Chapter 9: Orthognathic Surgery¶

Dentofacial diagnosis, virtual surgical planning, osteotomy techniques, and orthodontic-surgical coordination.

Introduction¶

Orthognathic surgery corrects dentofacial deformities that cannot be addressed by orthodontics alone. The oral and maxillofacial surgeon functions as the central figure in the surgical correction of skeletal malocclusion, working in close coordination with the orthodontist from the initial treatment planning phase through postoperative orthodontic finishing. The advent of virtual surgical planning (VSP) and patient-specific surgical guides has fundamentally transformed the accuracy and predictability of orthognathic procedures.

This chapter covers the diagnostic workup, planning methodology, operative techniques, and management of complications for the full spectrum of orthognathic procedures.

Dentofacial Diagnosis¶

Clinical Assessment¶

A thorough clinical examination precedes any imaging or planning. Key elements include:

Frontal Analysis:

Facial symmetry assessment (midsagittal reference: glabella, nasal tip, philtrum, chin point)
Facial thirds proportionality (trichion-to-glabella, glabella-to-subnasale, subnasale-to-menton)
Transverse maxillary width relative to facial width
Lip competence at rest (strain, mentalis muscle hyperactivity)
Smile arc (relationship of maxillary incisal edges to lower lip curvature)
Gingival display: ideal 1-3 mm; excessive gingival display (gummy smile) suggests vertical maxillary excess
Facial midline assessment relative to dental midlines
Cant of the occlusal plane

Profile Analysis:

Facial convexity/concavity (glabella-subnasale-pogonion angle; norm approximately 170 degrees)
Nasolabial angle (columella-subnasale-upper lip; norm 90-110 degrees for males, 100-120 degrees for females)
Chin projection (Ricketts E-plane, Gonzalez-Ulloa zero-meridian)
Lower facial height proportion
Lip position relative to the E-plane (Ricketts: upper lip 4 mm behind, lower lip 2 mm behind)

Intraoral Assessment:

Angle classification (Class I, II, III molar/canine)
Overjet and overbite
Transverse discrepancy (crossbite, scissorbite)
Curve of Spee
Dental compensation (proclination/retroclination of incisors compensating for skeletal discrepancy)
Periodontal status and gingival biotype
TMJ examination (clicking, crepitus, range of motion, pain, deviation on opening)

Cephalometric Analysis¶

Lateral cephalometric radiography remains a cornerstone of orthognathic diagnosis. Key measurements:

Parameter	Landmark	Norm	Clinical Significance
SNA	Sella-Nasion-A point	82 degrees (± 2)	Maxillary AP position relative to cranial base
SNB	Sella-Nasion-B point	80 degrees (± 2)	Mandibular AP position relative to cranial base
ANB	A point-Nasion-B point	2 degrees (± 2)	Skeletal AP relationship (Class I: 0-4, Class II: >4, Class III: <0)
Wits appraisal	AO-BO on occlusal plane	0-1 mm (males), -1 to 0 mm (females)	AP jaw relationship independent of cranial base
SN-GoGn	Sella-Nasion to Gonion-Gnathion	32 degrees (± 5)	Mandibular plane angle; high angle = vertical excess, low angle = deep bite tendency
U1 to SN	Upper incisor to SN plane	104 degrees (± 2)	Upper incisor inclination; increased = proclined (dental compensation for Class III)
IMPA	Lower incisor to mandibular plane	90 degrees (± 5)	Lower incisor inclination
Facial height ratio	N-ANS : ANS-Me	45:55	Vertical proportionality

Clinical Pearl

Cephalometric norms are population-specific. African American, Hispanic, and Asian cephalometric standards differ significantly from Caucasian norms (e.g., increased bimaxillary protrusion in African American patients is normal and should not be "corrected" to Caucasian standards). Treatment goals should reflect the patient's ethnic and personal esthetic preferences.

