• Journal of Technologic Dentistry
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• v.33 no.4
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• pp.263-270
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• 2011

Purpose: The grindability of binary Ti-X%Zr(X=10,20,40) alloys in order to develop a Ti alloy with better machinability than unalloyed titanium has been evaluated. Methods: Experimental Ti-Zr alloys were made in an argon-arc melting furnace. Slabs of experimental alloys were ground using a SiC abrasive wheel on an electric handpiece at circumferential speeds(12000,18000,25000 or 30000rpm) by applying a force(200gr). Grinding rate was evaluated by measuring the amount of metal volume removed after grinding for 1 minute and the volume ratio of metal removed compared to the wheel material lost, which was calculated from the diameter loss (grinding ratio). Experimental datas were compared to those for cp Ti(commercially pure titanium) and Ti-6%Al-4%V alloy were used controls. Results: It was observed that the grindability of Ti-Zr alloys increased with an increase in the Zr concentration. More, they are higher than cp Ti, particularly the Ti-20%Zr alloy exhibited the highest grindability at all circumferential speeds. There was significant difference in the grinding rate and grinding ratio between Ti-20%Zr alloy and cp Ti at any speed(p<0.05). Conclusion: By alloying with Zr, the Ti exhibited better grindability at all circumferential speeds. the Ti-20%Zr alloy has a great potential for use as a dental machining alloy.

• Journal of Technologic Dentistry
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• v.29 no.2
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• pp.141-150
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• 2007

The purpose of this study was to ascertain the bonding durability of self-etching dentin bonding agents to dentin by means of shear bonding strength. Several acid-etching dentin bonding system (ESPE Z100) and self-etching dentin bonding systems (DEN-FIL, GRADIA DIRET) were used. The occlusion surface of human molars were ground flat to expose dentin and treated with the etch bonding system according to manufactures instruction and followed by composite resin application. After 24hours of storage at 37$^{\circ}C$, the shear bonding strength of the specimens was measured in a universal testing machine with a 1mm/min crosshead speed. An one-way analysis of variance and the scheffe test were performed to identify significant differences (p<0.05). The bonded interfacial surfaces and treated dentin surfaces were examined using a SEM. Through the analysis of shear bond strength data and micro-structures of dentin-resin interfaces, following results are obtained. In dentin group, the shear bond strength of DEN-FIL showed statistical superiority in comparison to the other groups and followed by ESPE Z100 and GRADIA DIRECT (p<0.05).

• Journal of Technologic Dentistry
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• v.23 no.2
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• pp.179-188
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• 2002

With regard to the manufacture of dental prosthesis, all the dental mechanism is of vital significance at the aspect of activating its function by fixing the prosthesis to Patient's oral cavity. However, if there we will take our immediate action without the discretion about its process none the less for the importance of dental mechanism, then we might have a serious problem. Accordingly, there need to pay attention to the dilatability makes up for the shrinkage state occurring by the feature of metal materials and manufacturing process which appeared in the process of dental mechanism, which eventually is expected to playa very important role in casting a dental prosthesis appropriate to one's oral tissue. This study was designed to take into account of the effects on margin consistency of prosthesis according to the continued time of casting-ring in the course of the casting of dental alloy. For this, the researcher made an experiment on the casting of dental alloy, its dilatability, and the change of phase. The results of this study were as follows: First, the researcher could see that the sample which was cast under the condition of $650^{\circ}C/20$ Minutes(the continued time) was far superior to others at the aspect of margin consistency. Second, according to the measurement of expansion coefficient by Dilatometer, the researcher perceived the fact that the expansion-coefficient showed a maximum of $37.1{\mu}m$ considering the sample's length which was cast with ordinary temperature under the condition of $650^{\circ}C/20$ Minutes. Third, from the result of X-ray diffraction under the condition of $650^{\circ}C/20$ Minutes(the continued time), the researcher could find that there's no difference between the change of phase and its intensity. As mentioned above, the researcher could ascertain the fact that its contraction don't give rise to the change of phase.

