• Maxillofacial Plastic and Reconstructive Surgery
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• v.33 no.4
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• pp.323-330
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• 2011

Purpose: The present study examined the reproducibility of an operation plan by comparing the jaw position of STO with the postoperative mandibular set back measurement in sagittal split ramus osteotomy. Methods: Thirty patients with class III dental and skeletal malocclusion and who were treated with BSSRO were reviewed. Three plain radiographs such as the panoramic view, the lateral cephalogram and the submentovertex view were taken before and after operation. Also, paper surgery for STO and model surgery were used to evaluate the amount of mandibular set back. Results: On the panoramic view, the amount of mandibular set back in STO was similar to the postoperative results of model surgery, but the amount of mandibular set back on the lateral cephalogram was smaller than the postoperative result of model surgery and then the amount of set back on submentovertex view was similar to the postoperative result of model surgery. Conclusion: Precise tracing and paper surgery should be performed for a combined expected STO in order to predict the exact amount of preoperative mandibular set back.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.23 no.4
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• pp.348-356
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• 2001

The factors related to relapse in 20 skeletal class III patients who performed two-jaw surgery with Le Fort I maxillary osteotomy and bilateral sagittal split ramus osteotomy was investigated. All patients were fixed with miniplate on the maxilla and three screws at each mandible. Cephalograms taken at preoperative, immediate postoperative and 8 months postoperative after surgery were traced and digitized. 1.The horizontal and vertical relapse of maxilla and mandibular chin points was within 1mm postoperatively. Compare to the preceding report concerning the mandibular set-back surgery only group, this reveals two-jaw surgery for mandibular prognathism using rigid fixation is more stable. 2.Although there was no significant relapse tendancy was observed at chin points, the screw tip land-marks moves anterio-superiorly and each side of the screws moved as a one unit. The screw tip points moved similar direction to the masticatory force and this movements might be influenced by the muscular tension to the distal segment of the mandible. 3.According to the regression analysis, the amount of horizontal and vertical movement of mandibular set-back influenced the mandibular relapse. However, direction and amount of maxillary surgical movement did not inf1uenced the maxillary and mandibular relapse.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.36 no.1
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• pp.28-38
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• 2010

The factors influencing the relapse and recurrence of skeletal deformity after the orthognathic surgery include various factors such as condylar deviation, the amount of mandibular set-back, stretching force by the soft tissues and muscles around the facial skeleton. The purpose of this report is to recognize and analyze the possible factors of reoperation after orthognathic surgery, due to early relapses. Six patients underwent reoperation after the orthognathic surgeries out of 110 patients from 2006 to 2009 were included in this study. In most cases, clincal signs of the insufficient occlusal stability, anterior open bite, and unilateral shifting of the mandible were founded within 2 weeks postoperatively. Although elastic traction was initiated in every case, inadequate correction made reoperation for these cases inevitable. The chief complaints of five cases were the protruded mandible combined with some degree of asymmetric face and in the other one case, it was asymmetric face only. Various factors were considered as a major cause of post-operative instability such as condylar sagging, counter-clockwise rotation of the mandibular segment, soft tissue tension related with asymmetrical mandibular set-back, preoperatively existing temporomandibular disorder (TMD), poor fabrication of the final wafer, and dual bite tendency of the patients.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.36 no.5
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• pp.185-191
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• 2014

Purpose: Although there have been several studies of reduced airway space after mandibular setback surgery using the sagittal split ramus osteotomy technique, research on the risk factors for changes of the airway space is lacking. Therefore, this study was performed to examine airway changes and the position of the hyoid bone after orthognathic surgery, and to assess possible risk factors. Methods: In this retrospective study, 50 patients who underwent posterior displacement of the mandible by the bilateral sagittal split ramus osteotomy technique were included. Changes of the position of the hyoid bone and the airway space were analyzed over various follow-up periods, using cephalometric radiography taken preoperatively, immediately after surgery, eight weeks after surgery, six months after surgery, and one year after surgery. To identify risk factors, multiple regression analysis of age, gender, body mass index (BMI), posterior mandibular movement, and the presence of genioplasty was performed. Results: Inferor and posterior movement of the hyoid bone was observed postoperatively, but subsequent observations showed regression towards the anterosuperior aspect. The airway space also significantly decreased after surgery (P<0.05), and increased slightly up until six months after surgery. The airway space significantly decreased (${\beta}=0.47$, P<0.01) as the amount of mandibular setback increased. However, age, sex, BMI, and presence of genioplasty were not associated with airway reduction. Conclusion: The amount of mandibular set back was significantly associated with postoperative reduction of airway space. It is necessary to establish a treatment plan considering this factor.

• Journal of Dental Rehabilitation and Applied Science
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• v.22 no.4
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• pp.271-281
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• 2006

Long term prediction of surgical result of skeletal class III has not been evaluated adequately because the stability of orthognathic surgery would be affected by not only set back amount of mandible but also many other factors like skeletal pattern, hyoid position, and airway size. The aimof this study is to discriminate the factors which affect the stability of post-treatment result of surgical outcome of sagittal split ramus osteotomy. We have collected 37 patients (male: 17, female: 20) from patients who have been treated at Orthodontic Department in Dankook University. The patients underwent 3 times Cephalometric X-ray taking at pre-, post-orthognathic surgery and after 12 months retention. The subjects were divided into 2 groups (Stable group: 21, Relapse group: 16) according to their relapse amount. We have taken following results from Students t-test and discriminant analysis. The discriminant factors which discern relapse and stable groupe among treatment change variables were BX and Ba-HY. Hyoid bone moved to posterior and inferior position due to surgery and repositioned superiorly and posteriorly during retention period. Skeletal patterns of the relapse group are smaller mandibular plane angle, anterior mandibular position, and greater distance from hyoid bone to cervical bone and mandible respectively.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.39 no.5
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• pp.217-223
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• 2013

