Planning the surgical treatment of mandibular prognathism]

The method for calculating a required displacement of the mandible posteriorly in surgical treatment of prognathism by the technic of oblique osteotomy of the mandibular branches is suggested. The described technic was successfully employed by the author in 56 patients. The technic concerned would reduce the time of a surgical procedure (up to 50-60 min). The main advantage of the technic is that it completely excluded errors in calculating the displacement of the mandible posteriorly.     

Surgical treatment of mandibular prognathism in collaboration with orthodontic treatment in Korea

Mandibular prognathism is defined by John Hunter as follows: The lower jaw projecting too far forward so that the foreteeth pass before those of the upper jaw, therefore disfigurement and malocclusion are two of the main facial characteristics. Other distinguishing features are the coexistence of class III malocclusion, incomplete closure of lip, deviation of the midline, and decrease of labiomental fold. Generally, the functional occlusal relationship and balanced facial harmony cannot be obtained by surgical or orthodontic treatment alone. Its success depends on careful conjoint, supplementary diagnostic, and treatment planning. As a cardinal principle the authors made the following combined surgical and orthodontic treatment plans: (1) Orthodontic treatment relocates and decompensates the malpositioned teeth (remove the masking effect of teeth) and, therefore, skeletal deformity is exposed maximally. (2) Surgical treatment eliminates the maximally exposed skeletal defect. Therefore, dramatic facial balance and functional occlusal relationship are obtained. Treatment planning includes the pre- and postoperative orthodontic treatment, lateral cephalometric prediction tracing (LCPT), and model surgery with dental cast. The authors made it easy with the use of an acrylic dental wafer to coordinate exact occlusal relationship after surgery. We treated mandibular prognathism by using Dautrey's modification of the sagittal split ramus osteotomy (SSRO) (10 cases) and intraoral vertical ramus osteotomy (IVRO) (5 cases) and sometimes additional genioplasty (2 cases). IVRO was used in those cases where (1) the amount of setback was more than 10 mm and (2) where there was a flat gonial angle. Otherwise SSRO was used. Late postoperative relapses were detected from 7 to 38 months (mean 19.6 months), followed up in some degree by cephalometrics, but the functional occlusal relationship proved to be stable. Conclusively, all the patients obtained satisfaction for their facial balance and functional occlusal relationship following combined surgical and orthodontic treatment.     

Significant details regarding treatment of prognathism using angled osteotomy of the mandibular rami

A simplified technique for surgical correction of prognathism, consisting of an angled or L-shaped osteotomy in the mandibular ramus starting from the sigmoid notch and ending on the posterior border of the ascending ramus, has been performed on 365 patients. Modifications of the procedure allow for concomitant correction of mild and severe open-bite conditions. Morbidity was not significant; 12 patients experienced transient dysfunction of the facial nerve, which disappeared within an average of 60 days; in 10 patients, there was an accumulation of saliva in the preauricular area, which was relieved by 3 or 4 punctures. In some of the early open-bite cases, regression occurred, leading to modifications in the technique. There are many advantages to the procedure, including simplicity, low risk of infection, inconspicous scarring, no impairment of muscle strength, and low complication rate.Work presented at the IVth Brazilian Congress of Aesthetic Surgery, September 2–5, 1979, in Porto Alegre, Brazil.     

Mandibular symphyseal contouring in mild mandibular prognathism

K?lle's mandibular segmental osteotomy, with extraction of the bilateral first bicuspids, is often used in cases of mild mandibular prognathism. While mandibular prognathism is usually corrected by mandibular ramus osteotomy and the mandible is set back en bloc, the premolar region alone is set back by segmental osteotomy, retaining the protruding mental area. In Asians, particularly, the protruding chin is not preferred by our concepts of beauty. In mandibular segmental osteotomy, the entire mandibular symphyseal shape should be considered. Mandibular symphyseal contouring constitutes setting back the premolar region by segmental osteotomy, recession genioplasty, and chiseling out the protruding middle portion of the protruding chin. In 18 series of mild manibular prognathism in Asians patients, this procedure was used and satisfactory aesthetic results were obtained.     

骨性安氏Ⅲ类错患者行正颌手术后其口腔功能间隙的改变

目的:探讨骨性安氏Ⅲ类错患者行正颌手术后,口腔功能间隙面积的改变,了解口腔功能间隙与牙颌畸形发生的关系,为正颌临床诊断治疗提供有益的参考。同时研究口腔功能间隙的改变对术后保持与防止复发提供理论依据。方法:对在我院就诊的共20例骨性安氏Ⅲ类错患者进行研究,采用定位X线头影测量分析的方法,通过患者治疗前后的对照,比较正颌术后口腔功能间隙的改变。结果:骨性安氏Ⅲ类错患者行正颌手术后较术前1周口腔功能间隙减小(P<0.05),有统计学差异。下颌后退量与口腔功能间隙减少量存在明显的正相关性。结论:骨性安氏Ⅲ类错患者,经正颌治疗后,口腔功能间隙矢状向面积有所减小,其直接原因可能是正颌手术后退下颌骨造成的,并且口腔功能间隙变化量与下颌骨后退距离存在正相关性。     

Surgical correction of mandibular prognathism with a functionally stable osteosynthesis of the mandibular body

Several methods have been described for the surgical correction of mandibular prognathism. Current techniques favour surgical correction at the site of the anomaly itself and in the case of skeletal mandibular prognathism it is the mandibular body that must be cut and shortened. The authors describe two methods of oblique ostectomy and of sagittal splitting with ostectomy of the mandibular body, by which a planned and measured reduction of the size of the mandible can be achieved. The techniques provide a functionally stable osteosynthesis, the optimum conditions for post-operative bone healing and so reduce the period of intermaxillary immobilisation. The special problems of articular derangements of the temporo-mandibular joint due to a stable osteosynthesis can be avoided by the combined use of zygomatico-mandibular positioners and occlusal splints.     

正畸-正颌联合治疗骨性下颌前突口腔功能间隙变化的研究

目的：探讨正畸-正颌联合治疗骨性下颌前突病例,随着牙合关系的改变,口腔功能间隙面积的变化情况。方法：选择25例骨性下颌前突病例,用正畸-正颌联合治疗,采用治疗前后自身对照,观察口腔功能间隙面积的改变情况,采用配对t检验。20例骨性下颌前突患者观察期内不经任何治疗,作为对照组,采用完全随机设计两样本t检验。结果：术后较术前口腔功能间隙测量值减小（P〈0．05）,与对照组相比,术前口腔功能间隙面积实验组和对照组无差异（P〉0．05）,术后实验组口腔功能间隙面积小于对照组（P〈0．05）,对照组口腔功能间隙术前后无显著性差异（P〉0．05）。结论：正畸-正颌联合治疗骨性下颌前突可使口腔功能间隙明显减小,术后应防止发生舌咽功能紊乱,并防止复发。