• Journal of Technologic Dentistry
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• v.14 no.1
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• pp.81-90
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• 1992

1. The dental technicians are worn to a frazzle by a hard work. Therfore, the term of manufacturing denture should be prolonged as 4$\sim$5 days. 2. The dental technicians work under the harmful environments. It should be improved the working conditions for the dental technicians. 3. In case of the women dental technicians, they feel like being treated discriminality. It should be take over a portion of the work in dental laboratory as the accountant' section and the technical section. 4. It should be abolished a pressent instruction dentist system.

• Journal of Technologic Dentistry
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• v.8 no.1
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• pp.5-16
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• 1986

In order to provide the better and more effective dental health service, the study for manpower of dental laboratory technician with some relevant factors such as institutions for education and training, employment status and distribution of technicians, etc. was carried out through survey for 3,885 licensed technicians during 1965 - 1985. Results were obtained through the study as follows: 1. There are 14 junior health colleges in Korea and 3,106(79.9%) licensed dental technicians out of 3,885 graduated from health colleges and rest of them obtained their licenses through practical training in dental clinics. 2. 8,030 applicants have applied to the national examination which was carried out for 22 times during 1965 - 1985. The passing rate in the examination for 22 times showed 48.3% in average. 3. The dental technicians are working mostly in 404 dental laboratories and 2,522 dental clinics and hospitals through out the country. However, most technicians are dominantly working in large citis, because 255 (63.1%) dental laboratories and 1,537 (60.9%) dental clinics and hospitals are mainly located in Seoul and Busan. 4. Regarding distribution of the dental technician, 1,126(52.1%) technicians have been employed in the dental institutions, however, 530 (24.5%) could not have a job and the rest of them (504 technicians: 23.3%) were in leave absence from military service, travelling abroad and unknown reasons. 5. Through reference review, it was found that there were 95,886 dental technician (9/ 100,000 population) in the world during 1973$\sim$1977. However, 91,553 dental technicians lived in the developed countries (14/100,000 population)) also ratio between the dentist and the dental technician in the world showde 1:0.38. In such coentries where per capita income showed $100 in average, the distribution of the dental technician showed 0.272 per 100,000 population. 6. In an estimation of demand and supply for the dental technicians by the year from 1985 through 1996 in Korea, the supply is estimated by the capacity of educational institutions as over-production even through such estimation based on the future incresing of GNP and ratio between the dentist and the dental technicianas and also ratio between the dental technician and general population. At present such ratio shows less compared with the developed contries, however, it is estimated as over-supply in 1994.

• Journal of dental hygiene science
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• v.15 no.5
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• pp.536-541
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• 2015

The purpose of this study was to evaluate the marginal and internal gap of Cobalt (Co)-Chromium (Cr) sintering metal coping fabricated by dental computer-aided design/computer-aided manufacturing systems. Abutment tooth 46 of universal numbering system was selected for the study. Twenty Co-Cr metal copings of two groups were manufactured and scanned. Co-Cr cast metal copings (CCM) group of ten were fabricated using investment, burnout and casing after subtractive manufacturing of wax block. Also, Co-Cr sintering metal copings (CSM) group of ten were fabricated using sintering processing after subtractive manufacturing of Co-Cr soft metal bock. Marginal and internal gap of Co-Cr metal copings of twenty were measured by digital microscope (${\times}160$) with silicone replica technique. The data was analyzed from IBM SPSS Statistics ver. 22.0 Statistical software for Mann-Whitney U test (${\alpha}=0.05$). $Mean{\pm}standard$ deviation of marginal gap of CCM group was $90.12{\pm}61.73{\mu}m$ of CSM group was $60.17{\pm}24.83{\mu}m$. However, two groups was statistically not different (p>0.05). This study showed that CSM group was clinically acceptable adaptation.

• Journal of Technologic Dentistry
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• v.37 no.3
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• pp.157-167
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• 2015

