• Imaging Science in Dentistry
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• v.35 no.3
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• pp.167-173
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• 2005

Purpose : To investigate the relationship between three-dimensional (3D) bone imaging parameters and trabecular strength in the mandible. Materials and Methods : Bone specimens were obtained from the mandibles of five male pigs weighing around 110 kg each. Of those, 43 samples were selected for 3D analysis and measured by micro-computed tomography. The five morphometric parameters were trabecular thickness (Tb.Th), bone specific surface (BS/BV), percent bone volume (BV/TV), structure model index (SMI) and degree of anisotropy (DA). Through destructive mechanical testing, strength parameters were obtained. Results : BV/TV, SMI, BS/BV, and Tb.Th showed significant correlations with strength parameters. DA did not show any correlation with the other parameters. In multiple linear regression analysis, BV/TV alone explained $43\%$ of the variance in Young's modulus. By stepwise inclusion of SMI, the variance in the Young's modulus was better explained up to $52\%$. Conclusions : Predicting trabecular strength in the mandible through architectural analysis would be possible. Further study is needed to establish the tendency and variety of trabecular architecture and strength according to the locations within the mandible.

• Imaging Science in Dentistry
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• v.44 no.2
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• pp.121-128
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• 2014

Purpose: The present study was performed to compare the planning of implant placement based on panoramic radiography (PAN) and cone-beam computed tomography (CBCT) images, and to study the impact of the image dataset on the treatment planning. Materials and Methods: One hundred five partially edentulous patients (77 males, 28 females, mean age: 46 years, range: 26-67 years) seeking oral implant rehabilitation were referred for presurgical imaging. Imaging consisted of PAN and CBCT imaging. Four observers planned implant treatment based on the two-dimensional (2D) image data-sets and at least one month later on the three-dimensional (3D) image dataset. Apart from presurgical diagnostic and dimensional measurement tasks, the observers needed to indicate the surgical confidence levels and assess the image quality in relation to the presurgical needs. Results: All observers confirmed that both imaging modalities (PAN and CBCT) gave similar values when planning implant diameter. Also, the results showed no differences between both imaging modalities for the length of implants with an anterior location. However, significant differences were found in the length of implants with a posterior location. For implant dimensions, longer lengths of the implants were planned with PAN, as confirmed by two observers. CBCT provided images with improved scores for subjective image quality and surgical confidence levels. Conclusion: Within the limitations of this study, there was a trend toward PAN-based preoperative planning of implant placement leading towards the use of longer implants within the posterior jaw bone.

• Journal of the Korean Geotechnical Society
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• v.39 no.8
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• pp.17-28
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• 2023

Laboratory-scale hydraulic fracturing experiments were conducted on granite specimens at various viscosities and injection rates of the fracturing fluid. A series of cross-sectional computed tomography (CT) images of fractured specimens was obtained via a three-dimensional X-ray CT imaging method. Pixel-level fracture segmentation of the CT images was conducted using a convolutional neural network (CNN)-based Nested U-Net model structure. Compared with traditional image processing methods, the CNN-based model showed a better performance in the extraction of thin and complex fractures. These extracted fractures extracted were reconstructed in three dimensions and morphologically analyzed based on their fracture volume, aperture, tortuosity, and surface roughness. The fracture volume and aperture increased with the increase in viscosity of the fracturing fluid, while the tortuosity and roughness of the fracture surface decreased. The findings also confirmed the anisotropic tortuosity and roughness of the fracture surface. In this study, a CNN-based model was used to perform accurate fracture segmentation, and quantitative analysis of hydraulic stimulated fractures was conducted successfully.

