• Journal of Technologic Dentistry
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• v.33 no.4
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• pp.307-312
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• 2011

Purpose: The purpose of this study is a porous cube mechanical analysis for the dental implant. Methods: The porous cube with a side length of 10mm was designed for dental implant. To choose proper design, porous hexagon with a side 10mm which was drilled as a regular hexagon with diameter 0.8mm, 1.0mm, 1.2mm and a side 0.4mm, 0.5mm, 0.6mm each using Computer AUTO CAD(Autodesk, 2008). Each cube was carried out in the mechanical analysis. Results: The result of mechanical analysis was observed that the H0.8 was minimum stress 0.045068MPa, maximum stress 9.4565MPa and minimum strain $0.00389{\times}10^{-4}Mpa$, maximum strain $0.816{\times}10^{-4}Mpa$, the H1.0 minimum stress 0.001147MPa, maximum stress 9.099MPa and minimum strain $0.000099{\times}10^{-4}Mpa$, the maximum strain $0.784{\times}10^{-4}Mpa$, the H1.2 minimum stress 0.099393MPa, maximum stress 13.137MPa and minimum strain $0.0112{\times}10^{-4}Mpa$, maximum strain $1.13{\times}10^{-4}Mpa$. Conclusion: The mechanical analysis of porous hexahedron was that H1.0 is the best result. It will be applicable to the porous implants.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.10
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• pp.4484-4492
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• 2011

The purpose of this study was to analyze dental laboratory's self health recognition level and health behavior level and to examine its correlation. 250 dental technicians in Seoul, Incheon, and Jeonbuk area were selected. Survey was carried out from October 11, 2010 to November 25, 2010 by using self-administered questionnaire. The following are the analytical results in the collected data. The average in the self- health recognition was indicated to be high with 2.83, The average of health behavior was indicated to be high with 2.76. As for correlation between self health recognition and health behavior, most of variables were indicated to have reverse correlation, it was concluded that higher health behavior likely led to lower self health recognition. From the result of this study, the work environment of dental technician must be improved and do more Practice of Health Behavior to improve and maintain their health.

• Journal of Technologic Dentistry
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• v.21 no.1
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• pp.153-163
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• 1999

The 21st centurt, the era of change-space, is requesting us to readjust our education system. In other words, we should renew it by looking back into the past cultivate more advanced ideas. As a matter of fact junior colleges have been considered just as miniture of universities in every way such as curriculum, prossor emploment, school affairs, etc. Therefore we should change our existing education system not to be criticized for the next century. May students are trained for industry as dental technicians in our department of college. We should educate experiment and practice substantially as college professors as well as exert ourselves in developing our abilities to adapt to high diverse industrial technique, putting emphasis on practice more than theory. It is mecessary for us to sufficiently teach the technique to good students and make them display their abilities in order to produce high quality goods. Reinvestment ineducation is a condition precedent. Dental laboratories have just employed the students that graduated from our college. However it's time for a change. They should pay attention to our education and assist us in all respects with the thought of equally educating professional dental technicians together with us. The field practice system is subject to reinforcement so that our students have more opporunities of utilizing the tools and materials for practice. Finally we should not only carry out new reserch more deeply no less than dental technicians who are experienced in business for development of education system but endeavor to meet pratical education by adding what is pratically needed in dental laboratories to the existing education system.

• Journal of Technologic Dentistry
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• v.30 no.2
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• pp.105-119
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• 2008

This study explored the status of free time activities among the dental technicians who are working at Seoul, Gyonggido, and Gangwondo. On the basis of this research, we aim to present needs and applicable solutions to improve the working conditions and enhance the quality of life through more effective time management in free time activities that lead to their self development and far more enriched life. 500 subjects were randomly chosen and the questionary sheets were provided. Among them, 305 sheets were returned to be analysed through SPSS Win 10.0 software and the results are as follows; First, mean in the satisfaction of leisure activities was 3.44(SD=.73). Mean in sub categories was as follows; psychological factor(M=3.65, SD=.71), social factor(M=3.54, SD=.75), rest factors(M=3.52, SD=.63), physical factor(M=3.43, SD=.88), other factors(M=3.40, SD=.66), circumstantial factor(M=3.33, SD=.63), educational factor(M=3.24, SD=.73). Second, the most relevant sub categories in the satisfaction of leisure activities were social, educational, physical, and other circumstantial factors by sequence. Factors that affect leisure activities satisfaction were career and status of health, which shows statistical significance(p<.001). That is to say, contention of this study is that the general characteristics are closely related with and affect the types and the level of satisfaction in leisure activities of the subjects. Considering these results, the dental businesses and the associations of dental technicians should recognize the needs to improve the time management through more efficient cooperations between dentists and back office dental team, systemized working time, and introduction of incentive system among others. On the basis of this appreciation, the dental business should provide more time and various opportunities with the dental technicians. Dental technicians also need to reconsider their appreciations of leisure activities, that is, leisure activities are not just spending time doing something but they refresh them and enable them to be more active and faithful to home and work.

