• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.723-726
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• 2002

In the recent years, as the research and the development of micro and precision machinery become active, the interest of micro actuators using SMA(Shape Memory Alloy) has been increased. The dynamic characteristic analysis of SMA is necessary for actuator application and many common researches report the material characteristics of SMA sufficiently. However, the research of dynamic characteristics is very deficient. In this paper, the helical spring is fabricated with NiTi SMA wire of high resistivity The farce, response speed, temperature, and displacement are measured by digital force gauge, infrared thermometer, and laser displacement sensor so that the dynamic characteristics of this SMA actuator is analyzed.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.1577-1580
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• 2003

In the recent years, as the research and the development of micro and precision machinery become active, the interest of micro actuators using SMA(Shape Memory Alloy) has been increased. The dynamic characteristic analysis of SMA is necessary for actuator application and many common researches report the material characteristics of SMA sufficiently. However, the research on dynamic characteristics is very deficient. In this paper, the helical spring are fabricated with NiTi SMA wire of high resistivity. The force, response speed, temperature, and displacement are measured by digital force gauge, infrared thermometer, and laser displacement sensor so that the dynamic characteristics of this SMA is analyzed. Also, bidirectional actuator was fabricated and experimented for its performance.

• The korean journal of orthodontics
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• v.40 no.2
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• pp.106-114
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• 2010

Objective: The aim of this experimental study was to evaluate the effects of direct electrical current stimulation (DECS) on bone regeneration in response to an expansion of the inter-premaxillary suture in the rat. Methods: Sixteen 50 - 60 days old Wistar male rats were separated into two equal groups (control and experimental). Both groups were subjected to expansion, and 30-gram of force was applied to the maxillary incisors with helical-spring. In the experimental group, two metallic-screws were placed at lateral parts of the maxillary segments. Electrodes were connected to the screws. The device was activated with current adjustment to measure $10{\mu}A$ continuously and the current was monitored daily during the expansion and early-retention phase. Bone regeneration in the sutural area was histomorphometrically evaluated including new-bone area (${\mu}m^2$), bone perimeter (${\mu}m$), feret's diameter (${\mu}m$) and newly formed bone (%) parameters. Kruskal-Wallis rank and Mann-Whitney U tests were used for statistical evaluation at p < 0.05 level. Results: Statistical analysis showed significant differences between groups for all investigated histomorphometric parameters. New bone area (p = 0.002), bone perimeter (p = 0.004), feret's diameter (p = 0.002) and newly formed bone percentage (p = 0.002) measurements were significantly higher in the experimental group than the control group. Bone histomorphometric measurements revealed that bone architecture in the DECS group was improved. Conclusions: The application of DECS to an orthopedically expanded inter-premaxillary suture area during the early retention phase stimulated the formation of new bone.

• Journal of Biomedical Engineering Research
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• v.26 no.6
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• pp.393-398
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• 2005

An electromechanical type is the most useful mechanism in the various pumping mechanisms. It, however, requires a movement converting system including a ball screw, a helical cam, or a solenoid-beam spring, which makes the device complex and may lessen reliability. Thus, the authors have hypothesized that an electromagnetic actuator mechanism can eliminate the movement converting system and that thereby enhance the mechanical reliability and operative simplicity of an electro­pneumatic pump. The purpose of this study was to show a novel application of electromagnetic actuator mechanism in pulsatile pump and to provide preliminary data for further evaluations. The electromagnetic actuator consists of stators with a single winding excitation coil and movers with a high energy density neodymium-iron-boron permanent magnet. A 0.5mm diameter wire was used for the excitation coil, and 1000 turns were wound onto the stators core with parallel. A prototype of extracorporeal electro-pneumatic pump was constructed, and the pump performance tests were performed using a mock system to evaluate the efficiency of the electromagnetic actuator mechanism. When forward and backward electric currents were supplied to the excitation coil, the mover effectively moved back and forth. The nominal stroke length of the actuator was 10mm. The actuator dimension was 120mm in diameter and 65mm in height with a mass of 1.4kg. The prototype pump unit was 150mm in diameter, 150mm in thickness and 4.5kg in weight. The maximum force output was 70N at input current of 4.5A and the maximum pump rate was 150 beats per minute. The maximum output was 2.0 L/minute at a rate of 80bpm when the afterload was 100mmHg. The electromagnetic actuator mechanism was successfully applied to construct the prototype of extracorporeal electro­pneumatic pump. The authors provide the above results as a preliminary data for further studies.

• The korean journal of orthodontics
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• v.27 no.2
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• pp.335-347
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• 1997

