• Proceedings of the KACD Conference
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• 2004.05a
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• pp.304-308
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• 2004

Maxillary anterior crown fractures are a common form of injury that mainly affects children and adolescents. The position of maxillary incisors and their eruptive pattern carries a significant risk for trauma. In the pre-adhesive era, fractured teeth needed to be restored either with pin-retained inlays or cast restorations that sacrificed healthy tooth structure and were a challenge for dentists to match with adjacent teeth. But. recently the development of adhesive dentistry has allowed dentists to use the patient's own fragment to restore the fractured tooth. The purpose of this paper is to present 2 cases of reattachment of fractured teeth which had different fracture mode, and to evaluate prognosis of cases.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.15 no.2
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• pp.129-136
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• 1993

The purpose of this study is to evaluate whether the ashed tooth powder is utilized as an alternative material of the implant. For this purpose the author performed the experimental study to investigate the tissue response of sintered toothash and its histocompatibility. Bony defects to expose the body of marrow, $1{\times}1cm$ in size, were created in the right and left mandibular body of mature dog, and then the ashed tooth powders were filled in right side and the blood clot was filled in the left side as an control. The dogs were sacrificed at 4th, 7th, and 16th week after implantation and histologic examination was performed. The results of this study were obtained as follows : 1. Any inflammatory response was not noted after implanting of the ashed tooth powder during the whole experimental period. 2. At 4th week, ashed tooth powders were surrounded by mature connective tissue. And we could observe hydroxyapatite crystal structure within the ashed tooth powder. 3. At 7th week, we could observe that macrophage phagocyted the small granules of ashed tooth powders. 4. At 16th week, the union with host bone by growth of new trabeculae was observed. And there were remnants of ashed tooth power within some of new trabeculae.

• Journal of Periodontal and Implant Science
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• v.46 no.2
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• pp.107-115
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• 2016

Purpose: The aim of this study was to evaluate and compare tooth surface characteristics in extracted human molars after cervical enamel projections (CEPs) were removed with the use of three rotating instruments. Methods: We classified 60 extracted molars due to periodontal lesion with CEPs into grade I, II, or III, according to the Masters and Hoskins' criteria. Each group contained 20 specimens. Three rotating instruments were used to remove the CEPs: a piezoelectric ultrasonic scaler, a periodontal bur, and a diamond bur. Tooth surface characteristics before and after removal of the projections were then evaluated with scanning electron microscopy (SEM). We analyzed the characteristics of the tooth surfaces with respect to roughness and whether the enamel projections had been completely removed. Results: In SEM images, surfaces treated with the diamond bur were smoothest, but this instrument caused considerable harm to tooth structures near the CEPs. The piezoelectric ultrasonic scaler group produced the roughest surface but caused less harm to the tooth structure near the furcation. In general, the surfaces treated with the periodontal bur were smoother than those treated with the ultrasonic scaler, and the periodontal bur did not invade adjacent tooth structures. Conclusions: For removal of grade II CEPs, the most effective instrument was the diamond bur. However, in removing grade III projections, the diamond bur can destroy both adjacent tooth structures and the periodontal apparatus. In such cases, careful use of the periodontal bur may be an appropriate substitute.

• 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.

• The Journal of Korean Academy of Prosthodontics
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• v.60 no.1
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• pp.80-90
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• 2022

With the development of digital dentistry, it is being applied in various ways of dental treatment. This case report presents the definitive prosthesis designed in advance with a re-established vertical dimension and the digital technology, which determined the amount of tooth preparation, in order to preserve as much tooth structure as possible in a patient with pathological wear of the posterior teeth and loss of vertical dimension. For accurate tooth preparation, the guides of the occlusal and axial surfaces were digitally and additively manufactured. Then, aesthetics and anterior guidance were established at the provisional stage. The information of the provisional restoration was delivered to the definitive stage by double scanning. The digital technology, including the virtual planning and the guided tooth removal, produced the definitive restorations satisfactory to both the patient and clinician.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2001.04a
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• pp.352-357
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• 2001

In this study, residual stress was investigated to evaluate damaged layer in high speed machining through simulation. In machining steel(STDll), residual stress remaining in machined surface was mainly appeared as compressive stress. The scale of this damaged layer more depends on feed per tooth and radial depth than spindle speed. Damaged layer was measured by optical microscope and hardness method. The micro-structure of damaged layer was a martensite because of cutting force and cutting temperature. Thickness of damaged layer is increased with incresing of feed per tooth and radial depth.

• International Journal of Automotive Technology
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• v.8 no.1
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• pp.75-82
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• 2007

This paper presents practical work on the reduction of gear whine noise. In order to identify the source of the gear whine noise, transfer paths are searched and analyzed by operational deflection shape analysis and experimental modal analysis. It was found that gear whine noise has an air-borne noise path instead of structure-borne noise path. The main sources of air-borne noise were the two global modes caused by the resonance of an axle system. These modes created a vibro-acoustic noise problem. Vibro-acoustic noise can be reduced by controlling the vibration of the noise source. The vibration of noise source is controlled by the modification of structure to avoid the resonance or to reduce the excitation force. In the study, the excitation force of the axle system is attenuated by changing the tooth profile of the hypoid gear. The modification of the tooth profile yields a reduction of transmission error, which is correlated to the gear whine noise. Finally, whine noise is reduced by 10 dBA.

• Journal of Power System Engineering
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• v.15 no.4
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• pp.48-53
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• 2011

Upon reviewing recent trends for robots, it can be seen that robots are gradually being miniaturized. However, most commercially available speed reducers have limitations in terms of structure and vibration when applied to small robots. In this respect, a tooth profile manufactured using thin plates was designed using balls and data analyzed related to numerical and FEM analysis. The speed reducer was manufactured to check their performance. The manufactured thin plate type speed reducer imposes less compressive stress on its tooth profile and balls, which can greatly increase feasibility.

• Journal of the Korean Academy of Esthetic Dentistry
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• v.10 no.1
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• pp.56-70
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• 2001

The use of resin-bonded fixed partial dentures described in the early 1980s caused an conservative way to preserve tooth structure in the restorative dental community. The treatment of patients with requires long term analysis of clinical application and basic research. Failure rates of these prosthesis ranged from 3% to 55%. These varieties were orginated by different techniques, materials, tooth preparation methods and diverse clinical situations. This article review was focused on the standard long term results and in vitro studies on bond strength between metal and teeth. From this, many useful clinical guidelines to RBFPD could be adopted to clinical dentistry. For successful results, careful case selection and good clinical skills are needed. And appropriate techniques for each situations should be adopted. Also, RBFPD using new materials like all-ceramics, FRC/Ceromer was introduced.

• The Journal of the Korean dental association
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• v.54 no.6
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• pp.438-446
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• 2016

Severe tooth wear may cause the pathologic change of the TMJ and masticatory muscles, unesthetic facial appearance, pathogenic pulp and occlusal disharmony. Treating patients with severely worn dentition often requires full mouth rehabilitation with increasing vertical dimension. Proper diagnosis and treatment planning are important for esthetic and functional definitive restorations and the long term stability of the neuromuscular system and the TMJ. In this case, 66 year-old female presented with generalized worn dentition. Based on assessment, pathologic destruction of teeth structure on entire dentition was caused by masticatory force and diet habit without loss of vertical dimension. Subsequently, 3 mm increase of vertical dimension that based on incisor for tooth restoration and esthetic improvement was determined. After 8 weeks stabilization period with temporary fixed prostheses, definitive prostheses were fabricated. After 6 months follow up period, satisfactory outcomes were attained both functional and esthetic aspects through this procedure.