• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.21 no.2
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• pp.235-248
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• 1991

This study was designed to evaluate the diagnostic effect of the simulatneous multifilm individualized lateral tomography in the diagnosis of the temporomandibular disorders. The subjects consisted of 29 patients with symptoms of the temporomandibular disorders. The panoramic view, oblique lateral transcranial radiograph (OLTC) (Hirozontal angulation 0°, Vertical angulation 29°), submentovertex view, and simultaneous multifilm individualized lateral tomographs (SMFI) in centric occlusion (2.5㎜ thickness difference, 5 layers) were taken for the patients. This study compared the findings from each radiographs in the determining of mandibular condylar position with dual linear measurement of the subjective closest posterior and subjective closest anterior interarticular space and in the determining of bony changes on the studied 30 temporomandibular joints (TMJ) with symptoms of the temporomandibular disorders. The results were as follows: 1. The distribution of condylar position of OLTC and 5 layers of SMFI depended on the radiographs (p<0.05). The condylar position and the distribution of condylar position of OLTC were more similar to lateral sections of the SMFI than mesial sections, and in the distribution of the condylar position of SMFI, the more lateral sections of SMFI, the more concentric 2. positions. There were 10 cases in which all layers showed the same condylar position as that of OLTC. There were 3 cases in which no layers showed the same condylar position as that of OLTC. 3. In the SMFI of 30 Temporomandibular joints studied, there is 13 cases in which all five layers represented the same condylar position in the same TMJ and 11 cases in which 4 layers represented the same condylar position in the same TMJ and 6 cases in which 3 layers represented the same condylar position in the same TMJ. So at least 3 layers of SMFI represented same condylar position in the same TMJ. 4. The bony changes were not detected in conventional radiographs on the temporomandibular joint and the bony changes were not detected in simultaneous multifilm individualized lateral tomographs. The bony changes were detected in conventional radiographs on the temporomandibular joint and the bony changes were detected in simultaneous multifilm individualized lateral tomographs. SMFI provided a meams for a three dimensional visualization of the shape, the position and the extent of bony changes of TMJ.

• Archives of Craniofacial Surgery
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• v.17 no.1
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• pp.9-13
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• 2016

Background: Position of the facial foramina is important for regional block and for various maxillofacial surgical procedures. In this study, we report on anthropometry and morphology of these foramina using three-dimensional computed tomography (3D-CT) data. Methods: A retrospective review was performed for all patients who have undergone 3D-CT scan of the facial skeleton for reasons other than fracture or deformity of the facial skeleton. Anthropometry of the supraorbital, infraorbital, and mental foramina (SOF, IOF, MF) were described in relation to facial midline, inferior orbital margin, and inferior mandibular margin (FM, IOM, IMM). This data was analyzed according to sex and age. Additionally, infraorbital and mental foramen were classified into 5 positions based on the anatomic relationships to the nearest perpendicular dentition. Results: The review identified 137 patients meeting study criteria. Supraorbital foramina was more often in the shape of a foramen (62%) than that of a notch (38%). The supraorbital, infraorbital, and mental foramina were located 33.7 mm, 37.1 mm, and 33.7 mm away from the midline. The mean vertical distance between IOF and IOM was 13.4 mm. The mean distance between MF and IMM was 21.0 mm. The IOF and MF most commonly coincided with upper and lower second premolar dentition, respectively. Between the sex, the distance between MF and IMM was significantly higher for males than for female. In a correlation analysis, SOF-FM, IOF-FM and MF-FM values were significantly increased with age, but IOF-IOM values were significantly decreased with age. Conclusion: In the current study, we have reported anthropometric data concerning facial foramina in the Korean population, using a large-scale data analysis of three-dimensional computed tomography of facial skeletons. The correlations made respect to patient sex and age will provide help to operating surgeons when considering nerve blocks and periosteal dissections around the facial foramina.

• Journal of Dental Rehabilitation and Applied Science
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• v.19 no.4
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• pp.257-268
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• 2003

The purpose of this study was to assess the loading distributing characteristics of implant prosthesis according to position and direction of load, under vertical and inclined loading using FEA analysis. The finite element model was designed according to standard fixture (4.1mm restorative component x 11.5mm length). The crown for mandibular first molar was made using UCLA abutment. Each three-dimensional finite element model was created with the physical properties of the implant and surrounding bone. This study simulated loads of 200N at the central fossa in a vertical direction (loading condition A), 200N at the outside point of the central fossa with resin filling into screw hole in a vertical direction (loading condition B), 200N at the centric usp in a $15^{\circ}$ inward oblique direction (loading condition C), 200N at the in a $30^{\circ}$ inward oblique direction (loading condition D) or 200N at the centric cusp in a $30^{\circ}$ outward oblique direction (loading condition E) individually. Von Mises stresses were recorded and compared in the supporting bone, fixture, and abutment screw. The following results have been made based on this study: 1. Stresses were concentrated mainly at the ridge crest around implant in both vertical and oblique loading but stresses in the cancellous bone were low in both vertical and oblique loading. 2. Bending moments resulting from non-axial loading of dental implants caused stress concentrations on cortical bone. The magnitude of the stress was greater with the oblique loading than with the vertical loading. 3. An offset of the vertical occlusal force in the buccolingual direction relative to the implant axis gave rise to increased bending of the implant. 4. The relative positions of the resultant line of force from occlusal contact and the center of rotation seems to be more important. 5. The magnitude of the stress in the supporting bone, fixture and abutment screw was greater with the outward oblique loading than with the inward oblique loading and was the greatest under loading at the centric cusp in a $30^{\circ}$ outward oblique direction. Conclusively, this study provides evidence that bending moments resulting from non-axial loading of dental implants caused stress concentrations on cortical bone. But it seems to be more important that how long is the distance from center of rotation of the implant itself to the resultant line of force from occlusal contact(leverage). The goal of improving implants should be to avoid bending of the implant.

