• The Journal of Korean Academy of Prosthodontics
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• v.49 no.3
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• pp.222-228
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• 2011

Purpose: The purposes of this study were to evaluate the stress distributions and the displacements of obturator for edentulous maxillectomy patients and to compare them with those of complete denture using three-dimensional finite element analysis. Materials and methods: Based on the CT image of edentulous patient, three-dimensional finite element model of edentulous maxillae was constructed. Three-dimensional finite element model of edentulous maxillae with palatal defect was also fabricated. On each model, complete denture and obturator prosthesis were created. Vertical static force of 200 N was applied on the left maxillary premolar and molar region. The von Mises stress values and the displacements of models were analyzed using three-dimensional finite element analysis. Results: Maximum von Mises stress values were recorded in the cortical bones of both models. The von Mises stress value in the complete denture model was 2.73 MPa and 2.69 MPa in the obturator model. High von Mises stress values were also observed on the tissue surface of prosthesis. The maximum value of the displacement in the obturator was higher than that of complete denture. Conclusion: The obturator showed a worse result in terms of stress distribution and displacement than complete denture. In the prosthodontic rehabilitation of edentulous maxillectomy patient accurate impression procedure based on patients'anatomy and application of prosthodontic principle should be considered.

• The Journal of Korean Academy of Prosthodontics
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• v.52 no.3
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• pp.233-238
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• 2014

Purpose: A method detecting change of jaw or alveolar bone density may be helpful in periodontal care, implant dentistry and evaluation of bone density of whole body. Materials and methods: In this study, bone density of intraoral periapical radiography using phantom-integrated XCP is compared with that of quantitative computed tomography (QCT). Results: Bone density of intraoral periapical radiography and the one measured by QCT showed high correlation (correlation coefficient = 0.92, P<.001) in alveolar bone, and relatively high correlation (0.73, P<.001) in cancellous bone. Conclusion: This study revealed possibility of scoring of bone density by intraoral periapical radiography.

• Proceedings of the KOSOMBE Conference
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• v.1996 no.11
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• pp.323-326
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• 1996

Dental implant is increasingly used to recover the mastication function of tooth. Several types of implant were designed to give an optimal stress distribution in surrounding bony regions. In this study, six types of implant were investigated using finite element method and it was studied i) how the variation of cortical bone thickness affects the stress distribution in surrounding bony regions depending upon implant types, ii) which type gives the best characteristics in the sence of stress distribution and stability. The hybrid-type implant with cylinder and screw gave the optimum properties in view of stability and response to the variation of cortical bone thickness.

• The korean journal of orthodontics
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• v.37 no.2 s.121
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• pp.89-97
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• 2007

Objective: The purpose of this study was to measure the insertion torque of orthodontic miniscrews regarding changes in their shape, diameter, and length. Methods: Torque values were measured during continuous insertion of the miniscrews into solid rigid polyurethane foam, using a torque tester of driving motor type with a regular speed of 3 rpm. Orthodontic miniscrews (Biomaterials Korea, Seoul, Korea) of cylindrical type and taper type were used. Results: Increasing the length and diameter of the miniscrews increased the maximum insertion torque value in both cylindrical and taper type screws. Insertion torque was increased at the incomplete head of the cylindrical type screw, and at the tapered part of the taper type screw. The insertion torque value of miniscrews was influenced most by diameter, then shape and length. As a result, it was shown that the diameter of the screw had the most influence on insertion torque, and the taper type screw had a higher torque value than the cylindrical type screw. Conclusion: Therefore, a large diameter or taper type screw are adequate for areas of thin cortical bone with a large interdental space, and a small diameter or cylindrical type screw are adequate in the mandibular molar area or the midpalatal area having thick cortical bone.

• The Korean Journal of Nuclear Medicine
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• v.31 no.4
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• pp.452-458
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• 1997

