独立战争导致旧世界的联系中断，这种变化直到19世纪的第三个十年才开始在美国发生。随着食物制作方法的改变，亚洲也应该发生类似的变化，中国的筷子和日本的桥牌都被用作日常餐具。中国的初步研究表明，现代复咬现象发生在宋代中国上层社会。宋朝文化对日本人的生活产生了深远的影响，这个项目的目的是为了检验中国食物制作和饮食习惯的采用（例如使用筷子）是否伴随着日本大和地区第一批日本农民及其后代的边缘对边缘咬食的变化，而这一变化紧随中国的第一次重大影响。这些调查将有助于阐明饮食、饮食行为、食物制备技术与牙列正常咬合之间的关系。

Until just over 200 years ago, the normal human bite was edge-to-edge. That is, when the molars were clenched together, the cutting edges of the upper and lower incisors met each other rather than overlapping as is now considered normal. The change took place in Europe following the adoption of the dinner fork and the changes in eating habits it indicated late in the 18th century. Because of the hiatus in Old World contacts caused by the American Revolution, that change did not begin to take place until the third decade of the 19th century in America. A similar change should have occurred in Asia following the change in food preparation methods that allowed chopsticks, kwai-zi in China and hashi in Japan, to be used as everyday eating utensils. Preliminary work in China indicates that the modern overbite occurred in upper class Chinese in the Song Dynasty. Song cultural influences had a profound effect on life in Japan, and the purpose of this project is to test whether the adoption of Chinese food preparation and eating habits exemplified by the use of chopsticks was accompanied by a change from the edge-to-edge bite of the first Japanese farmers and their descendants in Yamato Japan which immediately preceded the first major influences from China. These investigations will help clarify the relationships between diet, eating behavior, food preparation technology and normal occlusion of the dentition.