• Journal of Technologic Dentistry
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• v.37 no.4
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• pp.205-212
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• 2015

Purpose: The objective of this study was to compare the surface roughness according to polishing process in conventional laboratory techniques used for polishing three different acrylic denture base resins. Materials and methods: Specimen preparation and surface polishing procedures were conducted to manufacturer's recommendation with three heat-polymerized denture base resins. Surface roughness and gloss were measured by a contact type tester and a LED gloss checker using thickness 2 mm and diameter 10 mm. There were five specimens for each acrylic resin material and polishing procedures. Mean average surface roughness (Ra) values of each specimen group were analyzed using a one-way ANOVA analysis of variance and Scheffe's post hoc test. Surfaces after surface roughness and gloss testing according to each polishing process were evaluated under a stereoscopic microscope. Results: The highest mean average surface roughness was measured($Ra=2.43{\pm}0.47$) for surfaces finished with a denture tungsten carbide bur in Triplex. The lowest surface roughness values ($Ra=0.11{\pm}0.07$) were determined in Vertex polished with a lathe. In addition, all materials revealed that surface roughness determined highly in HP1 and HP2 than other procedures. All correlation between surface roughness and gloss showed highly with three heat-polymerized resins. Specially, topmost correlation revealed than other material in Triplex. Significant differences in mean average surface roughness were found between polishing process used high speed lathe and low speed hand-piece. Conclusion: Laboratory polishing used to high speed was found to produce the smoothest surface of heat-polymerized denture base acrylic resin. Therefore, we recommended that high polishing process need to get smooth surface.

• Journal of Technologic Dentistry
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• v.20 no.1
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• pp.121-138
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• 1998

With 1002 students around 8 colleges nationwide joining, the survey was on their knowledge before entering their school, and thereafer, the degree of their satisfaction in their major and professors & lectures. 1. When they chose their major, the most influential was their parents and relatives, the largest number of 435(43.5%) replied, About the motivation for selection their jajor, 454(45.4%) answered the most it seemed to be a bright future specialty. On that question, more freshmen(51.0%) answered theyu expected good trend than sophomores and juniors and more women students(48.8%) did so than men ones.(P<.05) 2. While 619(61.8%) were familiar with major before applying, only 68(6.85%) knew their major very well at that time. More freshmen(62.5%) applied in the state of well-knowing what their major is than sophomores and juniors did.(P<.01) More women students(40.9%) applied not knowing it than the counterpart. About the time for choice, 795(79.5%) answered the most one of application days. More women students(81.0%) chose their major during the application time(P<.01) 3. The satisfaction survey shows 438(43.8%) are satisfied and 165(16.5%) are not. More men students(47.2%) are satisfied.(P<.01) The factor their satisfaction is their major come together with aptitude(44.7%), 196ppl), and the dissatisfaction factor is the difficulty of the theory and practice.(30.8%, 171ppl) 4. If they could change their major, 454(46.6%) wouldn't do so, while 541(54.4%) would shift their major to other fields. More freshmen(49.5%) wouldn't change than sophomores and juniors. Neither did more men students(4938%) than women. Within the same grade, there's no meaninful difference.(P<.01) 5. On the satisfaction in the lectures of the professors of their major, 464(46.5%) said the lecutres are excellent, 102(10.2%), they are not. About the lectures of the liberal subjects, 193(19.4%) said are excellent, 365(36.6%) are not.

• Journal of Technologic Dentistry
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• v.33 no.3
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• pp.193-202
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• 2011

Purpose: The aim of this study was to evaluate the effect of pre-treatment of core and hydrothermal treatment on the bond strength and flexural strength of ceramic veneered zirconia. Methods: 3Y-TZP specimens(KaVo Zr, $25mm{\times}3mm{\times}1mm$)were prepared by five pre-treatment methods and divided into seven groups including control two groups, subsequently the specimens veneered with the E-MAX ceram according to manufacturer's information(total specimen thickness 1.5mm). Two groups from ceramic-zirconia specimens(n=105, n=15 per group)were assigned into two experimental fatigue conditions, namely storage in an autoclave at $134^{\circ}C$ for 5h, thermo-cycling(3,000cycles, between 5 and $55^{\circ}C$, dwell time 45s, transfer time 2s). A flexural strength test was performed in a universal testing machine(crosshead speed: 0.5mm/min). Data were statistically analyzed using one-way ANOVA and Tukey's test(${\alpha}$=0.05). Results: The ceramic-zirconia bond strength value for liner application group(LLW, $27.3{\pm}3.8$) were significantly lower than those of the pre-treatment groups($30.72{\pm}5.3$). The ceramic-zirconia bond strength and zirconia flexural strength was not affected by thermo-cycling(p>0.05), whereas it was affected by storage in an autoclave at $134^{\circ}C$ for 5h(p<0.05). Conclusion: The results indicated that the ceramic-zirconia bond strength and zirconia flexural strength was affected by low temperature degradation.

