• Journal of Technologic Dentistry
• /
• v.18 no.1
• /
• pp.73-94
• /
• 1996

This study was aimed for evaluating the validity of relative-productivity index on the basis of working hour(RPHW index) designed by author as new productivity index and drawing up a plan of bettering productivity to cope with financial difficulty of dental laboratories. Fortyeight dental laboratories extracted by cluster-sampling method form all the dental laboratories in Seoul were subjected for this study. And in each of them, the term of establishment which was divied into three group as short-term, mid-term and long-term group, the scale of dental laboratory which as divided into two group by number of dental technician as small-scale group and large-scale group, the salary system which was composed of salary criteria, pay according to ablility criteria and collectiveagree, the salary level, simple labor productivity index(SLP index), relative-productivity index on the basis of worker number(ROWN) and relative-productivity index on the basis of working hour(RPWH index) were surveyed through the self-administractive questionaires. The results as follows : Most of dental laboratories(93.6%) were managed by non-professional managers. The establishment rate per year of dental laboratory was the increase. The mean number of employees of dental laboratories was $7.00{\pm}3.90$ person. The ratio of smallscale group(under the 5 employees) was 42.6% and as the term of establishment was shorter, the ratio of small-scale group was higher. The mean establishment area of dental laboratories was $24.49{\pm}10.97$ unit and the mean establishment area per head of dental laboratories was $4.05{\pm}3.90$ unit. The estabilshment area and area per head were not significantly associted with the term of establishment, but as the term of establishment was shorter, the estabkishment area per head was slightly wider. The establishment area per head in small-scale group was significantly wider than large-scale group(over the 6 emplayees) The salary criteria(54.4%), pay according to ability(79.2)m ability criteria(77.1%) and collectiveagree(79.2%) as salary systems were used in the most of all dnetal laboratoies. The all salary systems were not significantly associated with the term of establishment and the scale of dental laboratories. The monthly mean salary level of dental laboratoies was $125.64{\pm}31.06$ milion won. The monthly salary level was not significantly associated with the term of establishment and the scale of dental laboratores. But the monthly salary level in the short-term group and the small-scale group were slightly lower than others. The SLP index, the RPWN index and the RPWH index of dental laboratories were $132.16{\pm}48.41$, $382.41{\pm}128.76$ and $76.06{\pm}25.11$, respectively. The SLP, the RPWN and the RPWH of dental laboratories were not significantly associated with the term SLP, the RPWN and the RPWH of dental laboratories were significantly associated with the area of dental laboratory and the salary level. Except for only the association salary criteria among salary system with RPWH of dental laboratories, all other salary system were not associated with the SLP, the RPWN and the RPWH of dental laboratories.

• Journal of the Korea Convergence Society
• /
• v.11 no.11
• /
• pp.95-101
• /
• 2020

This study was conducted to identify the convergence relation of critical thinking disposition, problem-solving ability and college life adaptation and to find out the factors that influence college life adaptation. The survey was collected on 172 2nd and 3rd grade students majoring in dental laboratory technology from three-year colleges in Chungbuk and Jeonbuk. The analysis results showed that the critical thinking disposition was 3.50, problem-solving ability of the study subjects was 3.55 and college life adaptation was 3.27. The most influential factor in college life adaptation was critical thinking disposition followed by major satisfaction and college satisfaction in that order. In order to improve the level of college life adaptation of dental laboratory technology students, it is necessary to reform the educational environment and develop a variety of educational program to increase critical thinking, major satisfaction and college satisfaction.

