• Imaging Science in Dentistry
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• v.43 no.4
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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.

• Imaging Science in Dentistry
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• v.50 no.2
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• pp.161-168
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• 2020

Purpose: The aim of this study was to evaluate the influence of voxel size and different post-processing algorithms on the analysis of dental materials using micro-computed tomography (micro-CT). Materials and Methods: Root-end cavities were prepared in extracted maxillary premolars, filled with mineral trioxide aggregate (MTA), Biodentine, and Intermediate Restorative Material (IRM), and scanned using micro-CT. The volume and porosity of materials were evaluated and compared using voxel sizes of 5, 10, and 20 ㎛, as well as different software tools(post-processing algorithms). The CTAn or MeVisLab/Materialise 3-matic software package was used to perform volume and morphological analyses, and the CTAn or MeVisLab/Amira software was used to evaluate porosity. Data were analyzed using 1-way ANOVA and the Tukey test(P<0.05). Results: Using MeVisLab/Materialise 3-matic, a consistent tendency was observed for volume to increase at larger voxel sizes. CTAn showed higher volumes for MTA and IRM at 20 ㎛. Using CTAn, porosity values decreased as voxel size increased, with statistically significant differences for all materials. MeVisLab/Amira showed a difference for MTA and IRM at 5 ㎛, and for Biodentine at 20 ㎛. Significant differences in volume and porosity were observed in all software packages for Biodentine across all voxel sizes. Conclusion: Some differences in volume and porosity were found according to voxel size, image-processing software, and the radiopacity of the material. Consistent protocols are needed for research evaluating dental materials.

• The Korea Journal of Herbology
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• v.29 no.6
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• pp.95-102
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• 2014

Objectives : The purpose of this study is to prove the effect of GamiBangkeehwangkee-tang (f$\acute{a}$ngj$\check{i}$hu$\acute{a}$ngq$\acute{i}$-t$\bar{a}$ng, BHT) ethanol extract on the immunity and rheumatoid arthritis related inflammatory cytokines. Methods : We checked viability in RAW 264.7 cell after treat by BHT. Then we measured inflammatory and immunity factors of DBA/1 mice with rheumatoid arthritis induced by collagen after BHT oral administration. Also, we checked micro-CT image, bone volume and bone inflammation ratio in micro-CT and structural parameter test. Results : BHT showed cell viability of 95% or higher in all concentration in RAW 264.7 cells. BHT treated group decreased level in serum of IgM and IgG test by 36% and 25% respectively. And BHT treated group showed significant decrease in WBC, neutrophil, lymphocyte and monocytes immune cell ratio in blood by 47%, 22%, 56% and 85% respectively. Also, BHT treated group decreased level in serum of $IL-1{\beta}$, IL-6, IL-17, $TNF-{\alpha}$ and hs-CRP tests by 29%, 33%, 32%, 24% and 56% respectively. Finally, BHT treated group showed increase ratio of bone volume that decrease ratio of bone inflammation. Conclusions : In this study, the results were observed rheumatoid arthritis factors cytokine decrease in serum. And BHT showed immunoglobulin and immune cells ratio decrease in serum and blood. Also, BHT depending on effects of inflammatory and immunity in hs-CRP test, micro-CT, structural parameter test. Thus, these results can used as a effective drug of BHT for inflammation and immunity.

• Journal of Dental Rehabilitation and Applied Science
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• v.19 no.1
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• pp.7-15
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• 2003

This study used FEM(Finite Element method) based on micro-CT images to see the effects of occlusal force distribution with varying bone density and structure. the mandibular premolar region from human cadaver, thickness of 10mm was imaged using micro-CT. the cross sectional images were taken every $10{\mu}m$. these were reconstructed and the longitudinal image at the mid point of mesiodistal of the speciman was obtained for the specimen for the FEM. The stress disribution produced by a vertical force at 100N and 100N horizontal were analyzed by MSC Nastran FEM Package. according to the result of this study the occlusal force distribution depends on the structure of cancellus bone and for further information on the occlusal force distribution on the tooth and the surrounding structure requires further studies on cancellus bone structure. CEJ of all model show the highest peak and region whice meet teeth and bone show second high peak. Original model and cortical bone add model show different stress distribution. Stress distribution changed according to bone structures and densities.

