Bimaxillary osteotomy, often called “Bimax,” is a type of corrective jaw surgery that simultaneously repositions both the upper and lower jaws. This comprehensive treatment corrects severe skeletal and dental discrepancies to improve functional capability and facial harmony. Bimax is typically reserved for cases where jaw misalignment is too extensive to be managed by orthodontics alone, ensuring proper bite alignment and facial balance.
Defining Bimaxillary Osteotomy
The term Bimaxillary Osteotomy means the surgical cutting and reshaping of both the maxilla (upper jaw) and the mandible (lower jaw). The maxilla is the fixed bone containing the upper teeth, while the mandible is the mobile lower jaw. The objective of Bimax surgery is to detach these bone segments and move them into a predetermined, correct anatomical relationship.
This simultaneous correction addresses complex three-dimensional issues, including vertical, horizontal, and transverse misalignments. The goal is to align the underlying skeletal structure so the teeth meet correctly, achieving Angle Class I occlusion. By repositioning the jaws, the procedure fundamentally alters the foundation of the lower and middle thirds of the face.
The surgery requires extensive preoperative planning using advanced imaging and virtual modeling. The surgeon accounts for the specific anatomy and the desired final position of the jaws to ensure stability and optimal function. A successful outcome relies on the precise movement of the tooth-bearing segments of bone to establish a stable and balanced bite.
Reasons for the Procedure
Patients pursue Bimaxillary Osteotomy when jaw misalignment causes significant functional problems. A primary indication is severe malocclusion, specifically Class II (overbite) or Class III (underbite) discrepancies. When the skeletal difference between the upper and lower jaws exceeds the limit of what braces alone can correct (e.g., greater than 7-8 millimeters), skeletal correction is required to achieve a stable bite.
The procedure is also an effective treatment for obstructive sleep apnea (OSA) caused by structural issues. By performing maxillomandibular advancement, the surgeon moves both jaws forward. This action pulls the soft tissues of the tongue and pharynx away from the airway, significantly enlarging the airway space and resolving severe breathing difficulties during sleep.
Other reasons include temporomandibular joint (TMJ) dysfunction stemming from underlying jaw misalignment. Correcting the skeletal position often reduces TMJ symptoms like pain and joint clicking. Finally, Bimax can correct significant facial asymmetry or a canted occlusal plane by repositioning the jaws into a balanced position.
How the Surgery is Performed
Bimaxillary osteotomy is performed under general anesthesia in a hospital setting. It is executed entirely through intraoral incisions made inside the mouth, meaning there are no visible external scars. The operation typically takes between three to six hours, depending on the complexity of the planned movements.
The procedure involves two distinct components, starting with the Le Fort I osteotomy on the upper jaw. The surgeon makes an incision above the upper teeth to access the maxilla, then uses a specialized saw to make a precise horizontal cut. This separates the tooth-bearing segment from the facial skeleton, allowing the maxilla to be moved into its new, pre-planned position, which may involve advancement, setback, impaction, or rotation.
Next, the surgeon performs the Bilateral Sagittal Split Ramus Osteotomy (BSSRO) on the lower jaw (mandible). This technique involves controlled cuts through the ramus—the vertical part of the mandible—to split the bone into two layers on each side. This splitting allows the front, tooth-bearing portion of the lower jaw to be moved forward or backward independently from the condyles (joint components).
Once both jaws are in their final positions, they are secured using small, medical-grade titanium plates and screws for rigid internal fixation. The entire process is guided by preoperative virtual surgical planning (VSP), where the surgeon uses three-dimensional imaging to map out the exact bone cuts and final jaw placement. The incisions inside the mouth are then closed with dissolving sutures.
Post-Surgical Recovery and Timeline
The immediate aftermath involves a hospital stay, typically lasting a few days, where initial swelling and pain are managed. Significant facial swelling is expected, peaking around the third day, and gradually resolving over the next few weeks. Patients manage swelling by keeping their head elevated and using cold compresses during the first 48 hours.
Pain is controlled with prescribed medication; temporary numbness or tingling in the lower lip and chin is common. A strict liquid diet is required immediately after surgery, as patients must refrain from chewing for approximately six to eight weeks to allow bone healing. This initial diet includes nutrient-rich shakes, soups, and pureed foods.
The transition phase begins after six to eight weeks, once the surgeon confirms sufficient bone healing. The diet progresses to very soft, non-chewing foods like scrambled eggs and soft pasta. Full functional recovery, where bone segments solidify and muscle function adapts, can take several months to a year. Meticulous oral hygiene, utilizing a soft toothbrush and prescribed rinses, is paramount throughout recovery to prevent infection.