Mandibular augmentation procedure
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I now have comprehensive information from Cummings Otolaryngology Head and Neck Surgery and Mulholland and Greenfield's Surgery to write a detailed, well-organized response.
Mandibular (Chin) Augmentation Procedure
Mandibular augmentation - collectively called mentoplasty or genioplasty - corrects deformities of the lower jaw (chin) in the horizontal (anteroposterior), vertical (superoinferior), and transverse planes. Choosing the right technique depends on the type and extent of the deformity.
1. Preoperative Assessment
Clinical analysis:
- Three standardized photos: anteroposterior, lateral (profile), and oblique
- Evaluate chin relative to lips, nose, neck soft tissues, and dental occlusion
- Assess in three dimensions - horizontal projection, vertical height, transverse symmetry
- Mentalis muscle tone and soft tissue ptosis should be noted
- Dental occlusion must be examined; malocclusion may require orthodontics or orthognathic surgery first
Radiographic analysis:
- Panoramic radiograph: cortical mandibular outline, vertical height, positions of tooth roots, inferior alveolar canals, and mental foramina
- AP + lateral cephalometric views if bony genioplasty is planned
- The mandibular canal exits as the mental nerve 2-3 mm superior to the mental foramen; osteotomies must be placed at least 5 mm below the mental foramen
Anthropometric norms:
- Ideal horizontal projection: soft tissue pogonion ~4 mm posterior to the Frankfurt horizontal vertical
- Males: pogonion at the level of the lower lip vermillion perpendicular; females: slightly posterior to this line
- Lower face = 57% of the middle + lower two-thirds height (nasion-to-subnasale : nasion-to-menton = 0.43)
2. Procedure Selection by Deformity Type
| Horizontal | Vertical | Transverse | Procedure |
|---|---|---|---|
| Deficient | Normal or slight | Normal | Chin implant, genioplasty, or filler |
| Deficient | Excessive | Normal | Genioplasty (advancement + possible osteotomy for vertical excess) |
| Deficient | Deficient | Normal | Bony advancement with downgrafting |
| Deficient | Normal | Asymmetric | Bony osteotomy ± bone resection/downgrafting, or filler |
| Excessive | Normal | Normal | Bony osteotomy with setback |
| Excessive | Excessive | Normal | Bony osteotomy with ostectomy |
(Cummings Otolaryngology, Table 27.1)
Key rule: Alloplastic implants correct only horizontal (AP) deficiency. For vertical or transverse deformities, osseous genioplasty is required.
3. Surgical Techniques
A. Alloplastic Chin Implant (Mentoplasty)
Anesthesia: General or IV sedation with mental nerve block (1% Xylocaine with 1:100,000 epinephrine)
Incision options:
- Extraoral (submental): 2-3 cm incision in the submental crease, through dermis and subcutaneous fat
- Intraoral: Horizontal or vertical gingivolabial sulcus incision
Dissection plane:
- Supraperiosteal plane centrally (to minimize mandibular bone resorption)
- Subperiosteal plane laterally (improves fixation, places lateral wings deep to mental nerve)
- Mental nerves must be identified and preserved during lateral dissection
Implant types:
- Central button implant - smaller, for isolated central projection; more prone to visible malposition
- Extended anatomic implant - tapered, longer; allows lateral mandibular augmentation; more forgiving with small positional changes
Implant materials:
| Material | Trade Name | Tissue Interface | Pros | Cons |
|---|---|---|---|---|
| Polydimethylsiloxane (silicone) | Silastic | Fibrous capsule | Carvable, removable | Bone resorption, exposure risk |
| ePTFE | Gore-Tex | Limited ingrowth | Sheet/tubular forms | Palpable |
| High-density polyethylene | MEDPOR | Fibrovascular ingrowth | Versatile, infection-resistant | Difficult to remove |
| Hydroxyapatite | Bone Source | Osseointegration | Paste form, moldable | Infection risk (sinus sites) |
(Cummings Otolaryngology, Table 27.2)
Fixation: Precise pocket creation (small-pocket technique) or titanium monocortical screws through implant into anterior mandible (4-5 mm depth); suture fixation also used.
