• 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.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.29 no.3
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• pp.173-181
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• 2003

Purpose : This study was intended to evaluate the positional relationship between the hyoid bone and the mandible in patients with mandibular protrusion after mandibular set-back surgery by means of 3D-CT. Materials and methods : Preoperative(3 weeks before) and postoperative (6 weeks after) 3D-CT & cephalogram were taken on 32 patients(12 male, 20 female, mean age of 23.2) treated by bilateral sagittal split osteotomy with rigid fixation. The angular measurement on 3D-CT basilar view were deviation of Me & H, long axis angle of left & right cornu majus. The lineal measurement on 3D-CT basilar view were composed of intercondylar line and coordinates(x,y) of Me & H. The angular & lineal measurement of lateral cephalogram were composed of mandibular plane angle, SNA, SNB, ANB, FH-NA & FH-NB, and coordinates(x,y) of B, Pog, Me & H, PAS, Lpw, MPH and IAS. On the frontal cephalogram, deviation of Me were evaluated. Results : The mean mandibular set-back was 8.0mm horizontally and mandibular plane angle was slightly increased. The hyoid bone was displaced postero-inferiorly, the distance between MP(mandibular plane) and H(hyoid bone) was increased and the posterior airway space values (PAS, Lpw, IAS) were decreased. The coordinates Me(x,y), H(x,y) and deviation angle Me'& H' were revealed the strong positive correlation. Conclusion : The results revealed that the horizontal, vertical and transverse relationship of the mandibular and the hyoid bone movements were significantly correlated in patients performed mandibular set-back surgery.

• 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.13 no.1
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• pp.100-103
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• 1991

In the treatment of mandibular prognathism with concomitant features of narrow alar base and some paranasal deficiency, simultaneous paranasal augmentation for the additional esthetic effect can be considered, if it is determined to correct the mandibular prominence and class III by a mandibular set-back. Alloplastic augmentation has several advantages upon the autogenous means in the respect of dimensional stability and simplicity of operation. This is a case report of silastic paranasal augmentation performed simultaneously with mandibular set-back surgery which has a period of 15 months of follow-up postoperatively.

• 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.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.19 no.4
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• pp.351-361
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• 1997

This study was performed to evaluate the change of the soft tissue facial profile after mandibular set back surgery during time intervals. For this study, 33 patient, 8 males and 25 females, were selected and their lateral cephalograms were taken and analyzed periodically. Hard and soft tissue changes during postoperative time intervals, correlation between surgical skeletal changes and postoperative soft tissue changes, and prediction for long-term soft tissue changes were established through varying statistical methods. The results were as follow : 1. There were meaningful changes of anteroposterior skeletal position at 6 months and 2 years after mandibular set back by mandibular ramus osteotomy. Two years postoperatively, there was 30%, 32%, 29% relapse on B point, pogonion, menton each. 2. Two years after the mandibular ramus osteotomy, the relative changes of the soft tissue to their osseous counterparts showed 76% on the lower lip and 91% on the pogonion. 3. The movements of the mandibular landmarks in correlation to anteroposterior position of the lower lip and soft tissue of the chin showed to be effective on a long-term basis. 4. Using surgical changes of pogonion, prediction of changes in soft and hard tissue pogonion was useful and the coefficient of determination was 0.46 each and their reliability decreased 2 years postoperatively. 5. The upper lip position after the mandibular set back surgery was somewhat anterior 2 years postoperatively, but that has no statistical meanings.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.23 no.1
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• pp.21-30
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• 2001

The purpose of this study was to evaluate the skeletal relapse pattern of the mandibular prognathic patients after mandibular set back surgery by sagittal split ramus osteotomy. The horizontal and vertical position of the cephalometric points were measured before, after surgery and after one-year follow up period. The next, the positional change of the proximal and distal mandibular segment were evaluated respectively. The obtained results were as follows; 1. The horizontal and vertical position of Cd was not changed before and after surgery, and it was maintained its original position during the observation periods. 2. As the mandibular prognathism of the patients was severe before surgery, the more skeletal relapse tendency was observed during follow-up period(p<0.05). 3. As the horizontal positional change of the mandible which was obtained by mandibular set-back surgery was large, the more horizontal relapse tendency was observed during follow-up period(p<0.05). 4. The corpus axis angle decreased by sagittal split ramus osteotomy(p<0.01), but it was kept its reoriented position during follow-up period. 5. During the follow-up period after mandibular set-back by sagittal split ramus osteotomy, the forward relapse of mandible correlated with not only the forward rotation of the proximal segment but also the forward movement of the distal segment(p<0.05).

• 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 the Korean Association of Oral and Maxillofacial Surgeons
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• v.34 no.3
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• pp.300-305
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• 2008

Purpose: The purpose of our study was to evaluate the volume of pre- and post operative masseter muscle and bite force in mandibular prognathic patients treated with SSRO with the use of the 3D CT imaging technique and occlusal force meter. Materials and methods: The study group consisted of 12 patients with mandibular prognathism (5 males and 7 females) who underwent mandibular setback surgery (BSSRO) in the Department of Oral and Maxillofacial Surgery, Samsung medical center. Bite force was measured at pre op, post op 3, 6 and 12 months by occlusal force meter(GM10, Nagano Keiki, Japan) The preoperative CT examination of subjects was performed between one month prior to operation and one year after to operation. And muscle volume was measured. Result: As compared to preoperative measurements at 1 year postoperatively the masseter & internal pterygoid muscle volume were diminished (p<0.05) The bite force steadily recovered, so at postoperatively 6 months reached the preoperative level. And at 1 year after operation, the maximum bite force was significantly greater than preoperative levels. No significant correlation was presented between masseter muscle and bite force (p>0.05), internal pterygoid muscle and bite force (p>0.05). Conclusion: In this study, the results showed that volume and bite force of the masticatory muscles decreased significantly immediate after orthognathic surgery for mandibular set-back. However, reduction of maximum bite force disappears within 6 months after surgery.

• The korean journal of orthodontics
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• v.43 no.6
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• pp.263-270
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• 2013

Objective: To evaluate condylar head remodeling after mandibular set-back sagittal split ramus osteotomy (SSRO) with rigid fixation in skeletal class III deformities. The correlation between condylar head remodeling and condylar axis changes was determined using cone-beam computed tomography (CBCT) superimposition. Methods: The CBCT data of 22 subjects (9 men and 13 women) who had undergone mandibular set-back SSRO with rigid fixation were analyzed. Changes in the condylar head measurements and the distribution of the signs of condylar head remodeling were evaluated by CBCT superimposition. Results: The subjects showed inward rotation of the axial condylar angle; reduced condylar heights on the sagittal and coronal planes; and resorptive remodeling in the anterior and superior areas on the sagittal plane, superior and lateral areas on the coronal plane, and anterior-middle and anterior-lateral areas on the axial plane (p < 0.05). Conclusions: The CBCT superimposition method showed condylar head remodeling after mandibular set-back SSRO with rigid fixation. In skeletal class III patients, SSRO with rigid fixation resulted in rotation, diminution, and remodeling of the condylar head. However, these changes did not produce clinical signs or symptoms of temporomandibular disorders.