• Journal of Technologic Dentistry
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• v.15 no.1
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• pp.27-41
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• 1993

Degree of noise by personal dental laboratory working process and degree of noise by complex dental laboratory working process were measured separtely. The time of exposure to noise greater than 70dB was analyzed. Then, the whole degree of noise in dental laboratory was estimated on the basis of afore-mentioned information. Questionaire were employed to investigate the mental, emotional and physiological effects of noise in dental technicians, The purpose of this study was to provide basic information on keeping dental techneicans who are exposed to noise pollution in good working condition and good health. Results obtained are as follows ; 1. Polishing process in each working part showed high degree of noise greater than 70dB in terms of degree of noise by personal working. 2. Degree of noise by complex working process in each working part was greater than that of personal working process. 3. Time of exposure to noise complex working process the part of porcelain 150min, partial denture 120 min, crown and bridge 100 min, full denture 80 min. 4. Degree of noise by time in dental laboratory was 80dB in general for polishing process and below 75dB for waxing process. 5. Effects of noise on mental and emotional state of dental technicians showed that they felt irritated every day(14%), irritated once in a while(29%) and easily ger mad(19%). 6. Effects of noise on heart and stomach were hyper-gastric acid(38%), gastric ulcer(11%), gastritis(5%), deuodenal ulcer(3%) and weak heart function(32%). 7. Effects of noise in the hearing ability were weak(39%), moderate(33%) and normal(14%) Data presented in this study demonstrated that noise in the dental laboratory exerts profound effect on dental technicians mentally, physiologically and emotionally, in light of the above results, therefore, it appears advisable to devots substantial on the management of working condition and put further(continuing) efforts in the investigation for reducing noise problem.

• Journal of Technologic Dentistry
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• v.31 no.3
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• pp.9-14
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• 2009

This study evaluated the mechanical properties of Ti-Cu alloys with the hope of developing an alloy for dental casting with better mechanical properties than unalloyed titanium. Ti-Cu alloys with four concentrations of Cu(2,5,10wt%) were made in an argon-arc melting furnace. The microstructure and micro-Vickers hardness were determined. X-ray diffraction pattern test was performed on the polished specimens. The microstructure of 2%Cu and 5%Cu alloys are shown acicular ${\alpha}Ti$ phase formed on the surfaces of previously formed $\beta$grains. The 10%Cu alloys has essentially a eutectoid structure; this structure includes lamella of ${\alpha}Ti$ and $Ti_2Cu$ phase that transformed from ${\alpha}Ti$ at the eutectoid temperature. The micro-Vickers hardness of CP Ti specimens was significantly(p<0.05) lower than that of any of the other alloys. Among the Ti-Cu alloys, the 10%Cu alloys exhibited a significantly(p<0.05) higher hardness value. but lower than that of Ti-6%Al-4%V alloy. From these results, it was concluded that new alloys for dental castings should be designed as Ti-Cu based alloys if other properties necessary for dental castings were obtained.

• Journal of Korean society of Dental Hygiene
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• v.12 no.4
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• pp.647-654
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• 2012

Objectives : To propose the data for prevention of oral health problems through assessment on the knowledge, cognition and practice about oral health care of the clients who visit dental clinics. Methods : The subjects were total 400 clients from the four dental clinics in Busan city. Their knowledge, cognition and performances about oral healthcare collected with questionnaire survey from February to March, 2011. The rate and mean compared by chi-square test, t-test, and ANOVA. Results : Mean level of their knowledge, recognition and practice were 72.5, 80.2, and 65.6, respectively. Theses levels were higher in women (p<0.01), in the group of higher interested (p<0.001), immediately treated (p<0.001), correct tooth brushing (p<0.05), toothbrushing educated (p<0.001), take regular scaling (p<0.001), use assistant hygiene items (p<0.001), instead no differences by age and education level. And, the rate of correct toothbrushing was higher as 1.24 (1.03~1.50) times in the group with higher knowledge level, the rate of immediate treatment and regular scaling were higher as 1.35 (1.07~1.70) times, and 2.26 (1.41~3.64) times in the group with higher recognition level, respectively. Conclusions : These results demonstrate that insufficient knowledge and recognition of oral health care are related to a lack of its practice. Though their primary goal of the visits was treatment, the clients' attention needed to raise the comprehensive knowledge and recognition levels for their oral health promotion, especially reach to the performance level rather than simple knowledge acquisition. And more, to achieve the efficient oral health promotion, the importance of early treatment and strengthened efforts for prevention should be emphasized.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.11
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• pp.5079-5086
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• 2011

