• Maxillofacial Plastic and Reconstructive Surgery
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• 제27권3호
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• pp.205-217
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• 2005

Distraction osteogenesis is a technique of lengthening bone including soft tissue by gradual separation of surgically divided bone surfaces. Although the biomechanical, histological, and ultrastructural changes associated with distraction osteogenesis have been widely described, the molecular mechanisms governing the formation of new bone in distracted bone segments remain largely unclear. However, such information has significant clinical implications because it may enable targeted therapeutic manipulations designed to accelerate osseous regeneration. The purpose of this study was to evaluate the expression of TGF-$\beta$1, IGF-I and bFGF in distraction osteogenesis according to different distraction rates in a rabbit's mandible. When twenty-four adult rabbits underwent open osteotomy between the premolar and mental foramen, an external bilateral distraction device was applied. Latency was allowed for five days before distraction. Three different distraction rates were 0.7 mm/day (A, n=8), 1.4 mm/day (B, n=8) and 2.4 mm/day (C, n=8). The distraction device was activated with the same distraction rhythms of twice a day until 4.9 mm (A & B group) and 8.4 mm (C group) length gains was achieved. The animals were sacrificed at postoperative 3, 7, 14 and 28 days. The bony specimens were stained with H&E for histologic examination, and RT-PCR analysis was done for the identification of the expression of TGF-$\beta$1, IGF-I and bFGF. The results obtained from this study were as follows : The 0.7 mm/day and 1.4 mm/day distraction rate groups were shown to improve regenerative bone formation on radiographic and histologic examination. Also, TGF-$\beta$1, IGF-I and bFGF expression increased in the 0.7 mm/day and 1.4 mm/day distraction rate groups. But the 2.4 mm/day distraction rate group specimen was different with adjacent normal bone and hardly expressed of growth factors. These findings suggest that improved new bone formation in the 0.7 mm/day and 1.4 mm/day distraction rates is associated with enhanced expression of TGF-$\beta$1, IGF-I and bFGF by mechanical tension stress. Additionally, the 0.7 mm/day and 1.4 mm/day distraction rate groups were significantly different from the 2.4 mm/day distraction rate group in the expression of growth factors. According to the above results, it seems possible to apply a distraction rate of up to 1.4 mm/day a day in rabbit's mandible. And further studies are needed to evaluate growth factors of TGF-$\beta$1 and IGF-I, which are excellent in expression.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제25권4호
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• pp.337-349
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• 1999

The extracellular matrix(ECM) is a complex network of different combination of collagens, glycosaminoglycans, laminin, fibronectin, and many other glycoproteins including proteolytic enzymes. The composition and organization of the ECM contributes to the uniques physical or biomechanical properties of a tissue. Fibronectins(FN) are dimeric glycoproteins located on cell surfaces, in the matrix of connective tissue, and in blood. Fibronectins mediate cell attachment to collagen substratum and have been implicated in a variety of important biological processes, including embryogenesis and cell differentiation. The purpose of this study was to determine the effects of surgical induction of anterior disk displacement(ADD) on distribution of fibronectin in the rabbit temporomandibular joint(TMJ) tissues included the articular cartilage, disc, retrodiscal tissue, articular eminence using an immunohistochemical technique. The left TMJ was exposed surgically, and all discal attachments were severed except for the posterior attachment. The disk was then repositioned anteriorly and sutured to the zygomatic arch. The right TMJ served as a shamoperated control. Normal joints were used as a nonoperated control. Fourty-five rabbits were used for experiments in total. For fibronectin immunohistochemical study, eighteen rabbits (one normal group and 5 experimental groups, each group consists of 3 rabbits) were used. The experimental rabbits were sacrified after operation period of 2, 3, 4, 6 and 8 weeks on fibronectin. The obtained results were as follows ; 1. Fibronectin immunoreaction on all TMJ tissues(mandibular condyle, articular disc, retrodiscal tissue, articular eminence) in the normal rabbit was observed. Especially the reverse cell layer and proliferation zone of articular cartilage of condyle show strong positive reaction. 2. Depletion of fibronectin in the all TMJ tissues except hypertrophic zone of articular cartilage occurred at 2 weeks following induction of ADD. 3. The restoration of immunoreaction at 4 weeks was observed and a progressive increasing reaction at 6 weeks, 8 weeks also was found. Our study generally showed degenerative changes in TMJ tissues after ADD although TMJ tissues adapted or degenerated to abnormal loads and stress distribution according to the remodeling capacity of TMJ tissues.

