1. Chapter 32: Mentoplasty & Facial Implants
Sameer Ahmed
11/14/2012

2. 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

3. 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

4. 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

5. 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
Trichion – Frontal hairline meets the forehead
Menton – Lowest point of chin

6. Transverse Analysis
Look for asymmetry of the bony midline in comparison to dental midline
Can occur in pts with Goldenhar’s syndrome or trauma
Goldenhar’s Syndrome -- Oculo-Auriculo-Vertebral (OAV) syndrome) is a rare congenital defect characterized by incomplete development of the ear, nose, soft palate, lip, and mandible. It is associated with anomalous development of the first branchial arch and second branchial arch. Common clinical manifestations include limbal dermoids, preauricular skin tags, and strabismus

7. 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
A, B, C : Pre-op
D: Post –op (Face lift and surgical correction of mentalis muscle)

8. 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

9. Chin Implant Technique (Mentoplasty)
Extraoral incision (submental incision) = 2-3 cm
Divide mentalis muscles, get on top of the periosteum
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
Implant should be at inferior border of mandible
Reapproximate mentalis muscle
Chin strap dressing
***For intraoral route, use gingivolabial incision initially

10. 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

11. Osseous Genioplasty Technique
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
For vertical lengthening, bone graft can be placed
For vertical shortening, parallel osteotomy or burr away bone
Fixation with plates, screws, or interosseus wires
Intraoperative photograph of the preformed rigid genioplasty plate. Note that two small wires are used in this patient to ensure stability of the bony movement.

12. Mentoplasty Algorithm
Horizontal (Anteroposterior)
Deformity Vertical
Transverse
Procedure D
N or sl D N
Chin implant or genioplasty E
Genioplasty (advancement with possible ostectomy if significant vertical excess)
Bony advancement (with down-grafting for chin lengthening)
Asymmetric
Bony osteotomy (with resection of down-grafting)
Bony osteotomy (with setback)
Bony osteotomy (with ostectomy)
N – Normal. D = Deficient. E = Excessive. Sl = Slight

13. 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

14. The End

15. 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.

16. 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

17. What type of occlusion?

18. What type of occlusion?
Grade 2