• The Journal of Advanced Prosthodontics
• /
• v.7 no.4
• /
• pp.294-302
• /
• 2015

PURPOSE. The purpose of this study was to verify the clinical-feasibility of additive manufacturing by comparing the accuracy of four different manufacturing methods for metal coping: the conventional lost wax technique (CLWT); subtractive methods with wax blank milling (WBM); and two additive methods, multi jet modeling (MJM), and micro-stereolithography (Micro-SLA). MATERIALS AND METHODS. Thirty study models were created using an acrylic model with the maxillary upper right canine, first premolar, and first molar teeth. Based on the scan files from a non-contact blue light scanner (Identica; Medit Co. Ltd., Seoul, Korea), thirty cores were produced using the WBM, MJM, and Micro-SLA methods, respectively, and another thirty frameworks were produced using the CLWT method. To measure the marginal and internal gap, the silicone replica method was adopted, and the silicone images obtained were evaluated using a digital microscope (KH-7700; Hirox, Tokyo, Japan) at 140X magnification. Analyses were performed using two-way analysis of variance (ANOVA) and Tukey post hoc test (${\alpha}=.05$). RESULTS. The mean marginal gaps and internal gaps showed significant differences according to tooth type (P<.001 and P<.001, respectively) and manufacturing method (P<.037 and P<.001, respectively). Micro-SLA did not show any significant difference from CLWT regarding mean marginal gap compared to the WBM and MJM methods. CONCLUSION. The mean values of gaps resulting from the four different manufacturing methods were within a clinically allowable range, and, thus, the clinical use of additive manufacturing methods is acceptable as an alternative to the traditional lost wax-technique and subtractive manufacturing.

• The Journal of Advanced Prosthodontics
• /
• v.9 no.4
• /
• pp.239-243
• /
• 2017

PURPOSE. The purpose of this study is to compare single and three-unit metal frameworks that are produced by micro-stereolithography. MATERIALS AND METHODS. Silicone impressions of a selected molar and a premolar were used to make master abutments that were scanned into a stereolithography file. The file was processed with computer aided design software to create single and three-unit designs from which resin frameworks were created using micro-stereolithography. These resin frameworks were subjected to investment, burnout, and casting to fabricate single and three-unit metal ones that were measured under a digital microscope by using the silicone replica technique. The measurements were verified by means of the Mann-Whitney U test (${\alpha}=.05$). RESULTS. The marginal gap was $101.9{\pm}53.4{\mu}m$ for SM group and $104.3{\pm}62.9{\mu}m$ for TUM group. The measurement of non-pontics in a single metal framework was $93.6{\pm}43.9{\mu}m$, and that of non-pontics in a three-unit metal framework was $64.9{\pm}46.5{\mu}m$. The dimension of pontics in a single metal framework was $110.2{\pm}61.4{\mu}m$, and that of pontics in a three-unit metal framework was $143.7{\pm}51.8{\mu}m$. CONCLUSION. The marginal gap was smaller for the single metal framework than for the three-unit one, which requires further improvement before it can be used for clinical purposes.

• The Journal of Advanced Prosthodontics
• /
• v.10 no.5
• /
• pp.367-373
• /
• 2018

PURPOSE. To evaluate the fit of a crown produced based on a 3D printed model and to investigate its clinical applicability. MATERIALS AND METHODS. A master die was fabricated with epoxy. Stone dies were fabricated from conventional impressions (Conventional stone die group: CS, n=10). Digital virtual dies were fabricated by making digital impressions (Digital Virtual die group: VD, n=10). 3D data obtained from the digital impression was used to fabricate 3D printed models (DLP die group: DD, n=10, PolyJet die group: PD, n=10). A total of 40 crowns were fabricated with a milling machine, based on CS, VD, DD and PD. The inner surface of all crowns was superimposed with the master die files by the "Best-fit alignment" method using the analysis software. One-way and 2-way ANOVA were performed to identify significant differences among the groups and areas and their interactive effects (${\alpha}=.05$). Tukey's HSD was used for post-hoc analysis. RESULTS. One-way ANOVA results revealed a significantly higher RMS value in the 3D printed models (DD and PD) than in the CS and DV. The RMS values of PD were the largest among the four groups. Statistically significant differences among groups (P<.001) and between areas (P<.001) were further revealed by 2-way ANOVA. CONCLUSION. Although the fit of crowns fabricated based on the 3D printed models (DD and PD) was inferior to that of crowns prepared with CS and DV, the values of all four groups were within the clinically acceptable range (<$120{\mu}m$).