• Journal of Technologic Dentistry
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• v.15 no.1
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• pp.89-94
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• 1993

The tooth size and shape of the permanent incisor teeth have been studied and analyzed about the mean size, S.D, S.E, etcs and percentage from stone model of 100 Korean male and 74 Korean female. The results were as follows. 1. The crown length of permanent incisor teeth were longer in males than in females statistical differences of males and female were not found. 2. the mesio-distal diameters of permanent incisor teeth were larger in males than in females and statistical differences of males and females were found in mandibular lateral incisor and the bigest were max. central incisor, 2nd max. lateral incisor, 3rd man. lateral incisor and the smallest were man. central incisor. 3. The square form in max. central incisor was the greatest percentage and the tapering form in max. lateral incisor and man, incisor was the greatest percentage but tapering form and ovoid form and other shape were found in max. lateral at the same ratio. 4. Concerning the labial developmental groove "midium" was the greatest percentage in the max. central incisor and "low" was the greatest percentage in the man incisor. Concerning the incisal line, straight line was the greatest percentage in the max, incisor and man, incisor and concerning the lingual tubercle "none" was the greatest percentage in the max. incisor. 5. In comparison between left side and right side of incisor, the ratio of same shape ware 22.4%-36.2% but similar or dissimilar cases were more frequently found.

• Journal of Technologic Dentistry
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• v.41 no.2
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• pp.103-112
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• 2019

Purpose: This article tried to find the relations between periodontal diseases, body mass index and clinical level for Korean adults over the age of 19, utilizing data of the 6th national nutrition survey. Methods: In the collected data, 14,940 adults aged 19 years or older were included in the study to determine the relationship between the general health status of Korean adults and periodontal disease. Results: As the result, 28.6% of Korean adults had periodontal diseases, there were significant differences depending on gender, age, smoking, residential aria, education level, body mass index, HDL-cholesterol, leukocyte value and fasting blood sugar. When general factors were controlled for multiple logistic regression analysis, there was significance as BMI cross rate was 1.029(95% C1, 1.007-1.051). HDL-cholesterol cross rate was 0.989(95% C1, 0.980-0.999), leukocyte cross rate was 1.086(95% C1, 1.040-1.134) and fasting bloody sugar cross rate was 1.006(95% C1, 1.003-1.009), so there were significance. In conclusion, there was a significance relation between periodontal diseases, body mass index, HDL-cholesterol and fasting bloody sugar. Conclusion: Based on the results of this study, oral health education should be used to manage and maintain healthy oral cavity by improving periodontal disease management and awareness. In addition, it will be necessary to develop periodic oral examinations and age - specific oral health education programs, and it can be used as a basic data for public oral health plan.

• Journal of Technologic Dentistry
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• v.32 no.4
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• pp.387-401
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• 2010

Purpose: The work of Dental technician which is part of national dental health, is more specialized recently. This research provides fundamental data from analyzing student's career consciousness according to needs of a career education. Here is the conclusion of the analysis about student's career consciousness, that is for a right choice of career. Methods: This study did questionnaire to a dental Laboratory Technology student who locate in Taegu. Question response student number was 570 people. Response contents analyzed to 506 people except imperfect questionnaire. Data used windows sas 8.0 program and did descriptive statistical analysis. Results: There is a meaningful difference in what they want to know about an occupation according to ages. (${\rho}$ < 0.01) All ages are similar to their occupational thinking, however they who are under twenties consider working environment. Most motives of an entrance are similar, there is a meaningful difference. (${\rho}$ < 0.05) According to a grade of college, there is a meaningful difference how to obtain informations of a career. (${\rho}$ < 0.05) Sophomores and juniors obtain information from seniors or family, however freshmen obtain from the internet because of an accessibility. There is a meaningful difference of a job meaning between men and women. (${\rho}$ < 0.01) Men are working for a means of living. But women give weight to a self-development. The older they grow, the more they know about their aptitude. Selecting subjects are different choosing time & motive. According to ages and where they are from, there is a meaningful difference how much know about their aptitude. (${\rho}$ < 0.05) Older Students know more than young students. Selecting subjects are different choosing time & motive. In accordance with a grade, ages, and where they are from, there are different degrees about how much know their interests. There is a meaningful difference of a choosing major period and choosing informations. (${\rho}$ < 0.01) And also there is a meaningful difference where they are from and why they enter to College. (${\rho}$ < 0.001) In accordance with a grade, ages, and where they are from, there are different degrees about how much know their aptitude. There is a meaningful difference of a choosing major period. (${\rho}$ < 0.01) And also there is a meaningful difference why they enter to College. (${\rho}$ < 0.001) Conclusion: Although we know that a career education is very important, however lots of students select a career without their aptitude & interest & character. We need to teach a career education systematically; considering students career consciousness, with a proper career guidance, cultivating career consciousness.

