• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.22 no.1
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• pp.7-22
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• 1992

The stress distributions on a human mandible for 18 load cases under two different boundary conditions (mouth open and closed), using the three dimensional finite element modeling were studied. Also, the expected fracture loads for each load cases were calculated by using the Von-Mises yield criterion. The model of a mandible with all teeth was composed of 2402 hexahedron elements and 3698 nodes. CAD techniques were used to analyze the 3-dimensional results. The conclusions of this study were as follows: 1. In the mouth open state, the maximum stress occured at the condyle neck; when the lateral load was exerted, the maximum stress occured at the load side condyle. 2. In the mouth closed state, when the loads were exerted on the mandibular body and chin, the maximum stress occured at the loaded area, and when the loads were exerted on the angle and ramus, the maximum stress occured at the condyle neck. 3. The expected fracture loads in each load case were calculated using the Von-Mises yield criterion, and it was confirmed that the mandible in the mouth open state was more easily fractured than that in the mouth closed state, and the expected fracture loads are lesser in the cases that load direction is parallel at mandibular plane than 45°. 4. The magnitudes of the expected fracture loads increased in the order of angle, ramus, body and chin in case of the mouth closed state, while chin, body, angle and ramus in case of the mouth open state. 5. The Von-Mises stress concentration regions analyzed by F.E.M. corresponded well with the results of clinical studies.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.30 no.1
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• pp.100-107
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• 2008

First of all a good surgical access is considered among various approach methods to the cystic lesion. A poor surgical access can lead to a failure of the whole treatment. A sagittal split ramus osteotomy (SSRO) on the large cyst occurring in the mandibular ramus lets us not only reduce operation time, but can additionally contribute to a good visual field. In addition, a merit exists that it lets this operating method provide soft tissue adhesion for proximal and distal segment and decrease post operative necrosis. We experienced three cases of a large cyst on the mandibular angle and ramus. By employing a sagittal splitting of the mandible, it provided good surgical access and operation results without recurrence during a follow-up period. The surgical technique described may be helpful in treating similar large cysts.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.34 no.1
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• pp.34-40
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• 2012

Purpose: The study was performed to compare patients with anatomical variations in facial asymmetry with patients in the normal range using cone-beam computed tomography (CBCT) and to take the preoperative condition into consideration in the case of a sagittal split ramus osteotomy (SSRO). Methods: The study was conducted on 46 adult patients composed of 2 subdivided groups, an asymmetry group (n=26) and a symmetry group (n=20). The asymmetry group was divided between patients with hemimandibular hyperplasia (HH, n=8) and hemimandibular elongation (HE, n=18). Using cross-sectional computed tomography images, the thickness of cancelleous bone in the buccal area of the mandible, thickness of buccal cortex in the buccal aspect of the mandible, thickness of cancellous bone in the inferior aspect of the mandible, thickness of buccal cortex in the inferior aspect of the mandible, and cross-sectional surface area of the mandible were measured. Results: In the asymmetry group, the cross-sectional area of the mandible including the inferior alveolar nerve positioned on the affected side was significantly different from the symmetry group. Thickness of cancelleous bone in the buccal aspect of the mandible, thickness of cancelleous bone in the inferior aspect of the mandible, and cross-sectional surface area of the mandible in the affected site of hemimandibular hyperplasia was significantly smaller than in the symmetry group. Conclusion: The inferior alveolar nerve runs lower and in a more buccal direction and shows a smaller cross-sectional surface of the mandible in the hemimandibular hyperplasia patients with asymmetry.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.41 no.4
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• pp.208-212
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• 2015

Keratocystic odontogenic tumor (KCOT) is a common benign tumor of osseous lesions in dental and maxillofacial practice. We describe three cases of large KCOT located in the posterior part of the mandible extending to the angle and ramus region, which were enucleated via sagittal split osteotomy (SSO) of the mandible. There are cases in which a conventional enucleation procedure does not ensure complete excision of the entire lesion without damage to vital structures like the inferior alveolar nerve. In such cases, a SSO approach could be a better choice than conventional methods. The purpose of this article is to describe our experience using unilateral mandibular SSO for removal of a KCOT from the mandible.

• Journal of Dental Rehabilitation and Applied Science
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• v.17 no.4
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• pp.225-230
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• 2001

Morphological characteristics of the asymmetric mandible in 135 adult male patients were investigated. Panoramic X-ray images were recorded. Age, ramus height, antegonial notch height, condylar height, coronoid process height, ramus body height and condylar neck angle were calculated and measured. Statistical analysis of unpaired two-tailed t-test and correlation coefficients was performed to find the morphologic differences between short ramus height side and the other. Condylar height and ramus body height in short ramus height side were smaller than those of the other side. Antegonial notch height, coronoid process height, condylar neck angle showed no differences. Condylar neck height was correlated with condylar neck angle.

• 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.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.35 no.4
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• pp.253-256
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• 2009

Schwannoma(neurilemmoma) is a benign neoplasm that originates from the Schwann cells. Schwannoma most commonly arises in the soft tissue of the head and neck. Intraoral lesions are uncommon, however, and intraosseous schwannoma are even rare. The most common site of occurrence for these unusual lesions is the mandible. This article documents a case of an intraosseous schwannoma located in the mandibular ascending ramus. The lesion was surgically removed and no radiographic evidence of recurrence was observed after 1 year.

• 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.18 no.2
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• pp.200-207
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• 1996

In patients with unilateral condylar hyperplasia, increased length of the condylar neck causes deviation of the mandible to the opposite site, resulting in facial asymmetry, but the arch form and general contour of the displaced mandible is approximately symmetric. So, the unilateral condylectomy have been prefered surgical method among the surgeons. The purpose of this study is to analyze the postoperative results comparatively following two different surgical methods, condylectomy and ramus surgery, in unilateral condylar hyperplasia. Case of 6 patients with the unilateral condylar hyerplasia were analyzed in this study, 3 case of the condylectomy only, 3 cases of the ramus surgery, Clinical and radiographic evaluations were tried for comparison. In conclusion, comparative results between two groups did not show any significant difference, but we confirmed that unilateral condylectomy could be a excellent surgical methods in unilateral condylar hyperplasia thinking over the unique morphological characteristics of it.

• 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.