Transcript PPT - UCLA Head and Neck Surgery

Chapter 32:
Mentoplasty & Facial
Implants
Sameer Ahmed
11/14/2012
Background
• Chin anatomy/deformity should be thoroughly examined in
any patient requesting facial plastics
• Especially in relation to the lips, teeth, and nose
• Malocclusion and dental abnormalities
• May need to be addressed first with orthodontic therapy
• Mentalis muscle evaluation
When to get radiographs
• If the chin deformity is complex, (e.g., vertical chin excess with
horizontal deficiency or transverse bony asymmetry)
• AP and Lateral xrays
• When considering bony genioplasty
• Panorex
• Shows mandible, mandible height, tooth roots, mental foramen,
inferior alveolar canal
Ideal Chin Position
• The most frequently used evaluation of the chin drops a
perpendicular line from the vermilion border of the lower lip
and compares the AP position of this line with the soft tissue
pogonion (the anterior-most projecting chin point)
• For males, the pogonion should be at this line
• For females, the pogonion should be slightly posterior to this line
• This technique misses vertical and transverse deformities
Vertical Analysis of the Chin
• Simple technique  divide
the face into thirds
• Trichion  Glabella
• Glabella  Subnasale
• Subnasale  Menton
• Divide the lower third into
2 equal parts:
• subnasale  vermilion of
the lower lip
• lower lip vermilion 
menton
Transverse Analysis
• Look for asymmetry of the bony midline in comparison to
dental midline
• Can occur in pts with Goldenhar’s syndrome or trauma
Soft tissue deformity
• Witch’s Chin:
• Weakening of the muscular
attachments of the mentalis
and depressor labii
inferioris muscles
• Soft tissue pad of the chin
falls below the mandibular
line  deep horizontal
crease in submental region
• Tx: Remove ellipse of skin in
submental region, elevate
elliptical flap, plicate tissue,
re-approximate mentalis
Chin Implants
• Chin implant augmentation good for minor chin deformities
• For vertical/transverse chin deformities, an implant can make the
appearance worse
• Types: Silastic, Goretex, Medpor, Bone Source
• Complications of Silastic, Goretex, Medpor  extrusion,
malposition
• Medpor more resistant to infection
• Complications of Bone Source  Exposure, infection
Chin Implant Technique
(Mentoplasty)
1. Extraoral incision (submental incision) = 2-3 cm
2. Divide mentalis muscles, get on top of the periosteum
3. Stay supraperiosteal centrally and go subperiosteal laterally
• Subperiosteal is good in that it prevents migration of the implant
but can cause resorption/erosion of the mandible….so this is a
compromise
• Preserve mental nerves when doing subperiosteal dissxn
4. Implant should be at inferior border of mandible
5. Reapproximate mentalis muscle
6. Chin strap dressing
***For intraoral route, use gingivolabial incision initially
Osseous Genioplasty
• Horizontal osteotomy & down fracture of chin
• Advancement or retrusion in the AP plane
• Lengthening and shortening in the CC plane
• Allows you to correct transverse asymmetries
Osseous Genioplasty Technique
1.
2.
3.
Gingivolabial incision, go more towards labial
side
Elevate subperiosteally, preserve mental nerves
Mark osteotomy sites
• Horizontal osteotomy for AP advancement
• Oblique osteotomy for vertical manipulation
• When going laterally, stay at least 5mm below
mental foramen
4.
For vertical lengthening, bone graft can be
placed
• For vertical shortening, parallel osteotomy or burr
away bone
5.
Fixation with plates, screws, or interosseus wires
Mentoplasty Algorithm
Horizontal
(Anteroposterior)
Deformity Vertical
Transverse
D
N or sl D
N
D
E
N
D
D
N
N
N
Asymmetric
E
N
N
E
E
N
Procedure
Chin implant or
genioplasty
Genioplasty
(advancement with
possible ostectomy if
significant vertical
excess)
Bony advancement
(with down-grafting
for chin lengthening)
Bony osteotomy (with
resection of downgrafting)
Bony osteotomy (with
setback)
Bony osteotomy (with
ostectomy)
N – Normal. D = Deficient. E = Excessive. Sl = Slight
Complications (rare)
• Mentoplasty Complications:
• Malpositioning of implants
• Extrusion, migration
• Bothersome to patients
• Infection (w/ intra-oral or extraoral incision)
• Anterior mandible resorption
• Genioplasty complications
• Mental nerve injury
• Malunion, non-union of bone segments
The End
Anatomical Considerations
• The inferior alveolar nerve, a branch of the third division of
the fifth (trigeminal) cranial nerve, travels through the
mandibular canal and exits the mental foramen as mental
nerve.
• Mental foramen opposite to 2nd premolar
• The mental nerve supplies sensation to the skin and mucous
membranes of the lower lip and chin.
• The mandibular canal is often located 2 to 3 mm below the
level of the mental foramen.
• Bony osteotomies should therefore be performed at least 5 mm
below the mental foramen to avoid injury to the neurovascular
bundle.
Occlusion Grading
• Grade 1 (proper occlusion): The mesiobuccal cusp of the
upper first molar should align with the buccal groove of the
mandibular first molar
• Grade 2 (retrognathism): The upper molars are placed not in
the mesiobuccal groove but anteriorly to it.
• Grade 3 (Prognathism): The upper molars are placed not in
the mesiobuccal groove but posteriorly to it.
• Can be from large mandible and/or small maxilla
What type of occlusion?
What type of occlusion?
Grade 2