Surgical Orthodontics — Orthognathic Treatment for Adults

Mandibular Advancement Surgery

Mandibular advancement involves surgically repositioning the lower jaw (mandible) forward. This is achieved via a bilateral sagittal split osteotomy (BSSO) — a well-established procedure in which the mandible is divided on each side and moved to the planned position, then stabilised with titanium plates and screws.

Indications include:

• Skeletal class II malocclusion (recessed lower jaw, prominent overbite)
• Lower jaw deficiency affecting facial profile and aesthetics
• Obstructive sleep apnoea, where advancement of the lower jaw significantly increases the oropharyngeal airway and reduces collapsibility of the upper airway

Mandibular advancement surgery — particularly as a component of maxillomandibular advancement (MMA) — is a highly effective intervention for sleep-disordered breathing and is increasingly used in collaboration with sleep medicine physicians for patients who cannot tolerate CPAP or where a skeletal contribution to airway compromise has been identified.

Bimaxillary Advancement Surgery

Bimaxillary advancement involves the simultaneous surgical repositioning of both the upper jaw (maxilla) and the lower jaw (mandible). This is carried out via a Le Fort I osteotomy of the upper jaw combined with a bilateral sagittal split osteotomy of the lower jaw.

Indications include:

• Significant skeletal discrepancy involving both jaws
• Cases where the aesthetic and functional goals require coordinated movement of both the upper and lower jaw
• Severe obstructive sleep apnoea where maxillomandibular advancement (MMA) is indicated — simultaneously advancing both jaws to achieve the maximum improvement in airway volume and function
• Facial skeletal asymmetry requiring movement in multiple planes of space

Bimaxillary surgery allows a high degree of three-dimensional control over the position of both jaws and the overall facial aesthetic outcome. Treatment planning — including the sequence and degree of jaw movements — is agreed collaboratively between the orthodontist, surgeon, and patient using detailed imaging, digital planning tools, and surgical simulation.

Not all orthognathic cases require movement of both jaws. Where the skeletal discrepancy is confined to the upper jaw, a Le Fort I osteotomy of the maxilla alone may be performed to advance, impact, or reposition the upper jaw without altering the lower jaw surgically.

Upper jaw advancement is indicated where the maxilla is deficient in its forward position, resulting in a flat mid-face, a compromised upper lip position, or a skeletal class III appearance driven by maxillary rather than mandibular factors.

Upper jaw impaction is particularly relevant in cases with a significant anterior open bite. In these cases, the back of the upper jaw is surgically impacted (moved upward), which causes the mandible to autorotate upward and forward in a counterclockwise direction. This autorotation of the mandible is a powerful and predictable mechanism for closing an open bite and improving the facial profile — achieving correction not by moving the lower jaw surgically, but by allowing it to rotate into a more favourable position as a consequence of the upper jaw movement. This approach is often more stable than attempting to close an open bite through lower jaw surgery alone.

The direction and magnitude of upper jaw movement is planned precisely using 3D imaging and surgical simulation, and the orthodontic preparation is designed to allow the jaws to meet in their planned relationship at the time of surgery.

In adult patients with a narrow upper jaw, palatal expansion often requires a surgical component to release the resistance of the fused midpalatal suture. Surgical facilitation in this context refers to procedures that allow orthodontically or device-driven expansion of the upper jaw to proceed more predictably.

This includes surgically assisted rapid maxillary expansion — where corticotomy cuts are made around the maxilla to reduce skeletal resistance — as well as more complex procedures where expansion is combined with simultaneous Le Fort I repositioning of the maxilla.

Where expansion is part of a broader surgical orthodontic plan, it is sequenced and planned alongside other jaw movements to achieve the best overall result.

For a more detailed overview of expansion techniques used in adults, see the Palatal Expansion page.