Orthognathic surgery includes various types of surgical procedures performed on the jaw bones. The surgery can be carried out for functional and aesthetic purposes. In orthognathic surgeries the jaw bones are intentionally sectioned or trimmed at various regions to correct the underlying dentofacial deformity and then reposition the jaw bones at a desired position. Two major processes involved in orthognathic surgeries are osteotomy and ostectomy. Simple splitting of bone is referred as osteotomy and removal of part of the bone is known as ostectomy.
Majority of the times the basic skeletal problems associated with the jaws are as follows :
- Excess of mandibular growth (lower jaw elongation).
- Deficiency of mandible (small lower jaw).
- Excess of maxillary bone (large upper jaw).
- Deficiency of maxillary bone (small and narrow upper jaw).
- Combination of the above seen in bimaxillary protrusion (elongated upper and lower jaws).
- Cleft lip associated with restricted growth of the bones.
- Facial asymmetry.
- Unilateral condylar hyperplasia.
- Hemi-facial hypertrophy (enlarged of one side of the face).
Before undertaking any type of orthognathic surgery, a detailed orthodontic evaluation and expert orthodontic opinion is essential. The orthodontic evaluation comprises of study of patients dentition and skeletal growth. Personal data from the patient is collected such as information regarding habits, postures, previous photographs and allergies. The facial analysis is done with the help of several facial radiographs known as lateral cephalograms. The face is studied from both the frontal and lateral aspects.
Study models using impression of the teeth are made to determine the exact position of the teeth within the dental arches. The required orthodontic procedures are carried out before the surgery to aid in proper alignement of the teeth after the surgical procedures. The procedures involves relieving dental crowding, closing excess spacing in-between two teeth, correcting rotated teeth and eliminating gross dental discrepancies.
Maxilla (Upper Jaw)
The orthognathic surgeries of maxilla can be done for single tooth or multiple teeth sections or the entire jaw. The surgical procedure employed for the whole of the maxilla is known as LeFort I osteotomy. Horse-shoe shaped osteotomy, maxillary advancement and superior repositioning of the maxilla are a few variants of total maxillary osteotomies.
Mandible (Lower Jaw)
The orthognathic surgeries of mandible are further divided into mandibular body osteotomies, mandibular ramus osteotomies and genioplasty.
- The mandibular body osteotomies involve the manipulation of the middle, curved portion of the lower jaw. They are further classified in to anterior body osteotomies, posterior body osteotomies and mid symphisis osteotomies. These surgeries are generally performed with an intraoral incision.
- Mandibular ramus is the side portion of the lower jaw bone. By manipulating this segment of the bone, widening or heightening of the lower jaw can be achieved. Sagittal split osteotomies and sub-sigmoid osteotomies are few variations of orthognathic surgeries involving the ramus.
- Geneoplasties are groups of surgeries performed on the chin bone. The surgeries can be done to increase the height of the chin by augmenting bone grafts or decreasing the chin length by removing excess amount of bone.