Skeletal Anchorage and Orthognathic Surgery
Skeletal anchorage
Understand the principles of temporary anchorage devices (TADs): mini-implants, miniplates, and palatal implants. Know the anatomic sites and their risks - interradicular placement risks root contact, the infrazygomatic crest offers strong anchorage, and the palate provides thin keratinized tissue in some zones. Know indications such as en masse retraction, molar intrusion, and correction of severe discrepancies that would otherwise require surgery.
Orthognathic surgery
Know the common procedures: Le Fort I osteotomy, bilateral sagittal split osteotomy, and genioplasty, and understand their indications and sequencing. Understand the role of presurgical orthodontics in decompensating the occlusion, and the concept of model surgery and surgical splints. Know the difference between one-jaw and two-jaw surgery and the factors that determine which is needed.
Traps
A classic trap is using skeletal anchorage without considering the biomechanics of the whole arch - a TAD can intrude a segment but may worsen the occlusal plane. Another trap is confusing the direction of surgical movement with the desired dental change. Questions may also test whether you can identify when surgery is preferable to camouflage, especially in a patient with a severe skeletal discrepancy and no growth remaining.
Worked example
A patient with a 10 mm overjet and a severely retrognathic mandible, no growth remaining. Rule of thumb: if the discrepancy exceeds what camouflage can reasonably correct and the profile is a major concern, consider orthognathic surgery with presurgical decompensation rather than extraction camouflage.