Over growth of the ramus of the mandible forms a big mandible bone and thus frequently causes an underbite occlusion. The surgery to correct this condition is called a Sagittal Splitting Ramus Osteotomy (SSRO). However in some other situations the oversized mandible bone is not caused by the overgrowth of the ramus but by the overgrowth of the front part or the body of the mandible bone. In this instance SSRO is not the best choice of selection, instead the front part or body osteotomy of the mandible bone may improve the facial figure. The incision line on the bone of the front part osteotomy locates in front of the mental foramen, so there is less chance of inferior alveolar nerve injury by surgery compared to the mandible body osteotomy. But the width of bone removal is limited in this surgery because the curvature structure at the osteotomy site makes the reunion of the severed front end of the mandible bone difficult if big chunk of bone is removed.

The girl at this page had a big long chin, pointing forward. Her occlusion looked normal after a teeth alignment correction treatment, which made her incisors leaning backward. She came to see Dr. Ma wanted a smaller chin and got rid of the new moon like facial outline in profile. Her CT scan showed that the frontal part of her mandible bone was oversized and the size of the other parts of the bone was normal. She was a good candidate for Front Part Osteotomy. As a preparation process the fourth teeth on the mandible bone normally needed to be extracted to create rooms for the front part of the mandible bone setback. For her only the fourth tooth on the left side needed te be removed because her fourth tooth on the right side was already been extracted in the previous orthodontic treatment.

Front part wedged osteotomy of the mandible bone
Before and after surgery photos of the front part wedged osteotomy of the mandible bone.

Wedged osteotomy mandible bone reduction
The front part wedged osteotomy surgery made the chin smaller and short of this girl. This change is best demonstrated in profile view as this.

chin reduction before and after
In front view the face is shorter and more square after surgery and the right deviation of the chin is corrected.

demonstration of the front part osteotomy of the mandible bone
Tooth distraction orthodontic process can’t reduce size of the chin but make the incisors leaning backward. Wedged osteotomy of the mandible bone could really make the chin bone smaller and shorter.

This girl was long unsatisfied with her big chin. In order to make it smaller she tried orthodontic treatment after teeth distraction from the lower jaw. It ended up only the inclination of the lower incisors. The chin size was not reduced but relatively augmented because of the indentation of the lips caused by the leaning back of the incisors.

It seems there is not much changes in the frontal view comparison photos. Only the facial outline became a little square because of the setback of the chin. This kind of result is opposite to that of the chin sliding forward surgery. This girl didn’t treat this change as an unwanted side effect. On the contrary she told Dr. Ma that she was very happy to see her right deviation of the chin was been corrected and her face looked more symmetric than before surgery. In profile view her chin size changed remarkably. During the surgery a piece of 8MM width mandible bone was removed vertically from each side of the front part of the mandible bone. In the one year post surgery photo above the chin is not protruding anymore, the mouth is not indented and the relationship between the upper and lower lips restored to the ideal upper in front setting.

Many candidates concern that the reduction of the chin bone may cause skin sagginess. In fact this kind of worry is unnecessary. First of all the skin in the chin area is tight a chin bone setback of couple of millimeters will not be able to form skin sagginess. Secondly the surgery reducing the size of the chin bone and there is a thick layer of soft tissue in between the skin and the bone at this area. The sized change of the bone will not directly effect the skin. Thirdly as the candidates who undergo this surgery originally have a big pointing chin, which augmenting the soft tissue and the skin making an unnatural look chin. During surgery only the extra bone is trimmed off, no skin looseness is formed by excessive bone removal.

By: mafushun

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