Chapter 32 mentoplasty facial implants
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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

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Chapter 32: Mentoplasty & Facial Implants

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Chapter 32 mentoplasty facial implants

Chapter 32:Mentoplasty & Facial Implants

Sameer Ahmed

11/14/2012


Background

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

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

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

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

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

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 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 m entoplasty

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


Osseous genioplasty

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

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


Mentoplasty algorithm

Mentoplasty Algorithm

N – Normal. D = Deficient. E = Excessive. Sl = Slight


Complications rare

Complications (rare)

  • Mentoplasty Complications:

    • Malpositioning of implants

      • Extrusion, migration

      • Bothersome to patients

    • Infection (w/ intra-oral or extraoralincision)

    • Anterior mandible resorption

  • Genioplasty complications

    • Mental nerve injury

    • Malunion, non-union of bone segments


The end

The End


Anatomical considerations

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

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?


What type of occlusion1

What type of occlusion?

Grade 2


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