• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.40 no.4
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• pp.173-180
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• 2014

Objectives: The purpose of this study was to investigate the neurogenic differentiation of human dental pulp stem cells (DPSCs), periodontal ligament stem cells (PDLSCs), and stem cells from apical papilla (SCAP). Materials and Methods: After induction of neurogenic differentiation using commercial differentiation medium, expression levels of neural markers, microtubule-associated protein 2 (MAP2), class III ${\beta}$-tubulin, and glial fibrillary acidic protein (GFAP) were identified using reverse transcriptase polymerase chain reaction (PCR), real-time PCR, and immunocytochemistry. Results: The induced cells showed neuron-like morphologies, similar to axons, dendrites, and perikaryons, which are composed of neurons in DPSCs, PDLSCs, and SCAP. The mRNA levels of neuronal markers tended to increase in differentiated cells. The expression of MAP2 and ${\beta}$-tubulin III also increased at the protein level in differentiation groups, even though GFAP was not detected via immunocytochemistry. Conclusion: Human dental stem cells including DPSCs, PDLSCs, and SCAP may have neurogenic differentiation capability in vitro. The presented data support the use of human dental stem cells as a possible alternative source of stem cells for therapeutic utility in the treatment of neurological diseases.

• Journal of Technologic Dentistry
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• v.26 no.1
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• pp.59-67
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• 2004

The purpose of this study was to research the recognition of Korean Dental Technicians in Busan region about retitle of the name of 'Dental Technician'(DT), then to figure out the reality of retitle of the name(DT), so to provide data for whole country survey and to drive of the retitle of DT by Korea Dental Technicians Association. For these purpose, 250 subjects were sampled out of dental technicians in Busan, and the survey was performed with self-administered questionnaire. Out of all collected questionnaires, 192 pieces(76.8%) were addressed for this study. 1) Their desires on changing of the name(DT), 57.4%(74/129) was agreed. 2) If they could change the name(DT), they hope 3 main new names and the others, Dental Lab Art Technician(39.2%), Certified Dental Technician(23.0%), Dental Prosthetic Technician(23.0%), the others(14.8%).

• Journal of Technologic Dentistry
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• v.34 no.2
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• pp.121-128
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• 2012

Purpose: The aim of this study was to determine the reliability and accuracy of measurements in digital models(CEREC$^{(R)}$ AC) compared to stone models. Methods: A master model(500B-1, Nissin Dental Product, Japan) with the prepared upper full arch tooth was used. Conventional impression and then stone model(n=10) were produced from this master model, and on the other hands, digital impressions were made with the CEREC$^{(R)}$ AC intra-oral scanner(n=10). One examiner measured two times the intercanine, intermolar distance, dental arch length. The stone model were measured using a digital caliper. The t-student test for paired samples and intraclass correlation coefficient(ICC) were used for statistical analysis. Results: The measurement of two methods showed very good reliability. At the intra-examiner reliability of measurement, ICC at the stone and CEREC$^{(R)}$ AC model were 0.81 and 0.94. The mean difference between measurements made directly on the stone models and those made on the CEREC$^{(R)}$ AC model was 0.20~0.28mm, and was statistically significant(P=0.001). Conclusion: These in vitro studies show that accuracy of the digital impression is similar to that of the conventional impression. These results will have to be confirmed in further clinical studies.

• Journal of Technologic Dentistry
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• v.29 no.2
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• pp.163-171
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• 2007

The purpose of this study is comprehension for relationships between job stress and mental health for dental technicians in performing their duties. and this study can make use of opportunity of accumulation of data on dental technician's health care and work environment in future. Job stress for dental technicians served in general hospital dental laboratory were more highly effected than in local dental laboratory. and this result was statistically reliable. There were no meaningful differences in mental health between dental technician in dental laboratory in dental climic dental laboratory and commercial dental laboratory. and this result was not statistically reliable. The analysis of this study could be used by preliminary data to further research of relationships between job stress and mental health for dental technicians in the future. This study was made progress partially under limited members of dental technician in Seoul. so future studies are suggested that the more advanced total figure study for whole dental technicians in Korea.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.1
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• pp.328-335
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• 2013

The purpose of this study was to evaluate the height of workbench in dental lab for ergonomic body type which dental technicians are suitable and suggest to effective improvement of workspace. For this purpose, we measured the height, weight, body sizes of total 77 junior majoring in dental laboratory science where they study school located in Gyeonggi and Chungcheong area and we research uncomfortable body type when they had a clinical training. For comparative analysis we had visited 15 dental lab and 2 dental lab of general hospital and we had measured the height of workbench and desk including chair and then We had statistical analysis measured value. Especially we analyzed the important factor causing inconvenience for work environment. As a result, we had examined, we found following results The sand table was the most uncomfortable equipment, when they have clinical training. There is no correlation between sexual characteristics of junior in college and selection of uncomfortable equipment. It is reasonable to assume that sand table which is lower than recommended height brings out inconvenience. It is analyzed that the optimum height of sand table in dental lab for junior in college is lower than the recommended height. The optimum height of sand table in dental lab has deviation according to height of junior in college. The height of worktable in dental lab was lower than recommended height. The recommended range could not apply to posture of dental technician with different height uniformly.

