• Journal of Periodontal and Implant Science
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• v.46 no.2
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• pp.96-106
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• 2016

Purpose: Stress distribution and mandible distortion during lateral movements are known to be closely linked to bruxism, dental implant placement, and temporomandibular joint disorder. The present study was performed to determine stress distribution and distortion patterns of the mandible during lateral movements in Class I, II, and III relationships. Methods: Five Korean volunteers (one normal, two Class II, and two Class III occlusion cases) were selected. Finite element (FE) modeling was performed using information from cone-beam computed tomographic (CBCT) scans of the subjects' skulls, scanned images of dental casts, and incisor movement captured by an optical motion-capture system. Results: In the Class I and II cases, maximum stress load occurred at the condyle of the balancing side, but, in the Class III cases, the maximum stress was loaded on the condyle of the working side. Maximum distortion was observed on the menton at the midline in every case, regardless of loading force. The distortion was greatest in Class III cases and smallest in Class II cases. Conclusions: The stress distribution along and accompanying distortion of a mandible seems to be affected by the anteroposterior position of the mandible. Additionally, 3-D modeling of the craniofacial skeleton using CBCT and an optical laser scanner and reproduction of mandibular movement by way of the optical motion-capture technique used in this study are reliable techniques for investigating the masticatory system.

• 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.

• The korean journal of orthodontics
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• v.24 no.2
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• pp.349-366
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• 1994

The method of treatment in skeletal Class III malocclusion must be chosen according to an etiology and timing of the treatment. Maxillry protraction has been used as an effective treatment method in growing children with maxillary deficiency. The efficacy of maxillary protraction has been viewed as a result of downward-backward displacement of mandible and compensatory dental displacement during the treatment rather than forward -downward growth of maxilla itself. In this study, 104 subjects treated with maxllary protraction, and 19 males and 21 females with known annual growth amount have been chosen longitudinally as treated group and normal group, respectively. And changes in position of maxilla, mandible and dentition have been comparatively analyzed on the lateral cephalometric radiographs by age. The results were as follows : 1. Treated group showed more forward movement of maxilla compare to the normal group and the mandible displaced backward compare to the normal group. 2. Downward movement of maxilla in treated group was similar to that of normal group with statistical signigicance in female 12 year old group and downward movement of mandible in treated group was similar to that of normal group. 3. In treated group, maxillary central incisor moved more forward than the normal group with statistical significance in male 8, 10 year-old groups and female 8, 9, 10 year-old groups. In treated group, downward movement of maxillary central incisor was similar to that of the normal group with statistical significance in male and female 7,8 year-old groups. Considering the above results and the duration of the treatment, the forward movement of maxilla due to maxillary protraction was effective compared to normal growth amount of the normal group.

• The korean journal of orthodontics
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• v.18 no.1 s.25
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• pp.141-154
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• 1988

This study was designed to investigate the difference between craniofacial characteristics of the normal occlusion and those of Class II Div. 1 malocclusion. The sample was divided into 2 groups, the 50 subjects of Normal occlusion, the 50 subjects of Class II Div. 1 malocclusion in both sexes. Both groups aged from 11 to 14 years. The results of this study were as follows; 1. No significant difference was observed in cranial base shape between both groups, but anterior cranial base size of Class II Div. 1 malocclusion group was larger than that of normal group. 2. No significant difference in antero-posterior position of Maxilla to cranial base was founded between both groups. 3. No difference in Mandibular shapes and Mandibular plane angles to the cranial base was observed between Class II Div. 1 malocclusion and normal occlusion, but Mandibular position in Class II Div. 1 malocclusion was posterior to that of normal group. 4. Antero-posterior relationship of Maxilla and Mandible was significant difference between both groups, but vertical relationship of those was no difference. 5. Maxillary incisor position to cranial base of Class II Div. 1 malocclusion was anteior to normal occlusion, and Maxillary posterior teeth was posterior. Mandibular incisor and mandibular posterior teeth position was no difference. 6. Upper and lower lip position to esthetic line of Class II Div. 1 malocclusion was anterior to normal occlusion.

