• The korean journal of orthodontics
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• v.31 no.2 s.85
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• pp.271-281
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• 2001

The Purpose of this study was fourfold - to evaluate the general laws of friction applied to orthodontic conditions, to compare archwire materials under these controlled conditions, to compare ligation method, and to measure the effect of the artificial saliva on friction with these materials Three wire alloys (Cobalt-chromium, Nickel-titanium, Beta-titanium) in two size wires (.016" , .016" ${\times}$.022" ) were examined respect to the bracket (.018" ${\times}$.025" standard), and two ligature material (stainless steel, elastomeric) in dry and wet conditions The results were as follows, 1. The order of frictional force against alloy materials was Co-Cr (lowest), Ni-Ti, and ${\beta}$-Ti(highest) - with the exception of elastomeric ligation under wet conditions. 2. S.S. ligation gave rise to significantly greater friction than elastomeric ligation did. 3. Testing in the presence of saliva, rather than in dry conditions, decreased the frictional force for S.S. ligation with .016" Co-Cr, Ni-Ti, ${\beta}$-Ti. but, increased the frictional force for S.S. ligation with .016" ${\times}$ .022" Co-Cr, Ni-Ti, ${\beta}$-Ti. 4. .016" ${\times}$.022 " wire generated more friction than .016" wire.

• Journal of dental hygiene science
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• v.15 no.4
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• pp.509-517
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• 2015

This study attempted to identify the entrance exam stress levels in high school students and analyze the relationship this entrance exam stress and perceived oral health status. Self-administered survey was conducted in total 304 students attending in academic high schools in Bucheon. For analysis, SPSS was used to perform t-test and one-way ANOVA. As a result of the study, the entrance exam stress level of academic high school students was 2.71. The level of sub-factors were that tension for exam/poor result was highest by 3.08 and the next were future uncertainty (2.81), parents pressure (2.56), and insufficient free time (2.52). The group with high entrance exam stress showed significantly high perceived degrees of temporomandibular disorder, oral mucosal disease and xerostama. Among sub-factors of stress, the group with high tension for exam/poor result stress had significantly high perceived degrees of dental caries, teporomandibular disorder, oral mucosal disease and xerostama. Because perception on oral health issues increased with high entrance exam stress in high school students, it is necessary to seek some ways to decrease oral health problems even though entrance exam stress is intensified. To do so, it is inferred that it will be very important to promote oral health education to develop ability of high school students to practice correct oral management method.

• Journal of the korean academy of Pediatric Dentistry
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• v.28 no.3
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• pp.374-382
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• 2001

The purpose of this study was to investigate the surface morphology and measure shear bond strength of Er : YAG lased enamel. To determine the most effective energy density of laser for improving bonding strength of human enamel, 24 specimen were lased from 30mJ to 150mJ at 1Hz used focused, defocused beam. After irradiation, the lased specimen were observed scanning electron microscope. To determine the resin shear bond strength of Er : YAG lased enamel, the 90 specimen were divided into 3 groups. The Control group was etched with 37% phosphoric acid for 15seconds and rinsed. Group 1 was only laser irradiaton(60mJ, 10Hz), Group 2 was irradiated as Group 1 regimen, followed 37% phosphoric acid etching. The following results were obtained: 1. In both focused and defocused Er : YAG lased enamel surface are similar to acid-etched enamel more than 60mJ in SEM evaluation. 2. The more increased laser energy, the more observed fissuring surface. 3. The highest mean shear bond strength value was observed in control group with the statistical significance(p<0.05) between all the other groups and the shear bond strength in group 1 was the lowest with significant difference among the other groups.

• Journal of the korean academy of Pediatric Dentistry
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• v.26 no.2
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• pp.427-436
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• 1999

