When it comes to orthodontics in fact, there is a most simple principle is space + force, we usually say that the extraction is actually to create space for the teeth to move, and the force required to move the teeth refers to the light force. In the past, orthodontics, doctors used to stick brackets to the teeth, through the square wire arch thin wire arch to apply the force required to move the teeth, and then gradually found that many young women who love beauty can not accept this “steel teeth girl” image, so the metal brackets into ceramic, but the metal arch wire still exists, only to say that the patient part aesthetic needs. In the 1970s, another technique called lingual orthodontics emerged, where brackets were glued to the backs of the teeth, which solved the aesthetic needs, but patients began to complain about the oral mucosa grinding out many ulcers. As people’s standard of living continued to improve, the need for aesthetics and comfort also increased, until the end of the 20th century in the United States appeared Invisalign technology, which successfully applied 3D printing technology, biomechanics technology, material technology technology to digital orthodontics, through a pair of transparent invisible braces to achieve the effect of straightening teeth.