• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제32권5호
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• pp.447-452
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• 2006

Purpose: In order to clarify the correlation of mandibular setback using bilateral intraoral vertical ramus osteotomy (BIVRO) and post-surgical transverse mandibular width (TMW), this study examined the pre- and postsurgical changes in hard and soft tissues of TMW and the relationship of TMW and the amount of mandibular setback. Patients and Methods: One-hundred seven patients who had undergone BIVRO were evaluated radiographically and clinically. A comparison study of the changes in hard and soft tissue after surgery in all 107 patients was performed with preoperative, 1 month, 3 month, 6 month and 1 year postoperative posteroanterio cephalograms and clinical photographs by tracing. And this changes were evaluated in parts to amounts of mandibular setback. Results: Statistically significant increases of TMW in hard and soft tissue from preoperative to postoperative 1 month were seen. TMW in hard tissue from 1 month to 1 year postopertive were gradually decreased. TMW in soft tissue was not changed uniformly but almost equal to pre-operative width. And there was no significant correlation between TMW and amount of mandibular setback. Conclusions: The results show that mandibular setback using BIVRO did not significantly influence increasing of TMW in soft tissue.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제22권2호
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• pp.184-190
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• 2000

Objective : To compare two different methods of rigid fixation in postoperative stability after mandibular setback. Material and Methods : 28 patients with Class III malocclusion were treated by bilateral sagittal split ramus osteotomy(BSSRO) and mandibular setback were selected for this study. Group A(n=14) had the bone segments fixed with monocortical miniplate on the lateral side of the mandibular body and Group B(n=14) had three noncompressive bicortical screw inserted at the genial area through a transcutaneous approach. Cephalograms were taken preoperatively, postoperatively within 1 weeks and at a follow-up period (mean 8.9 months after surgery) and the amount of setback and postoperative change were measured. Results : Postoperative relapse between two groups was minimal in setback of the mandible. Statistical analysis showed no significant difference in postoperative relapse. Conclusion : This study suggests that both methods of skeletal fixation investigated give comparable postoperative stability and their use in mandibular setback appears to be a fairly stable clinical procedure .

• 대한치과교정학회지
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• 제53권2호
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• pp.99-105
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• 2023

Objective: The study aimed to evaluate the changes in mandibular width after sagittal split ramus osteotomy (SSRO) in patients with mandibular asymmetric prognathism using cone-beam computed tomography (CBCT). Methods: Seventy patients who underwent SSRO for mandibular setback surgery were included in two groups, symmetric (n = 35) and asymmetric (n = 35), which were divided according to the differences in their right and left setback amounts. The mandibular width was evaluated three-dimensionally using CBCT images taken immediately before surgery (T1), 3 days after surgery (T2), and 6 months after surgery (T3). Repeated measures analysis of variance was applied to verify the differences in mandibular width statistically. Results: Both groups showed a significant increase in the mandibular width at T2, followed by a significant decrease at T3. No significant difference was observed between T1 and T3 in any of the measurements. No significant differences were found between the two groups (p > 0.05). Conclusions: After mandibular asymmetric setback surgery using SSRO, the mandibular width increased immediately but returned to its original width 6 months after surgery.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제38권6호
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• pp.354-359
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• 2012

Objectives: The purpose of this study was to investigate whether the age factor would be related with stability of mandibular setback surgery for patients with mandibular prognathism. Materials and Methods: We compared the relapse patterns of 47 patients divided into three age groups (termed younger, adult, and older). The younger group consisted of patients between 15 and 17 years old; the adult group was made up of patients between 21 and 23 years old, and the older group was made up of patients more than 40 years old. The positional change of B point was evaluated at preoperative, postoperative, and follow-up states. Results: The horizontal relapse ratio was 21.7% in the younger group, 15.3% in the adult group, and 15.7% in the older group. Although relatively higher degrees of relapse were found in the younger group, this increase was not statistically significant. Spearman's correlation analysis was performed to explore other factors contributing to relapse. We subsequently found that the amount of relapse was related to horizontal setback. Conclusion: Although the degree of relapse in younger patients is not significant;y higher compared to other groups. The major contributing factor to relapse after sagittal split ramus osteotomy is amount of setback rather than age when the surgery was performed to patients over than 15 years of age.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제31권4호
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• pp.294-305
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• 2009

