• Journal of Periodontal and Implant Science
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• v.29 no.4
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• pp.893-914
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• 1999

Tooth mobility may be the decisive factor that determines whether dental treatment of any kind is undertaken. Although tooth mobility in isolation says little in itself, the finding of increased tooth mobility is of both diagnostic and prognostic importance. Only the detection of an increase or decrease in mobility makes an evaluation possible. Thus prior to treatment, we must understand the pathologic process causing the observed the tooth mobility and decide whether the pattern and degree of observed tooth mobility is reversible or irreversible. And then it must be decided whether retention and treatment or extraction and replacement. The purpose of this study was to compare tooth mobility at different time period during root planing and flap operation and to relate changes in mobility to each treatment method. Twenty-one patients (287 teeth) with chronic adult periodontitis were treated with root planing(control group) and flap operation(experimental group), and each group was divided 3 subgroups based upon initial probing pocket depth (1-3mm, 4-6mm, 7mm and more). Tooth mobility was measured with $Periotest^{(R)}$ at the day of operation, 4 days, 1 week, 2 weeks, 3 weeks, 4 weeks, 8 weeks, 12 weeks after each treatment. Tooth mobility, attachment loss, radiographic bone loss, and bleeding on probing were measured at the day of operation, 4 weeks, 8 weeks and 12 weeks after treatment. 1. In group initial probing depth was 1-3mm, tooth mobility had no significant difference after root planing and flap operation. 2 . In group initial probing depth was 4-6mm, 7mm and more, tooth mobility had decreased in 12 weeks after root planing(p<0.01). And the mobility had increased after flap operation(p<0.01) and was at peak in 1 week, and decreased at initial level in 4 weeks, below the initial level in 12 weeks(p<0.01). 3. In 1 week, significant difference in tooth mobility between control and experimental group was found(p<0.01) but, in 12 weeks no difference between two groups was found. 4. Change of immediate tooth mobility after treatment was more larger in deep pocket than in shallow one. In group with the same probing pocket depth, the change of tooth mobility in molar group was greater than that of premolar group. 5. Tooth mobility before treatment was more strongly correlated with radiographic bone loss (r=0.5325) than probing depth, attachment loss and bleeding on probing, in 12 weeks after treatment, was more strongly correlated with attachment loss($r^2$=0.4761) than probing depth and bleeding on probing. Evaluation of the treatment effect and the prognosis after root planing and flap operation were meaningful on tooth initial probing depth 4mm and more. After flap operation, evaluation of the prognosis should be performed at least in 4 weeks and in 12 weeks after treatment, no difference in tooth mobility between two groups was observed. Radiographic bone loss and attachment loss were good clinical indicators to evaluate tooth mobility.

• 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.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.30 no.5
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• pp.438-443
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• 2004

Objectives : The proper development of the facial structures relies upon a sequence of tightly regulated signaling interactions between the ectoderm and mesoderm involving the participation of several families of signaling molecules. Among these, bone morphogenetic proteins (BMPs) have been suggested to be a key signal that regulates the development of the mandible and the initiation and morphogenesis of the teeth. The aim of this study was to examine the artificial development of the mandibular structures and to examine the role of BMPs on tooth morphogenesis and differentiation using an organ culture system. Materials and Methods : The tooth germs from Ed 11.5, 13.5 mice were dissected, and transplanted into the diastema of the mandible primordia. The mandibles containing the transplanted tooth germs were cultured in vitro. During this period, beads soaked with BMP4 were implanted around the transplanted tooth germs. In addition, a diastema block containing the transplanted tooth germ was dissected, then transferred to an adult mouse kidney. After the organ culture, the developing mandibular explant was removed from the kidney and prepared for the tissue specimens. Odontogeneis of the transplanted tooth germs was examined after Hematoxylin-eosin, Masson-trichrome staining. Results : Proliferation and differentiation of the tooth germs cultured in the diastema was observed. In the BMP4-treated tooth germs, the formation of the first and second molars was noted. The crown of the developing tooth showed the formation of a mature cusp with the deposition of enamel and dentin matrix. In conclusion, it was confirmed that BMP4 is involved in the formation of a dental crown and the differentiation of ameloblasts and odontoblasts of the molar tooth during the development of the transplanted tooth germs.

• Korean Journal of Health Education and Promotion
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• v.13 no.2
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• pp.167-183
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• 1996

Human teeth vary widely in color. Practitioner and patients are concerned with preventing and correcting discolored or dark teeth to achieve and maintain stain-free, white teeth. Tooth brushing cannot alter tooth color but it can remove adhering films and stains. The esthetics of natural dentition can be improved by bleaching and this process can be applied to intrinsically and extrinsically stained teeth. The need for a brighter, more attractive smile has made rapid growth in the market for tooth whiteners. There is no doubt these products work as whiteners, at least on mild to moderate stains, but the safety of these products are unclear. In this experiment, the effect of tooth whitener application on the color and microhardness of extracted human enamel was measured. RMS, RMT and NWT were used as tooth whiteners, and tooth paste(ETQ) and hydrogen peroxide solution(HPO) were used as controls. 35 caries-free extracted human molars were embedded and polished with the exposed enamel diameter of 4 mm. The tooth whiteners and control agents were applied according to the manufacturers' instructions or clinically simulated procedures for eight weeks, and measurements were repeated every two weeks. Value(L＊) difference was measured using Differential Colorimeter(Model TC-6FX, Denshoku Co., Japan), and microhardness was measured using microhardness tester(Mitsuzawa Seiki Co., Japan). The results were as follows; 1. After application of agents for eight weeks, the Vickers hardness increased significantly in the ETQ, RMS and RMT application group(p〈0.01), and that decreased significantly in NWT application group(p〈0.01), but in HPO application group there was no significant change. The change in microhardness was greatest in NWT application group(p〈0.01). 2. After application of tooth whiteners and controls for eight weeks, the value change of toothpaste application group was significantly lower than those of other agents groups(p〈0.01), and there was no significant difference in value(L＊) change among tooth whitener groups(p〉0.01). 3. The application of tooth paste and paste type tooth whitener made gradual value change, but hydrogen peroxide gel type tooth whitener and hydrogen peroxide solution made rapid value change during initial application period.