• Archives of Craniofacial Surgery
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• v.20 no.1
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• pp.31-36
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• 2019

Background: After closed reduction, patients are sometimes concerned that their external nasal shapes have changed. The aim of this study was to investigate and explain changes in nasal shape after surgery through objective photogrammetric anthropometry measurements taken through three-dimensional (3D) reformed computed tomography (CT) images. Methods: Our study included 100 Korean patients who underwent closed reduction of isolated nasal bone fracture from January 2016 to June 2017. Using the ruler tool in Adobe Photoshop CS3, we measured preoperative and postoperative nasal base heights, long nostril axis lengths, both nasal alar angles, and amount of nasal deviation through the 3D reformation of soft tissue via CT scans. We then compared the dimension of nose. Results: The amount of postoperative correction for nasal base height was 1.192 mm. The differences in nostril length between each side were found to be 0.333 mm preoperatively and 0.323 mm postoperatively. The differences in the nasal alar angle between each side was $1.382^{\circ}$ preoperatively and $1.043^{\circ}$ postoperatively. The amount of nasal deviation was found to be 5.248 mm preoperatively and 1.024 mm in postoperatively. Conclusion: After the reduction of nasal bone fractures, changes in nasal dimensions were noticeable in terms of nasal deviation but less significant in nasal tips, except for changes in nasal alar angles, which were notable.

• Archives of Plastic Surgery
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• v.39 no.5
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• pp.477-482
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• 2012

Background The bone graft for the alveolar cleft has been accepted as one of the essential treatments for cleft lip patients. Precise preoperative measurement of the architecture and size of the bone defect in alveolar cleft has been considered helpful for increasing the success rate of bone grafting because those features may vary with the cleft type. Recently, some studies have reported on the usefulness of three-dimensional (3D) computed tomography (CT) assessment of alveolar bone defect; however, no study on the possible implication of the cleft type on the difference between the presumed and actual value has been conducted yet. We aimed to evaluate the clinical predictability of such measurement using 3D CT assessment according to the cleft type. Methods The study consisted of 47 pediatric patients. The subjects were divided according to the cleft type. CT was performed before the graft operation and assessed using image analysis software. The statistical significance of the difference between the preoperative estimation and intraoperative measurement was analyzed. Results The difference between the preoperative and intraoperative values were $-0.1{\pm}0.3cm^3$ (P=0.084). There was no significant intergroup difference, but the groups with a cleft palate showed a significant difference of $-0.2{\pm}0.3cm^3$ (P<0.05). Conclusions Assessment of the alveolar cleft volume using 3D CT scan data and image analysis software can help in selecting the optimal graft procedure and extracting the correct volume of cancellous bone for grafting. Considering the cleft type, it would be helpful to extract an additional volume of $0.2cm^3$ in the presence of a cleft palate.

• Imaging Science in Dentistry
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• v.34 no.3
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• pp.151-157
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• 2004

Purpose : To evaluate the quantitative accuracy of three-dimensional (3D) images by means of comparing distance measurements on the 3D images with direct measurements of dry human skull according to slice thickness and scanning modes. Materials and Mathods : An observer directly measured the distance of 21 line items between 12 orthodontic landmarks on the skull surface using a digital vernier caliper and each was repeated five times. The dry human skull was scanned with a Helical CT with various slice thickness (3, 5, 7 mm) and acquisition modes (Conventional and Helical). The same observer measured corresponding distance of the same items on reconstructed 3D images with the internal program of V-works 4.0/sup TM/(Cybermed Inc., Seoul, Korea). The quantitative accuracy of distance measurements were statistically evaluated with Wilcoxons' two-sample test. Results: 11 line items in Conventional 3 mm, 8 in Helical 3mm, 11 in Conventional 5mm, 10 in Helical 5mm, 5 in Conventional 7mm and 9 in Helical 7mm showed no statistically significant difference. Average difference between direct measurements and measurements on 3D CT images was within 2mm in 19 line items of Conventional 3mm, 20 of Helical 3mm, 15 of Conventional 5mm, 18 of Helical 5mm, II of Conventional 7mm and 16 of Helical 7mm. Conclusion: Considering image quality and patient's exposure time, scanning protocol of Helical 5mm is recommended for 3D image analysis of the skull in CT.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.39
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• pp.30.1-30.7
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• 2017

Background: The positions of the mandibular lingula and foramen have been set as indexes for inferior alveolar nerve (IAN) block and ramus osteotomies in orthognathic surgery. This study aimed to evaluate the anatomical structures of mandibular ramus, especially the mandibular lingula and foramen, by analyzing the cone-beam computed tomography (CBCT) data of young adults. Methods: We evaluated 121 sides of hemi-mandibular CBCT model of 106 patients (51 male and 55 female patients; 18 to 36 years old). All the measurements were performed using the 2- and 3-dimensional rulers of $OnDemand3D^{(R)}$ software. Results: Statistical analysis of the data revealed that there was no significant difference in the mandibular angle between the genders. The mandibular lingula was found to be located at the center of ramus in males, but a little posterior in relation to the center in females. The mandibular lingula was rarely located below the occlusal plane; however, the position of the mandibular foramen was more variable (84.3% below, 12.4% above, and 3.3% at the level of the occlusal plane). Conclusions: The results of this study provide a valuable guideline for IAN block anesthesia and orthognathic surgery. CBCT can be considered effective and accurate in evaluating the fine structures of the mandible.

