• The Journal of Korean Academy of Prosthodontics
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• v.61 no.2
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• pp.113-124
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• 2023

Purpose. The purpose of this study is to help increase the success rate by analyzing the types and characteristics of implant prosthesis and the survival rate. Materials and methods. Among implants placed between 2011 and 2020 at Sanbon Dental Hospital, College of Dentistry, Wonkwang University, a case restored by a prosthetic surgeon was investigated for the characteristics and correlation of failure. The causes of failure were classified as failure of osseointegration, peri-implantitis, fixture fracture, abutment fracture, screw fracture, screw loosening, prosthesis fracture, and loss of prosthesis retention. Prosthetic method, cantilever presence, placement location, etc. were analyzed for their correlation with implant failure. Results analysis was derived through Chi-square test and Kaplan-Meier survival analysis using SPSS ver 25.0 (IBM, Chicago, IL, USA). Results. A total of 2587 implants were placed, of which 1141 implants were restored with Single Crown and 1446 implants with Fixed Partial Denture, and the cumulative survival rate was 88.1%. The success rate of SC was 86.2% (984) and the success rate of FPD was 89.6% (1295), showing statistically significant differences, among which factors that had significant differences were abutment fracture, screw fracture, and screw loosening (P < .05). Conclusion. As a result of the 10-year follow-up, more failures occurred due to biomechanical factors than biological factors. Further studies on the success of implants will be needed in the future.

• Journal of Korean Neurosurgical Society
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• v.44 no.1
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• pp.8-14
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• 2008

Objective : The purpose of this study was to determine the efficacy of short segment fixation following postural reduction for the re-expansion and stabilization of unstable burst fractures in patients with osteoporosis. Methods : Twenty patients underwent short segment fixation following postural reduction using a soft roll at the involved vertebra in cases of severely collapsed vertebrae of more than half their original height. All patients had unstable burst fracture with canal compromise, but their motor power was intact. The surgical procedure included postural reduction for 2 days and bone cement-augmented pedicle screw fixations at one level above, one level below and the fractured level itself. Imaging and clinical findings, including the level of the vertebra involved, vertebral height restoration, injected cement volume, local kyphosis, clinical outcome and complications were analyzed. Results : The mean follow-up period was 15 months. The mean pain score (visual analogue scale) prior to surgery was 8.1, which decreased to 2.8 at 7 days after surgery. The kyphotic angle improved significantly from $21.6{\pm}5.8^{\circ}$ before surgery to $5.2{\pm}3.7^{\circ}$ after surgery. The fraction of the height of the vertebra increased from 35% and 40% to 70% in the anterior and middle portion. There were no signs of hardware pull-out, cement leakage into the spinal canal or aggravation of kyphotic deformities. Conclusion : In the management of unstable burst fracture in patients with severe osteoporosis, short segment pedicle screw fixation with bone cement augmentation following postural reduction can be used to reduce the total levels of pedicle screw fixation and to correct kyphotic deformities.

• The Journal of Korean Orthopaedic Ultrasound Society
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• v.6 no.2
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• pp.60-64
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• 2013

After volar locking plating of distal radius fracture, complications arising from unrecognized dorsally prominent screws penetrating the extensor compartments are increasingly reported. However, standard radiography and fluoroscopy may not adequately visualize screw lengths, because of complex shape of dorsal cortex of the distal radius. We presented case of ultrasonography diagnosis of extensor tenosynovitis caused by dorsal screw prominence after volar plate fixation of distal radius fracture.

• Journal of the Korean Arthroscopy Society
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• v.13 no.3
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• pp.254-258
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• 2009

Tibial eminence fracture is caused by distortion, excessive flexion and extension, varus and valgus injury of the knee joint in the form of avulsion fracture. A failure over the exact anatomical reduction of fragment can lead to instability and limitation of joint motion. Recently, a variety of arthroscopic assisted reduction and fixation technique have been used. In the tibial eminence fracture, we created an arthroscopic pull-out wire fixation technique using a cannulated screw that is easy and more convenient than in the conventional technique. So we report this technique with a review of current literatures.

