• The korean journal of orthodontics
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• v.36 no.5
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• pp.349-359
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• 2006

Objective: Nickel-titanium alloy wire possesses excellent spring-back properties, shape memory and super-elasticity. In order to adapt this wire to clinical use, it is necessary to bend as well as to control its super-elastic force. The purpose of this study is to evaluate the effects of heat treatment on the load-deflection properties and transitional temperature range (TTR) of nickel-titanium wires. Methods: Nickel-titanium wires of different diameters ($0.016"\;{\times}\;0.022"$, $0.018"\;{\times}\;0.025"$ and $0.0215"\;{\times}\;0.028"$) were used. The samples were divided into 4 groups as follows: group 4, posterior segment of archwire (24 mm) without heat treatment; group 2, posterior segment of archwire (24 mm) with heat treatment only; group 3, anterior segment with bending and heat treatment; group 4, anterior segment with bending and 1 sec over heat treatment. Three point bending test was used to evaluate the change in load-deflection curve and obtained DSC (different scanning calorimetry) to check changes in $A_f$ temperature. Results: In the three point bending test, nickel-titanium wires with heat treatment only had higher load-deflection curve and loading and unloading plateau than nickel-titanium wires without heat treatment. Nickel-titanium wires with heat treatment had lower Af temperature than nickel-titanium wires without heat treatment. Nickel-titanium wires with heat treatment and bending had higher load-deflection curve than nickel- titanium wires with heat treatment and nickel-titanium wires without heat treatment. Nickel-titanium with heat treatment of over 1 sec and bending had the highest load-deflection curve. Nickel-titanium wires with heat treatment and bending had lower Af temperature, Nickel-titanium wires with heat treatment of over Af sec and bending had the lowest Af temperature. Conclusion: From the results of this study, it can be stated that heat treatment for bending of Nickel-titanium wires does not deprive the superelastic property but can cause increased force magnitude due to a higher load-deflection curve.

• The korean journal of orthodontics
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• v.28 no.4 s.69
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• pp.517-531
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• 1998

The purpose of this study was to investigate the changes in the craniofacial skeleton subsequent to chincap therapy in the juvenile skeletal Class III malocclusion with more appropriate control samples. The experimental group consisted of 29 Korean children(14 males, 15 females) who had skeletal Class III malocclusion with prognathic mandible and were undergone chincap thorny from the beginning of treatment. The control group was composed of 21 Korean children(10 males, 11 females) who had no orthodontic treatment, but with similar skeletal discrepancies to experimental group. Lateral cephalometric radiographs at the age of 7, and 2 years later were analyized and compared with student's t-test(p<0.05). The results of this study were as follows; 1. The control group without chincap therapy had not shown any improvement of the skeletal discrepancies, but had grown to be much severe. This means that the untreated Class III patient with prognathic mandible would not be corrected by growth. For the experimental group with chincap therapy, the anterior-posterior skeletal discrepancies and mandibular prognathism were both improved. 2. Neither significant restraint nor acceleration of growth was found in the cranial base and maxilla by chincap treatment. 3. The inhibition of mandibular growth could not be accepted, but the changes of the direction of growth and morphological changes were found. 4. Vertical growth tendency was increased with chincap therapy. 5. When Putting together the results of the analyses , it seems to be the rotation and displacement of the mandible that the major treatment effects of chincap we. The changes of the direction of growth and the morphological changes also seems to contibute to the treatment effect partly. In summary, the chincap doesn't restrain the mandibular growth. But, it is considered as a useful treatment modality for correction of skeletal discrepancies and reduction of mandibular prognathism in growing Class III patients with madibular prognathism.