To evaluate the pinhole scintigraphic findings and its significance, authors retrospectively compared the pinhole bone scintigrams and corresponding radiograms of 16 lesions in 14 patients with fibrous dysplasia. They were diagnosed pathologically in 10 lesions and radiologically in 6 lesions. The mean age of patients was 41.1 years. The mean interval between two studies was 1.1 days. Locations were ribs 7, pelvic bone 4, clavicle 1, long bones 4(femur 2, tibia 1, humerus 1). The radiographic findings were as follows : the central portions were radiolucent(n=9), ground-glass opacities(n=5) or sclerotic(n=2) and the peripheral appearance were sclerotic rim(n=5), septation(n=7), cortical perforation (n=10) and invisible cortical thinning(n=9). Pinhole scintigraphic findings were as follows; Central portions showed normal 1+ uptake in 6 cases(radiolucent 5, ground-glass opacity 1), slightly increased 2+ upta- ke in 7 cases(radiolucent 4, ground-glass opacity 3), and marked 3+ uptake in 3 cases(ground-glass opacity 1, sclerotic 2). The 15 of 16 lesions showed more intense uptake in the peripheral portion: slightly increased 2+ uptake corresponding to the sclerotic rim(5/5) and unvisible cortical thinning(1/9), and irregular foci of marked 3 + uptake corresponding to septation(7/7), cortical perforation(10/10) and invisible cortical thinning (8/9). One of 16 lesions showed homogeneous 2+ uptake. In conclusion, pinhole scintigram provides information on regional activity of the fibrous dysplasia, which would be helpful in diagnosis, prediction of prognosis and determination of treatment plan.

• The Journal of the Korean bone and joint tumor society
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• v.8 no.1
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• pp.20-26
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• 2002

Fibrous dysplasia is a benign pathologic condition in which the normal cancellous bone is replaced by the fibro-osseous tissue. It is found mostly in the femur, tibia, skull, rib, and humerus. Clinically it may develops pain, progressive deformity, and pathologic fracture. Curettage with bone graft has been the most popular treatment method thesedays. A 17-year-old female who had fibrous dysplasia of the humerus combined with multiple cystic lesion was treated by intralesional steroid injection into the lesion total 2 times. The follow-up plain X-ray which was taken 11 months after steroid injection reveals decrease in size and increase in bone density and cortex thickness. The follow-up MRI reveals significant decrease in size and signal intensity. The signal intensity was decreased to that of normal bone marrow in T2 weighted image. She complains no pain and lives symptom free in last follow-up at 2 years and 8 months after steroid injection.

• Korean Journal of Cleft Lip And Palate
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• v.3 no.1
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• pp.1-9
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• 2000

목적 : 치조파열 환자에 있어서 이차 치조골 이식술을 시행한 후 그 결과를 알아보고자 방사선학적 분석을 통하여 평가하였다. 본 연구의 목적은 수술전 골결손부 인접치아의 치조정 높이와 수술후 골결손부 인접치아의 치조정 높이를 근심측과 원심측에서 각각 측정함으로써 치조정의 높이가 과연 통계적으로 유의성 있게 증가하는지와 치조골 이식술의 성공률이 치조열의 너비와 상관관계가 있는지의 여부를 알아보는 것이다. 환자 및 방법 : 1991년부터 1999년까지 서울대학교병원 구강악안면외과에서 자가장골 채취 후 분쇄피질망사골 형태 또는 block 피질망상골 형태로 이식한 편측성 치조열을 가진 환자 중 최소한 6개월이 경과한 환자 56명을 연구대상으로 하였고 두 술자에 의해 시술되었다. 수술전 골결손부 인접치아의 치조정의 높이와 치조열의 너비 및 수술후 이식한 골의 높이와 절흔의 양은 치과용 파노라마 방사선 사진을 이용하여 측정하였고, 치조열의 너비는 모델이나 환자의 골결손부 근심치아의 근원심 폭경을 이용하여 환산하였다. 그리고 이식한 골의 높이와 절흔의 양을 1995년 Long이 제시한 방법으로 측정하여 술전의 측정치와 비교하였다. 결과 : 치조열의 너비는 평균 6.9mm(1.9mm-12.1mm) 였다. 근심에서의 치아는 골이식 당시 중절치가 52개(92.9%), 측절치가 4개(7.1%)였고, 49명의 환자에서 완전맹출을, 6명의 환자에서 부분맹출(측절치 2개, 중절치 4개)을 보였다. 원심측에서의 치아는 골이식 당시 측절치가 25개(44.6%), 견치가 29개(51.8%), 소구치가 2개(3.6%)였고, 완전 맹출이 32.1%, 부분 맹출이 57.2%, 미맹출이 10.7%로서 완전히 맹출하기 전에 골이식한 경우가 67.9%였다. 모든 환자에 있어서 bony bridge가 나타났고, 절흔이 인접치 아래로 연장되지 않았으며, 치조골 이식술 후 oronasal fistula를 보인 환자는 한 명도 없었으므로 성공률은 100%였다. 술후 근심측에서의 치조정의 높이는 근심측 치아 치근길이의 79%(평균), 원심측에서의 치조정의 높이는 원심측 치아 치근길이의 87%(평균)로서 통계적으로 유의성 있게 증가하였다. 결론: 이차 치조골 이식술을 시행한 후 치조정의 높이는 골결손부 근심측과 원심측에서 모두 유의성있게 증가하였고, 근심측에서보다 원심측에서 통계학적으로 더 유의성 있게 증가하였다. 치조열의 너비와 절흔의 양, 치조정의 높이 및 치조골이식 성공률과는 유의성 있는 관련성이 없었다.

