• Journal of dental hygiene science
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• v.6 no.2
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• pp.55-63
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• 2006

The purpose of this study was to provide the basic data for preventing dental caries, and maintaining and enhancing oral health. The subjects of this study were 138 male and female students who were in the 6th grade of elementary schools in Gimpo city. This study investigated the number of decayed tooth and the factors related to the number of decayed tooth, by using the results of questionnaire and oral health survey over such subjects. So, this study obtained the following conclusions. 1. For the number of decayed tooth, 'nothing(D = 0)' was the highest as 37.7%, and 'from two to three' was 23.9%, 'more than four' was 21%, and 'one' was 17.4% in order. 2. For the frequency of visiting dental clinics within the last one year, 'one to two times' was the highest as 52.2%, and the children who have not visited dental clinics even one time during one year were 23.9%. 3. For average daily tooth brushing frequency, 'two times' was the highest as 71.7%. For the use of oral health devices besides toothbrushes, 'I don't use' was the highest as 54.3%. For the experience of sealant and fluoride application, 'nothing' was the highest as 86.9% and 71.3% respectively. For the recognition on the use of fluoride dentifrice, 'I don't know' was the highest as 66.9%. 4. The socio-demographic factors related to the number of decayed tooth were mother's age, mother's background, mother's employment, and after-school fosterer(p > 0.05). 5. The oral health care factors related to the number of decayed tooth were average daily tooth brushing frequency, the use of oral health devices besides toothbrushes, and the experience of fluoride application.(p > 0.05) 6. The snack intake factors related to the number of decayed tooth were tooth care foods intake frequency and decaying foods intake frequency(p > 0.05). 7. The oral health belief item related to the number of decayed tooth was susceptibility(p > 0.05). 8. According to the results of regression analysis, the less mother was employed, the more the average daily tooth brushing frequency was, the more the tooth care foods intake frequency was, the less the decaying foods intake frequency was, and the higher susceptibility was, the lower the number of decayed tooth. 9. In order to prevent and cure early the dental caries which occur frequently in elementary school students, the establishment of oral health centers within schools should be expanded to promote tooth brushing instruction, fluoride solution rinsing, diet control, periodic oral examination.

• Journal of the korean academy of Pediatric Dentistry
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• v.37 no.2
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• pp.159-167
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• 2010

The purpose of this study was to identify patterns of caries in the dentition of preschool children using cluster analysis and multidimensional scaling. 815 preschool children aged 36-71 months old were examined for caries experience. The first four clusters in the cluster analysis were (1) molars, (2) upper incisors, (3) lower 1st molars, and (4) upper 1st molars in teeth, (1) occlusal surfaces of lower molars and upper 2nd molars, (2) mesial surfaces of upper central incisors, (3) occlusal surfaces of lower 1st molars, and (4) separation between occlusal surfaces of upper and lower 2nd molars in tooth surfaces, and (1) proximal surfaces of upper anterior teeth, (2) occlusal surfaces of lower molars, (3) buccolingual surfaces of upper anterior teeth and (4) buccolingual, proximal, and occlusal surfaces of upper molars and buccolingual and proximal surfaces of lower molars in tooth surfaces groups. In the multidimensional scaling analysis, teeth could be divided into lower 1st molars, upper 1st molars, upper central incisors, upper lateral incisors, lower 2nd molars, upper 2nd molars, and the rest(canines, lower incisors), tooth surfaces could be divided into occlusal surfaces of lower molars, mesial surfaces of upper central incisors, occlusal surfaces of upper molars, and the rest, and tooth surface groups could be divided into proximal surfaces of upper anterior teeth, buccolingual surfaces of upper anteiror teeth, occlusal surfaces of lower molars, and the rest in the order of the distance from others. In the cluster analysis and the multidimensional scaling analysis, caries patterns were different according to the age.

