http://en.wikipedia.org/wiki/Orthodontics

Today's orthodontics involves repositioning of the teeth and underlying roots, providing better support for the crown of the tooth. No matter what your age, orthodontics can protect your bite (occlusion), maximize your teeth's effectiveness in performing their functions and create a well-aligned smile. In addition, well-aligned teeth make oral hygine easier to maintain. Orthodontic treatment is now associated with the benefits of greater esthetic appeal, increased comfort and reduced treatment time.