• 한국정밀공학회지
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• 제17권6호
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• pp.83-88
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• 2000

In machining large screws such as those of extruders, it takes long time to machine them on conventional machines which usually use single-tipped fixed tools. And it is also difficult to use an existing CAD/CAM coftware when trying to get over the problems of conventional machines and making use of CNC machines. In this paper, generation of machining program using rotational tools for large screws defined by longitudinal-section profile is descrebed. Use of rotational tools in machining plays an important role in saving machining time. In the sort of extruder screws, it is easy to define a screw shape by longitudinal-section profile, and by which improvement of dimensional accuracy can be expected. The CAM software developed in this paper is based on user's and designer's friendliness.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제40권5호
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• pp.233-239
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• 2014

Implants are typically placed after performing ridge expansion by inserting screws of gradually increasing thickness and good clinical outcomes are often obtained. We placed 11 implants in 6 patients, and one implant failed during osseointegration but it was replaced immediately after removal and successful prosthetic treatments were completed. During these surgeries, buccal cortical plate complete fractures do not occur. Inserting screws for ridge expansion is a successful and predictable technique for implant placement in narrow alveolar bone.

• 대한치과보철학회지
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• 제41권4호
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• pp.519-531
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• 2003

Statement of problem : Chronic implant screw loosening remains a problem in restorative practices. Some implant manufactureres have introduced abutment screws with treated material, surfaces and macrostructures in an effort to reduce potential loosening. Purpose : This study evaluated the materials and loading cycles on detorque value after dynamic continous fatigue test in the sinulated conditions of posterior single restoration. Material and method : Fourteen of each of the following abutment screws - titanium alloy, gold alloy, gold-tite, and titanium alloy modified - were used in test. SEM is used to verify macrostructures of each screws. $ZrO_2/Al_2O_3$ composite abutment was tightened on $4{\times}10.0mm$ titanium external implant at 30 Ncm. Cyclic loading machine delivered dynamic loading forces between 20 and 320N for 100,000, 200,000, 300,000, 500,000, and 1,000,000 cycles at frequencies 14Hz. Torque and detorque value after loading was measured. Results : All measued screws had different screw length and thread form. Titanium modified screw had greater detorque value than others before and after cyclic loadings(p<0.05). All abutment screws had no significant change in mean percentage of detorque value after loading to initial value after less than 500.000 cyclic loadings, but significant lower value after 1,000,000 cycles(p<0.05). Conclusion : Within limintations of this study all abutment screws may be loosend after about 1 year use. Annual check-up is nessasary to prevent screw loosening.

• 대한족부족관절학회지
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• 제8권2호
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• pp.171-175
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• 2004

Purpose: We evaluated the clinical and radiological results of arthroscopic ankle fusion using 2 medial screws which had advantages of less morbidity, early weight-bearing and high union rate. Material and Methods: From April, 2002 to March, 2004, 8 patients who had ankle osteoarthritis were treated by ankle fusion using 2 medial screws under arthroscopy; five patients with post-traumatic osteoarthritis, two with post-infectious arthritis and one with paralytic foot. There were 5 male and 3 female. Average age was 67 years old ranging from 57 to 71 years. We evaluated them clinically preoperative and postoperative using AOFAS score, VAS pain scale and patient's satisfaction. In regard to radiological fusion, we checked them by simple AP, lateral and mortise view. Follow up period was average 11 months (range, $6{\sim}24$ months). Results: All ankles were successfully fused with 2 medial screws under arthroscopy. The mean time of fusion was 10.5 weeks (range, $8{\sim}14$ weeks). Patient's satisfaction checked at 6 months after operation had favorable results (excellent and good 75%). One case had pain on medial malleolar area because of screw's protrusion. Conclusion: Arthroscopic ankle fusion using 2 medial screws was good modality of ankle fusion with less morbidity and early weight-bearing in some cases of ankle arthritis.

