• 대한소아치과학회지
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• 제34권2호
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• pp.222-233
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• 2007

치과 수복 재료 검사 시 가장 중요하고 기본적인 것은 치아와 수복물 사이의 미세누출에 대한 평가이다. 미세 누출을 평가하는 방법은 여러 가지가 있지만 이들 대부분은 많은 단점들을 가지고 있다. 최근에 개발된 미세 단층촬영법(micro-CT)을 이용하면 시편을 비파괴적으로 처리하여 특정 밀도에 해당하는 부분의 3차원적 영상을 얻을 수 있으므로, 이를 이용하면 정확하고 정량적인 미세누출 평가도 가능할 것이다. 이 연구의 목적은 micro-CT를 사용하여, 레진 수복물의 미세 누출도를 정량적이고 비파괴적으로 측정할 수 있는 새로운 방법을 찾아내고, 이 새로운 방법을 기존의 색소 침투법과 비교해보는 것이다. 이를 위해, 위의 두 가지 방법을 사용하여 두 종류의 상아질 접착 시스템의 미세누출도가 평가되었다. 사람의 건전 소구치 40개를 임의로 20개씩 두 군으로 나누고 다음과 같이 처리하였다. Group 1 : $Adper^{TM}$ Singe Bond 사용 후 제 V급 와동 레진 수복, Gourp 2 : $Adper^{TM}\;Promp^{TM}$ L-pop 사용 후 제 V급 와동 레진 수복 모든 치아의 5급 와동은 $Filtek^{TM}$ Supreme으로 수복하였다. 그 후 각 군 중 10개의 치아는 micro-CT를 사용하여 미세 누출도를 평가하고, 나머지 10개는 기존의 색소 침투법으로 평가하였다. 이 연구의 결과는 다음과 같았다. 1. Micro-CT를 사용한 경우, 1군은 2군보다 통계적으로 유의성 있게 적은 양의 미세 누출을 보였다(p<0.01). 2. 기존의 색소 침투법을 사용한 경우에서 1군은 2군보다 적은 미세누출을 보였으며 이는 통계적으로 유의성이 있었다. (p<0.01). 3. 두 군간의 미세 누출도는 micro-CT를 사용한 방법에서 더 현저한 차이를 보였다. 4. 두 가지 방법 모두에서 법랑질 변연 부분보다 상아질 변연 부분에서 더 많은 미세 누출을 보였다.

• Journal of Multimedia Information System
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• 제6권2호
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• pp.67-74
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• 2019

Bone density is one of the factors in the early failure of dental implants and doctors should make a preoperative assessment of jaw bone density using patient's CT data before dental implant surgery in order to find out whether the patient has osteoporosis and osteopenia. The main goal of this study was to propose a method that based on image processing techniques in order to provide accurate information about where to drill and place an abutment screw of implants in the jaw bone for doctors and reduce human activity for the estimation of the local cancellous bone density of mandible using CT data. The experiment was performed on a computed tomography data of the jaw bone of two different individuals. We assumed that the result of the estimation of jaw bone density depends on the angle of drilling and average HU (Hounsfield Unit) values were used to evaluate the quality of local cancellous bone density of mandible. As a result of this study, we have been developed a toolbox that can be used to estimate jaw bone density automatically and found a positive correlation between the angle of the drill and time complexity but a negative correlation between the diameter of the drill and time complexity.

• 대한전자공학회논문지SP
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• 제41권3호
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• pp.163-174
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• 2004

치과 분야에서는 치아교정이나 수술 시뮬레이션을 위해서 각 치아를 개별적으로 조작할 수 있는 3차원 치아모델이 필요하다. 치아 CT 영상으로부터 이러한 치아모델의 재구성을 위해서는 각 치아를 이웃한 치아나 치조골로부터 정확하게 분리할 수 있어야 한다. 본 연구에서는 치아 영역을 효과적으로 분리하기 위한 영상정규화 방안과 최적임계화방안을 제안한다. 제안된 방법은 연속적인 CT 영상 슬라이스들에서 치아영역의 형태와 밝기는 점진적으로 변한다는 사실을 근거로 이전 슬라이스에서 추정된 임계치를 이용하여 현 슬라이스의 임시치아경계를 결정하고 이것을 바탕으로 보다 정확한 임계치를 계산한다.

