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Maxillofacial Surgery
Facial Symmetry and Asymmetry
Built from Facial Aesthetics — Concepts and Clinical Diagnosis
What’s inside
11 sections · 161 slides
Overview
- What this topic covers
What symmetry means
Definitions, normal variation and the link with proportion
- Two sides that match
- No face is a perfect mirror
- The whole body is a little lopsided
- Where in the face asymmetry shows up
- 5%
- Symmetry is not the same as proportion
- Where the idea comes from
- “
- Balance and harmony: say what you mean
- Use quantifiable words instead
- “
Why a face becomes uneven
Aetiology and a working classification
- Getting to a diagnosis
- Some syndromes announce themselves
- Three groups of cause
- Why classify at all
- Three kinds of congenital defect
- Timing shapes the defect
- Developmental: a jaw that outgrows its partner
- Acquired: injury and disease
- Arthritis in the adult jaw joint
- Reading the classification table
- A classification of the aetiology of facial asymmetry
- A classification of the aetiology of facial asymmetry (continued)
Examining the face
Purpose, natural head position and the frontal view
- What the examination is for
- Look, measure, look again
- Photographs record, they do not replace
- Start in natural head position
- A tilted head hiding an uneven face
- Severe asymmetry is hard to judge
- Building the facial midline
- Facial midline from a true vertical
- The upper lip as a midline landmark
- Midline through glabella and the upper lip
- Checking the dental midlines
- Marking the midpoints on the face
- When the interpupillary line can be trusted
- Vertical reference lines
- Vertical reference lines on the face
- Horizontal reference lines
- Horizontal reference lines on the face
- Measuring vertical levels
- Comparing the levels of paired structures
- Is the bite level canted?
- A wooden spatula across the upper teeth
- Fox's occlusal guide plane
Looking from other angles
The photographic views that reveal what the front view hides
- Five more ways to look at the face
- The superior, bird's eye view
- The submental, worm's eye view
- Profile and three-quarter views
- Photographing the bite plane
- Occlusal plane view with a cheek retractor
- Occlusal plane view with photographic retractors
The face in motion
Jaw displacement, pseudo-asymmetry and asymmetrical animation
- Where the jaw sits at rest
- The ideal path of closure
- How one early tooth contact fakes an asymmetry
- Displacement, or functional shift
- A jaw that has slid to one side
- Premature contact and the shift that follows
- Testing for a displacement
- Midlines meeting on mouth opening
- When the shift hides itself
- Guiding the jaw by hand
- Why this check is not optional
- True asymmetry made worse by a shift
- Asymmetry that only appears on movement
- Video captures what a photograph misses
Dental midlines and the chin
Three places the lower midline can shift from, and telling chin asymmetry from jaw asymmetry
- Two midlines to check
- Three layers the lower midline sits on
- Reading the three segments
- Three landmarks for the lower dental midline
- When the chin sits centrally on the jaw
- When the chin does not match the jaw
- Chin problem or jaw problem?
- Why the distinction matters
- Chin asymmetry compared with mandibular asymmetry
What the X-rays add
PA and lateral cephalograms, triangular analysis and the panoramic view
- The posteroanterior cephalogram
- Five ways to find the midsagittal plane
- Method one: draw a true vertical
- True vertical and horizontal on a PA film
- Method two: perpendicular to a horizontal plane
- How a small tilt swings the midline
- Harvold's more reliable landmarks
- Harvold's horizontal plane
- Method three: joining midline landmarks
- Method four: midpoints of paired structures
- Method five: radiopaque soft tissue markers
- Radiopaque soft tissue markers in place
- Know what the midline cannot tell you
- Vertical reference planes on the film
- Vertical reference lines on a PA film
- Horizontal reference planes on the film
- Horizontal reference lines on a PA film
- Triangular analysis
- Setting up the triangles
- The three triangles
- Maxillary, mandibular and chin triangles
- What the triangles show
- Right-sided hemimandibular hyperplasia
- The lateral cephalogram
- Two mandibular borders on a lateral film
- The panoramic radiograph
- Excess ramus height on a panoramic film
Three-dimensional records
Study casts, surface scans, CT, printed models and virtual planning
- Why go three-dimensional
- Dental study casts
- Ruled grid over a dental study cast
- Watching the bite change over time
- From plaster to digital models
- Three-dimensional facial soft tissue scans
- Serial 3D facial scans one year apart
- Computed tomography
- CT sections through the maxilla and mandible
- A 3D CT reconstruction of severe asymmetry
- Vertical planes on the 3D image
- Vertical lines on a 3D CT reconstruction
- Three holes that should line up
- The trigeminal foramina in a vertical line
- Horizontal planes: where to start
- Horizontal planes: further down the face
- Horizontal planes across a symmetrical skull
- The maxillofacial frame
- The maxillofacial frame
- Models you can hold
- A stereolithographic model of the jaws
- Three-dimensional virtual surgical planning
- Virtual planning of the jaw movements
- Set the planning session up properly
- Magnetic resonance imaging
Growth and treatment timing
Has growth stopped, and what happens if you operate too soon
- Three questions before treating
- Why the three questions matter
- Restricted growth needs treatment
- Treating excessive growth in a child
- The same appliance in deficient growth
- Why some cases must wait
- Superimposing serial cephalograms
- Choosing the reference line
- Two lateral films superimposed on the cranial base
- Other ways to track change
- Colour map of soft tissue growth change
- “
- Can growth be predicted?
- The prediction paradox
- Height tracks jaw growth
- Reading a growth chart
- A standard height growth chart
- 14 ± 2 yr
- How much height the spurt adds
- Bone scanning with technetium-99m
- A hot condyle on a bone scan
- How to read the scan result
- SPECT and the limits of bone scanning
- What a hot spot cannot tell you
Pulling it together
What to carry away and where the evidence came from
- Key points: what asymmetry is
- Key points: finding the cause
- Key points: examining the patient
- Key points: imaging and timing
- References
- References (continued)
- References (continued)
- References (continued)
- Facial Aesthetics: Concepts and Clinical Diagnosis, 2nd Edition