This term refers to a branch of dento-facial surgery that is concerned with the surgical lengthening of either a part of a jaw or of a whole jaw where there is a pronounced deviation in the position of the jaw itself. The most common intervention involves moving the position of the lower jaw forwards, backwards or sideways, which is normally carried out today via a Bi-Sagital Split Osteotomy (BSSO). A BSSO involves cutting the lower jaw into two on both sides of the vertical mandible, so that the middle section of jaw bearing the teeth can be repositioned. The three segments are then fixed together again using surgical screws or plates. In the post-op phase, the jaws are often fixed together using wires or strong elastic. Whilst some surgeons no longer do this, the length of time needed for so-called fixation to take place can range from one to two weeks. In addition to all the usual risks that surgery involves, BSSO does entail two particular risks: damage to the nerves of the lower jaw (the third branch of the N. Trigeminus) and damage to the jaw joint itself. The lower jaw nerve innervates the teeth, the lower lip and part of the chin but not the muscle structure itself which is actually served by the facial nerves and is never damaged. If damage does occur to the lower jaw nerve, it normally manifests itself as reduced feeling or numbness in the lower lip, usually just on one side. This generally disappears during the first year after surgery. Whilst some minor adverse effects may be observed in about a quarter of patients, any serious problems are rare. And in the jaw joint itself, there is often restricted movement and sometimes pain and a clicking noise.
The second most common intervention is a Lefort 1 osteotomy of the upper jaw. This involves separating the part of the upper jaw from the skull at the level of the nose floor. The only thing still connecting the upper jaw is the soft gum tissue which carries the nerves and the blood supply. Once it has been detached, the upper jaw can basically be repositioned or rotated in any direction so that it can then be quickly fixed with surgical plates. Unlike a BSSO of the lower jaw, there are no particular risks associated with this procedure. A BSSO and a Lefort 1 Osteotomy are often carried out at the same time because better results can be achieved than by just operating on one jaw. Since their introduction, both interventions have been continuously improved and have been routine procedures for decades now. What is important in weighing up the risks, impact and possible usefulness of any intervention is that most of the times, dysgnathia surgery is elective and not associated with urgent indications. Therefore, patients should always be well informed and make their own personal decision as to whether or not they would like to have a dysgnathic surgical intervention. In appropriate cases, dysgnathia surgery significantly expands the range of orthodontic treatment and can result in dramatic improvements in function and aesthetics.