• Anatomy & Biological Anthropology
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• v.26 no.1
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• pp.41-49
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• 2013

Dental epithelial and mesenchymal cells that form the teeth undergo dynamic changes in cell cycle during tooth development and morphogenesis. Although proliferation has been known as a key event during odontogenesis, the cell cycle phases and their relations with the complicated molecular mechanisms of tooth development are not fully understood yet. This study comparatively examined the expression patterns of Ki-67, cyclin A, and cyclin D1 during tooth development in the mouse incisor and molar in order to identify the cell-cycle characteristics during odontogenesis. We found that Ki-67 and cyclin A were expressed in the proliferating cells in the dental epithelial and mesenchymal tissues at the bud, cap and bell stages. Cycln D1 showed distinct expression in the incisor odontoblast region and the enamel knot, in which Ki-67 nor cyclin A was expressed. Our results provide specific information on the cell cycle phases during tooth development that may provide clues to relate them with the complex odontogenic mechanisms. Furthermore, we suggest that our findings enlightened the previous studies on the incisor odontoblasts and the enamel knot during tooth development.

• Development and Reproduction
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• v.17 no.3
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• pp.215-220
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• 2013

Recently, the RNA/DNA-binding protein FUS, Fused in sarcoma, was shown to play a role in growth, differentiation, and morphogenesis in vertebrates. Because little is known about Fus, we investigated its expression pattern in murine tooth development. In situ hybridization of mouse mandibles at specific developmental stages was performed with a DIG-labeled RNA probe. During early tooth development, Fus was detected in the dental epithelium and dental mesenchyme at 11 days postcoitum (dpc) and 12 dpc. From 14 dpc, Fus was strongly expressed in the dental papilla and the cervical loop of the dental epithelium. At postnatal day 4 (PN4), Fus expression was observed in the odontoblasts, ameloblasts, the proliferation zone of the pulp, and the cervical loop. At PN14, the expression pattern of Fus was found to be maintained in the odontoblasts and the proliferation zone of the pulp. Furthermore, Fus expression was especially strong in the Hertwig's epithelial root sheath (HERS). Therefore, this study suggests that Fus may play a role in the HERS during root development.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.7
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• pp.1166-1173
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• 1997

Due to progress in manufacturing techniques, the performance of the harmonic drive has been improved but not sufficiently. One of the important problems which the current harmonic drive has is that while there is the potential for having a wider tooth contact area, the total number of teeth engaged simultaneously is still small. This is mainly due to the involute tooth profile. Hence, in this study, the cycloid-type tooth profile is developed to improve this problem. This paper represents the design methodology and performance evaluation f the cycloid-type harmonic drive. Cycloide tooth profile was derived by analyzing geometry of the tooth engagement and the contact mechanisms of the tooth which were examined and analyzed by load analysis. The stress due to elastic deformation of a flexspline was also obtained by approximate formula and computer analysis. Finally, the cycloid-type harmonic drive with 1:100 speed ratio was manufactured and the performance of the harmonic drive was evaluated.

• Journal of Oral Medicine and Pain
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• v.41 no.3
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• pp.85-90
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• 2016

Purpose: The aim of this study was to develop an automated software to extract tooth and pulpal area from sectional cone-beam computed tomography (CBCT) images, which can guarantee more reproducible, objective and time-saving way to measure pulp/tooth volume ratio. Methods: The software program was developed using MATLAB (MathWorks). To determine the optimal threshold for the region of interest (ROI) extraction, user interface to adjust the threshold for extraction algorithm was added. Default threshold was determined after several trials to make the outline of extracted ROI fitting to the tooth and pulpal outlines. To test the effect of starting point location selected initially in the pulpal area on the final result, pulp/tooth volume ratio was calculated 5 times with different 5 starting points. Results: Navigation interface is composed of image loading, zoom-in, zoom-out, and move tool. ROI extraction process can be shown by check in the option box. Default threshold is adjusted for the extracted tooth area to cover whole tooth including dentin, cementum, and enamel. Of course, the result can be corrected, if necessary, by the examiner as well as by changing the threshold of density of hard tissue. Extracted tooth and pulp area are reconstructed three-dimensional (3D) and pulp/tooth volume ratio is calculated by voxel counting on reconstructed model. The difference between the pulp/tooth volume ratio results from the 5 different extraction starting points was not significant. Conclusions: In further studies based on a large-scale sample, the most proper threshold to present the most significant relationship between age and pulp/tooth volume ratio and the tooth correlated with age the most will be explored. If the software can be improved to use whole CBCT data set rather than just sectional images and to detect pulp canal in the original 3D images generated by CBCT software itself, it will be more promising in practical uses.

• International Journal of Oral Biology
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• v.48 no.4
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• pp.33-44
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• 2023

In this review, the regulatory mechanisms of autophagy were described, and its interaction with apoptosis was identified. The role of autophagy in embryogenesis, tooth development, and cell differentiation were also investigated. Autophagy is regulated by various autophagy-related genes and those related to stress response. Highly active autophagy occurrences have been reported during cell differentiation before implantation after fertilization. Autophagy is involved in energy generation and supplies nutrients during early birth, essential to compensate for their deficient supply from the placenta. The contribution of autophagy during tooth development, such as the shape of the crown and root formation, ivory, and homeostasis in cells, was also observed. Genes control autophagy, and studying the role of autophagy in cell differentiation and development was useful for understanding human aging, illness, and health. In the future, the role of specific mechanisms in the development and differentiation of autophagy may increase the understanding of the pathological mechanisms of disease and development processes and is expected to reduce the treatment of various diseases by modulating the autophagic phenomenon.

