You can straighten your teeth at 40 years old. Generally speaking, there is no strict age limit for orthodontic treatment. Patients who meet the indications for orthodontic treatment, such as no diabetes, hypertension and other underlying diseases, and good periodontal condition, 40 years old can also be orthodontic treatment, but the orthodontic time will generally be longer than young people, the speed of bone recovery is slower than that of young people, and may be faced with more risks. Therefore, when undergoing orthodontic treatment, it is important to choose a regular medical institution, an experienced doctor, and develop an appropriate program, in addition to relatively controlling the speed of orthodontic treatment, otherwise it is easy to cause loosening of the teeth, necrosis of the dental nerve and so on. If 40-year-old patients want to do orthodontic treatment, it is recommended to go to a regular medical institution and follow the doctor’s instructions.