Purpose: This retrospective study evaluated the changes in hyoid bone and tongue positions as well as oral cavity volume after mandibular setback by BSSRO. Materials and Methods: 18 Koreans who underwent BSSRO to correct mandibular prognathism were studied. Lateral cephalograms were taken and traced preoperatively (T0), immediately (T1) and approximately 6 months postoperatively (T2). Submentovertex radiograghs were taken and traced before surgery (T0) and about 6 months after surgery (T2). The area and volume of oral cavity, the vertical and horizontal dimensions of the hyoid bone and tongue dorsum were measured. Results: Mandibular setback surgery resulted in a significant reduction of lower oral cavity volume. The hyoid bone displaced posteroinferiorly immediately after surgery, and it tended to return to its original vertical position at 6 month after mandibular setback by BSSRO. The retropalatal space around tongue was maintained and the retrolingual space around tongue was reduced immediately postoperatively. The readaptation of tongue was not evident for that the follow up period was not long enough. No significant statistical correlations between the amounts of mandibular setback and the changes of oral cavity volume were observed. Conclusion: Mandibular setback surgery resulted in a significant reduction of lower oral cavity volume, which was most likely attributable to the posterior movement of the mandible. More subjects and long-term observations should be performed to assess the changes of oropharyngeal configuration following mandibular setback surgery.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제41권5호
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• pp.224-231
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• 2015

Objectives: The purpose of this study was to evaluate changes in the pharyngeal airway space and hyoid bone position after mandibular setback surgery with bilateral sagittal split ramus osteotomy (BSSRO) and to analyze the correlation between the amount of mandibular setback and the amount of change in pharyngeal airway space or hyoid bone position. Materials and Methods: From January 2010 to February 2013, a total of 30 patients who were diagnosed with skeletal class III malocclusion and underwent the same surgery (BSSRO) and fixation method in the Division of Oral and Maxillofacial Surgery, Department of Dentistry at the Ajou University School of Medicine (Suwon, Korea) were included in this study. Lateral cephalograms of the 30 patients were assessed preoperatively (T1), immediately postoperatively (T2), and 6 months postoperatively (T3) to investigate the significance of changes by time and the correlation between the amount of mandibular setback and the amount of change in the airway space and hyoid bone position. Results: Three regions of the nasopharynx, oropharynx, and hypopharynx were measured and only the oropharynx showed a statistically significant decrease (P<0.01). A significant posterior and inferior displacement of the hyoid bone was found 6 months after surgery (P<0.01). Analysis of the correlation between the amount of mandibular setback and the amount of final change in the airway space and hyoid bone position with Pearson's correlation showed no significant correlation. Conclusion: In this study, the oropharynx significantly decreased after mandibular setback surgery, and changes in the surrounding structures were identified through posteroinferior movement of the hyoid bone during long-term follow-up. Therefore, postoperative obstructive sleep apnea should be considered in patients who plan to undergo mandibular setback surgery, and necessary modifications to the treatment plan should also be considered.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제36권5호
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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.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제33권3호
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• pp.218-224
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• 2011

Purpose: The purpose of this study is to evaluate the post-operative skeletal stability after surgical correction of patients with mandibular prognathism by bilateral sagittal split ramus osteotomy (BSSRO) and to evaluate the horizontal relapse tendency after the surgery. Methods: Twenty-six patients with Class III dental and skeletal malocclusion were selected for this retrospective study. Fifteen of them underwent BSSRO for mandibular setback and eleven of them underwent two-jaw surgery (Lefort I and BSSRO). In each patient, lateral cephalometric radiographs were taken pre-operatively, post-operatively within 1 week, and post-operatively after eight months. After tracing of the cephalometric radiographs, various parameters were measured. The analyses were done by linear measurement to evaluate the change in position of hard tissue B point, pogonion and mandibular plan angle by examination on lateral cephalograms. Results: The horizontal relapse rate was 27.1% at B point and 31.6% at pogonion in patients who underwent BSSRO. The horizontal relapse rate of the group where the amount of correction exceeded 10 mm was 25.69% at B point. Conclusion: There were no statistical differences on the magnitude of setback and direction of rotation of the mandible in mandibular stability. There were also no statistical differences between single mandibular surgery and two-jaw surgery for mandibular stability.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제27권4호
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• pp.334-345
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• 2005

The purpose of this study was to compare the postoperative stability and relapse according to 2 different fixation methods after bilateral sagittal split ramus osteotomies in mandibular prognathic patients. Tweenty one patients with Class III dental and skeletal malocclusion who were treated with bilateral sagittal split ramus osteotomy were selected for this retrospective study. We classfied the patients into two groups according to the fixation methods of bony segments after osteotomies. Group W (n = 10) had the bone segments fixed with nonrigid wire and Group S (n = 11) had bicortical screws inserted in the gonial area through a transcutaneous approach. 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. Before surgery, both groups were balanced with respect to linear and angular measurements of craniofacial morphology. Mean posterior sagittal setback amounts of the mandibular symphysis was 8.6 mm in the wire group and 6.79 mm in the rigid group, Six months postoperatively, the wire group had 33.1% relapse of the mandibular symphysis and 22.8% in the rigid group relapse. Both groups experienced changes in the orientation and configuration of the mandible. It is thought that Rigid screw fixation is a more stable method than nonrigid wire fixation for maintaining mandibular setback after sagittal split ramus osteotomy.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제39권5호
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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.