• Journal of Periodontal and Implant Science
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• 제37권4호
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• pp.681-690
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• 2007

Mini implants had been used provisionally for the healing period of implants in the beginning. But it becomes used for the on-going purpose, because it is simple to use, economic and especially suitable for the overdenture. But there is few studies about the stability of mini implants, that is most important factor for the on-going purpose, and particularly the implant parameters affecting the initial stability. The purpose of this study was to evaluate the stress and the strain distribution pattern of immediate-loaded screw type orthodontic mini-implant and the parameters affecting the initial stability of immediate-loaded mini-implant. Two dimensional finite element models were made and contact non-linear finite element analysis was performed. The magnitude and distribution of Von Mises stresses were evaluated. The obtained results were as follows: 1. The stress was concentrated on the thread tip of an implant in the cortical bone. 2. The direction of load is the most important factor for the stress distribution in cortical bone. 3. The diameter of an implant is the most important factor for the stress distribution in the trabecular bone. In conclusion, if the horizontal load vector is successfully controlled, mini-implants, which diameter is under 3mm, can be used for the on-going purpose.

• Advances in Traditional Medicine
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• 제6권2호
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• pp.79-85
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• 2006

In order to study the effect of acupuncture stimulation on bone mineral density (BMD), using the ovariectomized (OVX) rat model, we assessed the degree of osteopenia by dual-energy X-ray absorptiometry, measured the level of locomotor activity using a metabolism measuring system, and performed histological studies of bone tissue. Twenty-four female Wistar rats (8 weeks old, 160 - 180 g)were divided into three groups. Rats in the OVX-A group underwent ovariectomy followed by acupuncture stimulation. The OVX rats in the Vehicle control group were not treated with acupuncture as a control. The rats in the control group received neither ovariectomy nor acupuncture. Acupuncture stimulation for 12 weeks in the OVX-A group inhibited the reduction in BMD of the femoral bones caused by ovariectomy. Moreover, in the two OVX groups, there was no clear difference in the level of locomotor activity between the active and resting phases prior to acupuncture stimulation in each rat, and the pattern of locomotor activity was irregular. After acupuncture stimulation of the OVX-A rats, the pattern of locomotor activity became diphasic with clear active and resting phases, as was observed in the Control group. On histological studies, the continuity of trabecular bone was maintained more favorably and bone mass was higher in the OVX-A group than in the vehicle control group. These results suggest that the increased locomotor activity that had been induced by acupuncture stimulation increased the BMD.

• Advances in biomechanics and applications
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• 제1권1호
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• pp.1-14
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• 2014

In this paper, a simple and accurate finite element model coupled to quasi-brittle damage law able to describe the multiple cracks initiation and their progressive propagation is developed in order to predict the complete force-displacement curve and the fracture pattern of human proximal femur under quasi-static load. The motivation of this work was to propose a simple and practical FE model with a good compromise between complexity and accuracy of the simulation considering a limited number of model parameters that can predict proximal femur fracture more accurately and physically than the fracture criteria based models. Different damage laws for cortical and trabecular bone are proposed based on experimental results to describe the inelastic damage accumulation under the excessive load. When the damage parameter reaches its critical value inside an element of the mesh, its stiffness matrix is set to zero leading to the redistribution of the stress state in the vicinity of the fractured zone (crack initiation). Once a crack is initiated, the propagation direction is simulated by the propagation of the broken elements of the mesh. To illustrate the potential of the proposed approach, the left femur of a male (age 61) previously investigated by Keyak and Falkinstein, 2003 (Model B: male, age 61) was simulated till complete fracture under one-legged stance quasi-static load. The proposed finite element model leads to more realistic and precise results concerning the shape of the force-displacement curve (yielding and fracturing) and the profile of the fractured edge.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제32권5호
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• pp.418-425
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• 2006

