• Restorative Dentistry and Endodontics
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• v.34 no.3
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• pp.232-239
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• 2009

The aim of this study was to compare the effects of anti curvature filing with stainless steel k-file versus nickel-titanium ProFile in the shaping of mesial root canals of extracted mandibular molars. A total of 60 canals from 30 mesial roots of mandibular molar teeth were randomly assigned to three groups with n=20 each. They were prepared with different instruments and methods: The first group with stainless steel k-file and circumferential filing. the second with precurved stainless steel k-file and anticurvature filing and the third with ProFile C06 taper) and anticurvature filing. Using a micro-computed tomography system (skyscan-1076, SKYSCAN, Antwerpen, Belgium), pre-and post-operative specimens were scanned. Subsequently, canal images were superimposed and changes in root dentin thickness were measured at distal side (danger zone) of the canal. The data was analyzed using a one-way ANOVA and the comparison of means was conducted using a post hoc multiple comparison Tukey test. There were significant differences in the change of root dentin thickness at the $7.5{\sim}8.5\;mm$ level between group 1 and 2, $3.5{\sim}6mm$ level between group 1 and 3 and $3.5{\sim}6mm$ level between group 2 and 3(n=20, P<0.05).

• Journal of dental hygiene science
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• v.15 no.2
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• pp.98-105
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• 2015

We investigated the effects of a mutan (water-insoluble ${\alpha}$-glucans) isolated from Streptococcus mutans on the healing of bone defect in rat. Sprague-Dawley rats were divided into control (saline-treated), lipopolysaccharide (LPS)-treated, and mutan-treated groups (n=6 per group). Experimental bone defects were surgically created with round fissure bur at the buccal surface of the left mandibular. The control groups was administered with saline solution (0.1 ml/100 g), while the LPS and mutan group was given LPS and mutan (1 mg/kg body weight) three times weekly. After 4 weeks the rats were sacrificed, the healing of bone defect was assessed by bone mineral density (BMD) and micro-computed tomography (${\mu}CT$) examination. Percent bone volume (bone volume/tissue volume [BV/TV]), trabecular thickness (Tb.Th), and trabecular number (Tb.N) parameters of ${\mu}CT$ showed higher values in control group than LPS and mutan group. Bone surface/volume ratio (BS/BV), trabecular bone pattern factor (Tb.Pf), and structure model index parameters of ${\mu}CT$ showed higher values in LPS group than mutan group. BMD values of mutan treated-alveolar bones were significantly lower for than that of the LPS group. Therefore, we suggest that mutan, water-insoluble ${\alpha}$-glucans from S. mutans may be induce the induction of periodontal diseases.

• Tunnel and Underground Space
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• v.29 no.3
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• pp.184-196
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• 2019

This study aims to extract a 3D image of micro-cracks generated by hydraulic fracturing tests, using the deep learning method and X-ray computed tomography images. The pixel-level cracks are difficult to be detected via conventional image processing methods, such as global thresholding, canny edge detection, and the region growing method. Thus, the convolutional neural network-based encoder-decoder network is adapted to extract and analyze the micro-crack quantitatively. The number of training data can be acquired by dividing, rotating, and flipping images and the optimum combination for the image augmentation method is verified. Application of the optimal image augmentation method shows enhanced performance for not only the validation dataset but also the test dataset. In addition, the influence of the original number of training data to the performance of the deep learning-based neural network is confirmed, and it leads to succeed the pixel-level crack detection.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.45 no.2
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• pp.97-107
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• 2019

Objectives: Small animal maxillofacial models, such as non-segmental critical size defects (CSDs) in the rabbit mandible, need to be standardized for use as preclinical models of bone regeneration to mimic clinical conditions such as maxillofacial trauma. The objective of this study is the establishment of a mechanically competent CSD model in the rabbit mandible to allow standardized evaluation of bone regeneration therapies. Materials and Methods: Three sizes of bony defect were generated in the mandibular body of rabbit hemi-mandibles: $12mm{\times}5mm$, $12mm{\times}8mm$, and $15mm{\times}10mm$. The hemi-mandibles were tested to failure in 3-point flexure. The $12mm{\times}5mm$ defect was then chosen for the defect size created in the mandibles of 26 rabbits with or without cautery of the defect margins and bone regeneration was assessed after 6 and 12 weeks. Regenerated bone density and volume were evaluated using radiography, micro-computed tomography, and histology. Results: Flexural strength of the $12mm{\times}5mm$ defect was similar to its contralateral; whereas the $12mm{\times}8mm$ and $15mm{\times}10mm$ groups carried significantly less load than their respective contralaterals (P<0.05). This demonstrated that the $12mm{\times}5mm$ defect did not significantly compromise mandibular mechanical integrity. Significantly less (P<0.05) bone was regenerated at 6 weeks in cauterized defect margins compared to controls without cautery. After 12 weeks, the bone volume of the group with cautery increased to that of the control without cautery after 6 weeks. Conclusion: An empty defect size of $12mm{\times}5mm$ in the rabbit mandibular model maintains sufficient mechanical stability to not require additional stabilization. However, this defect size allows for bone regeneration across the defect. Cautery of the defect only delays regeneration by 6 weeks suggesting that the performance of bone graft materials in mandibular defects of this size should be considered with caution.

