When the discrepancy between the jaws exceeds about 4 mm, a combined orthodontic and jaw surgery (orthognathic surgery) approach sometimes is recommended
The orthodontist first aligns the teeth and the Maxillo-Facial and Oral Surgeon (MFOS) then surgically places the jaws in the correct position for an improved bite and facial balance
Jaw surgery is usually only recommended at the end of general body growth, as determined by the left handwrist Xray
People with big lower jaws usually need to wait till 2 years after general growth is complete because a late mandibular growth spurt often occurs in these patients
Many patients opt not to undergo these procedures and prefer to accept imperfect bites, profiles, and facial proportions
Patients opting not to undergo surgical correction of their jaw relationships will usually need to wear retainers more often over the years and may be more susceptible to temporomandibular joint dysfunction (TMD).
SURGERY OF THE CHIN (GENIOPLASTY)
The chin may be made more or less prominent thereby creating a more pleasing profile and Lip-Chin-Throat angle
A genioplasty can also make the chin vertically shorter or increase the height of the chin depending on the aesthetic requirements of the face
- The genioplasty is often performed simultaneously with the surgical removal of impacted wisdom teeth.
LOWER JAW SURGERY
The lower jaw may need to be expanded, contracted, moved forward, backwards, upwards or downwards to achieve improved facial dimensions.
LOWER JAW SURGERY FOR:
SHORT LOWER JAW(CLASS II)
OVERCLOSED LOWER JAW (SKELETAL DEEP BITE)
LONG FACE LOWER JAW (SKELETAL OPEN BITE)
PROMINENT LOWER JAW (CLASS III)
In preparation for surgery in these patients full fixed orthodontic treatment will be aimed at coordinating and aligning the upper and lower dental arches so that they will fit properly after the jaw surgery
The upper incisors will be positioned to maintain a favourable nose-lip angle and tooth display on talking and smiling
Usually after 6-15 months, with the braces still on and often with the simultaneous removal of impacted wisdom teeth, a Bilateral Sagittal Split Osteotomy (BSSO) is performed, to place the lower jaw into the correct bite
- In patients with short lower jaws, the lower jaw is advanced
- In patients with over closed lower jaws, the lower jaw is rotated to open the bite increasing the lower face height
- In patients with long faces & open bites, the lower jaw is rotated to close the bite, decreasing the lower face height
- In patients with prominent lower jaws (class III), the lower jaw is moved backwards
- Following the orthognathic surgical correction, there will be 3-6 months of post-surgical orthodontic treatment to refine and stabilise the occlusion in a class l relationship
- Retainer wear and maintenance as described below
UPPER JAW SURGERY
The upper jaw area, also referred to as the mid-face may need to be expanded, contracted, moved forward, backwards, upwards or downwards to achieve improved facial dimensions, lip support or tooth display on talking and smiling
The upper jaw surgery most frequently employed is the Le Forte I osteotomy, which may involve moving the upper jaw in one, two or 3 pieces
If the upper jaw needs to be moved downwards, sometimes a small bone graft from the hip is used.
COMBINED UPPER & LOWER JAW SURGERY
Sometimes both upper and lower jaws need to be moved simultaneously to achieve more correct facial proportions