• Journal of Korean Neurosurgical Society
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• 제42권4호
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• pp.311-316
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• 2007

Objective : The objective of this study is to investigate the safety, surgical efficacy, and advantages of a polyaxial screw-rod system for posterior occipitocervicothoracic arthrodesis. Methods : Charts and radiographs of 32 patients who underwent posterior cervical fixation between October 2004 and February 2006 were retrospectively reviewed. Posterior cervical polyaxial screw-rod fixation was applied on the cervical spine and/or upper thoracic spine. The surgical indication was fracture or dislocation in 18, C1-2 ligamentous injury with trauma in 5, atlantoaxial instability by rheumatoid arthritis (RA) or diffuse idiopathic skeletal hyperostosis (DISH) in 4, cervical spondylosis with myelopathy in 4, and spinal metastatic tumor in 1. The patients were followed up and evaluated based on their clinical status and radiographs at 1, 3, 6 months and 1 year after surgery. Results : A total of 189 screws were implanted in 32 patients. Fixation was carried out over an average of 3.3 spinal segment (range, 2 to 7). The mean follow-up interval was 20.2 months. This system allowed for screw placement in the occiput, C1 lateral mass, C2 pars, C3-7 lateral masses, as well as the lower cervical and upper thoracic pedicles. Satisfactory bony fusion and reduction were achieved and confirmed in postoperative flexion-extension lateral radiographs and computed tomography (CT) scans in all cases. Revision surgery was required in two cases due to deep wound infection. One case needed a skin graft due to necrotic change. There was one case of kyphotic change due to adjacent segmental degeneration. There were no other complications, such as cord or vertebral artery injury, cerebrospinal fluid leak, screw malposition or back-out, or implant failure, and there were no cases of postoperative radiculopathy due to foraminal stenosis. Conclusion : Posterior cervical stabilization with a polyaxial screw-rod system is a safe and reliable technique that appears to offer several advantages over existing methods. Further biomechanical testings and clinical experiences are needed in order to determine the true benefits of this procedure.

• 대한치과교정학회지
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• 제41권1호
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• pp.6-15
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• 2011

마이크로 임플란트 시술의 중요한 위험요인 중 하나로 치근접촉 문제가 있으나, 관련 연구는 결과 분석에 치중되어 있고, 치근접촉이 마이크로 임플란트 안정성 상실로 이어지는 기전에 대한 연구는 아직 미흡한 것으로 보인다. 이에, 본 연구에서는 생역학적 측면에서 그 영향을 분석하였다. Absoanchor 마이크로 임플란트(SH1312-7, Dentos Inc., Daegu, Korea) 첨부가 치근에 접촉되어 있을 때, 저작압 전달에 의한 마이크로 임플란트 변위가 인접골에 가하는 압축응력을 축대칭 유한요소모델을 사용하여 계산하였다. 요소별 응력이 해면골의 최대압축강도나, 치밀골의 비정상 골개조 임계능력을 넘을 경우 해당 요소를 순차적으로 해석모델에서 제거하며 실행한 6단계해석의 결과, 마이크로 임플란트에 인접한 해면골의 전체적인 파절과 과부하에 따른 치밀골의 비정상 골개조가 임플란트 지지력 상실에 주 요인이 될 것으로 평가되었다. 치밀골의 과부하 영역은 초기에는 치밀골판의 하부에 존재하였으나 상부로 확장되었고, 응력 재분포로 인한 감소효과 없이 양성 되먹임(positive feedback)으로 결국 치밀골 전 두께로 확대됨을 관찰하였다. 본 연구를 통해 치근접촉된 마이크로 임플란트가 인접골을 훼손시켜 안정성 상실로 이어지는 과정을 모사할 수 있었으며, 이로부터 치근접촉에 따른 마이크로 임플란트의 불량한 예후에 대한 생역학적 측면의 원인을 파악할 수 있었다.