Implant placement landmark: Along the inferior border of the mandible; superior placement causes bone erosion and an unnatural appearance (Fig. 27.31 - too-superior placement causes significant bony erosion).
Closure: Two-layer (mentalis muscle + mucosa); chin-strap dressing for 3 days.
B. Osseous Genioplasty (Sliding Genioplasty)
First described by Hofer in 1942. The horizontal osteotomy of the bony mentum allows movement in all three planes.
Anesthesia: General (nasotracheal intubation preferred when rhinoplasty is not combined; orotracheal if combined with rhinoplasty) or IV sedation with mental nerve block.
Incision: Gingivolabial incision from canine to canine (labial side of sulcus to preserve adequate mucoperiosteal cuff for closure).
Steps:
- Subperiosteal dissection laterally with identification and preservation of both mental nerves
- Small inferior soft tissue cuff is preserved centrally over the mentum for vascular supply to the distal segment
- Bony midline inscribed vertically with a side-cutting burr (landmark for re-alignment)
- Osteotomy measured and marked with calipers (symmetrical); must stay below tooth roots and at least 5 mm below mental foramina
- Osteotomy created with reciprocating saw from lateral to medial
- Gentle digital downfracture of the bony segment
Movements achievable:
- Horizontal advancement/setback: horizontal osteotomy orientation
- Vertical shortening: oblique osteotomy; distal segment advances + shortens
- Vertical lengthening: bone graft (autogenous or allogenic) placed into downfractured gap
- Significant shortening: two parallel oblique osteotomies with intervening bone removed
Fixation: Adaptation (prebent genioplasty) plates, positional screws, or interosseous wires.
Closure: Two-layer - mentalis muscle with interrupted 3-0 catgut; mucosa with running locking 3-0 chromic catgut. Pressure chin-strap dressing for 5 days.
Postoperative care: Soft diet for 2 weeks; meticulous oral hygiene.
C. Noninvasive Chin Augmentation
Agents: Hyaluronic acid fillers (e.g., Juvederm Ultra Plus), autologous fat transfer.
Advantages over surgical options:
- Office-based, no anesthesia required
- Minimal downtime
- Hyaluronic acid is reversible with hyaluronidase
- True 3D augmentation - can address prejowl sulcus (lateral paragonal region) and central pogonion simultaneously
- Useful when vertical excess coexists with horizontal deficiency (fillers can correct projection without increasing apparent chin length)
Limitations: Not permanent; repeat injections required.
Complications: Ecchymosis, edema; vascular compromise and contour irregularities are uncommon given the thick soft-tissue envelope.
4. Complications
| Complication | Context |
|---|---|
| Mental nerve paresthesia/injury | Osteotomy too close to foramen; inadequate lateral dissection |
| Implant malposition/rotation | Inadequate fixation; pocket too large |
| Bone resorption | Subperiosteal implant placement centrally |
| Infection | Any alloplastic technique; MEDPOR most resistant |
| Extrusion | Alloplastic implants; rare |
| Dental injury | Osteotomy above tooth root level |
| Soft tissue ptosis | Inadequate mentalis resuspension at closure |
5. Combined Procedures
Genioplasty is commonly combined with:
- Rhinoplasty - to optimize the nasolabial and cervicomental angles and overall facial balance (cervicomental angle improved by advancement genioplasty)
- Orthognathic surgery (Le Fort I, BSSO) - for occlusal correction with simultaneous chin repositioning
- Facelift - with soft tissue ptosis correction
Sources:
- Cummings Otolaryngology Head and Neck Surgery, Chapter 27 (Mentoplasty)
- Mulholland and Greenfield's Surgery, Chapter on Genioplasty
Recent systematic reviews (Oranges et al., 2023 - Plast Reconstr Surg; Liao et al., 2023 - Ann Plast Surg; Alwathnani et al., 2026 - Aesthetic Plast Surg) confirm that both surgical and non-surgical techniques have high patient satisfaction, with surgical methods offering more durable results and non-surgical offering greater flexibility for 3D shaping.
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