Orthognathic surgery represents the surgical correction of severe dentofacial deformities that cannot be adequately managed through orthodontics alone. These deformities range from anteroposterior discrepancies (Class II mandibular deficiency or Class III mandibular protrusion) to vertical discrepancies (anterior open bite, anterior deep bite) to transverse asymmetries. Beyond functional improvements in mastication, phonation, and airway function, orthognathic surgery produces dramatic esthetic changes affecting facial profile, smile arc, and overall facial harmony. This article examines patient selection, comprehensive treatment planning, surgical techniques, and post-operative management in orthognathic surgery.
Classification of Dentofacial Deformities
Dental malocclusions are classified using Angle's classification describing anterior tooth relationships: Class I (normal), Class II (maxillary protrusion or mandibular retrusion), and Class III (mandibular protrusion or maxillary retrusion). However, Angle's classification addresses only anteroposterior discrepancy, omitting vertical and transverse problems.
Skeletal dentofacial deformities are more accurately described using three-dimensional terms: anteroposterior (sagittal), vertical, and transverse discrepancies. A patient might present with Class II malocclusion secondary to mandibular retrusion (anteroposterior deficiency), anterior open bite (vertical excess), and crossbite (transverse deficiency), requiring comprehensive surgical correction addressing all three dimensions.
Anteroposterior deformities include mandibular deficiency (inadequate mandibular projection), maxillary protrusion (excessive maxillary forward position), mandibular protrusion (excessive anterior mandibular projection), and maxillary retrusion. Severity ranges from mild (cosmetically concerning but functionally adequate) to severe (affecting mastication, speech, and airway).
Vertical deformities include anterior open bite (failure of anterior teeth to overlap vertically), anterior deep bite (excessive vertical overlap), and posterior open bite (lack of molar contact posteriorly). Anterior open bite creates mastication difficulty, speech problems, and often leads to tongue dysfunction.
Transverse deformities include maxillary constriction with crossbite, posterior crossbite from asymmetric maxillary growth, and mandibular asymmetry causing functional shift. Severe asymmetries create psychological distress and functional impairment.
Pre-Operative Evaluation and Diagnosis
Comprehensive evaluation begins with assessment of patient motivation, realistic expectations, and psychological stability. Orthognathic surgery produces significant change affecting self-image; patients must be emotionally prepared for adaptation and hold realistic goals. Some patients seek surgery for minor esthetic improvements, while others face functional limitations they hope surgery will resolve.
Thorough medical evaluation identifies conditions affecting surgical candidacy and healing. Diabetes, bleeding disorders, immunosuppression, severe cardiovascular disease, or active psychiatric illness may contraindicate surgery. Medications including anticoagulants affect perioperative management.
Cephalometric analysis provides precise measurements of skeletal and dental relationships. Lateral cephalograms reveal anteroposterior jaw discrepancies, vertical relationships, and dentoalveolar compensations. Reference points and planes enable quantitative assessment and surgical planning. Posterior-anterior (PA) cephalograms evaluate transverse discrepancies and asymmetry.
Dental models mounted on articulator in centric relation reveal current intercuspation and target occlusion post-operatively. Model surgery involves physically reorienting maxillary and/or mandibular models to predetermined positions, guiding surgical planning.
Contemporary 3D volumetric imaging (CBCT) and virtual surgical planning enhance traditional methods. CBCT enables precise bone morphology visualization, virtual segment repositioning, and surgical guide creation. Virtual surgery allows surgeons to preview results and communicate predicted changes to patients pre-operatively, improving outcomes.
Surgical Techniques and Approaches
Bilateral sagittal split osteotomy (BSSO) represents the standard mandibular surgical approach for anteroposterior corrections. The procedure involves bilateral intraoral incisions in the buccal sulcus, bone cuts separating the proximal and distal mandibular segments, and fixation of the repositioned distal segment using titanium plates and screws. BSSO enables significant mandibular advancement or setback with predictable results.
Le Fort I maxillary advancement involves horizontal osteotomy above the tooth apices, below the nasal floor, separating the maxilla from the skull base. The maxilla is repositioned forward, downward, or rotated as needed, with fixation using plates at buttress areas (zygomatic processes, piriform rims, pterygoid areas). Maxillary advancement corrects Class II malocclusions from maxillary retrusion and contributes to open bite correction.
Bimaxillary surgery combines BSSO and Le Fort I, permitting correction of complex deformities. Class II cases with maxillary protrusion and mandibular deficiency may require maxillary setback and mandibular advancement. Class III cases with mandibular protrusion and maxillary retrusion benefit from mandibular setback and maxillary advancement.
Anterior segmental osteotomy addresses severe anterior open bite by rotating the maxillary anterior segment inferiorly. Posterior segmental maxillary osteotomy rotates the entire palate, correcting asymmetric vertical discrepancies. These segmental procedures require careful preservation of vascular and neural supply.