• The korean journal of orthodontics
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• v.29 no.1 s.72
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• pp.83-94
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• 1999

The purpose of this study was to evaluate the changes of cancellous and cortical bone and the effect of estrogen in ovariectomized rats. Fifty female rats, 250gm in body weight, were divided into three groups : ovariectomized group(OVE), ovariectomized and estrogen-injected group(OVE-EST), and sham operated and estrogen-injected group(EST). Bilateral ovariectomy was performed at the onset of the experiment. In OVE-EST group and EST group, estrogen was injected $50{\mu}g/kg$ B.W. every other days from 3 weeks after surgery to sacrifice. Each five rats were sacrificed after 5, 6, 7 weeks. One side of mandibular body was radiographed with a soft x-ray apparatus(Hitex Co., Ltd., Japan). Thereafter the obtained microradiographs were used for the morphometric analysis using a Image analyzer. The morphometric analysis was perforrmed for parameters such as total bone area, cortex bone area and medullary bone area. The other side of the mandibular bone was decalcified and embedded in paraffin as using a general method. The specimens were sectioned and stained with Mallory's anilline blue and observed light microscopically. The results were as follows. 1 In all groups, the proportion of cortex to total bone area was not significantly different. 2. In ovariectomized(OVE) group, the proportion of marrow cavity to medullary bone area increased significantly from 5 to 7 weeks(p<0.05). In ovariectomized and estrogen-injected(OVE-EST) group, it decreased significantly at 7 weeks, and in estrogen-injected(EST) group, it decreased significantly from 6 weeks(p<0.05). 3. Microradiogram and histopathologic findings revealed that marrow cavity was enlarged and osteoclasts were observed around irregular bone surface in OVE group. In OVE-EST group, the size of marrow cavity at 7 weeks was similar to that of control group. In EST group, as dense trabecular bone increased from 5 to 7 weeks, marrow cavity decreased.

• The korean journal of orthodontics
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• v.29 no.4 s.75
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• pp.457-466
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• 1999

It has been reported that skeletal relapse and dental change after mandibular setback do occur not only after intermaxillary fixation(IMF) removal but also during IMF The side effects of skeletal relapse during IMF have clinical importance because they can cause many Postoperative orthodontic Problems. Generally, the Prevention of solid union between segments, compensatory tooth movement, anterior openbite, etc. have been cited as the side effects of jaw displacement. The purpose of this study was to evaluate the skeletal relapse and dental change during IMF. The material consisted of 28 patients who were treated by BSSRO(bilateral sagittal split ramus osteotomy), wire osteosynthesis, IMF for correction of mandibular prognathism. Through cephalometric analysis, the amount and direction of surgical movement, skeletal relapse and dental change during IMF were measured. The correlation between surgical movement and skeletal relapse, between skeletal relapse and dental changes were evaluated. The following conclusions were obtained; 1. Distal segment was repositioned backward and upward, proximal segment showed clockwise rotation during surgery. 2. During ]m, anterior portion of distal segment was displaced backward and posterior portion was displaced upward. Proximal segment was displaced upward with forward movement of p-Go(gonion of proximal segment). Backward surgical movement of p-GO was significantly correlated with forward displacement of p-Go. 3. Overjet and overbite were not changed during IMF. The compensatory tooth movements during IMF were characterized by retroclination of upper incisors md retroclination, extrusion of lower incisors. These compensatory tooth movements had statistically significant correlation with upward displacement of d-Go (gonion of distal segment).

• The korean journal of orthodontics
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• v.31 no.3 s.86
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• pp.311-323
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• 2001

One of the various mechanics used to treat unilateral Class II malocclusion is head gear with asymmetric face bow. We made the finite element models of unilateral Class II maxillary dental arch and power arm asymmetric face bow. We designed this experiment to observe stress distribution of periodontal ligament, reaction force, and displacement and to understand force system, so to predict the therapeutic effect. On the basis of computerized tomograph of maxillary dental arch of 25 years old male with normal occlusion without extraction and orthodontic treatment history, we made finite element models of maxillary dental arch and periodontal ligament. Then we modified that model to unilateral maxillary Class II malocclusion model of which maxillary left molar displaced mesially. Also, We made finite element model of asymmetric face bow of which right outer bow shorter than left by 25mm(RMO, Penta-FormTM/Medium size, 0.045 inch iner bow, 0.072 inch outer bow). After that, retraction force of 250g, 300b, 350g were applied to maxillary first molar. We concluded as follow. 1. The Net force that both maxillary first molars were received increased as the retraction force increased. Mesially positioned tooth received more force than normally positioned tooth. But, both tooth were received distal force, so distal movement occured. 2. Both tooth received buccal lateral force. In analysis of force element, as the retraction force were increased, force of X-axis at mesially positioned tooth decreased, and force of X-axis at normally positioned tooth increased. so lateral force component moved to the side received less force from more force. 3. There were rotation, tipping with distal movement in maxillary first molar. As retraction force were increased, rotation and tipping also increased. More tipping and rotation occured at the side received more force, that is, mesially positioned tooth. Though it Is small change, displacement of same pattern occur in normally positioned tooth