• Journal of Biosystems Engineering
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• v.13 no.4
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• pp.9-19
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• 1988

The threshing of head-feed combine may be accomplished mainly by the action of impact between threshing teeth and rice. In this study, it was attempted to assess threshing performance characteristics of head-feed threshing teeth. And the characteristics of threshing teeth will be applied to the method which could analyze the time and order of impact between teeth and the rice, which was used as a basis for predicting the threshing performance and determining the optimum design parameters. The results of the study are summarized as follows: 1. About 50% of threshed material were threshed by the beginning 7 impacts on the rice bundle. Threshing torque decreased until 25 impacts and did not change thereafter. 2. There was significant difference in the threshability according to the shape of threshing teeth. The triangular-shaped tooth was the most efficient in threshability ratio and the semicircle-shaped tooth was the lowest. There was no significant difference in specific energy requirement for the varied teeth design. Torn-head ratio being generated by the semicircle-shaped and the triangular-shaped teeth in series was less than that by a single tooth with the triangular-shaped and the double setting of the triangular-shaped. Chaff generation ratio by the triangular-shaped and the semicircle-shaped teeth was less than the others tried. 3. The triangular-shaped teeth in series, which was newly designed for this study, showed an intermediate characteristics between the double setting of the triangular-shaped and the semicircle- shaped teeth. Threshability ratio of the triangular-shaped teeth in series was higher than that of the semicircle and lower than the double setting of the triangular-shaped tooth. Torn-head generation ratio for it was about same as that of the semicircle. Chaff being generated by the triangular-shaped teeth in series was about same as the double setting of the triangular-shaped teeth. 4. About 40% of threshed grains which passed through concave were concentrated under the threshing tooth and the rest of grains displayed a skew distribution toward the inlet of threshing chamber.

• International Journal of Oral Biology
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• v.41 no.4
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• pp.243-251
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• 2016

This study was undertaken to achieve a high bleaching efficacy with plasma, through longer application and reparative bleaching processes, by different shade evaluation methods. Extracted human teeth were divided into 6 groups (n=10). All teeth were treated in pairs. Low concentration of 15% carbamide peroxide (CP) was applied, with and without plasma, for 10, 20, and 30-min tooth bleaching, respectively. The bleaching procedure was repeated once daily for four days. The teeth were maintained in a moist environment provided by artificial saliva. The Vitapan Classical shade guide and Commission Internationale de L'Eclairage (CIELAB) color system were collectively used to measure the bleaching efficacy. Color evaluation was statistically analyzed using Student t-test and one-way analysis of variance (ANOVA) complemented by Tukey's test. Combining the plasma with 15% CP showed significantly greater color changes compared to bleaching without plasma (p<0.05). A high bleaching efficacy with plasma is proportional to the repetitive application and the treatment time. A 30-min application with plasma provided the best bleaching. Repetitive bleaching showed lower probability of color relapse of the bleached tooth. The color change by shade guide correlated with the changes in CIELAB color system. A value of 1 color change units (CCU) conversion factor for overall color change (${\Delta}E$) values comparisons was 3.724 values. The two measuring methods provide a more accurate correspondence of color change. The repetitive and longer application for tooth bleaching, combined with plasma, has a strong bleaching effect and produces whiter teeth.

• Journal of Periodontal and Implant Science
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• v.35 no.3
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• pp.577-590
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• 2005

The purpose of this study was to evaluate the effects of toothpaste containing hydroxyapatite for patients who complained dental hypersensitivity. Before baseline of application of toothpaste with hydroxyapatite, tooth brushing instruction was done respectively and the several indices were measured at baseline, 2, 4, 8 weeks. Clinical indices were estimated, and responses to cold, compressive air, tactile stimulus were evaluated with verbal rating score. Relief effects and visual analogue scale were also evaluated. The results of this study were as follows 1. The occurrence rate of hypersensitivity in upper jaw was higher than that of lower jaws, and molar area showed more hypersensitivity than premolar and incisor area. Buccal site was hypersensitive followed by interproximal and lingual site. 2. Plaque index, gingival index and probing depth reduction were gradually improved after Tooth Brushing Instruction and using toothpaste. 3. Subjects showed most sensitive response to cold stimuli than compressive air and tactile stimuli. 4. The relief effect was increased during using tooth paste and complete relief was increased especially at 8 weeks. 5. Visual analogue scale was increased. In conclusion, it was confirmed that toothpaste containing microcrystalline hydroxyapatite have the relief effect of tooth hypersensitivity. During 8 weeks, stimulus responses were decreased and hypersensitivity relief effect was increased.