• The Journal of Korean Academy of Prosthodontics
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• v.56 no.3
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• pp.179-187
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• 2018

Purpose: The purpose of this study was to investigate the effect of heat applied to disintegrate cement on the removal torque value and fracture strength of titanium abutment and abutment screw. Materials and methods: Implants, titanium abutments and abutment screws were prepared for each 20 piece. Implant abutments and screws were classified as the control group in which no heat was applied and the experimental group was heated in a vacuum furnace to $450^{\circ}C$ for 8 minutes and cooled in air. The abutments and screws were connected to the implants with 30 Ncm tightening torque at interval 10 minutes and the removal torque value was measured 15 minutes later. And the fracture strength of abutment screw was measured using universal testing machine. Results: The mean removal torque value was $27.84{\pm}1.07Ncm$ in the control group and $26.55{\pm}1.56Ncm$ in the experimental group and showed statistically significant difference (P < .05). The mean fracture strength was $731.47{\pm}39.46N$ in the control group and $768.58{\pm}46.73N$ in the experimental group and showed statistically no significant difference (P > .05). Conclusion: The heat applied for cement disintegration significantly reduced the removal torque value of the abutment screw and did not significantly affect fracture strength of the abutment screw. Therefore, in the case of applying heat to disintegrate cement it is necessary to separate the abutment screw or pay attention to the reuse of the heated screw. However further studies are needed to evaluate the clinical reuse of the heated screw.

• The Journal of Korean Academy of Prosthodontics
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• v.47 no.4
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• pp.424-434
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• 2009

Statement of problem: Problems such as loosening and fractures of retained screws and fracture of implant fixture have been frequently reported in implant prosthesis. Purpose: Implant has weak mechanical properties against lateral loading compared to vertical occlusal loading, and therefore, stress analysis of implant fixture depending on its material and geometric features is needed. Material and methods: Total 28 of external hexed implants were divided into 7 of 4 groups; Group A (3i, FULL $OSSEOTITE^{(R)}$Implant), Group B (Nobelbiocare, $Br{\aa}nemark$ $System^{(R)}$Mk III Groovy RP), Group C (Neobiotec, $SinusQuick^{TM}$ EB), Group D (Osstem, US-II). The type III gold alloy prostheses were fabricated using adequate UCLA gold abutments. Fixture, abutment screw, and abutment were connected and cross-sectioned vertically. Hardness test was conducted using MXT-$\alpha$. For fatigue fracture test, with MTS 810, the specimens were loaded to the extent of 60-600 N until fracture occurred. The fracture pattern of abutment screw and fixture was observed under scanning electron microscope. A comparative study of stress distribution and fracture area of abutment screw and fixture was carried out through finite element analysis Results: 1. In Vicker's hardness test of abutment screw, the highest value was measured in group A and lowest value was measured in group D. 2. In all implant groups, implant fixture fractures occurred mainly at the 3-4th fixture thread valley where tensile stress was concentrated. When the fatigue life was compared, significant difference was found between the group A, B, C and D (P<.05). 3. The fracture patterns of group B and group D showed complex failure type, a fracture behavior including transverse and longitudinal failure patterns in both fixture and abutment screw. In Group A and C, however, the transverse failure of fixture was only observed. 4. The finite element analysis infers that a fatigue crack started at the fixture surface. Conclusion: The maximum tensile stress was found in the implant fixture at the level of cortical bone. The fatigue fracture occurred when the dead space of implant fixture coincides with jig surface where the maximum tensile stress was generated. To increase implant durability, prevention of surrounding bone resorption is important. However, if the bone resorption progresses to the level of dead space, the frequency of implant fracture would increase. Thus, proper management is needed.

• Journal of Dental Rehabilitation and Applied Science
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• v.26 no.4
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• pp.373-388
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• 2010

Fracture causes serious problems in many instance of prosthetic failures. But it is hard to find the definite causes when fractures occur. Fractography encompasses the examination of fracture surfaces that contain features resulting from the interaction of the advancing crack with the microstructure of the material and the stress fields. All fractured specimens(implant retaining screw) retrieved from Gangneung-Wonju national university dental hospital for 3 years(from 2007 to 2009). After pretreatment of samples, the scanning electon microscope were used for surface examination and fracture analysis. In case of most of the fractured specimens, fracture took place by fatigue fracture and fractured surface represents fatigue striation. Fatigue striation indicate the progression of the crack front under cyclic loading, are characteristic of stage 2 crack growth. The site of crack initiation and stage 1 crack growth were not easily identified in any of the failure, presumably because of the complex microstructural features of the polycrystalline sample. In case of fractured by overload, dimpled or cleavage surface were observed. Using the interpretation of characteristic markings(ratchet mark, fatigue striation, dimple, cleavage et al) in fracture surfaces, failure events containing the crack origin, crack propagation, material deficiency could be understand. Using the interpretation of characteristic markings in fracture surfaces, cause and mechanism of fractures could be analyzed.