• 대한족부족관절학회지
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• 제13권2호
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• pp.142-145
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• 2009

Purpose: The aim of this study was to retrospectively evaluate the clinical and radiological results of the first metatarsophalangeal joint arthrodesis with two crossed screws fixation. Materials and Methods: We treated 23 patients (24 cases) with arthrodesis of the first metatarsophalangeal joint using two crossed screws fixation between December 2000 and May 2005. There were 3 male patients and 20 female patients. Ages ranged from 28 to 74 years (mean, 50 years). Follow-up ranged from 4.1 to 8.2 years (mean, 6.5 years). The American Orthopaedic Foot and Ankle Society (AOFAS) score and their satisfaction was evaluated clinically, foot anteroposterior and lateral radiograph, radiologically. Results: Of the 24 cases, 6 had surgery for dorsal plate and screws fixation because of failure to acquire firm fixation with two crossed screws fixation. All 6 cases acquired bony union. Fusion of the hallux first metatarsophalangeal joint occurred in 16/18 cases (89%). Nonunion occurred in 2 cases (11%) and was asymptomatic. At last follow-up, hallux valgus angle ranged from 11 to 25 degrees(mean, 17.7 degrees), dorsiflexion ranged from 15 to 25 degrees (mean, 22 degrees).The mean preoperative AOFAS score of 37 points(range, 28 to 45 points) improved to a mean of 77 points (range, 65~90 points) postoperatively. The result of the procedure as rated subjectively by the patient was excellent for 5 cases, good for 11 cases and fair for 2. Conclusion: Comparatively, the arthrodesis of the first metatarsophalangeal joint with crossed screws fixation showed a satisfactory clinical results, we thought that require technical attention for firm fixation in operation.

• Journal of Korean Neurosurgical Society
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• 제63권2호
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• pp.210-217
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• 2020

Objective : To analyze the accuracy of iliac screws using freehand technique performed by the same surgeon. We also analyzed how the breach of iliac screws was related to the clinical symptoms resulting in revision surgery. Methods : From January 2009 to November 2015, 100 patients (193 iliac screws) were analyzed using postoperative computed tomography scans. The breaches were classified based on the superior, inferior, lateral, and medial iliac wall violation by the screw. According to the length of screw extrusion, the classification grades were as follows : grade 1, screw extrusion <1 cm; grade II, 1 cm ≤ screw extrusion <2 cm; grade III, 2 cm ≤ screw extrusion <3 cm; and grade IV, 3 cm ≤ screw extrusion. We also reviewed the revision surgery associated with iliac screw misplacement. Results : Of the 193 inserted screws, 169 were correctly located and 24 were misplaced screws. There were eight grade I, six grade II, six grade III, and four grade IV screw breaches, and 11, 8, 2, and 3 screws violated the medial, lateral, superior, and inferior walls, respectively. Four revision surgeries were performed for the grade III or IV iliac screw breaches in the lateral or inferior direction with respect to its related symptoms. Conclusion : In iliac screw placement, 12.4% breaches developed. Although most breaches were not problematic, symptomatic violations (2.1%) could result in revision surgery. Notably, the surgeon should keep in mind that lateral or inferior wall breaches longer than 2 cm can be risky and should be avoided.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제38권5호
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• pp.271-275
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• 2012

Objectives: This study evaluated a range of fixation methods to determine which is best for the postoperative stabilization of a mandibular osteotomy using three-dimensional finite element analysis of the stress distribution on the plate, screw and surrounding bone and displacement of the lower incisors. Materials and Methods: The model was generated using the synthetic skull scan data, and the surface model was changed to a solid model using software. Bilateral sagittal split ramus osteotomy was performed using the program, and 8 different types of fixation methods were evaluated. A vertical load of 10 N was applied to the occlusal surface of the first molar. Results: In the case of bicortical screws, von-Mises stress on the screws and screw hole and deflection of the lower central incisor were minimal in type 2 (inverted L pattern with 3 bicortical repositioning screws). In the case of plates, von-Mises stress was minimal in type 8 (fixation 5 mm above the inferior border of the mandible with 1 metal plate and 4 monocortical screws), and deflection of the lower central incisor was minimal in types 6 (fixation 5 mm below the superior border of the mandible with 1 metal plate and 4 monocortical screws) and 7 (fixation 12 mm below the superior border of the mandible with 1 metal plate and 4 monocortical screws). Conclusion: Types 2 and 6 fixation methods provide better stability than the others.

