• The Journal of Korean Academy of Prosthodontics
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• v.30 no.1
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• pp.93-101
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• 1992

The purpose of this study was to evaluate the effectiveness of core materials and luting agents on the retention of full veneer gold crown. The core materials used in this study was dental amalgam, and composite resin, and the luting agents were zinc phosphate cement, polycarboxylate cement, and glass ionomer cement. The obtained results were as follows. 1. In full veneer gold crown supported by composite resin core, the crown retention with zinc phosphate cement was the highest of all. 2. In full veneer gold crown supported by amalgam core, the crown retention was shown no statistical difference by luting agent. 3. There was no statistical difference in the crown retention between the full veneer gold crown supported by composite resin core and dental amalgam core.

• Journal of dental hygiene science
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• v.20 no.3
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• pp.146-154
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• 2020

Background: The objective of this study is to investigate the needs and importance of basic core competencies required for future society by dental hygienists' viewpoints who are working in the clinical practices and to provide the fundamental data to develop the educational programs based on the competencies in the 21st century so as to enhance their working capability. Methods: A total of 38 questionnaires were used in this study, 3 questionnaires on the general characteristics (age, service years, main job functions) and those in 11 sub-factors of basic core competencies including 4 questionnaires on creativity, 3 on collaboration, 3 on communication, 3 on interpersonal relationship, 3 on problem-solving, 4 on resource control, 4 on self-control and development, 2 on vocational ethics, 3 on knowledge information utilization, 3 on global mind, and 3 on emotional intelligence. Self-reported survey was conducted in the dental hygienists who were working in Seoul and Gyeonggi Province and a total of 195 data were analyzed. Results: Vocational ethics, communication, and collaboration showed the highest on both importance and needs with 4.49 points and 4.34; 4.41 and 4.28; and 4.39 and 4.22, respectively, while global mind showed the lowest with 3.51 and 3.59. Upon Importance-Performance Analysis, 7 items were defined to require maintain the status including vocational ethics, communication, collaboration, interpersonal relationship, self-control, emotional intelligence, and problem-solving while 4 items with lower priority were resource control and development, knowledge information utilization, creativity, and global mind. Conclusion: Based on this study results that suggested the basic core competencies of dental hygienists in alignment with their jobs in the future society, competitive dental hygienists should be developed with the educational programs applied with these competencies.

• The Journal of the Korean dental association
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• v.34 no.10 s.329
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• pp.733-741
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• 1996

• Journal of Korean society of Dental Hygiene
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• v.18 no.6
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• pp.1037-1045
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• 2018

Objectives: The purpose of this study was to evaluation the effect of translucency on CAD/CAM ceramic according to different core/veneer thicknesses. Methods: A total of 42 samples from 2 groups of 7 ceramic cores, each with 3 thickness values (0.8, 1.0, 1.2 mm) were manufactured. The veneers were also manufactured in 3 thicknesses (0.3, 0.5, 0.7 mm). The group names were based on the name of the ceramic core (IPS e.Max CAD; LD, and IPS Empress CAD; LR). The associated number was determined by the combined thickness of the core and veneer: 1 = (0.8 + 0.7); 2 = (1.0 + 0.5); 3 = (1.2 + 0.3). The translucency was measured using a spectrophotometer and defined via the contrast ratio (CR) and translucency parameter (TP). Two-way ANOVA was performed to compare the 2 groups (material and thickness). Results: As the core thickness increased, the TP value also increased, and the CR value (for LR group) decreased. The results of 2-way ANOVA demonstrated that the thicknesses of different core/veneer combinations significantly affected the translucency (p<0.05). Conclusions: The different core and veneer thicknesses affected the translucency of CAD/CAM ceramic.

• Journal of Korean society of Dental Hygiene
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• v.12 no.5
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• pp.1049-1058
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• 2012

Objectives : It will be necessary to make statement about the competence targeted in the dental hygienic education that adopts the competence-based curriculum from the standpoint of core competence which the students need to be equipped with in the society. Methods : To achieve the education objective of Dental Hygienics, the information available on the website of the Korean Dental Association, universities and graduate schools were used, and the education objectives of the concerned universities which were posted in the websites of 82 universities from July to August, 2011 were analyzed. Results : C7 and C1 accounted for 21.1%, the highest percentage, in the core capability, while HP1 comprised 79.6% in the health improvement and disease prevention. CM1 stood at 73.7%, the highest percentage, in the community involvement(CM) area, and PC4 accounted for 90.8%, the highest percentage, in the patient care(PC) area. In the professional growth and development(PGD) area, PGD1 was the highest, followed by PGD3. In relation to the comments on the occupational types after graduation, 63.1% of respondents mentioned the dental hygienists at the school, while 33.3% did not make any comment on the dental hygienists. Conclusions It was necessary to re-establish the essential objectives of the graduates based on the competence as the accomplishments of studying and learning in the department of dental hygiene. It may be a useful method to set the competency-based education objective on the basis of the implementation ability and the level of graduates.