• Journal of Technologic Dentistry
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• v.17 no.1
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• pp.41-57
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• 1995

This study was conducted to collect and analyze previous information in order to manage efficience, improve experience effect and promote employment rate. The questionnaire interview with 27 chief of dental Laboratory refered clinical experience in technology department about clinical experience in 14 Jumior colleges were also investigated. The results were summarried as follows : The portion of age of 35-39 among chief of dental Laboratory was 40.7% which was the highest, that of male was 96.3%, that of junior college graduate was 97.5%, that of 10years experience was 92.6% and that of ceramic technician was 85.2%, 63.0% dental laboratory for clinical experience was a bore space of 30pyong. Aspect of dental laboratory management, manufacturing all part of prosthetic restoration was 29.6%, othodontic appliance and ceramic restoration was 7.4%, 3.8%, each. The percentage of 40.7 was having connection with 30-3a dental clinics and referring case per day was 10-19 cases(40.7%), manufacturing time of referred prosthetic restoration was 3-4 days(77.8%), places preparing seminar room for education was 29.6%, above a place of 40pyong was 11.1% 30-34 pyong and 35-39 pyong was 7.4% each. During training of 2 years education course student, 18.5% was rack of thorough occupational career. While 44.4% will want the more salary among 3years education course student, 74.1% will expect the more dental techmicians would engaged in their field, 51.9% will hope improve of their theory and practice, 29.6% be expected better skill and 14.8% be expected better theory. Attitude of clinical experience places was distributed by 59.3% of offering only experience chance, 25.9% of wasting time and 29.0% of annoying. The big emphasis of climical experience was thorough occupational career(44.4%). The clinical experience places of our college were selected after direct visiting, so their condition of management was not that bad but most of dental laboratory were poor in management state and working environment. Therefore it is difficult to choose appropriate places and dental Laboratory are also limited manpower and time as suppliers. So that it recommended to induce flexible management of experience period by interval and rotation of experience places among college and to applicate intern-system for employment ant industry-college cooperation aspect.

• Journal of Technologic Dentistry
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• v.11 no.1
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• pp.47-63
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• 1989

The study was made to clarify the degree of fatigue of dental technicians in service at the general &local hospital or the dental laboratories in the large cith of korea. The objectives of this study were 235 dental technicians who replied the questionaire which was sent by postal service out of 600 dental technicians selected by random sampling among the workers of the each dental laboratory. The instruments used in this study was the same one as developed by Industry Fatigue committee of Japan Industry Hygiene Association. This instrument was included total 30 items which is consisted of 10 perceived symptoms of fatigue in physical, mental and neuro-sensory dimension respectably. Reliability was tasted with the data of objectives, in which value of Cronbach's $\alpha$ was 9457. The following results were obtained. 1. It was revealed that the influencing demographic variables on the perceived symptoms of fatigue of dental technicians were sex, age, marital status, educational background, job carrier, working part, working hour and commuting hour. The shorted the age or job carrier, thge higher dearee of the perceived symptoms of fatigue. The longer working hours of commuting hours, the higher degree of the perceived symptoms of fatigue. The degree of the perceived symptoms of fatigue in females, unmarried person, the one with higher educational background, workers except orthodontic appliances and poorcelain contouring were higher than the other group. 2. The higher degree of the rest & leisure condition, the lower degree of the physical, mental and neuro-sensory perceived symptoms. 3. The higher degree of environmental condition of the working, the lower degree of the physical, mental and neurosensory perceived symptoms.

• Journal of Technologic Dentistry
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• v.37 no.4
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• pp.243-250
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• 2015

Purpose: The aim of this study was to investigate the shear bond strength between various commercial zirconia coping and veneering ceramic, and to observe the failure mode. Methods: For each zirconia block (iJAM Emerald, LUXEN Smile block, ICE Zirkon transluzent), 10 rectangular specimens were layered with Cercon ceram kiss, IPS e.max ceram, ICE Zirkon ceramic according to recommended by the manufacturer. The shear bond strength tests of the veneering porcelain to zirconia were carried out until fracture by a universal testing machine. After the shear bond tests, failure modes were characterized visually, under a stereomicroscope, such as adhesive, cohesive, or mixed. Data were analyzed with One-way ANOVA followed by Scheffe's tests. Results: The shear bond strength ($mean{\pm}SD$) of zirconia-veneer ceramic were JC group $13.9{\pm}3.6MPa$; JE group $17.7{\pm}2.4MPa$; JI group $15.1{\pm}2.5MPa$; LC group $9.5{\pm}1.5MPa$; LE group $16.2{\pm}2.3MPa$; LI group $12.6{\pm}0.8MPa$; ZC group $16.0{\pm}2.3MPa$; ZE group $18.5{\pm}3.4MPa$; and ZI group $15.3{\pm}3.2MPa$. The One-way ANOVA showed a significant difference between groups (p<0.05). The failure mode in most experimental groups was mixed failure, except for the LC group, which showed adhesive failure, and JE group, LE group and ZE group showed cohesive failure. Conclusion: For IPS e.max ceram, the shear bond strength value was highest for all kinds of zirconia blocks. For ICE Zirkon transluzent, the shear bond strength value was highest for all kinds of veneering ceramics. Most of experimental group interfaces revealed mixed failure mode.