Preservation of the remaining periodontal ligament cells on an avulsed tooth is very important to the successful outcome of replantation. HBSS is recommended as the most suitable storage medium for the avulsed tooth that cannot be replanted immediately. But their availability near the site of an accident is doubtful. The purpose of this in vitro study was to compare periodontal ligament cells stored in different storage media obtained easily on the spot. Human periodontal ligament cells were collected from the premolar teeth extracted for orthodontic treatment. Cells were cultured in ${\alpha}-MEM$ culture medium containing 20% FBS, at $37^{\circ}C$ 100% humidity, in a 5% $CO_2$ incubator. Cells were cultured in 96 well culture plate, $5{\times}10^4$ cells per well with ${\alpha}-MEM$ and incubated for 24 hours. After discarding the medium, those cells were cultured in ${\alpha}-MEM$ contained with 10% FBS, pasteurized milk, sterilized saline, unstimulated saliva and bench-dried state at $25^{\circ}C$ room temperature for 30, 60, 90, 120, 180 minutes respectively. And then each group was measured using MTT assay. The results were as follows. 1. Between the group of each time, there was statistically significant difference. Periodontal ligament cells viability was highest in pasteurized milk and was reduced stepwisely in sterilized saline, unstimulated saliva and bench-dried state(p<0.05). 2. between the time of each group, there was statistically significant difference(p<0.05) but was no statistically significant difference at 90-120 minutes in pasteurized milk and at 60-90 minutes and 120-180 minutes in sterilized saline(p>0.05). In conclusion, HBSS as storage medium of an avulsed tooth is not practical on the spot. Insteadily pasteurized milk can be recommended to maintain the periodontal ligament cells viability.

• Journal of Oral Medicine and Pain
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• v.33 no.1
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• pp.15-26
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• 2008

Purpose : To investigate the actual conditions of diagnosis and treatment of oral medicine inpatient with systemic disease. Methods : A total of 110 subjects, inpatient due to systemic disease for diagnosis and treatment of oral disease was requested to answer the medical history and dental treatment record. Results : Systemic disease is composed of Non-insulin-dependent diabetes mellitus 26%, Cerebral infarction 25.2%, Intracerebral hemorrhage, Polyarthrosis, Coxarthrosis 4.7%, Nerve root and plexus disorders, Hypertensive heart and renal diseases, Ankylosing spondylitis 2.4%. Chief complain of oral disease is composed of toothache 28.6%, routine check 23%, tooth mobility 8.7%, hypersensitivity 7.1%, periodontal bleeding 6.4%. Oral disease is composed of Gingivitis and periodontal diseases 28.9%, Dental caries 17.1%, Diseases of pulp and periapical tissues 15.1%, Diseases of salivary glands 10.5%, Other diseases of hard tissues of teeth 8.6%, Within Normal Limit 5.3%. Treatment of oral disease is composed of periodontal treatment 17.95%, rejection of treatment 16.67%, medication for halitosis & dry mouth 13.46%, extraction 12.18%, prosthetic treatment 8.97%. Chief complain in oral medicine is composed of oral soft tissue problem 6.4%, craniomandibular disorders 5.6%, halitosis 4%, total 16%. Conclusion : These findings indicate that inpatient due to the systemic disease is significantly correlated to the oral disease. The patients of oral disease interrelationship between inpatient and outpatient of systemic disease should be validated by future research.

• Restorative Dentistry and Endodontics
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• v.35 no.3
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• pp.188-197
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• 2010

The purpose of this study was to compare radiopacity and radiographic discriminability of various FRC-Posts. Six FRC-Posts were investigated ; 1) FRC Postec Plus (Ivoclar Vivadent AG, Schaan, Liechtenstein), 2) Snowlight (Carbotech, Lewis center, OH, USA), 3) Dentin Post (Komet Brasseler, Lamgo, Germany), 4) Rely-X Fiber Post (3M ESPE, St.paul, MN, USA), 5) D.T.-Light Post (BISCO, Schaumburg, IL,USA), 6) Luxapost (DMG, Hamburg, Germany) The radiographs of each post with a reference 1 mm / 2 mm aluminum step-wedge was taken using digital sensor. The optical density were calculated by gray value of $10{\times}10$ pixel and compared in mm Al equivalent at five points. Six maxillary incisors of similar radiopacity were used. Radiographs of posts in Mx. incisors of lingual side of dry mandible were taken. We showed radiographs and asked the questionnaire to 3 radiologists, 3 endodontists, 3 general practitioners. The questionnaire was comprised of choices of the highest, lowest radiopaque individual post and the choices of best discriminable post at apical, coronal area. The following results were obtained. 1. Each post system showed various radiopacity. 2. There was change of discriminability between each post and simulated specimens regardless of examiner. Although each post showed various radiopacity, the difference of radiopacity did not affect on discriminability.