• Journal of Technologic Dentistry
• /
• v.39 no.4
• /
• pp.227-233
• /
• 2017

Purpose: The purpose of this study was to evaluate the validity of digital models fabricated by difference optical source of non-contact 3D dental scanner. Methods: A master model with the prepared upper full arch tooth was used. Stone model(N=10) were produced from master model, and on the other hands, digital models were made with the 3D dental scanner(Blue, white, red optical source). The linear distance between the reference points were measured and analyzed on the Delcam $Copycad^{(R)}$ graphic software. The results were statistically analyzed using the one-way ANOVA and Tukey's HSD test(${\alpha}=0.05$). Results: There were considerable differences in mean values between optical source within each color(blue, white, red), and this difference was not statistically significant(p>0.05). Conclusion : Three different color of dental scanner optical source showed clinically acceptable accuracies of full arch digital model produced by them. Besides, these results will have to be confirmed in further clinical studies.

• Journal of Technologic Dentistry
• /
• v.11 no.1
• /
• pp.5-22
• /
• 1989

We investigated 974 male and female students who are in 4th, 5th and 6th year of 8 elementary schools are located win Puan-kun, the farm area of Chollabuk-do, and the results are as follows. 1. Visiting dental clinic in order to be treated for dental caries hold the highest rate as 26.1% of male students and 30.3% of female students. 2. On fear when children visit dental clinic, first, 25.6% of male students and 35.1% of female students mark the highest rate as some what fear. Second, 23.1% of male students represent to be usual and 29.4% of female students represent to be very fear. There fore it speaks for dissimilarity in character between male and female students. 3. On reason of developing dental caries, 62.5% of male students and 55.8% of female students replied that it was developed because they frequently ate the sweet things. 4. Children who pull out decidous teeth alone mark the highest rate as 44.7% of male students and 38.6% of female students. 5. On important thing for ordinary dental health, 56.2% of male students and 58.5% of female students as the highest rate replied that they often brushed their teeth.

• Journal of the Korea Convergence Society
• /
• v.3 no.3
• /
• pp.13-19
• /
• 2012

Selecting one's career is one of the most important decisions for individuals because it will have a strong influence on his/her life. Especially for college students who are in the process of getting ready to step into the society after the graduation, career decision making becomes one of the most difficult tasks, and a real one. The purpose of this study was to analyze decision making styles and career decision making progress of Dental Laboratory Technology college students, and to test hypotheses which are related to the effects of counseling programs on students' decision making styles.

• Journal of Technologic Dentistry
• /
• v.22 no.1
• /
• pp.5-12
• /
• 2000

The gaps between the die margin worked and the casting body were measured with an optical microscope and compared after making crown prosthetic materials using three kinds of die material - dental stone, extra hard stone, epoxy resin - used in crown prosthesis. The results are as follows : 1. All the gaps between the cast cervical margin and the casting bodies were relatively good regardless of die materials used with the gaps under $50{\mu}m$, the allowable limit. 2. The cervical margin suitability of epoxy resin die was the highest among the three kinds of die material with the suitability value of $30.28{\pm}12.67$. 3. Among the four surfaces(buccal, lingual, mesial, distal) of all the casting bodies, buccal surface was the highest in the cervical margin suitability with the value of $25.93{\pm}15.51$.

• Journal of Technologic Dentistry
• /
• v.21 no.1
• /
• pp.123-130
• /
• 1999

I attempted to suggest a better method to separate a refractory cast in order to solve the problems caused by bonding between refractory casts and ceramics in the firing-processing of all ceramic crowns as a part of dental prosthodontics. I emphasize the advantages and effectiveness of easy separation after firing by using the separating materials about the refractory cast dies. 1. We must not usse HF(55%) that is used as the chemical separating methods. 2. We decrease such methods as grinding, blasting, bur, and point 3. We can save time, costs and manual labors by using this methods. 4. This method regulates the expansion and constriction of heat because of the chemical reaction of the separating materials. 5. This method contribute to the breaking down without modification by minimizing the chemical and mechanical damages of the marginal and interior parts.