• Journal of Technologic Dentistry
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• v.10 no.1
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• pp.5-10
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• 1988

The purpose of this study was to evaluate the effect of spure designs and air vent on the relative castability of the nonprecious alloys, commonly used to make ceamometal restorations. Samples of total 30 were constructed and devided into 6 groups according to two variables, sprue design and air bent. The total number of completly cast squares was counted, verified, and recorded. The results obtained were as follows: 1. The runner bar or Rousseau designs yield better castability than reservoir design(P<0.1) 2. When the air vent was attached, only the castability of reservoir design was significantly different from runner bar or Rousseau designs.

• Journal of Technologic Dentistry
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• v.37 no.4
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• pp.229-234
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• 2015

Purpose: The purpose of this study was to analysis the internal fitness of single crown fabricated by additive method technique. Methods: Study models were fabricated. Ten crowns were manufactured by additive method technique (AM group) and another ten crowns using conventional method were manufactured (CM group). The internal fitness of specimens were measured using silicone replica technique. Silicone replicas were sectioned one times (direction: from mesial to distal). The internal fitness were evaluated using by digital microscope. Statistical analyses were performed with independent samples t-test. (${\alpha}=0.05$). Results: Mean(SD) of all internal fitness were $92.1(20.0){\mu}m$ for AM group and $69.7(12.3){\mu}m$ for CM group. Two groups were statistically significant differences (p<0.001). Conclusion: All internal gaps of AM group were ranged within the clinical recommendation ($120{\ss}{\neq}$).

• Journal of Technologic Dentistry
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• v.23 no.2
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• pp.105-119
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• 2002

This study was designed to grasp the degree of job stress affecting dental technicians and the degree of the symptoms of their job stress. With this in mind, the researcher selected a total of 170 dental technicians living in Seoul and Incheon, conducting a research in a period ranging from August 1,2001, to August 20, 2001. The researcher made use of a structured questionnaire whose reliability and feasibility are proved. The questionnaire is composed of a total of 55 questions: thirteen questions related to the subjects' general characteristics; 28 questions connected to the measurement of job stress and fourteen questions linked with the measurement of job-stress symptoms. The researcher analyzed the findings with the aid of SPSS(Statistical Package for Social Sciences). The research came to draw the following conclusions on the basis of frequency, percentage, T-test, and F-test, multiple regression. I. The analysis into the job stress of the subjects indicates that there is a significant difference in difficult questions among their work places, working hours, academic background, job satisfaction and jobs(P<.05). The job stress stands at 3.48 on the average, and the area of conflict among too much work and job performance turns out to be highly perceived. 2. The analysis into the degree of the symptoms of the job stress of the subjects shows that there is a significant difference in work place, working hours, job satisfaction and the continual maintenance of job(P<.05). The symptoms of job stress accounts for 2.65 on the average. Physical symptoms turn out to be highly perceived; The response 'My arms and legs are killing me' proves to stand for 3.03. 3. The correlation between job stress and the symptoms of job stress turns out to be significant(r=0.519, P<0.001), and there is a significant correlation between the average points of each job-stress area and the average points of the symptoms of job stress. All in all, it is necessary that dental technicians themselves should make positive efforts to control and relieve stress and that more efficient programs should be implemented with a view to dealing with stress.

• Journal of Technologic Dentistry
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• v.20 no.1
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• pp.61-89
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• 1998

Having taken as cause of dental technicians separation from their service a variety of individual idiosyncrasies, function-related factors, external environment factors, functional satisfaction, organizational commitment, and intention to remain, the present study conducted a mail questionnaire poll and interviews on those dental technicians who are mow in the service with private dental technical workshops and dental technical workshops in general hospitals and private dental clinics. The resultant findings from analysis of the repondent's general characteristics of cause of separation form service were revealed, as follows : 1) It was shown that the higher the academic career, the considerably higher cause of position commitment among causes of individual idio-syncrasies, reflecting a statistically significant result(P<0.05) 2) The less the number of working hours as viewed from the average number of working hours per day, the higher the positive emotion, reflecting a significant relation(P<0.01) 3) Causes from performing duties among function-related causes diclosed a statistically significant relation among marital status, career, monthly income, and positions(P<0.01) 4) Causes from wages showed a statistically significant relation in the average number of working hours per day(P<0.01), monthly income(P,0.05), and positions(P<0.05) 5) Causes from supervision exposed a significant relation in workplaces(P<0.01) 6) Causes from promotion represented a significant relation in positions(P<0.001) 7) Causes from opportunnities for taking a job as seen from external environment causes also disclosed a statistically significant relation in workplaces(P<0.05) 8) Reponsibility for family sustenace reflected a statistically significant relation in sex, age, marital status, career, monthly income, work fields, term of employment, positions, and experience of separation(P<0.001) 9) Functional satisfaction showed a statistically significant relation in marital status, career, monthly income, and the average number of hours a day(P<0.05) 10) Oraganizational commitment disclosed a statistically significant relation in work experience, monthly income, term of employment, positions(P<0.05) and the average number of working hours a day(P<0.001) 11) The intention to remain indicated a statistically significant relation in age, marital status, work experience, monthly income, positions(P<0.001) and term of employment. the average number of working hours a day(P<0.01), and in the performing work field(P<0.05)