• Journal of Technologic Dentistry
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• v.41 no.1
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• pp.21-27
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• 2019

Purpose: To evaluate 2D and 3D of occulsal, mesial-occlusal and mesial-occlusal-distal cavity of composite resin inlay. Methods: Abutment tooth 16, 36 of FDI system was selected for the study. Inlay prostheses classified as occlusal cavity (OC group), mesial-occlusal (MOC) and mesial-occlusal-distal cavity (MODC) were prepared using composite resin. Composite resin was injected with composite resin in prepared tooth cavity and then photopolymerized with UV light. Additional thermal polymerization was performed. Marginal gap of composite resin inlays were measured by digital microscope(x160) with silicone replica technique. The data was analyzed from statistical software for Kruskal-Wallis test (${\alpha}=0.05$). 3-dimensional analysis was analyzed through superimposition method. Results: The smallest 2D marginal fit measure of the three groups was $47.0{\pm}21.6{\mu}m$ in the MOC group. The largest 2D marginal was $69.1{\pm}33.8{\mu}m$ in the MODC group. In the trueness of the three groups, the most accurate figure was $14.4{\pm}2.3{\mu}m$ for the MODC group. In Precision, the most accurate figure was $14.5{\pm}4.3{\mu}m$ for the MODC group. Conclusion : In this study, 2D marginal fit of OC, MOC, and MODC cavities fabricated with composite resin was applicable to all clinical applications. In the 3D inner surface accuracy evaluation, the MODC group showed the accuracy results.

• Journal of Technologic Dentistry
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• v.19 no.1
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• pp.21-35
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• 1997

The Ag-Pd-Cu alloys containing a small amount of Au is commonly used for dental purposes, because this alloy is cheaper than Au-base alloys for clinical use. However, the most important characteristic of this alloy is age-hardenability, which is not exhibited by other Ag-base dental alloys. The specimens used were Ag-20Pd-20Cu ternary alloy and Au addition alloy. These alloys were melted and casted by induction electic furace and centrifugal casting machine in Ar atmoshpere. These specimens were solution treated for 2hr at $800^{\circ}C$ and were then quenched into iced water, and aged at $350{\sim}550^{\circ}C$ Age-hardening characteristics of the small Au-containing Ag-pPd-Cu dental alloys were investigated by means of hardness testing, X-ray diffraction and electron microscope observations, electrical resistance, differential scanning calorimetric, emergy dispersed spectra and electron probe microanalysis. Principal results are as follows : Hardening occured in two stages, I. e., stage I in low temperature and stage II in high temperature regions, during continuous aging. The case of hardening in stage I was due to the formation of the Llo type face centered tetragonal PdCu-ordered phase in the grain interior and hardening in stage I was affedted by the Cu concentration. In stage II, decomposition of the $\alpha$ solid solution to a PdCu ordered phase(L1o type) and an Agrich ${\alpha}2$ phase occurred and a discontiunous precipitation occurred at the grain boundary. Form the electron microscope study, it was concluded that the cause of age-hardening in this alloy is the precipitation of the PdCu ordered phase, which has AuCu I type face-centered tetragonal structure. Precipitation procedure was ${\alpha}\to{\alpha}+{\alpha}2+PdCu\to{\alpha}1+{\alpha}2+PdCu$ at Pd/Cu = 1 Ag-Pd-Cu alloy is more effective dental alloy as ageing treatment and is suitable to isothermal ageing at $450^{\circ}C$.

• Journal of Technologic Dentistry
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• v.34 no.3
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• pp.249-261
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• 2012

Purpose: This study was carried out in order to examine the relationship of job satisfaction and quality of life on the dental technicians and to analyze its influence. Methods: A self-reported questionnaire survey was carried out by having convenience sampling as 220 dental technicians who work in Seoul Metropolis, Gyeonggi-do Province, Daejeon and Chungnam Province from March 12, 2012 to April 13. A research tool was used questionnaire that was proved reliability and validity. It was prepared with totally 50 questions such as 12 items for subjects' general characteristics, 18 items for job satisfaction measurement, and 20 items for life quality measurement. An analysis of the collected data was computationally processed by using SPSS Win 17.0 program. An analytical technique was made by using statistical techniques such as frequency & percentage, T-test or One-way ANOVA analysis. The following are the analytical results of the collected materials. Results: As a result of analyzing research subjects' job satisfaction level, there was significant difference(P<0.05) in items of religion, hobby life, working environment, and rest time out of daily work. The whole mean in job satisfaction was indicated to be relatively high with 3.13. However, job satisfaction with social recognition, salary, and safety was indicated lowly. As a result of analyzing research subjects' life quality level, there was significant difference(P<0.05) in items of religion, hobby life, working environment, and rest time out of daily work. The whole mean in quality of life was indicated to be relatively high with 3.10. However, the satisfaction was indicated lowly in the whole life quality and the life environment sphere. As a result of analyzing correlation between job satisfaction and life quality, all variables were indicated to be positive correlation in high significance level, thereby having been indicated that the higher job satisfaction leads to the higher life quality. Conclusion: As a result of research, the dental technicians' job satisfaction was indicated to have high correlation with quality of life. An effort is judged to be necessary for establishing fair compensation system, improving welfare policy and enhancing social recognition and position in order to promote dental technicians' quality of life.

