The treatment time of crowded teeth is mainly based on the degree of crowded teeth and the orthodontic treatment method used to determine the degree of crowded teeth clinically divided into mild crowding, moderate crowding and severe crowding: 1, mild and moderate crowding: the treatment method used clinically, mainly to expand the dental arch or adjacent slices of teeth to obtain clearance, this correction is a small movement of teeth, treatment time Relatively short, generally in about 1 year; 2, severe crowding: for example, more than 8mm crowded teeth, or with other malocclusion, such as the upper and lower arches of the relationship between the misalignment, and the cranial relationship of the incongruity, the clinical will usually be used to extract teeth or expand the arch, or even surgical treatment to solve these malocclusions, the treatment time is generally in 2 years or even longer.