• The korean journal of orthodontics
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• v.42 no.2
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• pp.56-63
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• 2012

Objective: To identify the right and left difference of the facial soft tissue landmarks three-dimensionally from the subjects of normal occlusion individuals. Materials and Methods: Cone-beam computed tomography (CT) scans were obtained in 48 normal occlusion adults (24 men, 24 women), and reconstructed into 3-dimensional (3D) models by using a 3D image soft ware. 3D position of 27 soft tissue landmarks, 9 midline and 9 pairs of bilateral landmarks, were identified in 3D coordination system, and their right and left differences were calculated and analyzed. Results: The right and left difference values derived from the study ranged from 0.6 to 4.6 mm indicating a high variability according to the landmarks. In general, the values showed a tendency to increase according to the lower and lateral positioning of the landmarks in the face. Overall differences were determined not only by transverse differences but also by sagittal and vertical differences, indicating that 3D evaluation would be essential in the facial soft tissue analysis. Conclusions: Means and standard deviations of the right and left difference of facial soft tissue landmarks derived from this study can be used as the diagnostic standard values for the evaluation of facial asymmetry.

• The korean journal of orthodontics
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• v.40 no.1
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• pp.6-15
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• 2010

Objective: The aim of this study is to find the most helpful midsagittal reference plane for diagnosis in PA cephalometry compared with 3D CT. Methods: The subjects consisted of 25 adults who showed no facial asymmetry by gross inspection. 3D CT and posteroanterior cephalogram of the subjects were taken. To find the most helpful midsagittal reference plane in PA cephalometry, we considered five kinds of midsagittal planes from which the distances to five landmarks were measured and compared the result with that of 3D CT. The midsagittal plane for 3D CT was determined by the landmarks Nasion, Sella and Basion. Results: PA measurements using the midsagittal reference plane on a perpendicular plane lying through the midpoint of the right and left latero-orbitales was closest to those of 3D CT. Conclusions: It was considered that latero-orbitale perpendicular could be used as the helpful midsagittal reference plane to assess facial asymmetry in PA cephalometry.

• Archives of Plastic Surgery
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• v.50 no.3
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• pp.254-263
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• 2023

Background The three-dimensional (3D) evaluation of skeletal stability after orthognathic surgery is a time-consuming and complex procedure. The complexity increases further when evaluating the surgery-first orthognathic approach (SFOA). Herein, we propose and validate a simple time-saving method of 3D analysis using a single software, demonstrating high accuracy and repeatability. Methods This retrospective cohort study included 12 patients with skeletal class 3 malocclusion who underwent bimaxillary surgery without any presurgical orthodontics. Computed tomography (CT)/cone-beam CT images of each patient were obtained at three different time points (preoperation [T0], immediately postoperation [T1], and 1 year after surgery [T2]) and reconstructed into 3D images. After automatic surface-based alignment of the three models based on the anterior cranial base, five easily located anatomical landmarks were defined to each model. A set of angular and linear measurements were automatically calculated and used to define the amount of movement (T1-T0) and the amount of relapse (T2-T1). To evaluate the reproducibility, two independent observers processed all the cases, One of them repeated the steps after 2 weeks to assess intraobserver variability. Intraclass correlation coefficients (ICCs) were calculated at a 95% confidence interval. Time required for evaluating each case was recorded. Results Both the intra- and interobserver variability showed high ICC values (more than 0.95) with low measurement variations (mean linear variations: 0.18 mm; mean angular variations: 0.25 degree). Time needed for the evaluation process ranged from 3 to 5 minutes. Conclusion This approach is time-saving, semiautomatic, and easy to learn and can be used to effectively evaluate stability after SFOA.