• Restorative Dentistry and Endodontics
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• v.23 no.2
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• pp.690-700
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• 1998

Rubber-toughened particles which are used in the field of chemical engineering are used to increase the fracture toughness of thermoset resin. The application of Core-Shell particles, one of rubber-toughened particles, as a filler for dental composite or restoration have not been examined. The purpose of this study was to evaluate possible use of Core-Shell particles for dental composite, and the hypothesis was that additional toughening mechanisms are activated by the addition of Core-Shell particles. After blending 50vol% quartz with Bis-GMA/TEGDMA resin matrix, the experimental resins were made by the addition of Core-Shell particles with varied content level as 0, 2.5, 5, 7.5, 10, 12.5, 15, and 20wt%. Fracture toughness was determined on three-point bending specimen with single-edge notch according to ASTM-E 399. Also, flexural properties, that is, strength and modulus were measured by three-point bending testing. Fractogragh of fracture toughness specimen was observed using SEM (JEOL 6400 SEM, MA). The following results from this study were obtained ; 1. Fracture toughness of composite resin added 2.5wt% Core-Shell particles was significantly higher than control group ($p{\leq}0.05$). 2. Flexural properties were decreased with increasing Core-Shell particle content, which showed a correlation statistically ($p{\leq}0.05$). 3. A toughening mechanism such as lamination and microcrack was observed in specimen determined high fracture toughness. 4. The dispersion of Core-Shell itself and quartz filler particles was limited present high content of Core-Shell particles, which decreased a resulting mechanical properties of composites. These results suggest that adequate Core-Shell particles can be used to enhance mechanical properties included toughening for dental composites.

• The Journal of the Korean dental association
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• v.28 no.7 s.254
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• pp.641-648
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• 1990

• Journal of Technologic Dentistry
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• v.40 no.2
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• pp.63-69
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• 2018

Purpose: The purpose of this study is to investigate the non-precious metal core materials used in the dental laboratory to fabricate the implant superstructure by CAD / CAM method. And to observe and compare the morphology and distribution of the osteoblasts in relation to implant osseointegration. Methods: In this study, the mandibular right first molar tooth model was selected as an international standard to produce a single core. Using this model, the impression was made with the silicone rubber, the tooth model was scanned, and a single core was designed and 5-axis milling was performed. The materials used were Cobalt-Chromium and Nickel-Chromium, and the cores for dental implant top structures were fabricated according to the procedures of the dental labs. After the fabrication, the marginal area of the core was separated and cell culture experiment was performed. The osteoblast cells used MC3T3-E1, which is currently widely used. For morphological analysis of osteoblasts, cells were posttreated and observed using CLSM (Confocal Laser Scanning Microscope) and compared. Results: The cell adhesion behavior of the specimen surface measured by CLSM was uniformly distributed in specimen A (Cobalt-Chromium) than in specimen B (Nickel-Chromium). The distribution and changes of the cells were different in the two specimens. Conclusion : It is possible to confirm that specimen A (Cobalt-Chromium) is suitable for the living body through adhesion and proliferation of osteoblasts related to implant osseointegration in the non-precious metal superstructure used after implantation. It is considered that it is preferable to use Co-Cr when fabricating the superstructure.

• The Journal of Advanced Prosthodontics
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• v.5 no.2
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• pp.187-197
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• 2013

PURPOSE. The purpose of this study was to evaluate various core designs on stress distribution within zirconia crowns. MATERIALS AND METHODS. Three-dimensional finite element models, representing mandibular molars, comprising a prepared tooth, cement layer, zirconia core, and veneer porcelain were designed by computer software. The shoulder (1 mm in width) variations in core were incremental increases of 1 mm, 2 mm and 3 mm in proximal and lingual height, and buccal height respectively. To simulate masticatory force, loads of 280 N were applied from three directions (vertical, at a $45^{\circ}$ angle, and horizontal). To simulate maximum bite force, a load of 700 N was applied vertically to the crowns. Maximum principal stress (MPS) was determined for each model, loading condition, and position. RESULTS. In the maximum bite force simulation test, the MPSs on all crowns observed around the shoulder region and loading points. The compressive stresses were located in the shoulder region of the veneer-zirconia interface and at the occlusal region. In the test simulating masticatory force, the MPS was concentrated around the loading points, and the compressive stresses were located at the 3 mm height lingual shoulder region, when the load was applied horizontally. MPS increased in the shoulder region as the shoulder height increased. CONCLUSION. This study suggested that reinforced shoulder play an essential role in the success of the zirconia restoration, and veneer fracture due to occlusal loading can be prevented by proper core design, such as shoulder.

• Journal of Technologic Dentistry
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• v.33 no.1
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• pp.7-14
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• 2011

Purpose: As the demand and importance of aesthetic aspects in dental treatment become higher, much attention is paid to materials used for dental prostheses. Thus, the marginal fidelity of most-commonly used alloy, IPS - Empress and ZrO2 ceramic is compared. Methods: The alloy core made by casting, IPS - Empress core made by pressing and ZrO2 ceramic core made by CAD/CAM are used to make 10 samples respectively. For each core, three points were measures and the optical microscope (Axio Imager.Alm,Zeiss co., Oberkochen, Germany) was used to observe the cores with a magnification of 100. Results: As for alloy, IPS - Empress and ZrO2 ceramic, the average and deviation of their marginal distance are $29.91\;{\pm}11.93{\mu}m$ for alloy, $33.45\;{\pm}8.61{\mu}m$ for IPS - Empress, and $31.55\;{\pm}9.85{\mu}m$ for ZrO2. The one-way ANOVA test was conducted to compare them. However, there was no statistically significant difference among them. Conclusion: The study on marginal fidelity of alloy, IPS - Empress, and ZrO2 ceramic shows they have no marginal fidelity problem clinically. Therefore, if a system is selected based on the patient's condition or treatment method, there will be no problem.