Objectives: Buccal fracture of the mandibular proximal bone segment during bilateral sagittal split ramus osteotomy (SSRO) reduces the postoperative stability. The primary aim of this study is to evaluate the effect of this type of fracture on bone healing and postoperative stability after mandibular setback surgery. Materials and Methods: Ten patients who experienced buccal fracture during SSRO for mandibular setback movement were evaluated. We measured the amount of bone generation on a computed tomography scan, using an image analysis program, and compared the buccal fracture side to the opposite side in each patient. To investigate the effect on postoperative stability, we measured the postoperative relapse in lateral cephalograms, immediately following and six months after the surgery. The control group consisted of ten randomly-selected patients having a similar amount of set-back without buccal fracture. Results: Less bone generation was observed on the buccal fracture side compared with the opposite side (P<0.05). However, there was no significant difference in anterior-posterior postoperative relapse between the group with buccal fracture and the control group. The increased mandibular plane angle and anterior facial height after the surgery in the group with buccal fracture manifested as a postoperative clockwise rotation of the mandible. Conclusion: Bone generation was delayed compared to the opposite side. However, postoperative stability in the anterior-posterior direction could be maintained with rigid fixation.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.29 no.6
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• pp.407-420
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• 2003

Purpose : The purpose of this study was to analyse the facial changes and factors contributing to then after bilateral sagittal split ramus osteotomy of mandibular prognathism. Materials and Methods : Forty patients with Class III dental and skeletal malocclusion who were treated with bilateral sagittal split ramus osteotomy were reviewed. Frontal and lateral cephalometric radiographs were taken preoperatively, immediate postoperatively and more than six months postoperatively in each patient. After tracing the cephalometric radiographs, various parameters were measured. Results : 1. Gonial angle at postoperative two days was decreased about $10.4^{\circ}$ than preoperatively and gonial angle at postoperative six months was increased about $6.8^{\circ}$ than postoperative two days. So, gonial angle at postoperative six months was decreased about $3.6^{\circ}$ than preoperative gonial angle. 2. Facial height postoperative two days was decreased about 0.8mm than preoperatively and facial height at postoperative six months was decreased about 0.7mm than postoperative two days. So, facial height at postoperative six months was decreased about 1.5mm than preoperative facial height. 3. Mandibular width postoperative two days was decreased about 1.0mm than preoperatively and mandibular width at postoperative six months was increased about 1.8mm than postoperative two days. So, mandibular width at postoperative six months was decreased about 2.8mm than preoperative mandibular width. 4. Amount of set back and mandibular plane angle were not influencing on relapse degree. Conclusion : It is thought that bilateral sagittal split ramus osteotomy in mandibular prognathic patients is effective to improve long face and steep gonial angle. More prudent operation and careful postoperative management is required to maintain stable face postoperatively. Further research for soft tissue changes and factors which are related with relapse is needed.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.33 no.4
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• pp.319-322
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• 2011

Purpose: The purpose of this study was to examine the appropriate degree of set-back of the mandible by evaluating the rate of relapse after surgery. Methods: Among the patients who visited our hospital from January 2002 to January 2007 and who underwent orthognathic surgery, of the patients available for follow-up observation, the rate of relapse after surgery was investigated according to the set-back degree. The patients were divided into groups by the degree of set-back, and relapse was evaluated by the radiographs performed the day after surgery, 6 months after surgery, 1 year after surgery, 2 years after surgery and 3 years after surgery. Results: In cases that exceeded the limit of posterior movement of the mandible (13 mm) or that had the wrong position of the condyle, a greater tendency toward relapse was shown. Conclusion: Based on the results of this study, among the cases that required a large amount of posterior movement of the mandible, two jaw surgeries accompanied by bilateral sagittal split ramus osteotomy (BSSRO) and LeFort I osteotomy are recommended.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.16 no.1
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• pp.33-42
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• 1994

Obwegeser II method and Rigid fixation conserving the condylar position has been performed on 5 patients with severe mandibular prognathism, and we obtained the result after the follow up study follows. 1. Obwegeser II method is considered to move the distal segment passively when surgical correction of severe open bite correction and large amount of set back above 15mm is needed. 2. In one case that has more change of condylar position after operation, documented immediate post-operative relapse have been occurred 3. In the others that have adequate control of condylar position, passive set back and firm skeletal fixation, more functional and esthetic improvement and more post-operative stability has been achieved

• Maxillofacial Plastic and Reconstructive Surgery
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• v.17 no.1
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• pp.32-45
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• 1995

This study was intended to evaluate condyle position and the relationship of condyle position change and post surgical relapse following the sagittal split ramus osteotomy for mandible setback in 25 patients by paired t-test and multiple regression analysis. We used oblique transcranial and cephalometric radiographs taken before operation, immediate after operation, and at least 6 months post operatively. 1. In oblique transcranial view, posterior joint space was decreased immediate after operation and increased 6 months after operation. To compare the measurement before and 6 months after operation, there was no statistically significant change in over all joint spaces(P>0.05). 2. The joint spaces changed under the 0.2mm were 30%, 0.2mm to 1.0mm were 60.7%, above 1.0mm were 9.3%. This result reveals that condyle position was relatively reproduced to pre-operative state. 3. Statistically, the amount of mandible set back didn't influence the post operative relapse(P>0.05). 4. Statistically, the amount of mandible set back didn't influence the condylar displacement(P>0.05), and the amount of joint space change didn't influence the post operative relapse.(P>0.05) The changes in joint space is in the standard tracing error or within the adaptive capacity of the individual, it was too small to influence the stability of surgery.