• Journal of dental hygiene science
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• v.23 no.3
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• pp.236-244
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• 2023

Background: The size of the tooth whitening market and toothpaste market is increasing worldwide. The purpose of this in vitro study is to confirm and compare the coffee stain removal effects of commercial whitening toothpaste in sound and demineralized teeth, respectively. Methods: A total of 112 flat permanent bovine teeth specimens were manufactured. Half of the surface of the specimen was coated with an acid-resistant varnish and deposited in an artificial demineralizing solution for 65 hours. The varnish applied to half of the specimen was removed and deposited in a coffee solution for 96 hours to induce coloring. Two control and five experimental group toothpastes for teeth whitening were selected and the main components were investigated. Toothbrushing was performed 50, 100, and 150 times for each toothpaste group. A total of four images were obtained: before the start and after 50, 100, and 150 times of brushing to obtain the lightness (L^*) values of the sound and the demineralized tooth surfaces. The difference in the average value between toothpaste groups at each treatment period was analyzed by one-way ANOVA. The difference in the L^* average value according to the number of the brushing was analyzed by repeated measure ANOVA. Results: All toothpastes in the seven groups contained abrasive agents and had different ingredients for each product. Compared to before brushing, the L^* value changed significantly in all toothpaste groups after brushing 50 times (p<0.05). This was common in both the sound and demineralized teeth surfaces. Demineralized teeth had significantly lower L^* values at all brushing times than that in sound teeth (p<0.05). Conclusion: The effect of whitening teeth was different for each toothpaste. Demineralized teeth were more likely to cause coloration than sound teeth, and the coloration was not removed well.

• The korean journal of orthodontics
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• v.21 no.2 s.34
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• pp.273-285
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• 1991

Crowded group is composed of 60 subjects who visited Yonsei University for orthodontic treatment and has no history of orthodontic treatment. Noncrowded group is composed of 26 subjects who has no crowding, considered to have a normal occlusion and no history of orthodontic treatment. Currently available and approved analytic method was used. Interrelationship between tooth size and arch size, and it's correlation on tooth crowding was studied and the following results were obtained. 1. In comparison of sum of mesiodistal width, of crown size of teeth was greater in noncrowded group than that of crowded group on both arch. (p < 0.01). 2. In comparison of arch lengths, the values measured from arch length 2 showed greater in noncrowded group (p < 0.01). Also in crowded group, arch length 1 showed greater value than arch length 2 on both arch (p < 0.01). 3. In comparison of arch widths, upper interlateral (p < 0.01) and upper intercanine width (p < 0.05) showed greater value in noncrowded group on upper arch and intermolar width showed greater value in noncrowded group on both upper and lower arches (p < 0.05). 4. In comparison of arch perimeters, arch perimeter 2 was greater value in noncrowded group on both upper and lower arches (p < 0.01). 5. Dentoalveolar disproportion was greater in noncrowded group on both upper and lower arches (p < 0.01). 6. In lower incisors MD/FL ratio, the central and lateral incisors were greater in crowded group, but statistial significance was only in lateral incisors (p < 0.01) 7. The irregularity index of lower incisors showed greater value in crowded group (p < 0.01).

• The korean journal of orthodontics
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• v.28 no.6 s.71
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• pp.981-989
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• 1998

Positions, angulation and mesiodistal dimension of lower incisors are important in esthetics, occlusion and post-treatment stability of tower arch. When lower incisor is congenitally missing, problems such as increased overjet and overbite, closing in of adjacent teeth and size/space discrepancies may occur. When creating treatment plans, incisor position and angulation, lip support, anteroposterior skeletal relationship canine-molar relationship, overjet overbite, remaining growth potential, crowding and anterior tooth ratio have to be considered. For an accurate analysis of incisal size discrepancy, diagnostic model set-up may be helpful. The two patients in this presentation both had two lower incisor missing, but the degree of crowding, skeletal relationship, lip support, molar relationship are different and therefore treatment plan was different as well. Long term follow-up may be necessary for stability and retention.

• The Journal of the Korean dental association
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• v.13 no.6
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• pp.559-562
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• 1975

This is a case of the patient, a 15 -year-old girl, presented a marked necrotic osteomyelitis due to misusage of the arsenic compound for devitaliaztion of the lower right 2nd molar in the right posterior part of the mandible. She was obtained good satisfactory results by sequestrectomy of necrotic bone and by removing of lower right 2nd molar and unerupted 3rd molar tooth germ.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.42 no.1
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• pp.51-54
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• 2016

The present case report describes an external auditory canal injury following extraction of the lower molar. The external auditory canal was torn in the same fashion that occurs in an anterior tympanic plate fracture. This case demonstrates one of the rare complications associated with dental extractions.