• Journal of Dental Rehabilitation and Applied Science
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• v.25 no.2
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• pp.171-181
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• 2009

The objective of this study was to analyse stress distribution of maxillary complex by use of face mask. The construction of the three-dimensional FEM model was based on the computed tomography(CT) scans of 13.5 years-old male subject. The CT image were digitized and converted to the finite element model by using the mimics program, with PATRAN. An anteriorly directed force of 500g was applied at the first premolar 45 degrees downwards to the FH plane and at the first molar 20 degrees downwards to the FH plane. When 45 degrees force was applied at maxillary first premolar, there were observed expansion at molar part and constriction at premolar part. The largest displacement was 0.00011mm in the x-axis. In the y-axis, anterior displacement observed generally 0.00030mm at maximum. In the z-axis, maxillary complex was displaced 0.00036 mm forward and downward. When 20 degrees force was applied at maxilla first molar, there were observed expansion at lateral nasal wall and constriction at molar part. The largest displacement was 0.001mm in the X-axis. In the Y-axis, anterior displacement observed generally 0.004mm at maximum. In the Z-axis, ANS was displaced upward and pterygoid complex was displaced downward. The largest displacement was 0.002mm.

• The korean journal of orthodontics
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• v.25 no.5 s.52
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• pp.543-555
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• 1995

In the orthopedic therapy, the biomechanical analysis of the appliance is necessary to get a desirable orthopedic effect. The purpose of this study was to investigate the desirable direction and application position of the protraction force. The protraction force of 500g was applied to the first premolar or to the first molar. The direction of force application was paralell or $20^{\circ}$ downward to the occlusal plane respectively. The stress distribution and the displacement within the maxilla was analyzed by a 3-dimensional finite element method. The findings obtained were as follows 1. Protraction forces caused a counterclockwise rotation of the maxilla. 2. The degree of maxillary rotation was less when the force was applied $20^{\circ}$ downward direction to the occlusal plane than when applied to the parallel direction. 3. The degree of rotation of maxilla was greater when the parallel force was applied to the 1st premolar than when applied to the first molar, whereas it was greater when force is applied $20^{\circ}$ downward than at the first premolar. In conclusion, the $20^{\circ}$ downward protraction from the first premolar induced the least counterclockwise rotation of the maxilla and was thought as the desirable direction and application position of the protraction force.

• Journal of Dental Rehabilitation and Applied Science
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• v.35 no.4
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• pp.260-269
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• 2019

The prolonged neglect of the posterior teeth missing area may cause mesial drift, extrusion, unexpected movement of the adjacent teeth and alveolar bone loss with occlusion collapse. Therefore it is recommended to treat that area by the prosthesis as soon as possible after tooth missing. However, if orthodontic treatment is applied to move the remained teeth, it can create improved biomechanical dentoalveolar environment. The use of the third molars in teeth missing area provides advantages as optimizing of prosthesis size. However, crown shape, location, soundness of the third molar and possible of eruption failure should be considered. In this case report, two patients closed a second teeth missing site and reduced the size of the first and second teeth missing area for an implant by protraction of impacted third molars. This case reports the considerations for closing or reducing the posterior teeth space with protracting the third molars by comparing two patients.

• The korean journal of orthodontics
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• v.36 no.6
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• pp.412-421
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• 2006

Objective: The result of finite element analysis depends on material properties, structural expression, density of element, and boundar or loading conditions. To represent proper elastic behavior, a finite element model was made using Hounsfield unit (HU) values in CT images. Methods: A 13 year 6 month old male was used as the subject. A 3 dimensional visualizing program, Mimics, was used to build a 3D object from the DICOM file which was acquired from the CT images. Model 1 was established by giving 24 material properties according to HU. Model 2 was constructed by the conventional method which provides 2 material properties. Protraction force of 500g was applied at a 45 degree downward angle from Frankfort horizontal (FH) plane. Results: Model 1 showed a more flexible response on the first premolar region which had more forward and downward movement of the maxillary anterior segment. Maxilla was bent on the sagittal plane and frontal plane. Model 2 revealed less movement in all directions. It moved downward on the anterior part and upward on the posterior part, which is clockwise rotation of the maxilla. Conclusion: These results signify that different outcomes of finite element analysis can occur according to the given material properties and it is recommended to use HU values for more accurate results.

• The korean journal of orthodontics
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• v.29 no.5 s.76
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• pp.521-534
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• 1999

The purpose of this study was to find the difference of stress distribution on canine altered by the application point of preangulated T-loop spring. For this study, the finite element models of upper left canine, upper left second premolar and upper left first molar were made. Also, the finite element models of $0.017{\times}0.025$ inch preangulated, preactivated T-loop spring and $0.018{\times}0.025$ inch stainless steel wire were made. Three types of T-loop spring were made . the middle of activated T-loop is positioned in accordance with the middle position of distance of bracket position of both the canine and first molar, 2mm anterior, 2mm posterior. We compared the forces and the distribution of stress that were generated by the difference of position of T-loop spring. The results were as follows. 1. All of the 3 types of T-loop spring showed the similar retraction forces. 2. All showed the similar amount & pattern of stress distribution. 3. The centers of rotation of canine in 3 types of T-loop spring were same and were positioned between C and D plane. 4. The canine showed the intrusive force by 2mm anterior positioned T-loop spring, but the extrusive force by 2mm posterior positioned T-loop suing. Neverthless, because of the small amount of the forces, the effect of vertical force was not significant.