• Imaging Science in Dentistry
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• 제45권1호
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• pp.7-13
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• 2015

Purpose: We have developed a new method of segmenting the areas of absorbable implants and bone using region-based segmentation of micro-computed tomography (micro-CT) images, which allowed us to quantify volumetric bone-implant contact (VBIC) and volumetric absorption (VA). Materials and Methods: The simple threshold technique generally used in micro-CT analysis cannot be used to segment the areas of absorbable implants and bone. Instead, a region-based segmentation method, a region-labeling method, and subsequent morphological operations were successively applied to micro-CT images. The three-dimensional VBIC and VA of the absorbable implant were then calculated over the entire volume of the implant. Two-dimensional (2D) bone-implant contact (BIC) and bone area (BA) were also measured based on the conventional histomorphometric method. Results: VA and VBIC increased significantly with as the healing period increased (p<0.05). VBIC values were significantly correlated with VA values (p<0.05) and with 2D BIC values (p<0.05). Conclusion: It is possible to quantify VBIC and VA for absorbable implants using micro-CT analysis using a region-based segmentation method.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제36권4호
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• pp.262-269
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• 2010

Introduction: Accurate diagnosis and treatment planning are very important for orthognathic surgery. A small error in diagnosis can cause postoperative functional and esthetic problems. Pre-existing 2-dimensional (D) chephalogram analysis has a high likelihood of error due to its intrinsic and extrinsic problems. A cephalogram can also be inaccurate due to the limited anatomic points, superimposition of the image, and the considerable time and effort required. Recently, an improvement in technology and popularization of computed tomography (CT) provides patients with 3-D computer based cephalometric analysis, which complements traditional analysis in many ways. However, the results are affected by the experience and the subject of the investigator. Materials and Methods: The effects of the sources human error in 2-D cephalogram analysis and 3-D computerized tomography cephalometric analysis were compared using Simplant CMF program. From 2008 Jan to 2009 June, patients who had undergone CT, cephalo AP, lat were investigated. Results: 1. In the 3 D and 2 D images, 10 out of 93 variables (10.4%) and 11 out 44 variables (25%), respectively, showed a significant difference. 2. Landmarks that showed a significant difference in the 2 D image were the points frequently superimposed anatomically. 3. Go Po Orb landmarks, which showed a significant difference in the 3 D images, were found to be the artificial points for analysis in the 2 D image, and in the current definition, these points cannot be used for reproducibility in the 3 D image. Conclusion: Generally, 3-D CT images provide more precise identification of the traditional cephalometric landmark. Greater variability of certain landmarks in the mediolateral direction is probably related to the inadequate definition of the landmarks in the third dimension.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2006년도 춘계학술대회 논문집
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• pp.175-176
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• 2006

The aim of the 3D medical imaging is to facilitate the creation of clinically usable image-based algorithm. Clinically usable imaging algorithm for image analysis requires a high degree of interaction to verify and correct results from registration algorithms, such as the Insight Toolkit (ITK) and the Visualization Toolkit (VTK) which are the class libraries. ITK provides segmentation algorithms and VTK has powerful 3D visualization. However, to apply those libraries to the medical images such as Computerized Tomography (CT), the algorithm based on the interactive construction and modification of data objects are necessary. In this paper we showed the 3D registration about mandibular premolar of human teeth acquired by micro-CT scanner. Also, we used the ITK to find the contour of pulp layer of premolar, furthermore, the 3D imaging was visualized with VTK designed to create one kind of view on the data of 3D visualization. Finally, we evaluated that the volume model of pulp layer would be useful for the tooth morphology in dental medicine.

• 한국컴퓨터정보학회논문지
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• 제23권3호
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• pp.17-23
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• 2018

In this paper, we propose the automatic detection method which find the middle part of tooth crown to start individual tooth segmentation. There have been many studies on the automation of individual tooth segmentation, but there are still many problems for full automation. Detection of middle part of tooth crown used as initial information for individual tooth segmentation is closely related to performance, but most studies are based on the assumption that they are already known or they can be represented by using a straight line. In this study, we have found that the jawbone curve is similar to the tooth alignment curve by spatially analyzing the CT image, and propose a method to automatically detect the middle part of tooth crown. The proposed method successfully uses the jawbone curves to successfully create a tooth alignment curve that is difficult to detect. As the middle part of tooth crown is in the form of a tooth alignment curve, the proposed method detects the middle part of tooth crown successfully. It has also been verified by experiments that the proposed method works well on real dental CT images.