Three-Dimensional Analysis¶

CBCT has largely supplanted 2D cephalometry for surgical planning, enabling:

True 3D cephalometric analysis (landmarks in all three planes)
Assessment of asymmetry with volumetric measurements
Airway volume analysis (particularly relevant in OSA patients)
Condylar morphology assessment (erosion, hyperplasia, osteophytes)
Evaluation of the inferior alveolar nerve canal position relative to planned osteotomy lines

Virtual Surgical Planning (VSP)¶

Overview¶

VSP has become the standard of care for orthognathic surgery planning, replacing traditional model surgery in most practices. The process involves:

Imaging acquisition: CBCT of the maxillofacial skeleton; intraoral optical scan of the dentition; stereophotogrammetry or 3D facial scan (optional).
Digital fusion: The CBCT, dental scan, and facial scan are merged into a single composite 3D model. The dental scan replaces the CBCT teeth (which have artifact from metallic restorations and brackets).
Virtual osteotomies and movements: The planning software simulates the surgical procedure, allowing precise repositioning of the maxilla, mandible, and chin in all three planes.
Splint design and fabrication: Intermediate and final occlusal splints are designed digitally and 3D-printed (typically nylon or photopolymer resin).

Major VSP Platforms¶

Platform	Manufacturer	Key Features
ProPlan CMF	Materialise (Synthes/DePuy)	Widely used; integrated with Synthes plating systems; virtual planning session with biomedical engineer
IPS CaseDesigner	KLS Martin	Independent planning by the surgeon; no mandatory virtual planning session; integrates with KLS Martin hardware
Dolphin 3D	Dolphin Imaging	Combined cephalometric analysis + 3D planning; strong orthodontic integration
BlueSkyPlan	BlueSkyBio	Open-source compatible; implant and orthognathic planning
3D Systems (VSP Orthognathics)	3D Systems	Virtual planning session model; patient-specific cutting guides and plates

Planning Workflow (Typical ProPlan CMF Session)¶

Data upload: CBCT DICOM files plus STL files from intraoral scan.
Segmentation: Automated and manual segmentation of maxilla, mandible, and chin.
Virtual planning session: Surgeon participates in a web-based session with a biomedical engineer:
- Define osteotomy lines (LeFort I, BSSO, genioplasty)
- Simulate maxillary movements (AP, vertical, transverse, roll, pitch, yaw)
- Simulate mandibular autorotation and repositioning
- Simulate genioplasty movements
- Verify condylar position (centric relation seating)
- Assess soft tissue prediction (if available)
- Design intermediate splint (seats maxilla to pre-op mandible) and final splint (seats mandible to post-op maxilla)
Guide and splint fabrication: 3D-printed surgical splints, cutting guides (for segmental osteotomies), and optionally patient-specific plates shipped to the surgeon.

Surgical Caution

The accuracy of VSP depends on correct condylar seating during the planning phase. If the condyles are not in centric relation when the CBCT is taken (e.g., deflected by a premature contact), the entire surgical plan will be based on an incorrect mandibular position. Some surgeons obtain the CBCT with a deprogramming splint or anterior jig to ensure CR. Additionally, intraoperative verification of condylar seating before fixation is critical.

Osteotomy Techniques¶

LeFort I Osteotomy (CPT: 21141-21160)¶

The LeFort I osteotomy is the workhorse of maxillary orthognathic surgery, permitting repositioning of the entire maxilla in all three planes.

Indications:

Maxillary anteroposterior deficiency or excess
Vertical maxillary excess (VME) or deficiency
Transverse maxillary deficiency (in conjunction with segmental osteotomy or SARPE)
Maxillary cant correction
Maxillary asymmetry

Surgical Technique:

Incision: Circumvestibular incision from first molar to first molar, approximately 5 mm above the mucogingival junction. Preserve the descending palatine arteries.
Subperiosteal dissection: Expose the piriform rims, lateral nasal walls, zygomatic buttresses, and pterygomaxillary junction bilaterally.
Osteotomy: Reciprocating saw or piezoelectric instrument from the piriform rim through the lateral maxillary wall to the pterygomaxillary junction bilaterally. The osteotomy line is typically 4-5 mm above the tooth apices.
Nasal septum: Nasal septum osteotomy with a septal osteotome.
Pterygomaxillary disjunction: Curved osteotome placed at the pterygomaxillary junction; single mallet blow directed anteriorly and medially. This is performed with caution to avoid fracture extension into the pterygoid plates or skull base.
Downfracture: The maxilla is mobilized inferiorly with digital pressure and Rowe disimpaction forceps. Complete mobilization in all directions is confirmed.
Repositioning: The maxilla is positioned per the surgical plan using the intermediate splint and placed into IMF with the mandible.
Fixation: Four-point fixation with L-shaped or straight miniplates (2.0 mm system): bilateral piriform rims and bilateral zygomatic buttresses. Minimum 4 plates with at least 2 screws above and 2 below the osteotomy on each plate.
Bone grafting: If significant advancement (greater than 6-8 mm) or impaction with gap creation is performed, bone grafting of the osteotomy gaps may improve stability.