• 생명과학회지
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• 제20권2호
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• pp.314-320
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• 2010

트라이애슬론은 수영, 사이클, 달리기로 구성된 스포츠로 단일종목의 스포츠에 참가할 때 보다 잠재적인 의학적 위험요인을 더 많이 포함하고 있다. 과사용은 스트레스의 증가와 뼈, 관절, 근육, 건 또는 신경의 손상을 일으키며, 지금까지 트라이애슬론 훈련과 경기 중에 발생될 수 있는 과사용 부상은 목통증, 요통, 근육과 건 부상, 인대부상, 만성적인 통증 등이며, 대부분의 과사용 부상은 달리기 훈련시 가장 많이 발생된다. 또한 트라이애슬론 참가자들은 다양한 자연환경과 경기거리에서 완주해야 하는 만큼 부상 이외의 의학적 문제에 직면할 수 있으며, 현재까지 트라이애슬론과 관련하여 보고되고 있는 의학적 위험요인들은 저체온증, 저나트륨혈증, 일사병, 자외선에 과도한 노출, 면역억압, 심리적인 탈진현상, 용혈증 등을 포함하고 있다. ID 경기 중에 발생 할 수 있는 의학적 문제들 가운데 가장 빈번하게 발생하는 증상은 탈진과 탈수현상이며, 그 다음으로 나타나는 문제점들은 저나트륨혈증, 열부상, 저혈압, 화상과 물집, 근육경련 등이다. 그러나 SD와 OD 경기 중에는 달리기 속도가 빠르고 더 높은 강도에서 경기가 진행되기 때문에 일사병의 발생 위험이 더 높고, 경기 시간이 짧은 관계로 저나트륨혈증은 발생하지 않는다. 본 연구는 트라이애슬론 훈련과 경기 중에 발생 될 수 있는 과사용 부상과 의학적 위험 요인에 대한 연구문헌들을 고찰하여 스포츠 활동에 직접 참여하는 엘리트 선수 및 동호인 그리고 스포츠 현장에서 선수들을 지도하는 코치와 대회를 주최하는 관계자들에게 트라이애슬론과 관련된 과사용 부상과 의학적 위험요인에 대한 기초자료를 제공하여 이러한 위험요인들을 미연에 예방하거나 감소시키는데 도움을 줄 수 있는 기초자료를 제시하고자 한다.

• 한국운동역학회지
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• 제21권5호
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• pp.521-528
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• 2011

The purpose of this study was to analyze the kinematic characteristics of the finalists in the women's 100 m event to provide important information to coaches and athletes. Three different biomechanics techniques were applied for analyzing sprinter motion: LAVEG, a panning technique, and 12 video cameras for 3 dimensional analysis of the 40 m - 70 m portion of the race. Carmelita Jeter(USA) performed the maximum speed of 10.54 m/s at the distance of 58.2 m. There was a tendency to show a better performance time with a high number of steps (p=.13) and shorter stride length (p=.14) among the 8 sprints. Furthermore, the stride frequency and the performance time were negatively correlated as a higher stride frequency had a positive impact on the performance time (p=.02). Based on 3 dimensional analysis, the 4 top ranked sprinters used the different strategies to maintain a high COM (Center of Mass) velocity during the mid portion of the race (40 m - 70 m). Carmelita Jeter(USA) showed more flexed knee and hip motion at heel contact (HC) to maintain a high COM velocity while S.A. Fraser-Pryce (JAM) showed more extended knee and hip motion at HC. On the other hands, Veronica Campbell-Brown (JAM) and Kelly-Ann Baptiste (TRI) showed a tendency to have high knee lifts during the swing phase to maintain the high COM velocity during the race. These biomechanical analyses of the women's 100 m final event in the 2011 WC, Daegu, will provide important scientific information to coaches and athletes for understanding the sprinting mechanism of today's top-class sprinters.