• The korean journal of orthodontics
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• v.25 no.3 s.50
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• pp.355-373
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• 1995

Craniofacial region is a musculodentoskeletal system that consists of many anatomical structures ; cranioskeletal structures, dental arches, and formation and functions of masticatory muscles have close correlations. Growth and development of craniofacial region are influenced by not only hereditory factors, but also environmental factors such as craniofacial muscles and surrounding tissues. On the contrary, however, study on changes in functions or adaptations of craniofacial muscles following changes of craniofacial skeletal structures has been somewhat insufficient. The author's purpose was to observe correlations between masticatory muscular functions and change patterns according to cranial skeletal structures and occlusion patterns, for this, comparative study of muscle activity changes of preand post- orthognathic surgery states in skeletal Cl III malocclusion patients was peformed. The selected sample groups were 15 normal male patients, 15 skeletal Cl III pre-orthognatic surgery patients and 15 skeletal Cl III post-orthognatic surgery patients. For each sample groups, cephalometric x-ray taking, masticatory efficiency test and measurements of muscle activities in anterior temporal muscle, masseter and upper lip in rest, clenching, chewing and swallowing were carried out. The following results were obtained : 1. In resting state of mandible, pre-surgery malocclusion group showed higher m. activities in ant. temporalis, masseter and upper lip than post-surgery group. Post-surg. malocc. group showed significantly high m. activity only in upper lip compared to the normal group. 2. In clenching state, post-surg. malocc. group showed higher m. activities in ut. temporalis, masseter and upper lip than pre-surg. malocc. group. 3. In chewing state, post-surg. malocc. group showed higher m. activities in ant. temporalis and masseter than pre-surg. malocc. group, on the other hand, decreased upper lip activity was noticed. 4. In swallowing state, post-surg. malocc. group showed lower upper lip activity than pre-surg. malocc. group but higher than that of the normal group. No significant difference in m. activities of ant, temporalis and masseter was noticed among the three groups. 5. Masticatory efficiency was lower in pre-surg. malocc. group than normal group, masticatory efficiency showed an increase in post-surg. malocc. group compared to the pre-surg. malocc. group. However, both groups showed significant differences compared to the normal group.

• The korean journal of orthodontics
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• v.28 no.3 s.68
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• pp.353-370
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• 1998

This study was conducted to investigate the changes in the structural parts of the craniofacial skeleton subsequent to chincap therapy in the juvenile skeletal Class III patients. The subject consisted of 29 Korean children(14 males, 15 females) who had skeletal Class III malocclusion and were undergone chincap therapy from the beginning of the treatment (and an auxilliary upper removable appliance, if necessary). The control group was composed of 21 children(10 males, 11 females) with skeletal Class III malocclusion who had no orthodontic treatment. Cephalometric data at the mean age of 7 and 2 years later were analyized by finite element method, and compared between groups by independent group t-test(p<0.05). The results of the present study were as follows; 1. There were no significant changes in the cranial base, posterior face, upper anterior face, ramus, chin and soft tissues by the chincap therapy. 2. The mandibular body showed significant differences in the minimum extention ratio and the overall shape ratio. This means that the vertical direction of growth was retarded by the chincap therapy. 3. The major direction of the growth in the maxillary basal bone was significantly more horizontal in the experimental group, which suggests that the vertical growth of maxilla was inhibited. 4. There was statistical difference in the major direction of the growth of the anterior face between groups. This may be due to the significant difference in the major direction of growth of the lower anterior face, supposed to be resulted from the mandibular rotation and/or displacement by the chincap therapy. The change in the oral functional space seemed to be caused by the same reason. 5. From the standpoint of these results, the retardation of growth, the changes of the growth direction and the morphological changes could be accepted partly, but the major effect of the chincap seems to be the rotation and the displacement of the mandible.