Modifications:

Segmental LeFort I: Division of the maxilla into 2-3 segments (anterior segment plus posterior segments) to correct transverse discrepancy or significant curve of Spee. Requires careful interradicular osteotomy with a thin fissure bur.
LeFort I with differential impaction: Asymmetric vertical impaction to correct cant.

Critical Safety

Descending palatine artery: This vessel exits the greater palatine foramen and courses anteriorly along the hard palate. It is the primary blood supply to the mobilized maxillary segment (along with the ascending pharyngeal and ascending palatine anastomoses). Avoid stripping the palatal mucosa from the bone during LeFort I osteotomy. If the descending palatine artery is lacerated during pterygomaxillary separation, control with electrocautery, bone wax, or ligation. Loss of both descending palatine arteries can compromise maxillary viability, though collateral circulation from the soft palate usually prevents avascular necrosis.

Bilateral Sagittal Split Osteotomy (BSSO) (CPT: 21195-21199)¶

The BSSO (Obwegeser-Dal Pont modification, later refined by Hunsuck and Epker) is the standard mandibular osteotomy for correction of mandibular prognathism, retrognathism, and asymmetry.

Surgical Technique:

Incision: Along the anterior border of the ramus from the coronoid notch region inferiorly to the external oblique ridge, then anteriorly along the external oblique ridge to the first molar region.
Dissection: Subperiosteal dissection medially to expose the lingula and the medial ramus surface. Identify the inferior alveolar nerve entry point at the lingula.
Medial horizontal osteotomy: Horizontal cut on the medial ramus just above the lingula using a Lindemann burr or reciprocating saw. This cut extends through the medial cortex only.
Sagittal cut: Along the external oblique ridge from the medial osteotomy anteriorly to the body of the mandible (first molar region), through the lateral cortex only.
Inferior vertical/oblique cut: Vertical osteotomy through the lateral cortex at the junction of the ramus and body, connecting the sagittal cut inferiorly through the inferior border.
Splitting: Smith spreaders or osteotomes inserted into the sagittal osteotomy to propagate the split between the medial (proximal, condyle-bearing) and lateral (distal, tooth-bearing) segments. The split follows the cancellous bone between the cortices.
IAN identification: After splitting, the inferior alveolar neurovascular bundle is identified running on the medial surface of the distal segment or within the marrow space. Handle with extreme care.
Repositioning: The distal (tooth-bearing) segment is repositioned per the plan using the final occlusal splint. IMF is established.
Fixation: Options include:
- Bicortical positional screws: Three 2.0 mm screws in an inverted-L or linear pattern (Paulus technique). Provides rigid fixation; no IMF needed postoperatively.
- Miniplates: Single miniplate across the osteotomy with monocortical screws. Preferred by some surgeons for advancement; may require short-term guiding elastics.
- Hybrid: Combination of screws and plates.

Complications specific to BSSO:

Complication	Incidence	Management
IAN paresthesia	30-40% immediate; 5-10% persistent at 1 year	Careful splitting technique; perioperative dexamethasone; most recover spontaneously
Bad split (unfavorable fracture)	2-5%	Recognized intraoperatively; fixation with additional plates/screws; may require modification of planned movement
Condylar sag	Variable	Proper condylar seating before fixation; rigid fixation; short-term guiding elastics
Relapse	5-10% for advancement; higher for large setbacks	Rigid fixation; overcorrection of 1-2 mm for large advancements; consider genioplasty as adjunct

Clinical Pearl

The rate of inferior alveolar nerve injury in BSSO can be reduced by: (1) careful identification of the IAN entry point (lingula) and keeping the medial osteotomy at or above the lingula level, (2) gentle splitting with controlled force, (3) avoiding excessive torque on the proximal segment, and (4) using a nerve retractor to protect the nerve during fixation screw placement. Sagittal split designs that minimize nerve manipulation (e.g., short medial cuts) may further reduce paresthesia rates (Epker modification).