• Journal of Technologic Dentistry
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• v.34 no.3
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• pp.263-271
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• 2012

Purpose: The purpose of this research was to examine department satisfaction for improving the competitiveness of department of dental technology and providing basic data for students successful guidance. Methods: The study subject were 560 students from 4 colleges, and they were selected by the convenient sampling method. Data for this survey was obtain by self-administration method. This questionnaire consist of general characteristics, the awareness of before entering department of dental technology, the satisfaction of department of dental technology, an opinion about change of one's course and temporary absence. Results: About the time of selecting their major, 70.1% of students answered the most before highschool. Department of dental technology and the most common source of information in selecting a majors is the person oneself(52.6%). The person who answers because of knowing a little bit for the question asking the priori knowledge of department of dental technology showed up as 66.3%. About the motivation for selection their major, 37.4% of students answered the most it seemed to be a future prospect. As to the extend of department satisfaction, the satisfaction showed up as 63.3%, but the extend of satisfaction was exposed to reduce as the grade increased. The dissatisfaction factor is the difficulty of the theory(29.8%). Many students do not want to change their majors even if they are provided with the chance to do so(68.7%). From the survey related to the experience of thinking over temporary absence and drop out, 56.8% of students responded they had experienced thinking about that. Current feelings after department selection was found to be the most significant factor that affects satisfaction of department of dental technology(Adjusted $R^2$=48.3%). Conclusion: The extend of satisfaction of the women is low. The extend of satisfaction reduces as the grade increases. The school subject extend of satisfaction can know that ratio about of considering the leave of absence and voluntary withdrawal increases. Therefore, the plan of education that women can adapt the women o the school subject well and that it can be satisfied is sought for. It is considered that effort promoting the extend of satisfaction is needed as the grade increases.

• 대한예방의학회:학술대회논문집
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• 2000.10a
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• pp.266-267
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• 2000

• Journal of Technologic Dentistry
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• v.41 no.2
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• pp.53-61
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• 2019

Purpose: The purpose of this study is to evaluate the discrepancy of scan process in dental intra oral scanner by comparing model scanner and anticipate possibility to introduce intra oral scan technique. Methods: 3D superimposition test was conducted to compare the scan discrepancy. The scanners used in this study are the e-oral scanner, the D750 model scanner, and the high precision CMM(3D Coordinate Measuring Machine). The standard of accuracy verification is ISO 5725-1; trueness and precision. Master model was manufactured by dental stone and scanned 5 times by intra oral, model scanner. Reference data was scanned 5 times by high accuracy CMM to evaluate the trueness. Results: Trueness of D750 scanner were $7.4{\mu}m$ $5.1{\mu}m$ $6.8{\mu}m$ at an abutment, an occluasal, a specific area. and trueness of e-scanner were $20.2{\mu}m$ $27.4{\mu}m$ $37.8{\mu}m$ at an abutment, an occluasal, a specific area. Precision of D750 scanner was $7.04{\mu}m$, e-scanner was $15.95{\mu}m$. Conclusion: When conducting in vitro test, The mean difference of trueness between e-scanner and D750 were $12.8{\mu}m$ at an abutment area, $22.3{\mu}m$ at an occlusal area, $31.0{\mu}m$ at a specific area and $8.91{\mu}m$ in precision. The scan discrepancies are within the range of clinical acceptance.

