Why a removable brace?
A removable brace can fix simple problems such as moving a top front tooth forwards into line with the others. Fixed braces (‘traintracks’) are used for complicated problems. They are excellent at straightening teeth but removable braces are better at straightening jaws. So we use expansion plates to widen narrow upper jaws (perhaps caused by years of thumbsucking). You could call this a side to side brace. We use functional appliances such as twin-blocks to improve teeth that stick out. You could call this a front-to-back brace to improve the profile.