Genioplasty (CPT: 21120-21123)¶

Osseous genioplasty provides precise 3D repositioning of the chin independent of the dental occlusion:

Indications:

Chin deficiency (microgenia) or excess (macrogenia)
Vertical excess or deficiency of the lower face
Chin asymmetry
Adjunct to orthognathic surgery for optimization of facial proportions

Technique:

Incision: Lower labial vestibular incision; preserve the mentalis muscle origin for re-attachment.
Exposure: Subperiosteal dissection to expose the chin from mental foramen to mental foramen. Identify and preserve the mental nerves bilaterally.
Osteotomy: Horizontal osteotomy below the mental foramen (minimum 5 mm below to protect the nerve) using a reciprocating saw or piezo. The cut extends bilaterally past the mental foramina to allow mobilization.
Repositioning: The distal chin segment is moved as planned (advancement, setback, vertical shortening, vertical lengthening with interpositional graft, lateral shift, or combinations).
Fixation: Step plate, ladder plate, or T-plate designed for genioplasty; or two miniplates. A single midline plate is adequate for advancement but may not resist rotational forces in asymmetric movements.

Sliding genioplasty vs. alloplastic chin augmentation:

Genioplasty is preferred in OMS for its versatility (can correct in all three planes), predictability, and permanent result.
Alloplastic implants (silicone, Medpor) are simpler but limited to augmentation only, carry infection/extrusion risk, and can cause bone resorption beneath the implant.

Segmental Osteotomies¶

Anterior maxillary osteotomy (Wassmund/Wunderer):

Repositioning of the premaxillary segment independent of the posterior maxilla.
Indicated for isolated protrusion or vertical excess of the anterior maxilla.
Blood supply considerations are critical: maintain palatal mucosal pedicle or buccal pedicle depending on approach.

Anterior mandibular subapical osteotomy (Kole):

Repositioning of the anterior mandibular dentoalveolar segment.
Indicated for lower anterior proclination not correctable orthodontically; rarely performed due to risk to the IAN and mental nerve.

Distraction Osteogenesis¶

Principles¶

Distraction osteogenesis (Ilizarov principle, applied to the craniofacial skeleton by McCarthy et al., 1992) involves gradual mechanical stretching of a bone callus to generate new bone:

Osteotomy: Partial or complete corticotomy at the desired site.
Latency period: 5-7 days of undisturbed healing to allow initial callus formation.
Activation (distraction): Gradual separation of bone segments at a rate of 0.5-1.0 mm/day (typically 0.5 mm twice daily).
Consolidation: Fixation maintained without activation for a period equal to or exceeding the distraction period (typically 8-12 weeks) to allow mineralization of the regenerate.

Applications in Orthognathic Surgery¶

Mandibular distraction: For severe mandibular hypoplasia (advancement greater than 10 mm, where BSSO stability is compromised). Particularly valuable in syndromic patients (hemifacial microsomia, Pierre Robin sequence, Treacher Collins). Internal (buried) or external (multiplanar) devices.
Maxillary distraction: LeFort I osteotomy with internal or external distractor for large maxillary advancements (e.g., cleft lip/palate patients with severe maxillary retrusion).
Alveolar distraction: Vertical augmentation of the alveolar ridge for implant site development.
Midface distraction (LeFort III): For midface retrusion in craniofacial syndromes (Apert, Crouzon).

Clinical Pearl

Distraction osteogenesis has the major advantage of gradually stretching the soft tissue envelope along with the bone, reducing relapse compared to large single-stage movements. For mandibular advancements greater than 10-12 mm, distraction or staged surgery should be strongly considered over single-stage BSSO due to high relapse rates and increased risk of condylar resorption with large advancements.

Surgery-First Approach¶

The surgery-first approach (SFA) reverses the traditional orthodontic-surgical sequence by performing orthognathic surgery before orthodontic treatment:

Traditional sequence: Pre-surgical orthodontics (12-24 months) -- Surgery -- Post-surgical orthodontics (6-12 months)

Surgery-first sequence: Surgery -- Post-surgical orthodontics (12-18 months total treatment time)

Advantages:

Significant reduction in total treatment time (average 14-16 months vs. 24-36 months)
Immediate improvement in facial esthetics and function
Regional acceleratory phenomenon (RAP) from the surgery enhances postoperative orthodontic tooth movement

Prerequisites for Surgery-First:

Minimal dental compensation (incisors not excessively proclined/retroclined)
Mild to moderate crowding (less than 5 mm)
Flat to mild curve of Spee
Experienced surgical-orthodontic team
Careful VSP to account for postoperative orthodontic movements