• Restorative Dentistry and Endodontics
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• v.24 no.2
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• pp.399-407
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• 1999

Apical extrusion of canal debris is occurred inadvertently during root canal preparation and this could produce interappointment discomfort or postinstrumentation pain. The purpose of this study was to investigate the influence of canal preparation methods on the apical extrusion of canal debris by means of comparing the amounts of apically extruded debris with several kinds of instrumentation methods. In the first experiment, 40 incisors were divided into four groups of 10 each. They were instrumented using one of the four techniques: Step-back, crown-down pressureless technique with stainless steel K-files, engine-driven instrumentation with Quantec series 2000, and Profile .04 taper series 29. Root canal irrigation was done with 2.52% sodium hypochlorite solution. In the second experiment, 80 incisors were divided into five groups of 16 each and instrumented using step-back, crown-down pressureless technique with stainless steel K-files, engine-driven instrumentation such as Quantec SC, Quantec LX, and Profile .04 taper series 29 No irrigation procedure was performed in this second experiment. Extruded debris from each tooth was collected in a container and weighed by the use of an electronic balance after desiccation. With or without canal irrigation, step-back technique produced significantly more amount of apical debris than the other groups (p<0.05). However, there was no significant difference among crown-down pressureless technique, engine-driven instrumentation with Quantec LX, Quantec SC, or Profile. Therefore, either by hand or engine-driven instrumentation, it is concluded that to minimize apical debris, techniques using reaming motion of files should be applied rather than filing motion.

• Journal of Digital Convergence
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• v.11 no.12
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• pp.607-614
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• 2013

This study has been conducted to investigate the effect of self awareness of halitosis on the quality of life related to oral health in patients with chronic renal failure undergoing hemodialysis and use basic data related to oral health of patients with chronic renal failure which is very rare in Korea. In terms of oral symptoms based on awareness of halitosis, there were significant differences in symptoms of teeth pain in the past one month, bleeding gums, symptoms of tongue or cheek pain, dry mouth, In terms of status of oral functions, there were significant differences in discomfort upon chewing foods, difficulty of pronunciation and presence of lost teeth. As the results of analysis of effect of self awareness of halitosis on the quality of life related to oral health in patients with chronic renal failure, it was shown that there were significant effects in psychological discomfort(B=-2.028, p<.01), poor social skills(B=2.596, p<.01) and social disadvantage(B=-2.173, p<.01). Thus, because self awareness of halitosis gives psychologically and socially negative effects, it could be an important factor to patients with renal failure whose number is rapidly increasing.

• Journal of the korean academy of Pediatric Dentistry
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• v.45 no.3
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• pp.344-353
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• 2018

The purposes of this study were to evaluate microleakage of Biodentine, one of the tricalcium silicate based pulp-capping materials, and to compare the shear bond strength between composite resin and Biodentine with different setting times. For microleakage evaluation, 70 bovine teeth were used. Cavities were formed on the labial surfaces and filled with Biodentine. The teeth were divided into seven groups, each consisting of 10 teeth. The specimens were prepared by applying the composite resin on the upper side after different setting times. To evaluate shear bond strength, 210 acrylic resin blocks with central grooves were prepared, and the grooves were filled with Biodentine. The acrylic resin blocks were divided into seven groups of 30 specimens each, and the specimens were prepared by applying the composite resin on the upper side after different setting times. In samples with setting time of 24 hours or longer period, the microleakage between composite resin and Biodentine was reduced significantly while the shear bond strength increased to offset the polymerization shrinkage of the composite resin. Setting Biodentine for more than 24 hours before composite resin restoration would lead to more favorable clinical result.

• Journal of the korean academy of Pediatric Dentistry
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• v.32 no.4
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• pp.611-619
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• 2005

The aim of this study was to apply the quantitative light-induced fluorescence(QLF) and use of fluorescein-enhanced QLF method for quantitative assessment of early enamel demineralization in vitro, comparing effectiveness of light sources : argon laser, halogen lamp, light emitting diode (LED) and plasma arc lamp. Sixty extracted teeth were used, prepared by gentle pumicing and coating in an acid-resistant nail-varnish, except for an exposure to a demineralizing solution. Teeth were removed at regular intervals (24, 48 and 72hrs), air-dried and QLF image were taken. Mineral loss, as measured by difference of optical density, was recorded. For dyeenhanced QLF a 0.075% sodium fluorescein dye was applied after QLF examination and mineral loss was recorded. The following result were obtained : 1. Comparing with mean difference of optical density, plasma arc lamp was higher than other light sources in all group (p<0.05). 2. Comparing each group with mean difference of optical density, there was significant different using plasma are lamp and halogen lamp. 3. For use of dye-enhanced QLF, comparing with mean difference of optical density, plasma arc lamp were higher than other light sources in all group(p<0.05). 4. With this model dye-enhanced QLF compared with QLF in optical density, dye-enhanced QLF was higher than QLF in optical density. From the results presented in this paper, it was concluded that plasma light source was more effective compared with other light source for the detection and the quantification of early enamel caries.