• Transactions of the Korean Society of Mechanical Engineers
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• v.9 no.5
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• pp.572-578
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• 1985

A composite gear with involute-circular are tooth profile and a tooth profile of the rack to cut this gear are theoretictically obtained. The composite gear has involute tooth profile in the vicinity of pitch point and has circular arc tooth profiles at addendum adn dedendum. The contact ratio(M$_{c}$), chordal tooth thickness (chordal tip tooth thickness S$_{t}$, chordal root tooth thickness S$_{t}$) of the composite gear are compared with those of involute gear. When module, number of teeth and pressure angle eqaul, S$_{t}$ of composite gear is much larger than that of involute gear. Under the same conditions, S/sib t/ and M$_{c}$ of composite gear become smaller than those of involute gear.lute gear.

• Imaging Science in Dentistry
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• v.40 no.3
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• pp.131-135
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• 2010

Purpose : The aim of this study was to investigate the timing and sequence of eruption of permanent canine and premolars, and to evaluate tooth calcification stage on emergence in Korean children. Materials and Methods : The sample was comprised of 1,266 children (male 720, female 546) aged from 7-13 years. Tooth eruption and calcification stages were determined through oral and panoramic radiographic examination, respectively. Probit analysis was used to calculate the timing of tooth eruption and tooth calcification stage from these cross-sectional data. Results : In both males and females, eruption occurred around the time when one third of tooth root or more was formed. The sequence was as follows: first premolar, canine, and second premolar in maxilla, and canine, first premolar and second premolar in mandible. Tooth eruption occurred earlier in girls compared with boys, averaging 0.63 years. Conclusions : Eruption sequence is identical in males and females with a trend for females to erupt earlier than males. Tooth eruption becomes earlier over the past decades in Korean children.

• Restorative Dentistry and Endodontics
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• v.39 no.1
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• pp.68-73
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• 2014

When a tooth shows discoloration and does not respond to the cold test or electric pulp test (EPT) after a traumatic injury, its diagnosis can be even more difficult due to the lack of proper diagnostic methods to evaluate its vitality. In these case reports, we hope to demonstrate that ultrasound Doppler might be successfully used to evaluate the vitality of the tooth after trauma, and help reduce unnecessary endodontic treatments. In all three of the present cases, the teeth were discolored after traumatic injuries and showed negative responses to the cold test and EPT. However, they showed distinctive vital reactions in the ultrasound Doppler test during the whole observation period. In the first case, the tooth color returned to normal, and the tooth showed a positive response to the cold test and EPT at 10 wk after the injury. In the second case, the tooth color had returned to its normal shade at 10 wk after the traumatic injury but remained insensitive to the cold test and EPT. In the third case, the discoloration was successfully treated with vital tooth bleaching.

• Journal of Electrical Engineering and Technology
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• v.8 no.5
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• pp.1131-1137
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• 2013

This paper introduces novel a two-phase permanent magnet BLDC (PMBLDC) motor with both an asymmetric tooth and an auxiliary tooth in order to improve the dead point, efficiency and torque ripple. To calculate the merits of introducing each of the asymmetric tooth and the auxiliary tooth, characteristic analysis is performed respectively using finite element method (FEM). To maximize performance, we propose a novel model which combines the asymmetric tooth and the auxiliary tooth. To maximize the efficiency of the novel model, an optimal design is processed using the Kriging method and a genetic algorithm. Finally, an experiment is used to confirm the initial and optimal design results.

• The Journal of the Korean dental association
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• v.55 no.5
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• pp.358-364
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• 2017

Nowadays, there has been an increasing interest in the preservation of natural dentition and the proper occlusion related to tooth wear for quality of life. Tooth wear means the loss of tooth enamel structure. This is happened by many causes which is the combined effects of many mechanisms. For keeping proper occlusion, dentists should check tooth wear status with acceptable methods and tools for the proper diagnosis. Until now, there have been many traditional qualitative ways to measure tooth wear which are intuitive, rapid, and simple. On the contrast, they are not objective nor reproducible. With the development of related technique, new quantitative methods using CAD and 3d scanners. This article aimed to introduce qualitative and quantitative methods for tooth wear measurements.

• Transactions of the Korean Society of Automotive Engineers
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• v.6 no.6
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• pp.243-251
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• 1998

A method of establishing the tooth modification for gear transmission of vehicles to reduce gear whine noise, caused by tooth impact phenomenon of mating gear, is introduced. The major causes of tooth impact are due to the deflections of gear teeth and shafts of transmission with the loaded condition including various kinds of manufacturing errors. The theoretical shape of tooth surface to avoid tooth impact is derived by the amount of elastic deformation of gear teeth and shaft and overall manufacturing error of machine tool. The surface function is converted with respect to the conventional commercial data usually communicated to the gear inspection system. The proposed method is applied to the gearbox of four wheel drive vehicle and shows the gear whine noise decreased to the 8 dB in the sound level.