• Journal of Korean society of Dental Hygiene
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• v.6 no.1
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• pp.79-91
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• 2006

Through the investigation and analysis for awareness about Tooth Bleaching treatment for general adults, to rethink the real ideas of Tooth Bleaching which adults has already had and to find the method for generalized Tooth Bleaching, this study made a survey about General Awareness and Common sense for Tooth Bleaching and Oral Health Knowledge and Generalization Methods for 570adult citizen in Busan from 1th August to 10th September. The obtained results were as follows 1. Tooth Shade self contentment was found low, self-discontent respondents were 73.5% and self-content respondents were 26.5%. 2. Tooth Bleaching recognition was found high, as for the recognition period, between 2 and 5 years is 65.5% and as for the recognition route, 33.9% were through broadcast medium. 3. General knowledge for Tooth Bleaching was found low as 2.34(1.12) of 5 score and it is similar to ages and occupations(pE0.001, pE0.05). 4. Tooth Bleaching treatment method appears Home Bleaching and In-Office bleaching was 73.5% and 26.5% respectively. The other side medical institution chosen for Tooth Bleaching treatment appears dental hospital or dental clinic and Home bleaching was 75.6% and 12.1% respectively. 5. To generalize the Tooth Bleaching Care, recommendations of oral health care team and oral health education and development of information data also need to be performed.

• Journal of the korean academy of Pediatric Dentistry
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• v.23 no.4
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• pp.775-787
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• 1996

The purpose of this study was to investigate the postnatal development of pulpal innervation with the tooth development and eruption process in developing rat mandibular molars (postnatal 1, 5, 10, 15, 20, 25, 35day-old and adult rats). Immunohistochemical method was carried out for the detection of nerve fibers, using the antibody against calcitonin gene-related peptide(CGRP). The results were as follows: The feature of CGRP-IR nerve fibers were shown in a bead-like appearance. The time of nerve entering into the dental papilla of tooth follicle began at the occured advanced dentinogenesis. The development of Raschkow plexus began at the formative stage of the roots and was accelerated at the stage of the crown emerged into the oral cavity. The number of nerve fibers entering the odontoblastic layer increased with the tooth eruption and mastication. The development of innervation was shown to be related with the stage of the development of individual teeth rather than the chronological age of the rat.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.17 no.3
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• pp.87-92
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• 2018

As gas turbines for power generation become increasingly more important for high capacity and high efficiency, the technological development and investment of companies are increasing globally. Gas turbine manufacturing technology is only owned by a few companies such as GE, Siemens, and MHI, and our country currently depends on imports of processing technology and component parts. The core part of the gas turbine is curvic coupling tooth processing technology that improves turbine efficiency by smoothly transmitting power to the turbine rotor. Curvic coupling tooth machining and evaluation research is restricted overseas, and it is not underway in Korea. Therefore, in this study, roughing and finishing process technology for curvic coupling tooth machining is developed and a quantitative evaluation method is proposed. For the development of machining technology, the analysis of critical parameters was performed through C & E analysis. In the roughing process, the conditions considering the minimum machining time and tool load ratio were determined. Finishing process conditions were determined based on the contact ratio between the tooth surfaces. The image-processing method is presented for evaluation of the contact ratio and a verification test was performed.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.35 no.2
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• pp.73-81
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• 2013

Purpose: Smad4 is a central mediator for transforming growth factor-${\beta}$/bone morphogenetic protein ($TGF-{\beta}/BMP$) signals, which are involved in regulating cranial neural crest cell formation, migration, proliferation, and fate determination. Accumulated evidences indicate that $TGF-{\beta}/BMP$ signaling plays key roles in the early tooth morphogenesis. However, their roles in the late tooth formation, such as cellular differentiation and matrix formation are not clearly understood. The objective of this study is to understand the roles of Smad4 in vivo during enamel and dentin formation through tissue-specific inactivation of Smad4. Methods: We generated and analyzed mice with dental epithelium-specific inactivation of the Smad4 gene (K14-Cre:$Smad4^{fl/fl}$) and dental mesenchyme-specific inactivation of Smad4 gene (Osr2Ires-Cre:$Smad4^{fl/fl}$). Results: In the tooth germs of K14-Cre:$Smad4^{fl/fl}$, ameloblast differentiation was not detectable in inner enamel epithelial cells, however, dentin-like structure was formed in dental mesenchymal cells. In the tooth germs of Osr2Ires-Cre:$Smad4^{fl/fl}$ mice, ameloblasts were normally differentiated from inner enamel epithelial cells. Interestingly, we found that bone-like structures, with cellular inclusion, were formed in the dentin region of Osr2Ires-Cre:$Smad4^{fl/fl}$ mice. Conclusion: Taken together, our study demonstrates that Smad4 plays a crucial role in regulating ameloblast and odontoblast differentiation, as well as in regulating epithelial-mesenchymal interactions during tooth development.

• Journal of the korean academy of Pediatric Dentistry
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• v.27 no.3
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• pp.383-387
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• 2000

Fusion is defined as union of two separate tooth buds at some stage in their development with confluence of dentin and characterized by separate root canal and large single crown, while gemination is defined as an attempt of the single tooth bud to incompletely divide and usually result in a single root with one root canal and two completely or incompletely separated crowns. It is sometimes difficult to decide whether an abnormally large tooth is the result of fusion of a normal and a supernumerary tooth, or of gemination; use of the term 'Double tooth' may make the clinicians avoid this difficulty(Brook & Winter). Commonly there are no symptoms, but the problems associated with these anomalies include esthetics, possible loss of arch length and delayed or ectopic eruption of the permanent teeth, caries along the line of demarcation, and periodontal disease. Commonly, it dose not need to be treated in primary dentition but in case of permanent dentition, it may be requested to be treated due to esthetics and other problems. In our case, a 8 years old girl showed a Double tooth, we attained the favorable results by performing hemisection with apexification.