Lower jaw surgery is done to correct abnormalities of the lower jaw (mandible), which may be too small or too large. The jaw can be advanced or retracted surgically. Rotation is also possible.
The most common operation to advance or retract the jaw is called a sagittal split osteotomy. This type of surgery allows for the placement of bone screws or plates. Consequently the jaws don’t have to be wired together at the end of the procedure.
Procedure of Lower Jaw Surgery
The operation is carried out almost entirely from inside the mouth to minimize visible scars on the skin of your face. It is performed under general anaesthesia.
Incisions are carried out completely inside of the mouth.
The lower jaw is split in a vertical (sagittal) plane on each side with a small saw behind the last tooth. The bone is split in a front to back direction so the two pieces can slide along each other and still overlap. The part of the lower jaw with the teeth is moved forward or backward as needed to obtain the desired bite and appearance.
It is then fixed with small screws and sometimes plates. It is often necessary to make a small puncture incision (a few mm long) low down on the side of the cheek to allow the screws to be inserted. These titanium screws, which are left in place permanently, do not set off metal detectors in airports.
The gum inside the mouth is sutured using dissolvable stitches that may take 3-4 weeks to dissolve Sometimes light elastics are placed between the teeth to guide the jaw into the new bite.
Lower jaw surgery may be performed as a single procedure or in combination with other orthognathic procedures.
Retraction of the lower jaw
When the lower jaw grows out too far in front of the upper jaw, this results in mandible prognathism. The lower teeth are more pronounced than the upper teeth—a condition called underbite.
Orthognathic surgery can be used to slide the lower jaw back.
Before retraction of the lower jaw.
After retraction of the lower jaw.
Advancement of the lower jaw
The underdevelopment of the lower jaw is called retrognatia. In this case, the lower teeth are positioned too far behind the upper front teeth (overbite).
This condition can be treated by surgically advancing the lower jaw.
Before advancement of the lower jaw.
After advancement of the lower jaw.
Mandibular wisdom teeth removed well in advance
It is generally wise to plan for the mandibular wisdom teeth to be removed well in advance of the mandibular split surgery, since they can make the surgery more difficult. Experienced surgeons can remove the tooth and obtain a successful split, but almost all try to avoid this situation because it may increase the risk of an unplanned mandibular fracture and can make the placement of the screws more difficult.
Numbness in lower lip/chin lasting from weeks to months
A major drawback of the sagittal split osteotomy is the risk to the mandbibular nerve, which innervates the lower lip and chin an this should be mentioned. The patient has to be informed about numbness of the lower lip and chin for some weeks to months postoperatively.
Risk of permanent 'altered sensation' in lower lip and chin
In most cases normal sensation returns though occasionally an altered sensation remains which does not lead to distortion, or impairment of the function of the lips. In most cases the patient gets accustomed to it.
Screws do not need removing
No intermaxillary fixation
An advantage of the sagittal split osteotomy is the possiblity of screw fixation avoiding the need for intermaxillary fixation during a number of weeks.
Problems of the temporomandibular joint
Postoperatively, temporomandibulair joint complaint are not uncommon, as during the operation the mouth is opened wider than normal, and the teeth do not always fit together completely afterwards. A 'tired feeling' around the cheeks and ears may occur temporarily and occasionally supportive physical therapy may be necessary.