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This study analysed 90 patients who underwent a bi-maxillary osteotomy for a class III malocclusion. There were 30 in each of three groups of patients based upon the Frankfort mandibular plane angle (FMA). They were divided into: greater than 32°, 22°-32°, and less than 22° as high, medium and low groups. The surgical outcome and stability were compared, and it was shown that those with a low FMA had a more consistent relapse than those with a normal or high FMA. Relapse was always in a forward and upward manner. Therefore, whilst finding that a bi-maxillary osteotomy is stable for mandibular prognathism regardless of the vertical facial pattern, they advocate that over correction of 1-1½mm in the mandibular setback was worth considering in those with a low FMA angle. They did not assess the cause of the relapse, whether this was due to positional changes, model of the condyle or soft tissue tension.

Relapse patterns of two-jaw surgical correction in patients with skeletal class III malocclusion and different vertical facial types.
Kuo JJC, Lin CH, Ko EWC.
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Stuart Clark

Manchester Royal Infirmary, Manchester, UK.

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