Facial asymmetry involving the maxilla and mandible may be congenital or acquired. The type of asymmetry determines the surgical procedures which may be needed for correction.
There are three anatomic planes in the maxillmandibular region:
(1) maxilla
(2) body of mandible (with dentition)
(3) symphysis of the mandible
|
Center of Maxilla
|
Center of Body of Mandible
|
Center of Symphysis of Mandible
|
Levels Aligned
|
Type of Asymmetry
|
|
midline
|
midline
|
midline
|
all 3
|
none (normal)
|
|
midline
|
midline
|
asymmetric
|
maxilla and body of mandible
|
I
|
|
midline
|
asymmetric
|
asymmetric
|
body and symphysis of mandible
|
II
|
|
midline
|
asymmetric
|
asymmetric
|
none
|
III
|
|
asymmetric
|
asymmetric
|
asymmetric
|
none
|
IV
|
(after Figure 1, page 349)
If the 3 anatomic levels show an occlusal cant discrepancy (not horizontal), then the type is designated type C as follows:
(1) if normal symmetry: C
(2) with asymmetry type I: IC
(3) with asymmetry type II: IIC
(4) with asymmetry type III: IIIC
(5) with asymmetry type IV: IVC
The type of asymmetry determines which surgical procedures should be used for correction.
|
Type of Asymmetry
|
Genioplasty
|
Mandibular Surgery
|
Maxillary Surgery
|
|
I
|
yes
|
|
|
|
II
|
|
yes
|
|
|
III
|
yes
|
yes
|
|
|
IV
|
yes
|
yes
|
yes
|
|
IC
|
yes
|
yes
|
yes
|
|
IIC
|
|
yes
|
yes
|
|
IIIC
|
yes
|
yes
|
yes
|
|
IVC
|
yes
|
yes
|
yes
|
|
C
|
|
yes
|
yes
|
(after Table page 351)
The specifics for the technique used to correct a deformity must be determined individually. When treating transverse occlusal cant discrepancies it is important to consider the vertical relationship of the maxillary incisors to the upper lip.