• Journal of Technologic Dentistry
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• v.45 no.2
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• pp.39-47
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• 2023

Purpose: This study aimed to confirm the applicability of gloss polishing using automatic barrel finishing with respect to three-dimensional (3D)-printed resin specimens. The surface roughness and grinding angle of the 3D-printed resin specimens were observed with respect to gloss polishing time using automatic dental barrel finishing. Methods: Herein, experiments were conducted on four types of 3D-printed resin specimens. The specimens, with a thickness of 100 ㎛ each, were printed using a 3D printer. Subsequently, light polymerization was performed on these specimens for 15 min. Post this surface treatment, the specimens underwent grinding for 25 min. This process was followed by gloss polishing at 5-min intervals for up to 25 min using automatic dental barrel finishing. The specimens were photographed using a 3D optical microscope, and their surface roughness and grinding angle were measured. Results: The Ra (centerline average roughness) values of all the specimens, except for crown & bridge 10 group and those in the control group that were not polished using automatic barrel finishing, were <0.2 ㎛. However, polishing time needs to be controlled to realize the desired surface roughness and grinding amount considering the hardness of the resin used. Conclusion: Gloss polishing of 3D-printed resin can be realized using automatic dental barrel finishing. However, polishing time needs to be controlled to realize the desired surface roughness and grinding amount considering the hardness of the resin used.

• Journal of Technologic Dentistry
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• v.45 no.2
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• pp.31-38
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• 2023

Purpose: This in vitro study aimed to compare the trueness of 3-unit fixed dental provisional prostheses (FDPs) fabricated by three different additive manufacturing and subtractive manufacturing procedures. Methods: A reference model with a maxillary left second premolar and the second molar prepped and the first molar missing was scanned for the fabrication of 3-unit FDPs. An anatomically shaped 3-unit FDP was designed on computer-aided design software. 10 FDPs were fabricated by subtractive (MI group) and additive manufacturing (stereolithography: SL group, digital light processing: DL group, liquid crystal displays: LC group) methods, respectively (N=40). All FDPs were scanned and exported to the standard triangulated language file. A three-dimensional analysis program measured the discrepancy of the internal, margin, and pontic base area. As for the comparison among manufacturing procedures, the Kruskal-Wallis test and the Mann-Whitney test with Bonferroni correction were evaluated statistically. Results: Regarding the internal area, the root mean square (RMS) value of the 3-unit FDPs was the lowest in the MI group (31.79±6.39 ㎛) and the highest in the SL group (69.34±29.88 ㎛; p=0.001). In the marginal area, those of the 3-unit FDPs were the lowest in the LC group (25.39±4.36 ㎛) and the highest in the SL group (48.94±18.98 ㎛; p=0.001). In the pontic base area, those of the 3-unit FDPs were the lowest in the LC group (8.72±2.74 ㎛) and the highest in the DL group (20.75±2.03 ㎛; p=0.001). Conclusion: A statistically significant difference was observed in the RMS mean values of all the groups. However, in comparison to the subtractive manufacturing method, all measurement areas of 3-unit FDPs fabricated by three different additive manufacturing methods are within a clinically acceptable range.

• Journal of Korean society of Dental Hygiene
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• v.14 no.3
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• pp.293-302
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• 2014

Objectives : The objective of this study was to investigate the relationship between the status and necessity of dental prosthesis and mastication function in the Korean elderly. Methods : This study investigated 4,557 elderly people aged over 65 in the 5th Korea National Health and Nutrition Examination Survey(2010-2012). Frequency analysis, ${\chi}^2$ test, and logistic regression analysis were used. Results : Those aged over 75 complained of greater discomfort in mastication function than those from 65 to 74, and it was statistically significant(p<0.001). Mastication discomfort was not so significant in those with higher education and higher income(p<0.001). Those who did not use prosthesis tended to have better mastication function(p<0.001). Denture users complained of mastication discomfort when they used it(p<0.001). Conclusions : This study verified the relationship between the discomfort in mastication and related factors, and will provide the basic data for the access to dental clinic services.

• Journal of Korean society of Dental Hygiene
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• v.15 no.6
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• pp.983-990
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• 2015

Objectives: The purpose of the study is to investigate the influencing factors of satisfaction and revisiting intention of dental implant patients. Methods: An interview and a self-reported questionnaire were completed by 190 patients in 10 dental clinics in Daegu, Gyeongbuk, and Gyeongnam from September 17 to October 31, 2015. The questionnaire consisted of the general characteristics of the subjects and satisfaction of implant. The instrument for implant interview was adapted form Pjetursson et al. by Likert 5 points scale. Cronbach's ${\alpha}$ in the study was 0.768. Data were analyzed by SPSS/AMOS version 21.0 program. Results: Cost satisfaction had direct effect on satisfaction of expectation and indirect effect on revisiting intent. Mastication satisfaction had the direct effect on satisfaction of expectation and revisiting intent, and indirect effect on revisiting intent. Satisfaction of aesthetic function had the direct effect on satisfaction of expectation, and the indirect effect on revisiting intent. Conclusions: The determining factors of successful dental implant included expenses, mastication function, and aesthetic satisfaction. The competent dental implant teamwork and appropriate expenses can satisfy the implant patients.