• Restorative Dentistry and Endodontics
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• v.39 no.1
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• pp.24-31
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• 2014

Objectives: The purpose of present study was to evaluate the internal adaptation of composite restorations using different adhesive systems. Materials and Methods: Typical class I cavities were prepared in 32 human third molars. The teeth were divided into the following four groups: 3-step etch-and-rinse, 2-step etch-and-rinse, 2-step self-etch and 1-step self-etch system were used. After the dentin adhesives were applied, composite resins were filled and light-cured in two layers. Then, silver nitrate solution was infiltrated, and all of the samples were scanned by micro-CT before and after thermo-mechanical load cycling. For each image, the length to which silver nitrate infiltrated, as a percentage of the whole pulpal floor length, was calculated (%SP). To evaluate the internal adaptation using conventional method, the samples were cut into 3 pieces by two sectioning at an interval of 1 mm in the middle of the cavity and they were dyed with Rhodamine-B. The cross sections of the specimens were examined by stereomicroscope. The lengths of the parts where actual leakage was shown were measured and calculated as a percentage of real leakage (%RP). The values for %SP and %RP were compared. Results: After thermo-mechanical loading, all specimens showed significantly increased %SP compared to before thermo-mechanical loading and 1-step self-etch system had the highest %SP (p < 0.05). There was a tendency for %SP and %RP to show similar microleakage percentage depending on its sectioning. Conclusions: After thermo-mechanical load cycling, there were differences in internal adaptation among the groups using different adhesive systems.

• Restorative Dentistry and Endodontics
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• v.46 no.2
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• pp.25.1-25.12
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• 2021

Objectives: This study used micro-computed tomography (µCT) to compare voids and interfaces in single-cone obturation among AH Plus, EndoSequence BC, and prototype surface pre-reacted glass ionomer (S-PRG) sealers and to determine the percentage of sealer contact at the dentin and gutta-percha (GP) interfaces. Materials and Methods: Fifteen single-rooted human teeth were shaped using ProTaper NEXT size X5 rotary files using 2.5% NaOCl irrigation. Roots were obturated with a single-cone ProTaper NEXT GP point X5 with AH Plus, EndoSequence BC, or prototype S-PRG sealer (n = 5/group). Results: The volumes of GP, sealer, and voids were measured in the region of 0-2, 2-4, 4-6, and 6-8 mm from the apex, using image analysis of sagittal µCT scans. GP volume percentages were: AH Plus (75.5%), EndoSequence BC (87.3%), and prototype S-PRG (94.4%). Sealer volume percentages were less: AH Plus (14.3%), EndoSequence BC (6.8%), and prototype S-PRG (4.6%). Void percentages were AH Plus (10.1%), EndoSequence BC (5.9%), and prototype S-PRG (1.0%). Dentin-sealer contact ratios of AH Plus, EndoSequence BC, and prototype S-PRG groups were 82.4% ± 6.8%, 71.6% ± 25.3%, and 70.2% ± 9.4%, respectively. GP-sealer contact ratios of AH Plus, EndoSequence BC, and prototype S-PRG groups were 65.6% ± 29.1%, 80.7% ± 25.8%, and 87.0% ± 8.6%, respectively. Conclusions: Prototype S-PRG sealer created a low-void obturation, similar to EndoSequence BC sealer with similar dentin-sealer contact (> 70%) and GP-sealer contact (> 80%). Prototype S-PRG sealer presented comparable filling quality to EndoSequence BC sealer.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2021.05a
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• pp.211-212
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• 2021

This study was conducted to derive quantitative air void volume calculation techniques in various complexes with porosity. Calculation of voids in a complex is an essential factor in improving mechanical properties, and quantitative measurement techniques are needed because the environment is not constant to apply the currently used ASTM criteria. Using the analysis technique obtained through 2D image analysis, it is believed that meaningful results can be derived through Micro CT analysis results and cross-check later.

