Orthognathic Surgery: Indications, BSSO and Le Fort I Guide

Orthognathic surgery ("straight jaw" surgery) corrects jaws that grew into the wrong position — a jutting lower jaw, a retruded upper jaw, a lopsided face, or an open bite where front teeth never meet. Braces straighten teeth, but when the bones themselves mismatch, only moving the bones fixes the bite, facial balance and often the airway.

The two signature operations are the bilateral sagittal split osteotomy (BSSO), sliding the lower jaw forward or back, and the Le Fort I osteotomy, repositioning the entire upper jaw. Planned to the millimetre and held with titanium plates, they change faces — and lives for people who could not bite, breathe or smile comfortably.

Key Concepts

• BSSO: the lower jaw is split lengthwise on both sides so the tooth-bearing part slides forward or backward — the workhorse for underbite and overbite.
• Le Fort I osteotomy: a horizontal cut above the upper teeth frees the whole maxilla to move up, down, forward or correct a tilt.
• Osteotomy: a planned surgical bone cut (unlike an accidental fracture).
• Decompensation: pre-surgical orthodontics that untilt teeth, revealing the true bone mismatch.
• Relapse: drift of moved bone back toward its old position; controlled by precise fixation.
• Class II / Class III: lower jaw too far back / too far forward — the commonest surgical indications.

How It Works

1. Orthodontics first (12-18 months). Braces align teeth within each jaw and remove dental compensations.
2. Plan digitally. 3D CT planning sets exact movements (e.g. maxilla forward 4 mm, mandible back 5 mm); printed splints transfer the plan to surgery.
3. Cut the upper jaw (Le Fort I). Through inner-lip incisions the maxilla is freed, repositioned and fixed with four titanium plates.
4. Split the lower jaw (BSSO). Each side is split sagittally, the front segment slides into place and is plated, protecting the inferior alveolar nerve.
5. Recover in weeks. Swelling peaks at 48-72 hours; routine resumes in 2-3 weeks on a soft diet, bone solid by 6-8 weeks.
6. Orthodontics again (6-12 months). Final detailing of the bite, then retainers hold everything.

Worked Example

A 22-year-old woman has a Class III underbite: lower teeth 9 mm ahead of upper teeth. Plan: Le Fort I advances the maxilla 4 mm; BSSO sets the mandible back 5 mm — total 4 + 5 = 9 mm, exactly the discrepancy. Surgery takes about 4 hours. The maxilla gets four 4-hole plates (16 screws); each mandible side gets one plate with 4 screws (8 screws) — 24 screws total. Soft diet for 6 weeks (42 days). At 3 months her teeth meet correctly and her profile is balanced.

Common Misconceptions

• "Braces alone can fix any bite." Braces move teeth, not bones — a 9 mm jaw mismatch cannot be camouflaged safely.
• "Jaw surgery is only cosmetic." Most patients gain chewing, speech and, with maxillary advancement, better breathing.
• "Jaws stay wired shut for months." Rigid fixation lets most patients open their mouths within days.

Real-World Applications

• Orthodontic-surgical clinics treating severe bite and asymmetry problems in late teens and adults.
• Sleep medicine: jaw advancement widening the airway in obstructive sleep apnoea.
• Cleft and craniofacial centres correcting post-repair jaw growth problems.

Orthognathic surgery — BSSO below, Le Fort I above — corrects what braces cannot: the bones themselves. With orthodontics on either side and millimetre-precise movements, it restores the bite, balances the face and often improves breathing in one planned transformation.