In general, a protruding chin is a condition that occurs when the lower jaw or the mouth protrudes forward and when the face is extremely long. To exactly categorize it, it can be divided into two; MACROGENIA (only the chin part is over-developed but the occlusion and mandible size itself is normal.) and MANDIBULAR PROGNATHISM – a condition where there is a malocclusion, where the lower front teeth are farther forward than the upper front teeth due to an overgrowth of mandible bone. Not only is the chin, but also the whole mandible bone protruding.
Therefore, the protruding chin can be corrected by Genioplasty in the case of MACROGENIA, but for MANDIBULAR PROGNATHISM, lower jaw surgery that is pushing the mandible in or a two-jaw surgery that is pushing both maxilla and mandible in is needed.
It can be performed when the occlusion is normal but only the chin structure is developed. If the lower chin grew forward or downward in the face, we don’t call it MANDIBULAR PROGNATHISM and it can be simply corrected by chin reduction surgery.
It can be performed when the face length is normal but it is MANDIBULAR PROGNATHISM. This is a way to move the lower mandible backward using a method that affects less of a burden to the jaw joint and protects lower jaw nerves at the same time.
At this time, we perform SSRO (Sagittal Split Ramus Osteotomy of Mandible) surgery to make a protruding mandible move backward by cutting the back of jaw bone and fixing it without overlapping.
If the face is short or long, it requires an upper jaw surgery at the same time with the lower jaw surgery.
We call it a two jaw surgery when the lower jaw osteotomy is done simultaneously with an upper jaw surgery that is cutting an upper jaw from upper teeth to just below the nose.
In the case of a protruding jaw with a long face, we make upper jaw move forward since it looks receding, make lower jaw move backward and reduce the long face length at the same time. However, in the case of a protruding jaw with a short face, the surgery which makes the upper jaw move forward and downward is needed because the chin is smaller than upper jaw and looks receding.
At this time, the lower jaw can be moved back according to the position of the upper jaw.