Purpose: This study was aimed at evaluating the histological changes of new bone and expression of osteopontin (OPN) after mandibular distraction osteogenesis. Materials and Methods: Unilateral mandibular distraction (0.5 mm twice per day for 10 days) was performed in eight adult dogs. Two animals were sacrificed at 7, 14, 28 and 56 days after completion of distraction, respectively. The distracted bones and contralateral non-distracted control bones were harvested and processed for histological and immunohistochemical examinations. Results: The new bone was arranged to tension direction after distraction osteogenesis. 7 days after distraction, numerous osteoblasts lining the immature trabecular bone and fibroblast-like cells in the fibrous intrezone were observed. 14 days after distraction, the new formed trabecular bones were thickened compared with 7 days after distraction. 28 days after distraction, the fibrous interzone was almost filled with newly calcified bone, and it was more hardened at 56 days after distraction. Increased OPN signals detected in the osteoblasts lining the trabecular bone and fibroblast-like cells in the fibrous interzone at 7 and 14 days after distraction. At 28 days after distraction, the OPN was weakly expressed in the osteoblasts, and it was not detected in all cellular components of distracted bone at 56 days later of distraction. Conclusions: After distraction osteogenesis, the distracted zone was completely calcified during the 56 days of consolidation period. In this study, the staining intensity of OPN increased in the osteoblasts and fibroblast-like cells at 7 and 14 days after distraction. The expression pattern of this protein shown here suggested that OPN play an important role in the osteogenesis during the early consolidation period.

• 구강회복응용과학지
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• 제27권4호
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• pp.359-370
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• 2011

임플란트의 골유착 성공 여부를 확인하기 위해서 방사선학적 분석방법을 사용하였다. 치근단 방사선 사진을 이용한 프렉탈 분석방법을 사용하여 기능하중 전 후의 임플란트 주변 골밀도를 분석하고 골유착에 실패한 임플란트와 성공한 임플란트 사이에 유의한 차이가 있는지 비교하였다. 본 연구에서는 원광대학교 치과병원에서 임플란트 식립 시술을 받은 30명의 환자에서 총 42개의 임플란트를 분석에 사용하였다. 환자는 14명의 남자와 16명의 여자로 구성 되었고 나이는 22세에서 73세 사이였다. 치조골의 trabecular 양상의 형태와 프렉탈 분석은 치근단 방사선 사진을 이용하였다. 총 2장의 치근단, 즉 임플란트 식립 직후와 임플란트 보철물 장착 후 기능 하중이 가해진 뒤 3개월 후의 방사선 사진이 사용되었다. 분석은 Image J(1.40s, National Institute of Health, Bethesda, USA)를 이용하여 시행하였다, 통계학적 분석방법은 one-way ANOVA(P<.05)를 이용하여 시행하였다. 그리고 Tukey multiple comparison test로 사후검정을 실시하였다. 프렉탈 분석 결과와 임플란트 주변의 골밀도 변화는 통계적으로 유의할만한 상관관계가 있으며 특히 하악에서 이런 결과가 더욱 명백하였다. 또한 두개의 실패한 임플란트의 경우 프렉탈 수치가 각각 1.2865에서 1.1521로, 1.1135에서 1.0478로 감소되는 경향을 나타냈다.

• 치위생과학회지
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• 제15권2호
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• pp.98-105
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• 2015

본 연구는 외과적으로 형성된 흰쥐 하악골 결손부에 S.mutan에서 분리 정제된 mutan을 주사하고, ${\mu}CT$로 촬영하여 골결손부의 치유에 미치는 영향을 3차원 골 미세구조 지표로 평가하기 위하여 실시하였다. 흰쥐 치조골에 임계 크기 결손부인 1.5 mm 지름의 원형 결손부를 형성하여 대조군에는 동일량의 saline을 투여하고, 실험군으로 LPS와, mutan을 주사하여 골치유에 미치는 영향을 관찰하였다. 수술 후 4주에 희생하고 치유 결과를 3차원 미세구조의 형태 계측학적 지표값을 비교 분석하여 다음과 같은 결론을 얻었다. 실험동물의 체중변화는 총 12회 투여 기간 동안 일정한 증가를 나타냈다. 8회차부터 mutan 처리군은 대조군과 비교하여 유의한 차이를 보였으며(p<0.05), 9회차에는 mutan 처리군이 대조군과 LPS 처리군과 비교하여(p<0.05), 10~12회차에는 LPS 처리군과 비교하여 유의한 체중증가를 나타냈다(p<0.01). Mutan이 생체 내에서 하악의 골치유 효과를 알아보기 위해 ${\mu}CT$를 통해 형태계측학적 지표 분석 결과, 대조군에 비해 LPS 처리군에서 뚜렷한 골결손부 치유 지연 및 골흡수 양상을 보였으며, mutan 처리군 은 LPS의 작용보다 미약하지만 골치유를 지연시키는 것으로 확인되었다. ${\mu}CT$를 통해 골밀도 분석 결과, 대조군과 비교하여 LPS와 muatn 처리군에서 낮은 골밀도치를 나타냈고, mutan은 LPS 처리군보다 유의하게 높은 골밀도치를 보였다(p<0.01).