• Journal of Oral Medicine and Pain
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• v.37 no.4
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• pp.205-211
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• 2012

A 35 year-old female presented with the complaint of sudden occurrence of bite change and concurrent opening limitation, as well as pain in the right temporomandibular joint (TMJ) during mouth opening. From her history it was revealed that she had simple clicking of right TMJ for several years before onset of these symptoms, and that the clicking sound subsided recently after development of opening limitation. On clinical examination, anterior open bite, midline shift of the mandible to right, and premature contacts on left posterior teeth were observed. Maximum mouth opening and lateral movement to left were also restricted. On magnetic resonance images, the right TMJ showed anterior disc displacement without reduction and the posterior joint space is greatly collapsed by retrusion of the condyle. It was thought that the sudden occurrence of occlusal change would be resulted from abrupt displacement of the mandible associated with development of the anterior disc displacement without reduction. The stabilization appliance traction therapy was performed initially for first 3 months along with physical and pharmacologic therapy. However, the anterior open bite and opening limitation didn't resolve and the position of mandible still remained altered. So the stabilization appliance was changed to intermaxillary traction device. Then the mandible returned progressively to normal position and the occlusion became more stable and comfortable. After 5 months of intermaxillary traction therapy, the anterior open bite was dissolved completely and the occlusion became stabilized satisfactorily along with recovery of normal mouth opening range. On post-treatment magnetic resonance image, remodeling of condylar head was observed.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.26 no.5
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• pp.446-454
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• 2000

Condylar process of mandible is an important and fuctionally versatile part of the mandible. There were quite large amount of investigations on the functional and anatomical adaptation of the temporomandibular joint(TMJ) to the surrounding tissues. But controversies on the mechanism of functional adaptation of the joint still exist. In this research, we investigated changes in the TMJ by the lateral deviation of the maxillary incisor to shift the mandible right, and bone the undecalcified microscopic sections with fluorescent microscope and von Kossa staining with bright field microscope. Results were as follows: 1. Lateral deviation rendered shifting and tilting of the mandible, There were, compressions in the right joint and opening of the left joint space at early stage. At the same time, both condyles shifted slightly to anterior. 2. After $2{\sim}4$ weeks, left condyle showed anterior displacement and compressions in the joint space. Right condyle showed only slight shift to the anterior. 3. Regardless of the direction of the lateral shift, anterior bite plate compressed both condyle heads until 2 weeks. 4. There are bone resorptions in the anterior aspect of the condyle head and apposition of posterior border. Bone remodeling were observed between 3 and 4 weeks. 5. After 8 weeks of the experiment, there were little differences in condylar morphology between experimental and control group, though slight shifting and compression were still present in the experimental group. Lateral deviation of mandible evoked active remodeling of the TMJ until functional and anatomical reconstruction of TMJ position was achieved.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.39
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• pp.16.1-16.6
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• 2017

Background: Mandibular reconstruction is performed after segmental mandibulectomy, and precise repositioning of the condylar head in the temporomandibular fossa is essential for maintaining preoperative occlusion. Methods: In cases without involvement of soft tissue around the mandibular bone, the autopolymer resin in a soft state is pressed against the lower border of the mandible and buccal and lingual sides of the 3D model on the excised side. After hardening, it is shaved with a carbide bar to make the proximal and distal parts parallel to the resected surface in order to determine the direction of mandibular resection. On the other hand, in cases that require resection of soft tissue around the mandible such as cases of a malignant tumor, right and left mandibular rami of the 3D model are connected with the autopolymer resin to keep the preoperative position between proximal and distal segments before surgical simulation. The device is made to fit the lower border of the anterior mandible and the posterior border of the mandibular ramus. The device has a U-shaped handle so that adaptation of the device will not interfere with the soft tissue to be removed and has holes to be fixed on the mandible with screws. Results: We successfully performed the planned accurate segmental mandibulectomy and the precise repositioning of the condylar head by the device. Conclusions: The present technique and device that we developed proved to be simple and useful for restoring the preoperative condylar head positioning in the temporomandibular fossa and the precise resection of the mandible.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.34 no.2
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• pp.166-179
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• 2008