• Journal of Technologic Dentistry
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• v.34 no.2
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• pp.105-111
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• 2012

Purpose: The purpose this study was to evaluate the marginal fitness of metal copings fabricated using rapid prototyping method and to compare the fitness with copings by conventional method. Then clinical availability of fixed dental prostheses (FDPs) fabricated using rapid prototyping method shall be confirmed based on marginal fitness. Methods: Ten same cases of3 unit FDPs epoxy models (abutment teeth 14 and 16) were manufactured. Each of ten epoxy models were scanned by 3shape D-700 scanner to be designed by experienced technician, and photopolymer 3 unit FDPs were fabricated using rapid prototyping methodand fabricated using Lost wax technique (LW) with same models. Marginal fitness of 3 unit FDPs were measured by silicone replica technique. T-test of independent sample for statistical analysis was executed with SPSS 12.0K for Windows. (${\alpha}$=.05) Results: Significantly higher mean (SD) marginal fitness (P<.000) were observed in the RP group $(95.9(18.0){\mu}m$ compared to the conventionally LW group $(80.1(13.8){\mu}m$. Conclusion: Marginal fitness of LW group showed excellent rather than RP group. However marginal fitness of 3 unit FDPs fabricated by RP method did not get out of clinical allowance value range significantly to allow clinical application.

• Journal of Technologic Dentistry
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• v.30 no.1
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• pp.41-47
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• 2008

This study was to evaluate the biaxial flexural strength of zirconia ceramics after glass-infiltration on zirconia core. The zirconia specimens were made with diameter-15mm, thickness-0.6mm using zirconia block which divided into 1) sintered group, 2) heat - treated group, 3) Glass - infiltrated group and experimented fracture strength by each 10 specimens in experimental group. The biaxial flexural test was performed at crosshead speed of 0.1${\beta}\;{\AE}$ min. The experiment result average fracture strength was shown 541.0${\beta}\acute{A}$ in sintered group and glass-infiltrated group as 662.2${\beta}\acute{A}$ river of 22.4% rise appear. Weibull coefficient sintered group is 3.462 and glass-infiltrated group improved believability about fracture strength from melting permeation processing of glass by 4.716.

• Journal of Technologic Dentistry
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• v.34 no.4
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• pp.369-377
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• 2012

Purpose: The aim of study was to compare the dimensional stability of digitized dental stone replica using different color of gypsum materials using a white light scanner with three-dimensional software. Methods: A master model(500B-1, Nissin dental product, Japan) with the prepared lower full arch tooth was used. Several type IV stones(white, yellow, green) were used for 30 stone casts(10 casts each) duplicated a master model of mandible. The master model and the replicas were digitized with the non-contacting white light scanner to create 3-dimensional digital models. The linear distance between the reference points were measured and analyzed on the Delcam Copycad$^{(R)}$(Delcam plc, UK) 3D graphic software. One-way analysis of variance(ANOVA) combined with a Tukey multiple-range test were used to analysis the data(${\alpha}$=0.05). Results: There were considerable differences in mean values between gypsum materials within each color(white, yellow, green), and this difference was statistically significant, p=0.001. Conclusion: Digitization of dental materials on optical scanner was affected by color. Three different color of gypsum materials 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
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• v.34 no.3
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• pp.213-220
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• 2012

Purpose: The aim of this study was to determine the repeatability and reproducibility of two dental scanners. Methods: The master die and the stone replicas(Kavo, Germany) were digitized in touch-probe scanner(Incise, Renishaw, UK), white light scanner(Identica, Medit, Korea) to create 3-dimensional surface-models. The number of points in the point clouds from each reading were calculated and used as the CAD reference model(CRM). Discrepancies between the points in the 3-dimensional surface models and the corresponding CRM were measured by a matching-software(Power-Inspect R2, Delcam Plc, UK). The t-student test for one samples were used for statistical analysis. Results: The reproducibility of both scanner was within $3{\mu}m$, based on mean value. The mean value between measurements made directly on the touch probe scanner digital models and those made on the white light scanner digital models was $2.20-2.90{\mu}m$, and was statistically significant(P<0.05). Conclusion: With respect to adequate data acquisition, the reproducibility of dental scanner differs. Three-dimensional analysis can be applied to differential quality analysis of the manufacturing process as well as to evaluation of different analysis methods.

• Journal of Technologic Dentistry
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• v.34 no.3
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• pp.283-290
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• 2012

Purpose: This study was aimed to know the perception about Certified Dental Technician system of students majoring in dental laboratory technology in Korea. Methods: A survey was conducted for four months from August through November 2011 with questionnaires. The responses from 1148 students majoring in dental laboratory technology in Korea were analyzed with SPSS 12.0 program, and frequency analysis and chi square test were implemented. Results: Total students who responded to the questionnaire were 1148 (100%). The population characteristic of this survey is that 691 (60.2%) are male. The respondents believed that the job skill could be expanded by implementing the system (85.6%). Also, they responded that they would be willing to acquire the Certified Dental Technician qualifications in the future (95.5%). Conclusion: Students majoring in dental laboratory technology in Korea believed that the execution of the system of Certified Dental Technician would expand the dental technology industry.