• 대한치과보철학회지
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• 제36권5호
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• pp.721-737
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• 1998

Abutment screw loosening of implant restorations is a common problem in the treatment of dental implant. The purpose of this study was to calculate stress and preload from the elongation measurements and to determine maximum tightening torque without plastic deformation of the screw. The length of each gold alloy UCLA screw was measured after tightening to the manufacturer's recommended torque of 32 N-cm. Similarity, titanium UCLA screws were measured after tightening to the manufacturer's recommended torque of 20 N-cm. Loosening torque was also measured after tightening to 32 N-cm torque for gold alloy abutment screws and 20 N-cm for titanium abutment screws. The results were as follows ; 1. There was a regressive relationship between screw elongation and tightening torque (gold alloy : $r^2=0.987$, titanium : $r^2=0.978$), and the mean preload calculated from elongation measurements was $501.11{\pm}26.85\;N$ (gold alloy) and $399.43{\pm}7.61\;N$ (titanium). 2. Stress calculated for the gold alloy and titanium screws at maximum recommended tightening torque was less than 60% of their respective yield strengths and with-in the elastic range. Maximum tightening torque without plastic deformation was 61 N-cm (gold alloy) and 39 N-cm (titanium). 3. For titanium screws, there was a significant difference between loosening after trial 1 and loosening after trials 2 to 5 (p<0.05). No statistically significant difference was seen in mean loosening torques between the first and subsequent trials for gold alloy screws.

• 대한치과보철학회지
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• 제45권1호
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• pp.119-130
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• 2007

Statement of problem: A few dry lubricants were applied to abutment screws for the improvement of joint stability. Purpose: The purpose of this study was to evaluate the surface change and fit of TiN-Coated abutment screw through the examination of tested screws in the field emission scanning electron microscope(FE-SEM;Netherland, Phillips co., model:XL 30 SFEG) after repeated closing and opening. Materials and method: Titanium(3i/implant Innovations Inc, USA) and Gold-Tite abutment screws(3i/implant Innovations Inc, USA) were selected for Group A and C respectively. TiN coated titanium abutment screws were also divided into two groups, Group B and D. Abutment screws of each group and the fit of abutment screw/implant fixture/abutment were observed on FE-SEM after repeated closing and opening test respectively. Results: 1. The abutment screws of TiN coated groups(Group B and D) showed more remarkable wear resistance in the threads of the screw than those of the other group(Group A and C). 2. There were more severe wear and defect of TiN coating in Group D tightened to 32 Ncm than Group B to 20 Ncm. 3. There was no difference in the fit of abutment screw/fixture/abutment among four groups, Group A, Group B, Group C and Group D. Conclusion: Under the conditions of this study, it is suggested that TiN coating of abutment screw be clinically acceptable and be expected to reduce the risk of abutment screw loosening. TiN coating of abutment screw showed good resistance against wear and the adequate fit of abutment screw/implant fixture/abutment.

• 대한소아치과학회지
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• 제35권2호
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• pp.339-344
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• 2008

상악 영구 견치의 매복에 비해 하악 영구 견치의 매복은 매우 드물게 일어난다. 치아가 매복된 경우 장애물 존재 여부와 매복 위치와 방향, 맹출 가능한 공간의 유무, 치근의 형성 단계 등의 요소에 따라 매복 치아의 발거 혹은 장애물의 제거 후 주기적 관찰, 맹출이 지연된 치아의 외과적 노출, 교정적 견인 등의 방법으로 치료하게 된다. 본 증례는 하악골의 골절 부위에 시행된 골간 강선 결찰과 미니 플레이트에 의해 하악 좌측 견치가 매복되어 있었던 경우로 CT 검사 결과 하악 정중부위 플레이트의 스크류가 맹출을 방해하고 있는 것으로 판단되어 전신 마취 하에 플레이트를 제거하였다. 이후 자연적인 맹출을 기대하였으나, 맹출력이 부족하여 교정적 견인으로 양호한 결과를 얻었기에 보고하는 바이다.