Vitamin D is known to exert its action by activating DNA and RBA within target cells to produce proteins and enzymes that can be used in bone resorption process. Particularly, the active form of vitmain D, 1,25-dihydroxycholecalciferol $[1,25-(OH)_2D_3]$, is considered to be one of the most potent stimulators of osteoclatic acitivity in vitro. The purpose of this study was to evaluate the effect of 1,25-Dihydroxyvitamin $D_3$ on the avtivity of periodotal ligament cells and, the experimental tooth movement. Human periodontal ligament cells were collected from the first premolar tooth extracted for the orthodontic treatment, and were incubated in the environment of $37^{\circ}C$, 5% $CO_2$ and 95% humidity. Microtitration(MIT) assay was done at 10, 25, 50 and 100ng/ml of 1,25-Dihydroxyvitamin $D_3$. 21 Sprague-Daft rats were divided into a control gmup(3), and experimental groups(18) where 100g of force from helical spring was applied across the maxillary incisors 1,25-Dihydroxyvitamin $D_3$ was injected into periodontal ligament at the mesial or distal surface of maxillary incisors so that we can compare the control side and the experimental side. Expreimental groups were sac rifled at 12, 24, 36, 48, 72hours and 7 days after force application, respectively. And the obtained tissues were evaluated histologically. The observed results were as follows. 1. The activity of periodontal ligament cells in l0ng/ml or 25ng/ml of 1,25-Dihydroxyvitamin $D_3$ 1,25-Dihydroxyvitamin $D_3$ was not significantly different to the control at the cultivation of 1, 2 and 3 days. 2. The activity of periodontal ligament cells was significantly increased at 3 days in 50 ng/ml of 1,25-Dihydroxyvitamin $D_3$ and 2, 3 days in 100g/ml of 1,25-Dihydroxyvitamin $D_3$. 3. Up to 7 days after force application, there was no difference in osteoblastic activity, tearing of periodontal ligament and proliferation of capillary at tension side between 1,25-Dihydroxyvitamin $D_3$ injection side and the control side. 4. The osteoclastic activity and the resorption of alveolar bone was greater in 1,25-Dihydroxyvitamin $D_3$ injection side than the control side at 36 hours after force application.

• The korean journal of orthodontics
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• v.29 no.1 s.72
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• pp.73-81
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• 1999

Midpalatal suture expansion is often used for patients haying narrow maxillary arch, cleft palate, respiratory handicap with narrow nasal cavity. CGRP has been known as a modulator of pain transmission in central nervous system and a local effector to peripheral tissue causing vasodilation, increase of blood flow, modulation of immune system, regulation of macrophagic function and stimulation of bone formation. To investigate changes of CGRP-immunoreactive nerve fibers in midpalatal suture during the expansion, immunohistochemical study was performed by using rats. Experimental rats (10 weeks, 250 gm) were divided into five groups (control, 1, 4, 7, 14 days group (each n=4) and applied orthodontic force (approximately 200gm) to upper anterior incisors. Frozen sections of midpalatal suture area were immunostained by using rabbit antisera. The results were as follows. ${\cdot}$ The CGRP-immunoreactive nerve fibers were hardly observed in control group. ${\cdot}$ In 1 day group, the CGRP-immunoreactive nerve fibers were more increased around the vessels than control group. ${\cdot}$ In 4 days group, the CGRP-immunoreactive nerve fibers were more increased than control group, but not more increased than 1 day group. Vascular diameter was more enlarged. ${\cdot}$ In 7 days group, especially, hematoxilin affinity of cells was remarkable and cells were arranged along the bone margin. The CGRP-immunoreactive nerve fibers were more reduced than 4 days group and vascular diameter was also reduced. ${\cdot}$ In 14 days group, the CGRP-immunoreactive nerve fibers were similar to those of 7 days group and the irregularity of bone margin was almost recoverd. In Conclusion, the CGRP-immunoreactive nerve fibers nay be related to initial neurogenic inflammatory reaction in expanding mid-palatal suture.

• The korean journal of orthodontics
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• v.28 no.2 s.67
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• pp.311-327
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• 1998

The purpose of this study was to evaluate the effects of Transforming Growth Factor-${\beta}$ (TGF-${\beta}$) on the viability of human periodontal ligament cells, in-vitro and on the experimental tooth movement in rat, in-vivo. Human periodontal ligaments were cultured from the first premolar tooth extracted for the purpose of the orthodontic treatment. 0.1, 1, 5 and 10ng/m1 of TGF-${\beta}$ was given to the cultured wells, respectively and the viability was evaluated by MTT assay. Twenty Sprague-Dawley rats were divided into 5 experimental groups(4 rats in each) where 100g of force was applied from helical spring across the maxillary incisors. TGF-${\beta}$ was injected via Hamilton syringe into the periodontal ligament at the mesial and the distal surface of a maxillary incisor of 2 rats in each experimental group. Phosphate buffer saline(PBS) was injected in 2 other rats as controls. Experimental groups were sacrificed at 1, 3, 7, 14 and 28 days after force application, respectively. The obtained tissues were evaluated histologically. The obtained results were as follows: 1. The viability of periodontal ligament cells in 0.1ng/ml of TGF-${\beta}$ was not significantly different from that of control at 1-, 2- and 3-day of cultivation. 2. The viability of periodontal ligament cells was significantly increased at 3-day in 1ng/ml or 5ng/ml of TGF-${\beta}$, and at 2-,3-day in 10ng/ml of of TGF-${\beta}$. 3. The zone of hyalinization in periodontal ligament in pressure side was smaller in TGF-${\beta}$ injection group than that in control group at 3-day after the application of experimental force in rat. But no difference was seen after 7-day. 4. Osteoclastic activity and capillary prolieferation in pressure side were greater in TGF-${\beta}$ injection group than that in control group at 3-day to 7-day. 5. Osteoblastic activity and new bone fomation in tension side were greater in TGF-${\beta}$ injection group than that in control group at 3-day to 14-day.