• Journal of Dental Rehabilitation and Applied Science
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• v.21 no.1
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• pp.1-14
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• 2005

The purpose of this study was to assess the loading distributing characteristics of implant prosthesis of internal connection system(ITI system) according to position and direction of load, under vertical and inclined loading using finite element analysis (FEA). The finite element model of a synOcta implant and a solid abutment with $8^{\circ}$ internal conical joint used by the ITI implant was constructed. The gold crown for mandibular first molar was made on solid abutment. Each three-dimensional finite element model was created with the physical properties of the implant and surrounding bone. This study simulated loads of 200N at the central fossa in a vertical direction (loading condition A), 200N at the outside point of the central fossa with resin filling into screw hole in a vertical direction (loading condition B), 200N at the centric cusp in a $15^{\circ}$ inward oblique direction (loading condition C), 200N at the in a $30^{\circ}$ inward oblique direction (loading condition D) or 200N at the centric cusp in a $30^{\circ}$ outward oblique direction (loading condition E) individually. Von Mises stresses were recorded and compared in the supporting bone, fixture, and abutment. The following results have been made based on this study: 1. Stresses were concentrated mainly at the ridge crest around implant under both vertical and oblique loading but stresses in the cancellous bone were low under both vertical and oblique loading. 2. Bending moments resulting from non-axial loading of dental implants caused stress concentrations on cortical bone. The magnitude of the stress was greater with the oblique loading than with the vertical loading. 3. An offset of the vertical occlusal force in the buccolingual direction relative to the implant axis gave rise to increased bending of the implant. So, the relative positions of the resultant line of force from occlusal contact and the center of rotation seems to be more important. 4. In this internal conical joint, vertical and oblique loads were resisted mainly by the implant-abutment joint at the screw level and by the implant collar. Conclusively, It seems to be more important that how long the distance is from center of rotation of the implant itself to the resultant line of force from occlusal contact (leverage). In a morse taper implant, vertical and oblique loads are resisted mainly by the implant-abutment joint at the screw level and by the implant collar. This type of implant-abutment connection can also distribute forces deeper within the implant and shield the retention screw from excessive loading. Lateral forces are transmitted directly to the walls of the implant and the implant abutment mating bevels, providing greater resistance to interface opening.

• The Journal of Korean Academy of Prosthodontics
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• v.56 no.3
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• pp.218-226
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• 2018

In partial edentulous patients, implant-assisted removable partial denture which provide additional retention and support by placing a small number of implants in strategic positions might be suitable treatment. This case of patient with loss of maxillary posterior teeth and moderate to severe wear of residual dentition, three implants were placed in the maxillary anterior edentulous area and then surveyed bridges were made including remaining anterior natural teeth. Posterior edentulous area was restored with distal extension removable partial denture (RPD). In addition, the worn mandibular natural teeth were restored with fixed prostheses. As a result, reduced vertical dimension and collapsed occlusal plane were rehabilitated, and improved functionally and aesthetically. The purpose of this case was to report the results of three-year follow-up of full mouth rehabilitation with anterior implant surveyed bridges and distal extension RPD.

• Journal of Oral Medicine and Pain
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• v.34 no.4
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• pp.421-427
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• 2009

Oromandibular dystonia is a focal neurological movement disorder characterized by involuntary sustained and often painful muscle contraction, usually producing repetitive movements or abnormal positions of the mouth, jaw and.or tongue. Patients suffering from oromandibular dystonia often experience difficulties in chewing, swallowing and speaking, resulting from the impairment of mandibular movements. At present there is no etiologic treatment for oromandibular dystonia, because the pathophysiology of primary and focal dystonia is still incompletely understood. Many treatments such as medication, behavioral therapy, surgery are suggested to decrease the involuntary movements. But these success rates are relatively low and they have a lot of complications. many studies suggested that chemodenervation with botulinum toxin is the most effective treatment for oromandibular dystonia. We reported the 2 cases which were treated oromandibular dystonia with botulinum toxin and reviewed the orofacial movement disorders(especially oromandibular dystonia) and botulinum toxin treatment for oromanfibular dystonia.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.25 no.2
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• pp.319-330
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• 1995

