Lower Jaw Surgery: Bilateral Sagittal Split Osteotomy

Upper jaw surgery is technically referred to as “Bilateral Sagiital Split Osteotomy” (BSSO).

Why is lower jaw surgery done?

The lower jaw can be lengthened to correct a retrusive lower jaw and excessive overbite. The lower jaw can also be shortened to correct a protrusive or enlarged lower jaw. The lower jaw can also be rotated to correct facial asymmetry.  Sometimes, the lower jaw surgery is done simultaneously with upper jaw surgery or chin surgery.

How is lower jaw surgery done?

An incision is made in the gums at the back of the lower jaw adjacent to the molar teeth.  There are no skin incisions and no facial scarring.  The bone in lower jaw is cut parallel to the jaw line (called “sagittal”) in order to allow a “sliding” of each segment of the jaw bone to lengthen, shorten or rotate the jaw. The bone segments are carefully “split” using specialised instrumentation to allow controlled separation of the bone segments and for greater nerve protection.  The nerve in the lower jaw is visualised and care is taken to ensure that the nerve is not transected or traumatised. The lower jaw can then be moved to the new planned position. If the jaw is lengthened, there is a small gap, but due to the sagittal split sliding design, bone will grow predictably and there is no need for a bone graft.  The movements have been precisely pre-planned prior to surgery using computerized 3-D software with 3-D printed surgical templates made to use during surgery to reproduce the planned movement. Using the templates, the new position of the lower jaw is fixated using titanium mini-plates and mini-screws. The plates and screws are made from medical grade titanium and are biocompatible.  They can stay indefinitely. Studies have shown titanium to be inert and integrate well with bone.  There are usually 1 or 2 mini-plates with 4 holes per plate per side. Each plate is precisely bent and shaped to fit over the bone to hold the jaw into the new position. The wires are then released and the jaws are no longer wired together as the plates and screws are now maintaining the new position.