• The korean journal of orthodontics
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• v.25 no.3 s.50
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• pp.273-286
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• 1995

The purpose of this study was to compare the difference of the growth aspects in three facial growth patterns. The biennial serial cephalometric radiographs of 33 samples(19males, 14females) with normal occlusion from 8.5 years to 18.5 yews of age were used in this study. The facial growth patterrn was categorized in 3 types(Drop type, Neutral type, Forward type) by the total amounts of the Y-axis which changed from 8.5 years to 18.5 years of age. The growth change of the craniofacial area during 10 years in each growth type was analyzed and was compared among the 3 growth types. The results of this study might be summarized as follows. 1. The samples that were classified by total change of the Y-axis during this study period were distributed to 52% of the neutral type, 27% of the forward type, 21% of the drop type. 2. The anterior growth of the maxilla to the cranial base(N per A) showed larger in the forward type than in other 2 types(p<0.05). 3. The palatal plane to the FH plane showed more anterior-superior inclination in the forward type with age during this study period. 4. The anterior growth of the mandible to the cranial base(N per Pog) appeared large in rank order, of largest the forward type, second the neutral type, and third the drop type(p<0.05). 5. During this study period the mandibular plane(SN/MN,FMA) showed more counterclockwise rotation in the forward type than in the drop type(p<0.05), and this tendency was stronger in males than in females(p<0.05). 6. The growth of the mandibular corpus length(Go-Me) showed smaller in the drop type than in the other 2 types(p<0.05). 7. In the forward type and the neutral type, the anterior growth of the mandible was larger than that of the maxilla(p<0.05). 8. In the craniofacial growth distances and angulations turned out to be somewhat variable, but the vertical proportion had a strong tendency whose original relation was maintained consistently during this study period. 9. Through these analyzed data, the profilograms on each growth type were constructed to evaluate individual growth pattern in the orthodontic diagnosis.

• The korean journal of orthodontics
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• v.37 no.2 s.121
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• pp.114-124
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• 2007

Objective: The purpose of this study was to examine how the mesio-distal angulation and the length of each tooth changes on panoramic radiograph at different bucco-lingual inclinations. Methods: After constructing an acrylic model based on the mean arch of 30 adults with normal occlusion, the wire was placed in the center of the teeth on the acrylic model. First, the wire was implanted in normal angulation and inclination and a panoramic radiograph taken. After changing the inclination from $I-5^{\circ}\;to\;I+15^{\circ}\;by\;5^{\circ}$, a panoramic radiograph was taken again and the mesio-distal angle and wire length on the panoramic radiograph were assessed. Results: When the wire was implanted at the normal angulation and inclination, the length measured in the panoramic radiograph was magnified $111{\sim}117%$ from the original length in the anterior region and $121{\sim}125%$ in the posterior region. Only the central and lateral incisors showed significant length differences when the inclination was changed from $l-15^{\circ}\;to\;I+15^{\circ}$ at fixed angulation. When the inclination was changed from $l-15^{\circ}\;to\;I+15^{\circ}$, the angulation of most teeth on panoramic radiograph appeared to be more disto-angulated than in reality, and the lateral incisor and canine showed the largest difference. Only $l-15^{\circ}\;to\;I+15^{\circ}$ groups of premolars and $I+15^{\circ}$ group of molars showed more mesio-angulation than in reality. As the labio(bucco)lingual inclination of all teeth were decreased, tooth angulation in the panoramic radiograph appeared to be more disto-angulated. Conclusion: The labio-liugual inclination of teeth should be considered because it affects panoramic image of teeth, such as length of incisors and angulation of other teeth.

• 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.