• Journal of Trauma and Injury
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• v.27 no.3
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• pp.57-62
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• 2014

Purpose: A hamate body coronal fracture is well known as a very rare fracture in the carpal bones and is also hard to diagnose in initial stage due to the bone's architecture. We report our experience in treatment of such a fracture, and we present a review of the relevant literatures. Methods: Four patients who experienced hamate body coronal fractures from October 2006 to October 2013 were enrolled in this study. One patient also had an associated Capitate fracture, and two patients had associated dislocations of the $4^{th}$ metacarpal joint. We performed open reduction and mini-screw fixation on the four patients. In addition, a K-wire was fixed for the two patients with dislocations. Results: The average follow-up period was 24.5 months after surgery, and bone union was observed at the $8^{th}$ week after surgery. We confirmed that bone union had been completed for all the patients, and functional tests showed that joint motion was in the normal range without complications. Conclusion: When a patient has consistent pain on the ulnar side of the wrist, a hamate fracture should be suspected. Computer tomography is better than a simple X-ray scan for confirming the diagnosis of a hamate body coronal fracture. An open reduction and mini-screw fixation led to a good result.

• The Journal of Korean Academy of Prosthodontics
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• v.35 no.4
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• pp.767-780
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• 1997

One of the most common problems of implant prosthesis is the screw loosening of abutment screws. This brings on discomfort in mastication, inflammation in the peri-implant tissue due to poor oral hygiene and fracture of prosthesis or loss of osseointegration. To prevent screw loosening, appropriate implantation to direct the occlusal force to the long axis of the implant, accurate design of the superstructure, decrease of the occlusal table, and adequate torque on the abutment screw are necessary. In this study the screw loosening torque was evaluated in implants with dimples or flutes in the internal surface of abutment screw holes. The abutments were fastened with slot type and hexagonal type abutment screws and were sealed with vinyl poly siloxane impression and bite registration material respectively. The screw loosening torque was evaluated after 1,800 and 12,600 times loading under a loading machine. The results were as follows. 1. The flute form group showed significantly higher loosening torque compared to the dimple form group and the group with no inner surface treatment (p<0.05). 2. There was no statistical difference in loosening torque according to the sealing materials. 3. The loosening torque according to the types of abutment screw showed no significant difference. 4. The loosening torque was significantly higher after 1800 times loading compared to 12600 times loading(p<0.05). From the above results. it is thought that formation of a flute in the internal surface of the screw hole decreases the chance of screw loosening, but the sealing materials and types of abutment screw did not show significant difference in prevention of screw loosening.

• Journal of Korean Foot and Ankle Society
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• v.20 no.2
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• pp.67-72
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• 2016

Purpose: The purpose of this study was to assess the 2-year follow-up results of patients with a trimalleolar fracture, who had undergone an anterior incision cannulated screw fixation of the posterior malleolar fragment, which had more than 25% of articular involvement or had no cortical continuity with the distal tibia. Materials and Methods: Among 28 patients with a trimalleolar fracture who had undergone fixation of the posterior malleolar fragment between February 2005 and February 2010, 14 patients, who underwent an anterior incision cannulated screw fixation of posterior malleolar fragment and were followed-up for more than 2 years, were selected. The postoperative clinical and radiological findings immediately and at the 1- and 2-year follow-up were compared. The clinical findings were evaluated as American Orthopaedic Foot and Ankle Society (AOFAS) score. The radiological assessment was evaluated as the maintenance of reduction, period to bone union, and the presence of nonunion, malunion, and complications. Results: The clinical outcome by mean AOFAS score revealed 83.0 points in the group with preoperative displacement below 2 mm and 80.7 points in the group with preoperative displacement above 2 mm postoperatively. The mean AOFAS score was 91.7 and 93.1 points in the group with preoperative displacement below 2 mm on 1- and 2-year follow-up, respectively, and 89.8 and 91.7 points in group with the preoperative displacement above 2 mm on 1- and 2-year follow-up, respectively. After a 2-year follow-up among 14 cases selected for this study, 13 cases showed an excellent reduction state and only 1 case (7.1%) showed a displacement of more than 2 mm. No complication were encountered in the group with preoperative displacement below 2 mm. On the other hand, among 8 patients in the group with preoperative displacement above 2 mm, there were 3 with limitations of the range of motion of the ankle joint (37.5%) and 1 post-traumatic arthritis (12.5%) at the 2-year follow-up. Conclusion: Anterior incision cannulated screw fixation of the posterior malleolar fragment could be a valuable method for the treatment of trimalleolar fractures that provides satisfactory results.