Orthodontics is a specialty of dentistry that deals with the diagnosis, prevention and correction of malpositioned teeth and jaws. It can also focus on modifying facial growth, known as dentofacial orthopedics.Abnormal alignment of the teeth and jaws is common. Nearly 50% of the population, according to the American Association of Orthodontics, has malocclusions severe enough to benefit from orthodontic treatment.[citation needed]: although this figure decreases to less than 10% according to the same AAO statement when referring to medically necessary orthodontics. Treatment can take several months to a few years, it involves the use of dental braces and other appliances to slowly move the teeth and jaws around. If the malocclusion is very severe, jaw surgery may be used. Treatment is usually started before a person reaches adulthood since bones can more easily be moved around in children.