Advantages: No surgical traces.

Disadvantages: it greatly increases the difficulty of the operation, but also increases the risk of the operation, and the postoperative recovery period is also longer. Perioperative nursing is easy to cause infection and the operation cost is high.

Extraoral incision:

Under local anesthesia, make a 2 -5cm long skin incision in the hidden position of the lower edge of mandible, then expose the masseter muscle and partially cut off the masticatory muscle. If there is hyperosteogeny of mandible, it is necessary to cut the appropriate part of mandible in an arc shape, and then smooth it with a bone file, so that periosteum, muscle, subcutaneous tissue and skin can be stitched layer by layer.

Advantages: simple operation, full exposure, accurate osteotomy, quick recovery and low cost.

Disadvantages: surgical marks are left on the face.