• Journal of Technologic Dentistry
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• v.30 no.1
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• pp.57-63
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• 2008

The purpose of this study was to ascertain the effect of different abutment height and different taper of abutment on retention force of cemented implant-supported prostheses. Test specimens consisted of different abutment height group(3mm, 4mm, 5mm, 6mm, 7mm) and different taper(degrees) abutment group($4^{\circ},\;5^{\circ},\;6^{\circ},\;7^{\circ},\;8^{\circ}$). The surfaces of abutments and crowns were manufactured and finished by automatic lathe(CNC). Luting cement(Tokuso Ionomer) was prepared according to the manufacturer's instruction. And the cylinders were sealed onto the abutments and loaded in compression at 5kg for 10minutes. Excess cement was removed from the abutment-cylinder junction and the specimens were stored at room temparature for 24 hours. Specimens were tested in tension using a universal testing machine. Within the limits of this study, the following conclusions were drawn: 1. The increase in abutment height result in improvement in retention strength(P<0.05). 2. The increase in taper of abutment result in decrease in retention strength(P<0.05). 3. The decrease in abutment height result in decrease in retention strength, besides has a significantly lower retention strength at 3mm abutment height. 4. The increase in taper of abutment result in decrease in retention strength, besides has a significantly lower retention strength at $7^{\circ}$ abutment.

• The Journal of Advanced Prosthodontics
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• v.10 no.4
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• pp.328-334
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• 2018

PURPOSE. To evaluate the reproducibility of scan-based abutments using a blue light model scanner. MATERIALS AND METHODS. A wax cast abutment die was fabricated, and a silicone impression was prepared using a silicone material. Nine study dies were constructed using the prepared duplicable silicone, and the first was used as a reference. These dies were classified into three groups and scanned using a blue light model scanner. The first three-dimensional (3D) data set was obtained by scanning eight dies separately in the first group. The second 3D data set was acquired when four dies were placed together in the scanner and scanned twice in the second group. Finally, the third 3D data set was obtained when eight dies were placed together in the scanner and scanned once. These data were then used to define the data value using third-dimension software. All the data were then analyzed using the non-parametric Kruskal-Wallis H test (${\alpha}=.05$) and the post-hoc Mann-Whitney U-test with Bonferroni's correction (${\alpha}=.017$). RESULTS. The means and standard deviations of the eight dies together were larger than those of the four dies together and of the individual die. Moreover, significant differences were observed among the three groups (P<.05). CONCLUSION. With larger numbers of abutments scanned together, the scan becomes more inaccurate and loses reproducibility. Therefore, scans of smaller numbers of abutments are recommended to ensure better results.

• Journal of Technologic Dentistry
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• v.30 no.2
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• pp.23-29
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• 2008

The purpose of this study is to evaluate possibility of using indirect composite resin instead of porcelain through the measurement of shear bond strength between zirconia core and indirect composite resin under treatment of $Rocatec^{TM}$ system for improving the adhesion of indirect composite resin. 20 cylindrical zirconia core specimens were divided into 2 groups, according to zirconia surface treatment and attached materials: 1) treated with sandblast and attached with indirect composite resin, 2) treated with sandblast + $Rocatec^{TM}$ system and attached with indirect composite resin. The shear bond strength of each experimental group was measured by MTS and the changes of zirconia core surface according to surface treatments were obtained by SEM observation and measurements of surface roughness. The mean shear bond strength values are $0.55\;{\pm}\;0.11MPa$(Group SC) and $1.16\;{\pm}\;0.46MPa$(Group SRC). The mean Ra values for the surface treatments were follows: $0.39\;{\pm}\;0.13$($100{\beta}_{{\mu}m}$ sandblast) and $0.50\;{\pm}\;0.03$($100{\beta}_{{\mu}m}$ sandblast + $Rocatec^{TM}$ system). In the analysis of EDS, Si element was detected in the Group SC. The shear bond strength between zirconia core and indirect composite resin was improved significantly by using $Rocatec^{TM}$ system.