This study was designed to evaluate the interrelationship between the condylar head position in transcranial view and the articular disc position in the arthrography. The condylar positions were assessed by subjective method and linear measurement method on the transcranial view. The subjects for this study consisted of 24 symptomatic joints with normal disc position, 37 joints with anterior disc displacement with reduction and 44 joints with anterior disc displacement without reduction that were classified by arthrotomography under the fluoroscopic guidance. The interrelationship between the condylar head position in transcranial view and the articular disc position in the arthrography was evaluated by Chi square test. The obtained results were as follows : 1. There was no significant interrelationship between the position of condylar head in closed mouth state on transcraniaJ view and articular disc position in the arthrography (p>0.05). 2. There was no significant interrelationship between the changes of interarticular distance in 1 inch opening state and articular disc position in the arthrography (p>0.05). 3. There was no significant interrelationship between the position of condylar head related to the apex of articular eminence in 1 inch opening state and articular disc position in the arthrography(p>0.05). 4. There was significant interrelationship between the changes of interarticular distance that is assessed by linear measurement method in maximum opening state and articular disc position in the arthrography(p<0.05), but there was no significant interrelationship when the condylar head position was assessed by subjective method(p>0.05). 5. There was significant interrelationship between the degree of condylar translation in maximum opening state and articular disc position in the arthrography(p<0.05). 6. The correlation coefficient between two methods to assess the position of condylar head were 0.7989: the condylar head position in articular fossa in closed state, 0.6847: interarticular space in 1 inch opening state, 0.8965: the degree of condylar translation in 1 inch opening state, 0.5944: the changes of interarticular space in maximum opening state, 0.9215: the degree of condylar translation in maximum opening state.

• Imaging Science in Dentistry
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• v.39 no.3
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• pp.149-156
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• 2009

Purpose : The purpose of this study was to develop a stent-based image guided surgery system and to apply it to oral and maxillofacial surgeries for anatomically complex sites. Materials and Methods : We devised a patient-specific stent for patient-to-image registration and navigation. Three-dimensional positions of the reference probe and the tool probe were tracked by an optical camera system and the relative position of the handpiece drill tip to the reference probe was monitored continuously on the monitor of a PC. Using 8 landmarks for measuring accuracy, the spatial discrepancy between CT image coordinate and physical coordinate was calculated for testing the normality. Results : The accuracy over 8 anatomical landmarks showed an overall mean of $0.56{\pm}0.16\;mm$. The developed system was applied to a surgery for a vertical alveolar bone augmentation in right mandibular posterior area and possible interior alveolar nerve injury case of an impacted third molar. The developed system provided continuous monitoring of invisible anatomical structures during operation and 3D information for operation sites. The clinical challenge showed sufficient accuracy and availability of anatomically complex operation sites. Conclusion : The developed system showed sufficient accuracy and availability in oral and maxillofacial surgeries for anatomically complex sites.

• The korean journal of orthodontics
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• v.52 no.2
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• pp.150-160
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• 2022

Objective: To provide reliable prediction models based on dentoskeletal and soft tissue variables for customizing maxillary incisor positions and to optimize digitalized orthodontic treatment planning. Methods: This study included 244 Chinese women (age, 18-40 years old) with esthetic profiles after orthodontic treatment with fixed appliances (133 in group I: 1° ≤ The angle between the nasion [N]-A point [A] plane and the N-B point [B] plane [ANB] ≤ 4°; 111 in group II: 4° < ANB ≤ 7°). Dental, skeletal, and soft tissue measurements were performed on lateral cephalograms of the participants. Correlation and multiple linear regression analyses were used to determine the influence of dentoskeletal and soft tissue variables on maxillary incisor position. Results: The ideal anteroposterior position of the maxillary incisor varied between sagittal skeletal patterns. The position of the maxillary incisor correlated with the sagittal discrepancy between the maxilla and the mandible (ANB), protrusion of the midface, nasal tip projection, development of the chin, and inclination of both the maxillary and mandibular incisors. Distance from the maxillary central incisor to nasion-pogonion plane predicted using multiple linear regression analysis was accurate and could be a practical measurement in orthodontic treatment planning. Conclusions: Instead of using an average value or norm, orthodontists should customize a patient's ideal maxillary incisor position using dentoskeletal and soft tissue evaluations.

• The Journal of Korean Academy of Prosthodontics
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• v.61 no.4
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• pp.284-292
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• 2023

Stable posterior occlusal support is crucial for adequate masticatory function and facial aesthetics. In elderly patients over the age of 65, masticatory ability has a significant impact on nutritional intake and overall health. This case report presents a prosthetic treatment of an elderly patient with edentulous maxilla and bilateral posterior edentulous mandible. The upper jaw was restored with a complete denture to establish an ideal occlusal plane, and the three-dimensional positions of the mandibular implants were determined accordingly. The implants were placed through computer-guided implant surgery and were immediately loaded with fixed provisional restorations. The implant-fixed zirconia final restorations were inserted in the lower posterior region, and the occlusal surface of posterior artificial teeth in the upper denture was substituted with cobalt-chrome alloy to resist occlusal wear. The patient's posterior occlusal support and masticatory function were promptly restored through this treatment process, and long-term stability against wear was also obtained.