Surgical Orthodontics
On this page
Direct answer
Orthognathic outcomes are built in the orthodontic laboratory before any osteotomy is cut: surgical orthodontics divides into a presurgical phase of roughly 12-18 months that aligns, levels, coordinates and — decisively — decompensates the arches so the jaws can be moved to their true positions; the surgical event itself planned by visual treatment objective, prediction tracing, model surgery and splints; and a postsurgical finishing phase of some 6-12 months that settles the occlusion with guiding elastics. The orthodontist's signature contribution is decompensation, reversing the dental compensations that camouflage the skeletal discrepancy — which makes the malocclusion look and function worse before surgery — and consent to that paradoxical worsening is the most tested counselling point in the subject. Timing is growth-dictated: operate after documented cessation, about 16-17 years in girls and 18-19 in boys.
What you must remember
- Presurgical orthodontics: align, level, coordinate arch widths, relieve crowding (extraction patterns often differ from camouflage plans — decompensation may demand lower premolar extraction in Class III), and position incisors at true inclinations so the osteotomy is not short-changed.
- Decompensation direction: Class III — procline lower incisors, upright uppers, worsening reverse overjet; Class II — retrocline lower incisors toward their skeletal position, worsening overjet; both deliberately make the occlusion look worse so the skeleton can be corrected fully.
- Planning tools: lateral cephalometric analysis with visual treatment objective and prediction tracings; facebow-mounted models and model surgery; virtual surgical planning with printed splints increasingly replacing plaster.
- Splint sequence in two-jaw surgery: an intermediate splint positions the first jaw (usually the maxilla) against the unoperated mandible; the final splint sets both jaws in the planned occlusion.
- Third molars in the line of sagittal split osteotomy are removed months beforehand to reduce bad-split risk; full orthodontic records and periodontal health precede surgery.
- Postsurgical orthodontics resumes within about 2-4 weeks after IMF release and jaw physiotherapy begin: light guiding elastics (Class II or III vectors as needed) settle the occlusion, brackets are used for finishing, total treatment typically 18-30 months.
- Surgery-first approach: operating before any orthodontics in selected adults, exploiting the postoperative remodelling window to shorten overall treatment; demands stable occlusal stops, predictable genetics of movement and precise planning.
- Proffit's stability hierarchy governs consent: maxillary impaction most stable; mandibular advancement with rigid fixation next; maxillary advancement then mandibular setback; down-grafting and expansion least stable.
Walking a case through the three phases
A 23-year-old man with a Class III skeletal pattern (ANB -4), reverse overjet 5 mm, and a concave profile proceeds as follows. Records first: lateral cephalogram, orthopantomogram with third molar removal booked six months ahead of a planned bilateral sagittal split, models and photographs, with documented growth cessation. Presurgical orthodontics second: fixed appliances for about 14 months align the arches, coordinate the transverse widths, and decompensate — his naturally retroclined lower incisors are proclined toward normal inclination, visibly deepening the reverse overjet to 7 mm; he was consented for exactly this at the outset. Planning third: a surgical visual treatment objective traces the planned Le Fort I advancement and mandibular setback onto the cephalogram, and model surgery or virtual planning translates it into an intermediate and a final occlusal splint. Surgery fourth: two-jaw correction with rigid fixation, IMF released early, physiotherapy from day one. Postsurgical fifth: guiding elastics settle the occlusion from about week three, appliances finish the detailing for 6-9 months, and retention follows with relapse surveillance for years.
How the exam frames it
The paradox question leads every viva: "Why does presurgical orthodontics make the bite worse?" — because operating into a compensated occlusion under-corrects the skeleton and hands the patient a compromised face with a passable bite; the decompensation is the price of a definitive skeletal correction, and candidates must be able to explain it to a patient, not just recite it. The second is the splint question: which splint does what — intermediate for the first jaw, final for both — and the third is timing: growth completion documented on serial cephalograms, roughly 16-17 in girls and 18-19 in boys, except where airway or severe psychosocial burden justifies earlier surgery. The surgery-first angle tests modern reading: candidates should know it exists, shortens treatment in selected adults, and depends on postoperative remodelling and stable occlusal stops rather than preoperative alignment.
Frequently asked questions
Why is presurgical decompensation performed?
To remove the dental camouflage hiding part of the skeletal discrepancy so the osteotomy achieves a complete correction; operating on compensated arches under-corrects the skeleton.
How long do the presurgical and postsurgical phases take?
Presurgical orthodontics about 12-18 months; postsurgical finishing about 6-12 months after surgery, resumed within 2-4 weeks once intermaxillary fixation is released.
Why remove third molars before a sagittal split osteotomy?
Their presence in the osteotomy line increases the risk of unfavourable (bad) splits, so removal months ahead is routine planning.
When is orthognathic surgery timed in growing patients?
After documented growth cessation — serial cephalograms, roughly 16-17 years in girls and 18-19 in boys — unless airway compromise or severe psychosocial distress forces earlier intervention.