• 한국운동역학회지
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• 제17권1호
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• pp.191-199
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• 2007

This study was conducted to examine the biomechanical characteristics of open spike in the volleyball to improve the technique of the volleyball spike. The subjects were six male college and high school athletes. The motions of volleyball spike were filmed by using two Sony VX 2000 Video Cameras. The mechanical factors were angle and angular velocity of body segments in the upper and the lower limbs. The conclusions were as follows; 1. The angle of the shoulder joint of the skilled showed larger than that of the unskilled in impacting of the volley ball spike. 2. The angle of the elbow joint of the skilled showed larger than that of the unskilled in impacting of the volley ball spike. 3. The angle of the wrist joint of the skilled showed smaller than that of the unskilled in impacting of the volley ball spike. 4. The angle of the hip joint of skilled showed larger than that of unskilled in impacting of the volley ball spike. 5. The angle of the knee joint of the skilled and the unskilled showed same in take off and impacting of the volley ball spike, and that of the skilled showed smaller than that of the unskilled in take-off touchdown and touchdown after impact of the volley ball spike. 6. The angle of the ankle joint of skilled showed larger than unskilled in take-off of the volley ball spike. 7. The angular velocity of the shoulder joint, elbow joint, wrist joint of the skilled showed faster than that of the unskilled in impacting of the volley ball spike. Taken together the result of them, I have come to conclusion that knee joint angle in touchdown of the take off should be decreased and knee joint angle in take off should be increased, and then stability of the take off should be made and, and that extension of the elbow joint should be made and wrist joint angle decreased and shoulder and hip joint angle increased, and then C.O.G of the arm and hand should be positioned ahead C.O.G of the body in impacting for effective impact of the spike, and that the transfer of the angular velocity of body segments for effective impact of the spike make from the proximal segment to the distal segment at spike in volleyball.

• 대한치과보철학회지
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• 제39권5호
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• pp.463-476
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• 2001

Since the treatment of edentulous patients with osseointegrated implant was first introduced more than 30 years ago, implant therapy has become one of the most important dental treatment modalities today. Based on the previous experience and knowledge, $Br{\aa}nemark\;Novum^{(R)}$ protocol was introduced with the concept of simplifying surgical and prosthetic technique and reducing healing time recently. This protocol recommends the installation of three 5mm wide diameter futures in anterior mandible and the prefabricated titanium bars for superstructure fabrication. This study was designed to analyze the stress distribution at fixture and superstructure area according to changes of fixture number, diameter and superstructure materials. Four 3-dimensional finite element models were fabricated. Model 1 - 5 standard fixtures (13mm long and 3.75mm in diameter) & superstructure consisted of type IV gold alloy and resin Model 2- 3 wide diameter fixtures (13mm long and 5.0mm in diameter) & superstructure consisted of type IV gold alloy and resin Model 3-3 wide diameter fixtures (13mm long and 5.0mm in diameter) & superstructure consisted of titanium and resin Model 4-3 wide diameter fixtures (13mm long and 5.0mm in diameter) & superstructure consisted of titanium and porcelain A 150N occlusal force was applied on the 1st molar of each model in 3 directions - vertical($90^{\circ}$), horizontal($0^{\circ}$) and oblique($120^{\circ}$). After analyzing the stresses and displacements, following results were obtained. 1. There were no significant difference in stress distribution among experimental models. 2. Model 2, 3, 4 showed less amount of compressive stress than that of model 1. However, tensile stress was similar. 3. Veneer material with a high modulus of elasticity demonstrated less stress accumulation in the superstructure. Within the limites of this study, $Br{\aa}nemark\;Novum^{(R)}$ protocol demonstrated comparable biomechanical properties to conventional protocol.