The purpose of this study was to examine the oral health status and knowledge of dental laboratory technology student for the community to improve oral health and oral health education to help. The subjects in this study were 160 students in dental laboratory technology at the University located in Chung-cheong and surveyed from November 2010 to December 2010. The finding of the study were as follows: The differences in oral care knowledge according general characteristics of subjects was statistically significant to the gender was higher in men than women, age was higher and higher the grade was higher in grade level(p<0.05). The differences in oral care knowledge according oral health status of subjects was statistically significant to regarding the frequency of tooth brushing was highest rate in five times, method was on the side tooth higher and using the dental floss and interdental brush are used by the higher availability(p<0.05). Thus, in the classroom oral health education and continuous learning from the people know that oral health care could differ. Oral health education in local communities to increase opportunities and people will need to improve oral health.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.23 no.1
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• pp.59-64
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• 2023

With the recent development of IT technology, medical image processing technology is also widely used in the dental field, and the treatment effect is enhanced by using 3D data such as CT. In this paper, open source libraries such as ITK and VTK are introduced to develop dental medical image processing software, and how to use them to develop dental medical image processing software centering on 3D CBCT. In ITK, basic algorithms for medical image processing are implemented, so the image processing pipeline can be quickly implemented, and the desired algorithm can be easily implemented as a filter by the developer. The developed algorithm is linked with VTK to implement the visualization function. The developed SW can be used for dental diagnosis and treatment that overcomes the limitations of 2D images..

• Journal of Korean society of Dental Hygiene
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• v.12 no.1
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• pp.27-35
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• 2012

Objectives : This study was performed to provide the basic data for oral health of infants, through the comparison of Streptococcus mutans activities(the representative bacteria of initial dental caries), in main nutritional foods for infants: breast milk, milk powder, and soya milk. Methods : The study targeted 30 infants and the saliva was sampled after the oral examination. The pH of sampled saliva was measured; and the sample of 'the saliva', 'the saliva and breast milk', and 'the saliva and formula milk' by researcher were produced; and the measurement was repeated 7 times. Results : As a result of examining the change of colony number of Streptococcus mutans by hour, the bacterial activity took in the source of nutrition took place in the first place; and in the group with dental caries, breast-feeding at night occurreds most frequently. Due to the combined activities, such as the increase in the contact time, the existence rate of dental caries appeared high. However, as the improvement of breast-feeding is closely related to the nutrition supply to babies, rather than the improvement of breast-feeding, the 12 hours after the culture in which Streptococcus mutans activities started was considered. Conclusions : In case of breast-feeding at night, it is necessary to remove the dental plaque in the mouth, before 12 hours has passed. Especially, using toothbrush and toothpaste to decrease the occurrence of dental caries, after the eruption of teeth, is recommended for oral administration.

• Journal of Technologic Dentistry
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• v.22 no.1
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• pp.113-128
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• 2000

The purpose of this study was to serve as a basis for the development of dental technology and for creating a condition that dental technicians could work with pride and right values, by examining what problems there were in their health care, what they thought about them, and how the problems could be solved, The findings of this study were as below: 1. The most serious and harmful element in dental technology workshop was a dust(57.5%) and a noise(33.3%). 2. Approximately 99.0% of the dental technicians investigated made a complain of air pollution caused by noise. Their opinion on a possible measure to remove noise air pollution was that the noise-generating machine should be replaced(64.1%) or that it should be isolated(28.8%). 3. 76.0% complained air pollution cause by dust deteriorates their working efficiency. As a way to eliminate it, they suggested a dust chamber(35.3%) or an air cleaner(27.5%) should be installde. 4. About 80% made a complain of gas air pollution. The most common related symptom was a headache(56.9%). They thought that gas-generating machine should be isolated(39.9%) or that an air purifier should be prepared(33.3%). 5. The largest impact of heat and light on their body was weakening their eyesight(56.9%). 47.1% got burn once though four times, and 34.3% did five times or more. The way to prevent them was to install an automatic casting machine(66.0%) or use protective glasses(28.1%). 6. Approximately 47.7% were considering a change of occupation, and the most common reason was heavy work(23.5%), followed by poor prospect(21.6%) and working environment(19.0%) in the order named. 7. 88.9% responded they were likely to have an occupational disease. Their idea about the proper frequency of regular health examination was once a year(53.6%), or once per every six months(41.8%). 8. The field they were most interested in was health care(39.2%), followed by academic research activities(31.4%). This fact indicated it's most urgently required to improve their working environment.