• Journal of the Korean Society of Radiology
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• v.15 no.3
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• pp.273-279
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• 2021

Metal material inserted into the body have a large difference in density from human tissues or bones around the Metal during CT scans.. Therefore, the Metal material inserted into the body produces Artifact. Metal Artifact, which occurs around Metals, can degrade the quality of CT images, causing confusion when medical team diagnose lesions. Through this experiment, we confirm that the occurrence of Artifacts decrease by using Dual energy CT and MAR algorithm in Single source Dual energy CT. We also want to present basic data on clinical application methods by comparing and analyzing the characteristics of images obtained by each method. Using GE 750HD CT, artificial implants were scanned using general method and Dual energy. Then we apply the MAR algorithm to each image obtained. And all previously acquired images were compared and analyzed the characteristics of the examination, such as image quality evaluation and dose evaluation. Images with MAR algorithm and Dual Energy confirmed a decrease in Metal Artifact. Images with MAR algorithm have reduced Metal Artifact, but have the disadvantage of distorting the details of artificial joint implants. On the other hand images teseted with Dual Energy have the advantage of being able to implement details than those applied with MAR algorithms, it takes longer to reconstruct the image and the exposure dose was about four times higher than those applied with MAR algorithm. In order to locate Metals, such as the post-operative follow-up period, it is useful to apply MAR algorithm to obtain images. And it is more useful to examine with Dual Energy when micro lesion identification, such as cardiac examination, and surgical planning or when tests are performed in diagnostic way.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.36 no.5
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• pp.323-330
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• 2023

The development of an analysis model that reflects the microstructure characteristics of polyvinyl alcohol (PVA) fiber-reinforced cementitious composites, which have a highly complex microstructure, enables synergy between efficient material design and real experiments. PVA fiber orientations are an important factor that influences the mechanical behavior of PVA fiber-reinforced cementitious composites. Owing to the difficulty in distinguishing the gray level value obtained from micro-CT images of PVA fibers from adjacent phases, fiber segmentation is time-consuming work. In this study, a micro-CT test with a voxel size of 0.65 ㎛³ was performed to investigate the three-dimensional distribution of fibers. To segment the fibers and generate training data, histogram, morphology, and gradient-based phase-segmentation methods were used. A U-net model was proposed to segment fibers from micro-CT images of PVA fiber-reinforced cementitious composites. Data augmentation was applied to increase the accuracy of the training, using a total of 1024 images as training data. The performance of the model was evaluated using accuracy, precision, recall, and F1 score. The trained model achieved a high fiber segmentation performance and efficiency, and the approach can be applied to other specimens as well.

• Journal of the Korean Society for Nondestructive Testing
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• v.29 no.3
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• pp.214-218
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• 2009

The occlusal force of the tooth leads to loss of tooth tissue owing to attrition and abrasion, and may cause abfraction and pathological change of the dentin. Thus, we developed finite element models, examined them by applying ordinary occlusal force, and analyzed the stress distribution. Specimens used were mandibular first premolars from 15 Korean males and 13 females and were made into finite element models from medical images that were obtained using a Micro-CT. We have found that the irregular feature of the tooth is not only useful to masticating and pronouncing as well known, but it is also suitable for protecting inner tissue by dispersing stress and delivering proper pressure to periodontal tissue to continue a physiological action. Also, image analysis could let us know the factor that is the cause of a disorder due to stress concentration in the cervical line. These results are expected to support the field of dental treatment planning, operating procedure and clinical trial, and the advance of technical expertise to develop implants and dentures.