Genioplasty, surgical repositioning of the anterior mandible (osseous chin), improves profile balance in patients with deficient chin projection or vertical excess. Mentoplasty can be performed concurrently with BSSO to address both jaw and chin deformities comprehensively.
Pre- and Intra-operative Considerations
Pre-operative orthodontic treatment, lasting 12-24 months, aligns teeth in each arch and corrects dentoalveolar compensations. Teeth are positioned to ideal inclination within their respective bony bases, removing dentoalveolar compensation that masks underlying skeletal discrepancy. Leveling and aligning the arches enables proper intermaxillary fixation (IMF) post-operatively and improves surgical outcomes.
Intra-operative positioning of the patient, maintenance of airway patency, and careful soft tissue handling minimize complications. Nasotracheal intubation maintains airway access during surgery without interfering with oral surgical access. Controlled hypotensive anesthesia reduces bleeding without compromising perfusion, facilitating visualization.
Securing proper occlusion during surgery requires either pre-operative wafer splints or intra-operative dentition-based guidance. A surgical wafer created from model surgery pre-operatively guides repositioning of the maxilla or mandible to predetermined position, ensuring accurate three-dimensional correction.
Airway and Breathing Considerations
Mandibular advancement improves airway dimensions in patients with obstructive sleep apnea (OSA), potentially providing therapeutic benefit beyond esthetic and occlusal improvement. Patients with OSA combined with Class II malocclusion from mandibular retrusion represent ideal candidates where surgery addresses both concerns simultaneously.
Conversely, maxillary advancement and downward rotation of the maxilla can increase posterior airway space, while setback procedures may compromise airway. Careful case selection and cephalometric analysis predict airway changes, though individual variation occurs. Sleep studies pre- and post-operatively quantify OSA changes when present.
Post-Operative Management
Immediate post-operative period involves pain management, swelling control, and airway monitoring. Patients typically remain hospitalized overnight for close observation. Most patients maintain IMF with elastics for 4-6 weeks, allowing bone healing while permitting elastic guidance of occlusion. Some surgeons perform rigid fixation eliminating need for IMF, improving diet, oral hygiene, and comfort.
Antibiotics provide prophylaxis against infection in the post-operative period. Soft diet for 6-8 weeks enables adequate nutrition while protecting healing areas. Progressive diet advancement as healing progresses maintains patient energy and nutrition.
Physical therapy including gentle jaw opening exercises and soft tissue mobilization promotes healing and prevents stiffness. Patients are typically cleared for normal activities within 4-6 weeks, though complete healing continues over several months.
Post-operative orthodontics lasting 6-12 months finalizes occlusion, using braces to refine tooth positioning relative to corrected skeletal relationships. Retention via fixed bonded retainers or removable retainers prevents relapse.
Stability and Relapse
Orthognathic surgical corrections demonstrate excellent long-term stability when adequate healing occurs and post-operative bracing is maintained. Most relapse occurs in the first 6 months post-operatively, stabilizing thereafter. Relapse rates of 5-10% of surgical movement are typical, though severe asymmetries show higher relapse potential.
Factors affecting stability include extent of surgical movement (larger movements show more relapse), surgical technique employed, post-operative orthodontics, and patient factors including growth continuation in younger patients. Stopping growth before surgery (typically age 16-17 in females, 18+ in males) minimizes relapse from continued growth.
Complications and Risks
Inferior alveolar nerve injury occurs in up to 30% of BSSO patients, with most recovering sensation within 6-12 months. Temporary paresthesia (altered sensation) is more common than permanent anesthesia (complete loss). Careful surgical technique and nerve identification reduce permanent injury.
Lingual nerve injury from intraoral incisions can cause tongue numbness, altered taste, or motor dysfunction affecting speech and swallowing. Prevention through careful soft tissue retraction and nerve identification is paramount.
Condylar displacement anteriorly can occur, potentially causing TMJ dysfunction. This is minimized through proper positioning in centric relation and careful surgical technique.
Relapse, discussed above, represents the most common post-operative complication, though usually mild. Infection, bleeding, and delayed healing occur infrequently but require prompt recognition and treatment.
Functional and Psychological Outcomes
Beyond esthetic improvement, orthognathic surgery often improves mastication, speech, swallowing, and breathing. Patients with severe anteroposterior discrepancies experience improved chewing efficiency and comfort. Open bite correction improves speech clarity. Mandibular advancement corrects OSA in appropriate candidates.
Psychological and quality of life improvements often exceed surgical expectations. Improved self-image, increased confidence, and enhanced social interaction positively impact patients' lives. Patient satisfaction exceeds 90% in most studies.
Orthognathic surgery represents a powerful intervention addressing severe dentofacial deformities combining functional improvement with dramatic esthetic transformation. Comprehensive planning, appropriate patient selection, and meticulous surgical technique ensure predictable results and high patient satisfaction.