Dental crowding, also known as crowding analysis, is an important basis for the diagnosis and treatment of dental crowding. Currently, in clinical crowding analysis, two measurements are taken, the arch due length and the existing arch length, and the difference between these two lengths is the degree of crowding. Clinically, the arch due length is measured by using a minute gauge or vernier calipers to measure the maximum width of each tooth on the dental model, and then the width of each tooth is added up to obtain the data of the arch due width, while the data of the arch existing length is generally obtained by using a brass wire with a diameter of 0.5 mm, which is passed through the proximal-middle of the first molar in the arch, along the top of the alveolar ridge, and then reaches to the other side of the arch in accordance with a certain marking point. The contact point of the first molar proximal to the other side of the arch, after straightening the brass wire, the length of the existing arch can be obtained, repeat each measurement 3 times, take the average that is the value of the existing length of the arch, subtracting the existing length from the desirable length, you can get the degree of crowding of the arch, the degree of crowding of the arch is of great help in clinical diagnosis and treatment, the degree of crowding of the arch is below 4mm, belongs to the mild crowding, 4-8mm belongs to the moderate crowding, more than 8mm belongs to the The degree of crowding is very helpful for clinical diagnosis and treatment.