• The korean journal of orthodontics
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• v.51 no.6
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• pp.366-374
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• 2021

Objective: This study investigated the impact of a single piezocision in the maxillary alveolar process on the speed of tooth movement. The null hypothesis was that the speed of tooth movement will be equal with and without piezocision. Methods: All maxillary molars on one side were moved against the combined incisors in 10 ten-week-old male Wistar rats. Under general anesthesia, a force of 25 cN was applied on either side using a Sentalloy closed coil spring. After placing the orthodontic appliance, vertical corticision was performed using a piezotome under local anesthesia, 2 mm mesial from the mesial root of the first molar on a randomly selected side; the other side served as the control. At the beginning of the treatment, and 2 and 4 weeks later, skull micro-computed tomography was performed. After image reconstruction, the distance between the mesial root of the first molar and the incisive canal, and the length of the mesial root of the first maxillary molar were measured. Moreover, the root resorption score was determined as described by Lu et al. Results: Significantly higher speed of tooth movement was observed on the corticision side; thus, the null hypothesis was rejected. The loss of root length and root resorption score were significantly more pronounced after piezocision than before. A strong correlation was observed between the speed of tooth movement and root resorption on the surgical side, but the control side only showed a weak correlation. Conclusions: Piezocision accelerates orthodontic tooth movement and causes increased root resorption.

• Journal of Korean Neurosurgical Society
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• v.65 no.2
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• pp.204-214
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• 2022

Objective : Osteoporosis result from age-related decline in the number of osteoblast progenitors in the bone marrow. Probiotics have beneficial effects on the host, when administered in appropriate amounts. This study investigated the effects of probiotics expressing specific genes, especially the effects of genetically modified bone morphogenetic protein (BMP)-2-expressing Lactobacillus plantarum CJNU 3003 (LP) on ovariectomized rats. Methods : Twenty-eight female Wistar rats (250-300 g, 12 weeks old) were divided into four groups : the sham (control), the ovariectomy (OVX)-induced osteoporosis group (OVX), the OVX and LP (OVX/LP), OVX and genetically modified BMP-2-expressing LP (OVX/LP with BMP) groups. The three groups underwent bilateral OVX and two of these groups were administered two different types of LP via oral gavage daily. At 16 weeks post-OVX, blood was collected from the heart and the bilateral tibiae were extracted and were scanned by ex-vivo micro-computed tomography and stained with hematoxylin-and-eosin (H&E) and Masson's trichrome stain for pathological assessment. The serum levels of osteocalcin (OC), rat C-telopeptide of type I collagen (CTX-I), BMP-2, and receptor activator of nuclear factor-ĸB ligand (RANKL) were measured. Results : The 3D-micro-computed tomography images showed that the trabecular structure in the OVX/LP with BMP group was maintained compared with OVX and OVX/LP groups. No significant differences were detected in trabecular thickness (Tb.Th) between control and OVX/LP with BMP groups (p>0.05). Furthermore, a tendency toward increased BMD, trabecular bone volume, Tb.Th, and trabecular number and decreased trabecular separation was found in rats in the OVX/LP with BMP groups when compared with the OVX and OVX/LP groups (p>0.05). The H&E and Masson's trichrome stained sections showed a thicker trabecular bone in the OVX/LP with BMP group compared with the OVX and OVX/LP groups. There was no difference in serum levels of OC, CTX and RANKL control and OVX/LP with BMP groups (p>0.05). In contrast, significant differences were found in OC and CTX-1 levels between the OVX and OVX/LP with BMP groups (p<0.05). Conclusion : Our results showed that the expression of genetically modified BMP-2 showed inhibition effect for bone loss in a rat model of osteoporosis.