• The Journal of Korean Academy of Prosthodontics
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• v.49 no.2
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• pp.168-176
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• 2011

Purpose: This study aims at investigating the influence of various insertion torques on thermal changes of bone. A proper insertion torque is derived based on the thermal analysis with two different implant designs. Materials and methods: For implant materials, bovine scapula bone of 15 - 20 mm thickness was cut into 35 mm by 40 - 50 mm pieces. Of these, the pieces having 2 - 3 mm thickness cortical bone were used as samples. Then, the half of the sample was immersed in a bath of $36.5^{\circ}C$ and the other half was exposed to ambient temperature of $25^{\circ}C$, so that the inner and surface temperatures reached $36.5^{\circ}C$ and $28^{\circ}C$, respectively. Two types of implants ($4.5{\times}10\;mm$ Br${\aa}$nemark type, $4.8{\times}10\;mm$ Microthread type) were inserted into bovine scapula bone and the temperature was measured by a thermocouple at 0.2 mm from the measuring point. Finite element method (FEM) was used to analyze the thermal changes at contacting surface assuming that the sample is a cube of $4\;cm{\times}4\;cm{\times}2\;cm$ and a layer up to 2 mm from the top is cortical bone and below is a cancellous bone. Boundary conditions were set on the basis of the shape of cavity after implants. SolidWorks was used as a CAD program with the help of Abaqus 6.9-1. Results: In the in-vitro experiment, the Microhead type implant gives a higher maximum temperature than that of the Br${\aa}$nemark type, which is attributed to high frictional heat that is associated with the implant shape. In both types, an Eriksson threshold was observed at torques of 50 Ncm (Br${\aa}$nemark) and 35 Ncm (Microthread type), respectively. Based on these findings, the Microthread type implant is more affected by insertion torques. Conclusion: This study demonstrate that a proper choice of insertion torque is important when using a specific type of implant. In particular, for the Microthread type implant, possible bone damage may be expected as a result of frictional heat, which compensates for initial high success rate of fixation. Therefore, the insertion torque should be adjusted for each implant design. Furthermore, the operation skills should be carefully chosen for each implant type and insertion torque.

• Clinics in Shoulder and Elbow
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• v.2 no.2
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• pp.187-198
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• 1999

Purpose: The authors compared the results of Ender nailing for the proximal humerus fractures with those of the conservative methods radiographically. Materials and Method: Nine patients(mean age: 69 years.) received Ender nailing, and the other nine patients, conservative treatments(mean age: 73 years). All fractures were 2 part fractures. The Ender nails were inserted either through posterior elbow approach or transepicondylar approach. A simple Velpeau bandage was applied to the conservative treatment group. The average follow-up was 15 months. Results: The initial status of the anatomical reduction, i.e., the values of the medial shift, overlapping and the varus agulation, were little changed at follow-up radiographs in both the Ender nailing group and the conservative treatment group. There was no significant difference for the status of anatomical reduction between the Ender nailing group and the conservative treatment group. The stability of fixation by Ender nails, i.e., the degree of fanning out of the nails was poor in most cases. Not a few problems/complications happened in cases of Ender nailing group; back­ing out of the nail in three cases, penetration of the nails into the humeral heads in 3, fractures or cracking of the humerus around the nail insertion area in 4 and reduction loss in one. Conclusion: We could not get better results with the use of Ender nail. We use no longer Ender nails for the proximal humerus fractures. Further studies are needed for the better option for the proximal humerus fractures.

• The Journal of the Korean bone and joint tumor society
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• v.8 no.3
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• pp.90-95
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• 2002

A 42 year old male patient complained of increasing pain and mass around the right ankle with 4 months duration. Simple Roentgenogram and CT showed ill-defined osteolysis and cortical perforation in the neck of the right talus. The pathologic findings showed high grade osteoblastic osteosarcoma. The tumor mass of the ankle increased and pulmonary metastasis was found in spite of administrating of two cycles of preoperative chemotherapy. Below-knee amputation and open wedge pulmonary resection were performed for primary lesion and multiple pulmoanry metastasis, respectively. However, the patient died with multiple pulmonary metastasis in spite of three cycles of postoperative chemotherapy at ten months after the operation.