Orthognathic and Craniofacial Surgery
Orthognathic and Craniofacial Surgery
This domain tests diagnosis and planning of skeletal discrepancies, including records, cephalometrics, virtual planning, and relapse risk. The exam expects you to decide whether surgery is indicated and how to sequence it.
Core rules
- Obtain photographs, models or intraoral scans, cephalometrics, and a focused airway and TMJ assessment.
- Decompensate the dentition before surgery so the skeletal problem is fully expressed.
- Le Fort I osteotomy moves the maxilla; bilateral sagittal split osteotomy moves the mandible; genioplasty affects chin projection.
- Virtual surgical planning improves osteotomy and plate placement but does not replace clinical assessment.
- Discuss inferior alveolar nerve injury, relapse, condylar resorption, and airway changes during consent.
Worked example
A patient has Class III malocclusion from maxillary hypoplasia and mandibular prognathism. Reasoning: presurgical orthodontics decompensates the incisors; a Le Fort I advancement corrects maxillary deficiency; a BSSO setback corrects the mandible. The plan must check transverse width and condylar position, because inadequate decompensation or condylar sag causes relapse.
Traps
Operating before decompensation; ignoring a transverse maxillary deficiency; promising skeletal stability; missing condylar resorption in a high-angle patient; failing to assess obstructive sleep apnea.