Purpose: This study studied and investigated the oral health behavior of students in the Department of Dental Technology at D College at D City. Methods: A self-administrated survey was conducted by students currently enrolled at the Department of Dental Laboratory Technology at D College (June 4, 2015 ~ June 12, 2015), and 320 copies that were available for statistical processing were statistically analyzed by using the SPSS 19.0 Program. Results: Among the survey respondents, 91.6% had experience of dental treatment. The highest response regarding the frequency of tooth brushing appeared to be 'twice' with 44.7%. The responses regarding the time of tooth brushing appeared to be highest for 'before sleeping' with 65.3%, which was followed by 'after breakfast' with 60.6%. To the question asking which areas are brushed during tooth brushing, the response of 'teeth, gum, and tongue' appeared to be highest with 44.4%. Among the respondents, 64.7% experienced scaling, however, the experience rate for scaling appeared to increase in proportion with the increase of class year (p< .001). Regarding the subjective feel for the importance of oral health and necessity of tooth brushing, the scores appeared to be both 4.56. However, the score appeared to be 3.27 regarding one's subjective perception of one's own oral health condition. Regarding one's subjective oral health knowledge level depending on gender, female students showed a meaningfully lower rate (3.12 points) compared to male students (3.29 points) (p< .05), and depending on class, the knowledge level appeared to be meaningfully higher along with the increase in class year (p< .001). The experience of receiving oral health education appeared to be 78.4%, and 88.8% of the respondents responded that there is need for oral health education, however, the intent to participate in an oral health education program appeared to be 56.6%. Conclusion: As a result of the study, it could be concluded that oral health management behaviors and awareness of the students at the Department of Dental Technology at D University to prevent oral diseases were rather poor.

• The Journal of Korean Academy of Prosthodontics
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• v.33 no.2
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• pp.358-394
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• 1995

The author studied the actual conditions on the production of dental prosthesis made in laboratories, and also studied interrelationships between dentists and laboratory technicians in both personal and technical aspects. Two hundred-eighty four technicians, work in dental laboratories presently, were surveyed via mail and direct contact during the period from June 1 to June 30 and August 27 to August 28 in 1994 respectively. The obtained results were as follows : 1. Among the respondents, 90.5% we re working in commercial dental laboratories and their laboratories were mainly located in the Seoul area(40.9%, P<0.05). The numbers of employees in these laboratories were less than 10 persons(70.0%, P<0.01), and 75.9% of these laboratories have been in operation less than 15 years. 2. Most laboratory procedures were accomplished according to established disciplines. However, procedures such as die trimming in fixed restorations and the qualifications of the people designing removable partial dentures were not. Other problem areas were boxing of the working cast, the person determining the posterior palatal seal area, selection and arrangement of artificial teeth, occlusion rim correction and laboratory remounting of the processed denture in complete denture restorations. 3. Only half of the requesting dentists could send work authorizations to the laboratories with their work and even so, its contents were quite lacking. Consequently, there must be some standards in writing work authorization. 4. Technicians most desired clean and accurate impressions in fixed and removable dentures, and enough tooth reduction in porcelain fused to metal restorations. 5. For the establishment of better relationships between dentist and dental technician, the respondents desired the establishment of equal footing first(33.5%), and frequent conversations and muture understanding second(25.9%).

• The Journal of Advanced Prosthodontics
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• v.8 no.3
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• pp.214-218
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• 2016

PURPOSE. We assessed the repeatability and reproducibility of abutment teeth dental impressions, digitized with a blue light scanner, by comparing the discrepancies in repeatability and reproducibility values for different types of abutment teeth. MATERIALS AND METHODS. To evaluate repeatability, impressions of the canine, first premolar, and first molar, prepared for ceramic crowns, were repeatedly scanned to acquire 5 sets of 3-dimensional data via stereolithography (STL) files. Point clouds were compared and the error sizes were measured (n=10, per type). To evaluate reproducibility, the impressions were rotated by $10-20^{\circ}$ on the table and scanned. These data were compared to the first STL data and the error sizes were measured (n=5, per type). One-way analysis of variance was used to assess the repeatability and reproducibility of the 3 types of teeth, and Tukey honest significant differences (HSD) multiple comparison test was used for post hoc comparisons (${\alpha}=.05$). RESULTS. The differences with regard to repeatability were 4.5, 2.7, and $3.1{\mu}m$ for the canine, premolar, and molar, indicating the poorest repeatability for the canine (P<.001). For reproducibility, the differences were 6.6, 5.8, and $11.0{\mu}m$ indicating the poorest reproducibility for the molar (P=.007). CONCLUSION. Our results indicated that impressions of individual abutment teeth, digitized with a blue light scanner, had good repeatability and reproducibility.

• The Journal of Advanced Prosthodontics
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• v.10 no.4
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• pp.321-327
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• 2018

PURPOSE. The purpose of this study was to compare the cutting method and the lamination method to investigate whether the CAD data of the proposed inlay shape are machined correctly. MATERIALS AND METHODS. The Mesial-Occlusal shape of the inlay was modeled by changing the stereolithography (STL). Each group used SLS (metal powder) or SLA (photocurable resin) in the additive method, and wax or zirconia in the subtractive method (n=10 per group, total n=40). Three-dimensional (3D) analysis program (Geomagic Control X inspection software; 3D systems) was used for the alignment and analysis. The root mean square (RMS) in the 2D plane state was measured within $50{\mu}m$ radius of eight comparison measuring points (CMP). Differences were analyzed using one-way analysis of variance and post-hoc Tukey's test were used (${\alpha}=.05$). RESULTS. There was a significant difference in RMS only in SLA and SLS of 2D section (P<.05). In CMP mean, CMP 4 ($-5.3{\pm}46.7{\mu}m$) had a value closest to 0, while CMP 6 ($20.1{\pm}42.4{\mu}m$) and CMP 1 ($-89.2{\pm}61.4{\mu}m$) had the greatest positive value and the greatest negative value, respectively. CONCLUSION. Since the errors obtained from the study do not exceed the clinically acceptable values, the lamination method and the cutting method can be used clinically.