Limitations:

Requires precise VSP to predict final occlusion
Intraoperative splint must account for planned orthodontic movements
Not ideal for severe crowding, significant transverse discrepancy, or complex decompensation needs

Orthodontic-Surgical Coordination¶

Pre-Surgical Orthodontics (Traditional Approach)¶

Goals of pre-surgical orthodontics:

Decompensation: Remove dental compensations (e.g., proclined lower incisors in Class III). This may temporarily worsen the malocclusion clinically but positions the teeth for optimal skeletal correction.
Arch alignment: Level and align the arches; resolve crowding (may require extractions).
Arch coordination: Ensure the maxillary and mandibular arches will fit together at the planned surgical position.
Surgical hooks: Place surgical hooks on the archwire for intraoperative IMF and postoperative elastics.

Typical pre-surgical orthodontic treatment duration: 12-24 months.

Post-Surgical Orthodontics¶

Begins 4-6 weeks after surgery (once initial healing allows bracket adjustment).
Goals: Final settling of the occlusion, closure of any residual spaces, coordination of dental midlines, final torque corrections.
Duration: 6-12 months.
Retention: Standard orthodontic retention (bonded retainers and/or removable retainers).

Custom Splints and Patient-Specific Hardware¶

CAD/CAM Surgical Splints¶

3D-printed occlusal splints from VSP have replaced hand-articulated model surgery splints in most practices:

Materials: Nylon (SLS printing), photopolymer resin (SLA/DLP printing), or milled PMMA.
Types: Intermediate splint (seats repositioned maxilla to un-operated mandible) and final splint (seats mandibular teeth to the repositioned maxilla).
Accuracy: Studies demonstrate mean error of less than 1 mm and less than 1 degree for VSP-guided orthognathic surgery (Stokbro et al., J Oral Maxillofac Surg 2014).

Patient-Specific Plates (PSP)¶

Custom-manufactured titanium plates designed to fit precisely on the patient's anatomy after virtual repositioning:

Eliminate the need for intraoperative plate bending
Serve as a fixation device AND positional guide (the plate dictates the final maxillary position, reducing reliance on the splint alone)
Available from Materialise (SurgiCase), KLS Martin (IPS), Stryker, and DePuy Synthes
Particularly valuable for complex multi-piece LeFort I osteotomies and asymmetry corrections

Stability and Relapse¶

Hierarchy of Stability (Proffit et al., Int J Adult Orthodon Orthognath Surg 1996)¶

Procedure	Stability	Expected Relapse
Maxillary impaction	Most stable	Less than 10%
Mandibular advancement (less than 8 mm)	Highly stable	Less than 10%
Maxillary advancement	Stable	10-20%
Mandibular setback	Moderate stability	15-25%
Maxillary inferior repositioning (downgrafting)	Least stable	20-40%
Transverse expansion (surgically assisted)	Variable	Depends on technique

Condylar Resorption¶

Progressive condylar resorption (PCR, also termed idiopathic condylar resorption or ICR) is a devastating complication:

Risk factors: Young female patients, high mandibular plane angle, large mandibular advancement, history of TMJ dysfunction, connective tissue disorders.
Presentation: Progressive anterior open bite, increasing overjet, mandibular retrognathia developing months to years after surgery.
Prevention: Conservative advancement movements, rigid fixation, avoidance of excessive intraoperative condylar torque, and consideration of total joint replacement in patients with pre-existing severe condylar pathology.

Critical Safety

In patients with pre-existing condylar resorption or significant TMJ pathology, orthognathic surgery alone may exacerbate the resorptive process. Combined TMJ surgery (total joint replacement or costochondral graft) with simultaneous orthognathic surgery should be considered in these cases to provide a stable condylar foundation for the skeletal correction (Wolford et al., Am J Orthod Dentofacial Orthop 2003).

Special Considerations¶

Obstructive Sleep Apnea (OSA)¶

Maxillomandibular advancement (MMA) is the most effective surgical treatment for moderate-to-severe OSA when CPAP fails:

Technique: LeFort I advancement plus BSSO advancement, typically 10-12 mm total advancement.
Efficacy: Success rate (AHI reduction greater than 50% and to less than 20) of 85-100% (Holty & Guilleminault, Sleep Med Rev 2010).
Mechanism: Expands the pharyngeal airway at the velopharyngeal and retrolingual levels by advancing the maxilla (and soft palate) and mandible (and tongue base).
CPT: Same orthognathic codes; medical necessity documentation required for insurance coverage.

