What is Jaw Deformity?

What is Orthognathic Surgery?

Orthognathic surgery refers to procedures performed under general anesthesia for patients diagnosed with jaw deformities. Surgeries for jaw deformities include osteotomies that reposition entire bones such as the maxilla (upper jaw) or mandible (lower jaw) forward, backward, up, down, or laterally. This technique involves cutting and moving sections of bone containing teeth to properly align the bite and facial appearance. Surgery is performed under general anesthesia, and the repositioned bones are secured with biocompatible screws and plates (either metal or absorbable). To ensure jaw stability, intermaxillary fixation (securing the upper and lower jaws together) is maintained for about one week initially. Subsequently, the fixation is adjusted according to the patient's condition, with intermaxillary fixation or limitation of mouth opening continuing for approximately one month. Generally, all surgical procedures are performed inside the mouth, leaving no visible external scars on the face. Since blood vessels and nerves run through the bones, there are various limitations and restrictions regarding the position and direction of bone cutting to ensure medical safety. Therefore, please understand that the jaw cannot be customized according to personal preferences. We believe the most important aspect of orthognathic surgical planning is to find the appropriate method for each patient and achieve it successfully. We prioritize proper occlusion (bite) and aim for harmony among the important functions of the jaw and face, working together with patients to explore treatment options and strive for the best possible results. In this regard, we pride ourselves on offering treatment that is distinct from purely cosmetic bone surgery.

1. Sagittal Split Ramus Osteotomy (SSRO)

At our clinic, we primarily use the Obwegeser-Dal Pont method, which is the most common mandibular osteotomy technique.

Indications: Skeletal mandibular prognathism, skeletal mandibular retrognathism, skeletal mandibular asymmetry, etc.

Advantages:

• ・After bone cutting and fragment repositioning, the contact surface area between bone surfaces is wide, promoting favorable healing conditions. Consequently, there is minimal relapse.
• ・The wide range of movement direction and amount is applicable to various jaw deformities.
• ・Genioplasty can be performed simultaneously.

Disadvantages:

• ・Since the bone cutting is performed along the neurovascular bundle within the mandible, there is a risk of nerve damage resulting in numbness of the skin in the chin or lower lip area.
• ・As a mandibular surgery, there is a possibility of post-surgery temporomandibular joint (TMJ) symptoms.

Surgical Procedure

1. 1. After disinfection of the face and oral cavity, draping is performed.
2. 2. Local anesthesia by injection is administered.
3. 3. An incision is made with a scalpel in the mucobuccal fold slightly below the right second premolar to second molar region, extending the incision line along the external oblique ridge to 10 mm below the papilla parotid.
4. 4. A mucoperiosteal flap is created to the lower border of the mandible and the posterior border of the ramus, and a retractor is inserted beneath the lateral periosteum of the ramus. The anterior border of the ramus is dissected including the temporal muscle fascia, and the lateral upper portion of the ramus is dissected from the outside until the mandibular notch can be identified. At the same height, parallel to the occlusal plane, a periosteal elevator is inserted on the medial side of the ramus for dissection. During this process, the mandibular notch and lingula are identified, and dissection continues between them to the posterior border of the ramus. A channel retractor is used to protect the surrounding tissues.
5. 5. Using a reciprocating saw, a horizontal cut is made on the medial side of the ramus at a height approximately 5 mm above the lingula, and the bone cut is extended to the anterior border of the ramus between the right first and second molars. At this point, the lateral cortical bone of the mandibular body is cut parallel to the tooth axis.
6. 6. A double-sided bone chisel is inserted from the anterior part of the bone cut and the split is advanced to above the mandibular canal, then further posteriorly while being mindful of the mandibular canal. A wedge is used to completely split the ramus. The same bone cutting procedure is performed on the opposite side.
7. 7. After completing the bone cuts on both sides, it should be confirmed that the distal fragment moves without interference from the proximal fragment. The distal fragment is moved posteriorly, the upper and lower jaws are brought into occlusion, and intermaxillary fixation is performed using wires and elastic bands.
8. 8. Using a reciprocating saw, the excess portion of the proximal fragment created by the movement of the mandibular body is removed, and the proximal and distal fragments are fixed with plates.
9. 9. After releasing the intermaxillary fixation, continuous suction drains are placed on the lateral side of both rami, the incision is sutured, and intermaxillary traction is applied with elastic bands to complete the surgery.

2. Le Fort I Osteotomy

This is the most common maxillary osteotomy technique. It is typically not performed alone but in combination with SSRO.

Indications: Skeletal maxillary protrusion, skeletal maxillary retrusion, gummy smile, etc.

Advantages

• ・Movement in all directions is possible, allowing for extensive improvement of occlusion and facial appearance. In particular, forward movement is relatively easy with minimal risk.
• ・Can provide skeletal correction for gummy smiles that cannot be addressed with gingival or upper lip surgery.

Disadvantages

• ・Facial swelling and bruising are relatively pronounced and may take several weeks to heal.
• ・Moving the maxilla can cause widening of the nasal base. Therefore, this is controlled during surgery by suturing from the inside.

Surgical Procedure

1. 1. After disinfection of the face and oral cavity, draping is performed.
2. 2. Local anesthesia by injection is administered.
3. 3. A scalpel incision is made slightly toward the crown from the mucobuccal fold between the canines on both sides, reaching subperiosteally, and a mucoperiosteal flap is created using a periosteal elevator. The piriform aperture, anterior and lateral walls of the maxillary sinus, and zygomaticomaxillary crest are exposed. The nasal mucosa is dissected from the lateral wall of the nasal cavity to near the posterior edge of the palatine bone and elevated.
4. 4. Using a bone saw, an osteotomy is performed from the margin of the piriform aperture to the maxillary tuberosity, and the nasal septum is cut using a nasal septum chisel.
5. 5. A bone chisel is used to split from the lateral wall of the nasal cavity to the pterygoid plates, and from the zygomaticomaxillary crest to the maxillary tuberosity. After downfracture, the bone fragment is mobilized.
6. 6. After confirming the fit between the intermediate splint for maxillary positioning and the dentition, the upper and lower jaws are fixed together with the splint using wires and elastic bands (intermaxillary fixation). Areas of interference between the mobilized bone fragments are removed using a bone saw.
7. 7. The proper fit between bone fragments is confirmed. Bone fixation is performed using miniplates on each side.
8. 8. To prevent the alar base from widening, a suture procedure is performed. The wound is then closed.

Genioplasty

Indications: Chin overgrowth, chin recession, etc.

Advantages

• ・Can improve front to back, vertical, and lateral abnormalities of the chin.
• ・Can be performed simultaneously with SSRO.
• ・Intermaxillary fixation is not necessary when performed as a standalone procedure.

Disadvantages

• ・Risk of nerve damage resulting in numbness of the skin in the chin or lower lip area.
• ・Postoperative bleeding and swelling in the floor of the mouth may occur.

Surgical Procedure

1. 1. After disinfection of the face and oral cavity, draping is performed.
2. 2. Local infiltration anesthesia is administered.
3. 3. A scalpel incision is made slightly above the mucobuccal fold from the right second molar to the left second molar, and a mucoperiosteal flap is created. Care is taken to avoid damaging the mental nerve during mucoperiosteal flap dissection, and the mental foramen is identified.
4. 4. A line is established from the apex of the mental protuberance to the bone edge below the mental foramen on both sides, and osteotomy or bone reduction is performed using a bone saw. The bone is split using a bone chisel.
5. 5. Areas where bone surfaces meet are smoothed with a round bur.
6. 6. The incision is sutured.