• Imaging Science in Dentistry
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• 제39권3호
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• pp.163-168
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• 2009

Purpose : To assess the clinical findings and hard tissue changes of osteomyelitis of the jaws using computed tomographic (CT) image analysis. Materials and Methods : We reviewed and interpreted the CT images of 163 patients (64 males and 99 females, age range from 10 to 87 years) who visited the Seoul National University Dental Hospital from April 23, 2006 to December 31, 2008 and were diagnosed as osteomyelitis of the jaws through clinical, radiologic, and histopathologic examination. Each CT findings was investigated for frequency, correlation with age and gender. Results : Of the 163 patients, 31 (19.0%) were affected on the maxilla, 135 (82.8%) were affected on the mandible, and 3 (1.8%) were affected on the both jaws simultaneously. The mean age of the patients who were affected on the maxilla was 61.0 years and that of the patients who were affected on the mandible was 56.2 years. On the maxilla, the most frequent site of disease was the posterior area (83.9%) and on the mandible, mandibular body (83.0%), followed by angle (48.1%), ramus (38.5%), condyle (13.3%), incisal area (9.6%), and coronoid process (3.0%). Among the 31 maxillary osteomyelitis, defect in the trabecular bone was observed in 28 (90.3%), osteosclerosis 20 (64.5%), defect in the cortical bone 27 (87.1%), sequestrum 17 (54.8%), and periosteal reaction 2 (6.5%). Among the 135 mandibular osteomyelitis, defect in the trabecular bone was observed in 100 (74.1%), osteosclerosis 104 (77.0%), defect in the cortical bone 116 (85.9%), sequestrum 36 (26.7%), and periosteal reaction 67 (49.6%). Conclusion : Of our cases, the maxillary osteomyelitis was visibly observed more frequently in females than males. The incidence is the highest in seventies (28.8%) and the lowest in teens (3.1%). The osteomyelitis of the jaws was observed more frequently in males than females before the age of 50, and observed more frequently in females after the age of 50. The most noticeable point was that the sequestrum was observed more often on maxillary osteomyelitis and the periosteal reaction was observed more often on mandibular osteomyelitis.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제32권4호
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• pp.359-362
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• 2010

The zygoma is second most commonly vulnerable facial bone in fracture, in number only by nasal fractures. It is difficult to evaluate reduction state intraoperatively, because almost surgeons reduce the fractured zygoma by blind method. We suggest the use of orthopedic C-arm intraoperatively. We use plain radiography, CT to evaluate preoperative state. Gilles approach or intraoral approach were used to reduce the fractured zygomatic arch. The C-arm was positioned at chin area, used to evaluate reduction intraoperatively. We got postoperative image by CT or submento-vertex view. There are variable methods to evaluate reduction intraoperatively: palpation, ultrasonography, CT, plain films. C-arm is considered superior diagnostic tool to other methods. The use of intraoperative C-arm was very efficient, it could bring better results.

• Imaging Science in Dentistry
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• 제43권4호
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• pp.227-233
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• 2013

Purpose: This study was performed to analyze human maxillary and mandibular trabecular bone using the data acquired from micro-computed tomography (micro-CT), and to characterize the site-specific microstructures of trabeculae. Materials and Methods: Sixty-nine cylindrical bone specimens were prepared from the mandible and maxilla. They were divided into 5 groups by region: the anterior maxilla, posterior maxilla, anterior mandible, posterior mandible, and mandibular condyle. After the specimens were scanned using a micro-CT system, three-dimensional microstructural parameters such as the percent bone volume, bone specific surface, trabecular thickness, trabecular separation, trabecular number, structure model index, and degrees of anisotropy were analyzed. Results: Among the regions other than the condylar area, the anterior mandibular region showed the highest trabecular thickness and the lowest value for the bone specific surface. On the other hand, the posterior maxilla region showed the lowest trabecular thickness and the highest value for the bone specific surface. The degree of anisotropy was lowest at the anterior mandible. The condyle showed thinner trabeculae with a more anisotropic arrangement than the other mandibular regions. Conclusion: There were microstructural differences between the regions of the maxilla and mandible. These results suggested that different mechanisms of external force might exist at each site.