• 대한세포병리학회지
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• 제1권1호
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• pp.98-102
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• 1990

Hepatoblastoma (HB) is a rare embryonic malignant tumor of the liver. Most morphological studies on HB have limited to the histological characteristics and only 3 cases of HB have been described in the cytology literature. We present 2 cases of HB occurring in children aged 1 year and 3 years, respectively. The distinctive cytologic features of fine needle aspiration of HB were clusters of tumor cells showing acinar and trabecular pattern, smaller tumor cells with a high nuclear-cytopalsmic ratio and hyperchromatic nuclei having prominent nucleoli, and the presence of extramedullary hematopoiesis and osteoid material. These features were also found in the cell block and the biopsy specimen, and appeared very useful in the differentiation of HB from hepatocellular carcinoma.

• 대한소아치과학회지
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• 제21권2호
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• pp.504-509
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• 1994

Achondroplasia is characterized by undergrowth of long bones and cartilages and by low height. The name of this disease had been called classical chondrodystrophy, dyschondroplasia, chondrodystrophy and micromelia before Parrot reported the term of this disease as Achondroplasia. We are reporting in this paper on an 3-year and 4-month-old boy with achondroplasia. The dental findings are as follows: 1. Open bite and relatively mandibular prognathism were observed in the front teeth. 2. The size, number, shape, structure of the teeth were usual and the tongue was a little bigger than the normal. 3. The metacarpal bones were short and broadening. Mesial, distal border of the prox. phalanges were irregular and also trabecular pattern was abnormal in the hand-wrist P-A view. 4. According to lat. cephalometric analysis, the cranial basis was underdeveloped.

• 한국임상수의학회지
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• 제34권6호
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• pp.481-483
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• 2017

A 2-year-old neutered male Bengal cat presented with a 6-month history of weight loss and chronic vomiting. An abdominal ultrasound revealed increased thickness of the pylorus and ascending duodenum with concurrent enlargement of the mesenteric lymph nodes. Histologically, branching and anastomosing trabecular pattern of dense collagen was the characteristic feature, and large populations of spindle cells were also observed. These large spindle-shaped cells were positive for smooth muscle actin and vimentin on immunohistochemical examination. Based on these findings, the cat was diagnosed with feline gastrointestinal eosinophilic slcerosing fibroplasia (FGESF), and immunosuppressive therapy was initiated immediately. Unfortunately, the cat's condition deteriorated despite treatment; the cat died 56 days after initiation of therapy. This is the first report of FGESF in South Korea.

• 대한세포병리학회지
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• 제19권1호
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• pp.9-15
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• 2008

The major categories of neuroendocrine tumors of lung are typical carcinoid, atypical carcinoid, large cell neuroendocrine carcinoma, and small cell carcinoma. The histologic classification criteria of neuroendocrine tumors are well documented in the "WHO Classification of Tumors" based on mitotic figures and necrosis. Cytologic characteristics of neuroendocrine tumors are trabecular, acinar, and solid arrangement of tumor cells and occasional rosette formation. Nuclear chromatin patterns are characteristically described as "salt and pepper chromatin pattern". Many of cytologic classifications documented in the literature are before the "WHO Classification". In this review, the cytologic features of pulmonary neuroendocrine tumors are documented according to the WHO classification, and recent concepts of neuroendocrine tumors of lung are discussed.