Orthodontic brace. Coloured three-dimensional computed tomography (CT) scan of an orthodontic brace (dark blue, upper frame) on a patient's teeth (brown). Orthodontics is the branch of dentistry that changes the position or angle of the teeth in order to improve their function or appearance. Tooth movement is achieved very slowly, over a period of months, usually by gluing a small bracket to each of the teeth. The brackets are linked by strong wire, which can be tightened in order to increase the pressure on the teeth. CT scans use X-rays to construct images of parts of the body.