Orthodontics is a specialty discipline of dentistry that focuses on alignment of the teeth and jaws to improve a person’s smile and oral health. Irregularities of the teeth are treated with the use of braces, which are fixed dental appliances, and removable dental appliances, when the braces are removed. These devices can be used to straighten teeth, correct an irregular bite, close unsightly gaps and bring teeth and lips into proper alignment. Crooked teeth that do not fit together correctly are harder to keep clean and are at risk of being lost early because of tooth decay or periodontal disease. The most common fixed treatment option, braces consist of brackets, elastic bands and an arch wire. Braces are adjusted every 4-6 weeks to bring about the desired results, which may be achieved in one to three years. Once braces are removed, a retainer is worn on either the upper or lower jaw or both for at least one year to hold the teeth into place in their new position. Early intervention takes advantage of the fact that a child's jaw is still growing. Early treatment is useful when the dental arches and jaws are not in the correct position. Functional appliances can fix or improve these problems. More treatment usually is needed later on, but it may be shorter and less involved.