• Journal of Technologic Dentistry
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• v.31 no.4
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• pp.67-84
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• 2009

The purpose of this study was to furnish data for a new curriculum of the "Bachelor's Degree Course at Junior College" in Korea. Domestic three colleges and one university were selected for comparative analysis about curriculum of the dental laboratory technology. Moreover, three colleges and three universities were selected in Australia, Canada, and USA which are preferred highly on overseas employment by the korea students of dental laboratory technology. From the six colleges and four universities, number of subjects and credit hours on special study were acquired and compared. Between domestics, an agreement on special study were compared. Transferable subjects from korea to foreign were acquired. From the number of subjects and credit hours on special study comparing, following results were obtained. The results were as follows; 1. The ratio of the number of subjects and credit hours on special study were averagely 78.2% and 83.7% in domestic college, 70.8% and 69.7% in domestic university. 2. The ratio of the number of subjects and credit hours on special study in Canada was similar to domestic but those in Australia and USA were less than domestic. 3. Between domestics, an agreement of subjects and credit hours on special study were 81.2% and 84.2% in Catholic University of Busan, 72.2% and 76.4% in Daejeon Health Science College, 71.2% and 72.8% in Gwangju Health College University, 65.1% and 65.9% in Shin Heung College University respectively. 4. Transferable subjects from Korea to Australia or Canada was more than USA. Those to Australia was similar to Canada. These results suggest that the degree of special study in domestic is more than foreign, transferable subjects from Korea to Canada should be profitable and those data is furnish for a new curriculum of the "Bachelor's Degree Course at Junior College" in Korea.

• Journal of Technologic Dentistry
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• v.42 no.3
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• pp.208-212
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• 2020

Purpose: This study aimed to analyze the shrinkage and expansion strain of ultraviolet (UV)-cured resin according to the wavelength of the light source and compare the shrinkage and expansion. Methods: We prepared the mold with according to the ISO 4049 specimen. The size of the circle in the mold was prepared with a height of 6.02 mm and a diameter of 4 mm. UV-curable resin for three-dimensional (3D) printing was injected into the circular mold. The control group was irradiated with a wavelength of 400~405 nm using UV-curing equipment (400 group), and the experimental group was irradiated with a wavelength of 460~465 nm (460 group). Both groups were produced ten specimens. The produced specimen was first measured with a digital micrometer. After the first measurement, the specimen was immersed in a constant temperature water bath for 15 days, after which the second measurement was performed, and the third measurement was taken after 30 days. The measured values were analyzed using the independent sample t-test (α=0.05). Results: In the non-immersion water tank, the contraction was 0.9% in the 400 group and 1.3% in the 460 group. In the constant temperature bath, the expansion was high at -0.4% in the 400 group for 15 days, and the smallest expansion was -0.03% for the 400 group for 30 days. There were significant differences between the two groups (p<0.05). Conclusion: The 400 group had a lower UV resin specimen strain than the 460 group. Therefore, it is recommended to use the wavelength required by the UV-curing resin.

• Journal of Technologic Dentistry
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• v.42 no.4
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• pp.334-340
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• 2020

Purpose: This study aimed to compare three-dimensional adaptation with the rinsing time of the temporary crown produced using the digital light processing method. Methods: The maxillary right first molar abutment was scanned with a dental scanner. A temporary crown was designed with the scanned abutment. The designed crown was made of 10 temporary crowns using a digital light processing printer. The crowns were divided into the 5-minute and 10-minute rinsing groups; 5 temporary crown washes were performed for each group. In order to obtain the internal data, each group was scanned for a temporary crown. The three-dimensional fit was measured by superimposing the scanned internal surface data and the abutment data. The average comparison of three-dimensional adaptation was analyzed using the Mann-Whitney U test. Results: The 5-minute rinsing group showed a significantly higher adaptation of 71.42±3.08 ㎛ as compared to the 10-minute rinsing group (67.52±0.92 ㎛) (p<0.05). Conclusion: When making a temporary crown with a digital light processing method, a rinsing time of 10 minutes is appropriate.