• The korean journal of orthodontics
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• v.34 no.1 s.102
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• pp.33-45
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• 2004

The purpose of this experimental study was to determine appropriate magnitude of the Gable bends to produce maximum retraction of the anterior teeth. The Calorific Machine was used to illustrate the tooth movement in three dimension. The experimental teeth except the first premolar were embedded in the artificial alveolar bone part. In a series of experiments, the extraction space was closed using arch wires with bull loops into which the gable bends of $10^{\circ},\;20^{\circ},\;30^{\circ}$ degrees were incorporated. The experiments were repeated three times for each degree of the gable bend. Before and after the space closure, radiographs were taken in the sagittal and occlusal directions using occlusal films. Analysis of variance and Scheffe post hoc test were used to determine significant differences among the three groups. The following results were obtained. 1. As magnitudes of the gable bends increased, more bodily anterior tooth movement was seen and the distance of retraction also increased. 2. As magnitudes of the gable bends increase, the amount of posterior tooth protraction decreased while intrusive and buccal movement increased. 3. The arch was coordinated by distal-in rotation of the canine and mesial-in rotation of the second premolar adjacent to the extraction space.

• The korean journal of orthodontics
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• v.31 no.1 s.84
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• pp.1-13
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• 2001

The extraction lot orthodontic treatment can be adopted for aligning crowded dentition, improving facial esthetics and solving a skeletal discrepancy as alternative for a surgical option. Mandibular second premolar extraction was often selected as treatment plan when there we very little or no space shortage in lower arch or limited retraction of the lower incisors was required. The primary object of this study was evaluate a pretreatment condition and examine the amount of tooth movement ior a mandibular second premolar extraction in growing patients. Pretreatment and posttreatment lateral cephalograms of 14 cases that had their four first premolar extracted (4/4 group), 15 cases with upper first and lower second premolar extraction (4/5 group) were selected. Structural method superimposition was conducted to evaluate a difference of dental change between 4/4 and 4/5 group. The results were as follows, 1. Pretreatment factor for 4/4 extraction or 4/5 extraction choice included maxillary incisor axis to occlusal plane, Class II molar relationship, IMPA and interincisal angle. 2. The amount of molar anterior movement in 4/5 group was greater than that of 4/4 group(p<0.05). 3. There was no significant difference between 4/4 group and 4/5 group in aspects of maxillary tooth movement(p<0.05).

• The korean journal of orthodontics
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• v.28 no.4 s.69
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• pp.563-580
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• 1998

This study was designed to analysis the displacement and stress distribution of individual tooth by orthodontic force during distal on masse movement of the maxillary dentition. In this study, three dimensional finite element analysis was used. Author made the finite element model of maxillary teeth, periodontal ligament, alveolar bone and bracket with anatomic and physiologic characteristics on computer. Author analysed and evaluated the displacement and stress distribution of individual tooth when extraoral force, Class II intermaxillary elastics, ideal arch wire, MEAW and tip back bend were used for distal on masse movement of the maxillary dentition. These analyses were also applied in the case of the maxillary second molar were not extracted. Author compared the results of the cases which maxillary second molar were extracted or not. The results were expressed quantitatively and visually. Author obtained following results, 1. When anterior headgear was applied, the posterior translation, posterior tipping, and vertical displacement of teeth were produced more in the anterior segment of the dentition. 2. When Class II intermaxillary elastics were applied in the ideal arch wire, the teeth displacement were usually produced in the anterior segment. But when tip back bend were added in the ideal arch wire, the orthodontic force produced by elastics were transmitted to the posterior segment. As increasing the tip back bend, posterior translation and lingual tipping of anterior teeth were decreased, posterior translation and tipping displacement of posterior teeth were increased, and extrusion of anterior teeth by Class II elastics were decreased 3. When MDAW and Class II elastics were applied, the teeth movement were sir flu with the case of ideal arch wire and Class II elastics, but more small and uniform teeth displacement were produced Compared with the ideal arch wire, posterior tipping of the posterior segment were more produced than lingual tipping displacement of the anterior segment. 4. When the maxillary second molar without orthodontic appliance existed, the displacement of maxillary first molar were decreased.

• The korean journal of orthodontics
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• v.37 no.2 s.121
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• pp.98-113
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• 2007

Objective: The purpose of this study was to evaluate the displacement pattern and the stress distribution shown on a finite element model 3-D visualization of a dry human skull using CT during the retraction of upper anterior teeth. Methods: Experimental groups were differentiated into 8 groups according to corticotomy, anchorage (buccal: mini implant between the maxillary second premolar and first molar and second premolar reinforced with a mini Implant, palatal: mini implant between the maxillary first molar and second molar and mini implant on the midpalatal suture) and force application point (use of a power arm or not). Results: In cases where anterior teeth were retracted by a conventional T-loop arch wire, the anterior teeth tipped more postero-inferiorly and the posterior teeth moved slightly in a mesial direction. In cases where anterior teeth were retracted with corticotomy, the stress at the anterior bone segment was distributed widely and showed a smaller degree of tipping movement of the anterior teeth, but with a greater amount of displacement. In cases where anterior teeth were retracted from the buccal side with force applied to the mini implant placed between the maxillary second premolar and the first molar to the canine power arm, it showed that a smaller degree of tipping movement was generated than when force was applied to the second premolar reinforced with a mini implant from the canine bracket. In cases where anterior teeth were retracted from the palatal side with force applied to the mini implant on the midpalatal suture, it resulted in a greater degree of tipping movement than when force was applied to the mini implant between the maxillary first and second molars. Conclusion: The results of this study verifies the effects of corticotomies and the effects of controlling orthodontic force vectors during tooth movement.