Cleft Orthognathic Surgery¶

Patients with repaired cleft lip and palate frequently require orthognathic surgery due to:

Maxillary hypoplasia (secondary to scar contracture from prior palatoplasty)
Class III malocclusion
Transverse maxillary deficiency
Velopharyngeal insufficiency (VPI) considerations with maxillary advancement

Surgical Caution

Maxillary advancement in cleft patients carries increased relapse risk due to scar tissue resistance and compromised blood supply to the maxilla. Distraction osteogenesis may be preferred for large advancements (greater than 6-8 mm). Additionally, maxillary advancement can worsen velopharyngeal function by increasing the velopharyngeal gap. Preoperative nasopharyngoscopy and collaboration with speech pathology are essential.

Coding Reference¶

CPT Codes -- Orthognathic Surgery¶

Code	Description
21141	Reconstruction midface, LeFort I, single piece, segment movement in any direction
21142	Reconstruction midface, LeFort I, 2 pieces, segment movement in any direction
21143	Reconstruction midface, LeFort I, 3 or more pieces, segment movement in any direction
21145	Reconstruction midface, LeFort I, single piece, with bone graft
21146	Reconstruction midface, LeFort I, 2 pieces, with bone graft
21147	Reconstruction midface, LeFort I, 3 or more pieces, with bone graft
21150	Reconstruction midface, LeFort II, anterior intrusion
21151	Reconstruction midface, LeFort II, any direction, requiring bone grafts
21154-21160	Reconstruction midface, LeFort III, various complexity levels
21195	Reconstruction mandibular rami, sagittal split, without internal rigid fixation
21196	Reconstruction mandibular rami, sagittal split, with internal rigid fixation
21198	Reconstruction mandibular rami and/or body, sagittal split; with bone graft
21199	Osteotomy, mandible, segmental
21120	Genioplasty; augmentation (autograft, allograft, prosthetic material)
21121	Genioplasty; sliding osteotomy, single piece
21122	Genioplasty; sliding osteotomy, two or more osteotomies
21123	Genioplasty; sliding, augmentation with interpositional bone grafts

ICD-10 Codes¶

Code	Description
M26.0	Major anomalies of jaw size (prognathism, retrognathism, macrognathia, micrognathia)
M26.1	Anomalies of jaw-cranial base relationship
M26.2	Anomalies of dental arch relationship (Class II, Class III)
M26.4	Malocclusion, unspecified
K07.0-K07.1	Major anomalies of jaw size
G47.33	Obstructive sleep apnea

Key References¶

Proffit WR, Turvey TA, Phillips C. Orthognathic surgery: a hierarchy of stability. Int J Adult Orthodon Orthognath Surg. 1996;11(3):191-204.
Wolford LM, Reiche-Fischel O, Mehra P. Changes in temporomandibular joint dysfunction after orthognathic surgery. J Oral Maxillofac Surg. 2003;61(6):655-660.
Stokbro K, Aagaard E, Torkov P, Bell RB, Thorn JJ. Virtual planning in orthognathic surgery. Int J Oral Maxillofac Surg. 2014;43(8):957-965.
Holty JE, Guilleminault C. Maxillomandibular advancement for the treatment of obstructive sleep apnea: a systematic review and meta-analysis. Sleep Med Rev. 2010;14(5):287-297.
McCarthy JG, Schreiber J, Karp N, et al. Lengthening the human mandible by gradual distraction. Plast Reconstr Surg. 1992;89(1):1-8.
Epker BN. Modifications in the sagittal osteotomy of the mandible. J Oral Surg. 1977;35(2):157-159.
Hernandez-Alfaro F, Guijarro-Martinez R. On a definition of the appropriate timing for surgical intervention in orthognathic surgery. Int J Oral Maxillofac Surg. 2014;43(7):846-855.
Swennen GR, Mollemans W, De Clercq C, et al. A cone-beam computed tomography triple scan procedure to obtain a three-dimensional augmented virtual skull model appropriate for orthognathic surgery planning. J Craniofac Surg. 2009;20(2):297-307.
AAOMS Parameters of Care: Clinical Practice Guidelines for Oral and Maxillofacial Surgery (ParCare), 6^th Edition.