• Journal of Korean Medicine Rehabilitation
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• v.30 no.3
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• pp.23-44
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• 2020

Objectives The purpose of this study is to evaluate the healing effect of Hyeolbuchugeo-tang (HC) in rats with rib fracture. Methods Rats were randomly divided into 5 groups (naive, control, positive control, HC-L and HC-H). All groups except naive group were subjected to bone fracture of rib. Naive group received no treatment at all. Control group was fed with phosphate buffered saline. Positive control group was orally medicated with tramadol. Experimental group was orally medicated with HC extract (50 mg/kg for low concentration [HC-L], 100 mg/kg for high concentration [HC-H]). X-ray and micro-computed tomography (micro-CT) were conducted to assess the effect of HC. We analysed the level of 2) transforming growth factor-β1 (TGF-β1), Ki67, alkaline phosphatase (ALP), receptor activator of nuclear factor kappa-β, runt-related transcription factor 2 (Runx2) and tartrate resistant acid phosphatase (TRAP) on 7 and 14 days after fracture. ALP, alanine aminotransferase, aspartate aminotransferase, blood urea nitrogen, creatinine was measured for safety assessment. Results X-ray and micro-CT, showed HC enhance bone repair process. Callus formation was increased in experimental group at 7 days after fracture, but decreased at 14 days after fracture. 7 days after fracture, the level of TGF-β1 in experimental group was decreased. The level of Ki67, Runx2 in HC-H, TRAP in HC-L was increased. 14 days after fracture, the level of Ki67 in HC-L and HC-H was decreased. The level of ALP, Runx2, BUN in HC-L, TRAP in HC-L and HC-H was increased. Conclusions Taken together the results, HC promoted healing of bone fracture. In conclusion, HC has a potential to promote healing of bone fracture.

• The Journal of the Korean dental association
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• v.54 no.4
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• pp.284-295
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• 2016

The aim of this study was to evaluate the effect of Epigallocatechin-3-Gallate (EGCG) on the alveolar bone metabolism in a collagen-induced arthritis (CIA) model in mice to enhance the understanding of rheumatoid arthritis (RA)-associated alveolar bone loss. Following the induction of CIA in animals (mice, n=16), mandibles were retrieved for micro-computed tomography (micro-CT) and isolation of alveolar bone cells (ABCs). In vitro osteogenic potentials of ABCs were evaluated and the mRNA expression of downstream effector genes was assessed. CIA was successfully induced in all animals, and micro-CT data showed that alveolar bone loss was significantly increased in the CIA group while the treatment of EGCG prevented the alveolar bone resorption. Osteogenesis by ABCs was significantly increased in the CIA+EGCG group in vitro. The analysis of mRNA expressions showed that osteoclastogenesis-associated genes were increased in CIA group while bone protecting genes were upregulated in EGCG treated group. The results demonstrate that EGCG downregulated the alveolar bone resorption in a CIA model in mice, and upregulation of bone protecting genes appear to be involved. Further studies are warranted.

• The Journal of the Korean dental association
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• v.55 no.10
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• pp.676-687
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• 2017

Objectives : The aim of this study was to evaluate the effects of a composite of bone substitute and collagen barrier membrane (bone patch) for local ridge augmentation at peri-implant dehiscence defects on the clinical efficacy and positional stability in dogs. Materials and methods : Implant placement and ridge augmentation procedure were performed at surgically created peri-implant dehiscence defects in canine mandible (n=6). Four treatment modalities were randomly applied: i) bone patch group, ii) Guided bone regeneration (GBR) without pin fixation group (bone graft and collagen membrane), iii) GBR with pin fixation group, and iv) negative control group. After 12 weeks, clinical, micro-CT and histological analyses were performed. Results : Histologic analysis showed that bone patch group had similar results to GBR group and GBR with fixation group in terms of new bone formation. Micro-CT analysis revealed similar results to histologic analysis in terms of total volume maintenance. Operating time was shorter in bone patch group compared to GBR group and GBR with fixation groups. Conclusions : GBR using bone patch could simplify the ridge augmentation procedure with reduced operating time and equivalent biological performance compared to the conventional procedure.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.10
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• pp.122-128
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• 2009

The aim of this study was to investigate, through a longitudinal tracking, whether gender influences morphological characteristics on trabeucular bone of tibia during unloading. 12 male and 15 female ICR mice at 6 week of age were used and randomly allocated into two groups in each gender; unloading and normal group, respectively Mice in unloading group were operated on denervation (sciatic neurectomy). The tibiae were scanned by using in vivo micro-computed tomography (micro-CT) at 0 day (before denervation) and after 14 days. Structural parameters and BMD on tibia were measured. In female, BV/TV (65%), Tb. Th (5%), Tb.N (61%) and BMD (62%) were significantly decreased and BS/BV (17%), Tb.Sp (54%), SMI (19%) and Tb.Pf (75%) were significantly increased after unloading (p<0.05). In male, BV/TV (1%) and Tb.N (10%) were significantly decreased and SMI (5%) was significantly increased after unloading (p<0.05). In addition, trabeuclar bone loss of female was significantly bigger than that of male (p<0.05). These results indicated that effects of unloading on trabecular bone in growing mice might have difference between female and male, although unloading result in loss of quantity and quality on trabecular bone both female and male.