• The Journal of Advanced Prosthodontics
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• 제1권2호
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• pp.107-112
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• 2009

STATEMENT OF PROBLEM. Macroscopic and especially microscopic properties of implant surfaces play a major role in the osseous healing of dental implants. Dental implants with modified surfaces have shown stronger osseointegration than implants which are only turned (machined). Advanced surface modification techniques such as anodic oxidation and Ca-P application have been developed to achieve faster and stronger bonding between the host bone and the implant. PURPOSE. The purpose of this study was to investigate the effect of surface treatment of titanium dental implant on implant stability after insertion using the rabbit tibia model. MATERIAL AND METHODS. Three test groups were prepared: sandblasted, large-grit and acid-etched (SLA) implants, anodic oxidized implants, and anodized implants with Ca-P immersion. The turned implants served as control. Twenty rabbits received 80 implants in the tibia. Resonance frequencies were measured at the time of implant insertion, 2 weeks and 4 weeks of healing. Removal torque values (RTV) were measured 2 and 4 weeks after insertion. RESULTS. The implant stability quotient (ISQ) values of implants for resonance frequency analysis (RFA) increased significantly (P <. 05) during 2 weeks of healing period although there were no significant differences among the test and control groups (P >. 05). The test and control implants also showed significantly higher ISQ values during 4 weeks of healing period (P < .05). No significant differences, however, were found among all the groups. All the groups showed no significant differences in ISQ values between 2 and 4 weeks after implant insertion (P >. 05). The SLA, anodized and Ca-P immersed implants showed higher RTVs at 2 and 4 weeks of healing than the machined one (P < .05). However, there was no significant difference among the experimental groups. CONCLUSION. The surface-modified implants appear to provide superior implant stability to the turned one. Under the limitation of this study, however, we suggest that neither anodic oxidation nor Ca-P immersion techniques have any advantage over the conventional SLA technique with respect to implant stability.

• Journal of Korean Neurosurgical Society
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• 제60권5호
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• pp.498-503
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• 2017

Objective : The purpose of the present study was to compare inter-fragmentary compression pressures after fixation of a simulated type II odontoid fracture with the headless compression Herbert screw and a half threaded cannulated lag screw. Methods : We compared inter-fragmentary compression pressures between 40- and 45-mm long 4.5-mm Herbert screws (n=8 and n=9, respectively) and 40- and 45-mm long 4.0-mm cannulated lag screws (n=7 and n=10, respectively) after insertion into rigid polyurethane foam test blocks (Sawbones, Vashon, WA, USA). A washer load cell was placed between the two segments of test blocks to measure the compression force. Because the total length of each foam block was 42 mm, the 40-mm screws were embedded in the cancellous foam, while the 45-mm screws penetrated the denser cortical foam at the bottom. This enabled us to compare inter-fragmentary compression pressures as they are affected by the penetration of the apical dens tip by the screws. Results : The mean compression pressures of the 40- and 45-mm long cannulated lag screws were $50.48{\pm}1.20N$ and $53.88{\pm}1.02N$, respectively, which was not statistically significant (p=0.0551). The mean compression pressures of the 40-mm long Herbert screw was $52.82{\pm}2.17N$, and was not statistically significant compared with the 40-mm long cannulated lag screw (p=0.3679). However, 45-mm Herbert screw had significantly higher mean compression pressure ($60.68{\pm}2.03N$) than both the 45-mm cannulated lag screw and the 40-mm Herbert screw (p=0.0049 and p=0.0246, respectively). Conclusion : Our results showed that inter-fragmentary compression pressures of the Herbert screw were significantly increased when the screw tip penetrated the opposite dens cortical foam. This can support the generally recommended surgical technique that, in order to facilitate maximal reduction of the fracture gap using anterior odontoid screws, it is essential to penetrate the apical dens tip with the screw.