Excessive concentration of stress which is occurred in occlusion around the implant in case of the implant supported fixed partial denture has been known to be the main cause of the crestal bone destruction. Therefore, it is essential to evaluate the stress analysis on supporting tissue to get higher success rates of implant. The purpose of this study was to evaluate the effects of stress distribution and deformation in 3 different types of three-unit fixed partial denture sup-ported by two implants, using a three dimensional finite element analysis in a three dimensional model of a whole mandible. A mechanical model of an edentulous mandible was generated from 3D scan, assuming two implants were placed in the left premolars area. According to the position of pontic, the experiments groups were divided into three types. Type I had a pontic in the middle position between two implants, type II in the anterior posi-tion, and type III in the posterior position. A 100-N axial load was applied to sites such as the central fossa of anterior and posterior implant abutment, central fossa of pontic, the connector of pontic or the connector between two implants, the mandibular boundary conditions were modeled considering the real geometry of its four-masticatory muscular supporting system. The results obtained from this study were as follows; 1. The mandible deformed in a way that the condyles converged medially in all types under muscular actions. In comparison with types, the deformations in the type II and type III were greater by 2-2.5 times than in the type I regardless of the loading location. 2. The values of von Mises stresses in cortical and cancellous bone were relatively stable in all types, but slightly increased as the loading position was changed more posteriorly. 3. In comparison with type I, the values of von Mises stress in the implant increased by 73% in Type II and by 77% in Type III when the load was applied anterior and posterior respectively, but when the load was applied to the middle, the values were similar in all types. 4. When the load was applied to the centric fossa of pontic, the values of von Mises stress were nearly $30{\sim}35%$ higher in the type III than type I or II in the cortical and cancellous bone. Also, in the implant, the values of von Mises stress of the type II or III were $160{\sim}170%$ higher than in the type I. 5. When the load was applied to the centric fossa of implant abutment, the values of von Mises stress in the cortical and cancellous bone were relatively $20{\sim}25%$ higher in the type III than in the other types, but in the implant they were 40-45% higher in the type I or II than in the type III. According to the results of this study, musculature modeling is important to the finite element analysis for stress distribution and deformation as the muscular action causes stress concentration. And the type I model is the most stable from a view of biomechanics. Type II is also a clinically accept-able design when the implant is stiff sufficiently and mandibular deformation is considered. Considering the high values of von Mises stress in the cortical bone, type III is not thought as an useful design.

• The korean journal of orthodontics
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• v.30 no.4 s.81
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• pp.399-411
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• 2000

This study was designed to evaluate the correlations between the morphology and growth of cranial base and the position of nasomaxillary complex and mandible in complete unilateral cleft lip and palate patients. Craniofacial skeletal morphology Pattern was analyzed on the lateral cephalometric radiographs of the 100 subjects of complete unilateral cleft lip and palate group and the 100 normal grower group and each group was divided three sub-groups by age-range like spheno-ethmoidal synchodrosis growing group, spheno-occipital synchondrosis growing group and finished synchondrosis growth group. These data were statistically analyzed to examine significant difference between both groups and between each sub-groups. The results of this study were as follows: 1. In complete unilateral cleft group, the length, thickness of clivus, and the rate of increase in length of clivus showed smaller amount by adolescence. The anterior length of cranial base and the rotation pattern of clivus with age showed no significant difference between two group. 2. In complete unilateral cleft group, nasomaxillary complex were located more posteriorly. This difference between two groups is larger by adolescent group than adult. Vertical position showed no significant difference between two groups. There was significant correlation between the cranial base of cleft group and the horizontal measurements(p<0.01). PtmS showed no significant increment in cleft group. This showed the deficiency of growth in posterior part of maxilla. 3. In mandible, there was no significant difference between normal group and complete unilateral cleft group but articular angle showed significantly smaller in cleft group than in normal one. And the measurements of nasomaxillary complex position, cranial base and the position of mandible had significant correlation(p<0.01).

• The Journal of the Korean dental association
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• v.18 no.3 s.132
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• pp.197-200
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• 1980

This study was undertaken to investigate the form and position of the mandible of upper prognathism in relation to craniofacial complex. The subjects consist of 20 males and 39 females with Class II, Division 1 malocclusion and measurements were achieved on lateral cephalograms. The results were a follows. 1. Infradentale was situated anteriorly to orbital plane, but point B, pogonion and menton were situated posteriorly. 2. Development of chin point area of female was poor than that of male. 3. In case of facial angle was large, ramus angle tend to be small, but gonial angle had tendency to be large.