Correction of Mandibular Asymmetry: Centering the Chin and Dental Midlines

Front view before and after surgery. Before surgery the chin and lower lip sat toward the patient’s left; after surgery they are centred under the nose.

BEFOREAFTER

‹ ›

Front · Before / AfterDrag to compare. Before at rest, braces on; after smiling (no at-rest front photo after surgery)

Front · BeforeAt rest, braces on

Front · AfterSmiling (no at-rest front photo after surgery)

Before · midline guideWhite line: facial midline, halfway between the eyes

After · midline guideSame line, same position

Individual results vary.

In the surgical plan, the chin (pogonion) was moved 10.1 mm toward the patient’s right, ending 0.1 mm from the facial midline. The lower incisor midline moved 8.5 mm to 0.1 mm from midline, and the upper incisor midline 3.4 mm to the midline. Forward movement was small (2.4 mm at the chin).

Before

Planned

Frontal · before → plannedDark line: upper facial midline. Before, the chin sits off the line; planned, it is centred on it.

Planned movementsRight-left column and final distance from midline (mm)

Lower-face asymmetry with a tilted bite. Before surgery the chin (pogonion) sat 10.0 mm and the lower incisor midline 8.4 mm to the patient’s left of the facial midline, and the upper incisor midline 3.4 mm to the left. The bite was canted: the upper canines sat 47.1 mm (left) and 49.3 mm (right) below the eye-socket rim.

Measured on the 3D surgical plan before surgery.

The movements were planned on a 3D model from the CT scan. In the surgical plan the upper jaw was rotated to level the occlusal plane: down 1.1 mm at the left canine and 1.6 mm at the left first molar, up by the same amounts on the right. The lower jaw was then brought to the centred upper jaw.

3D · PlannedFinal position

Before

Planned

3D · From belowBefore → planned

Planned final occlusionFrontal view of the planned bite

Segment	Planned movement	Amount (from plan)
Chin (pogonion)	Right / forward	10.1 mm / 2.4 mm
Mandible (lower incisor)	Right / forward	8.5 mm / 1.6 mm
Maxilla (upper incisor)	Right	3.4 mm
Maxilla (canines)	Cant correction	Left 1.1 mm down, right 1.1 mm up
Maxilla (first molars)	Cant correction	Left 1.6 mm down, right 1.6 mm up
SNA / SNB	Change	0.0° / +1.2°

Values as listed in the 3D surgical plan. Planned values; the operative result may differ slightly.

1. Upper jaw rotated to level the occlusal plane and centre the upper midline (Le Fort I osteotomy)
2. Lower jaw rotated toward the right and brought slightly forward (bilateral sagittal split osteotomy)
3. Both jaws fixed with titanium plates and screws (visible on the post-operative CT)

Bone views from the CT scans before and after surgery, at the same angle and size. After surgery the chin and both dental midlines line up with the middle of the face, and the plates and screws are visible.

Front · BeforeBraces in place

Front · AfterPlates and screws visible

Right side · Before

Right side · After

Individual results vary.

Treated at Maxillo-Facial Surgery Institute, Irvine. Our Surgeons