• 대한치과기공학회지
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• 제21권1호
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• pp.123-130
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• 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.

• 한국재료학회지
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• 제22권6호
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• pp.285-291
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• 2012

Hydroxyapatite (HA) is well known as a biocompatible and bioactive material. HA has been practically applied as bone graft materials in a range of medical and dental fields. In this study, two types of dense hydroxyapatite ceramics were prepared from natural bones and synthetic materials. The biocompatibility of HA ceramics for supporting osteoblast cell growth and cytotoxicity using an in vitro MG-63 cell line model were respectively evaluated. Artificial hydroxyapatite shows relative density of 93% with 1-2 ${\mu}m$ after sintering, but a hydroxyapatite compact derived from bovine bone has low sintered density of 85% with a small content of MgO. Irrespective of the starting raw materials, both types of sintered hydroxyapatite displayed similar biocompatibility in the tests. FE-SEM observations showed that most MG-63 cells had a stellar shape and formed an intercellular matrix containing fibers on sintered HA. The cells were well attached and grown over the HA surface, indicating that there was no toxicity.

• 한국세라믹학회지
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• 제39권11호
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• pp.1028-1034
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• 2002

용융침투법을 이용 스피넬/지르코니아-유리 복합체를 제조하여 지르코니아 첨가가 복합체의 기계적 특성에 미치는 영향을 조사하였다. 유리 침투시간이 증가할수록 침투깊이는 Washburn식에 의한 포물선 관계로 증가하였으며 유리 침투상수 K는 기공 크기의 함수로 지르코니아 첨가량이 증가할수록 감소하였다. 지르코니아가 20 wt% 첨가되었을 때 스피넬/지르코니아-유리 복합체의 최적의 강도값(308 MPa)이 관찰되었지만 지르코니아 양이 증가함에 따라 유리 침투 상수와 투과율(transmittance)이 감소하였다. 지르코니아 첨가가 스피넬/지르코니아-유리 복합체의 기계적 특성 향상에 미치는 증진 효과는 크지 않은 것으로 관찰되었다.

• The Journal of Advanced Prosthodontics
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• 제10권2호
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• pp.147-154
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• 2018

PURPOSE. This study was performed to evaluate the osteogenic potential of 3mol% yttria-stabilized tetragonal zirconia polycrystals (3Y-TZP) and niobium oxide containing Y-TZPs with specific ratios, new (Y,Nb)-TZPs, namely YN4533 and YN4533/Al20 discs. MATERIALS AND METHODS. 3Y-TZP, YN4533 and YN4533/Al20 discs (15 mm diameter and 1 mm thickness) were prepared and their average surface roughness ($R_a$) and surface topography were analyzed using 3-D confocal laser microscope (CLSM) and scanning electron microscope (SEM). Mouse pre-osteoblast MC3T3-E1 cells were seeded onto all zirconia discs and evaluated with regard to cell attachment and morphology by (CLSM), cell proliferation by PicoGreen assay, and cell differentiation by Reverse-Transcription PCR and Quantitative Real-Time PCR, and alkaline phosphatase (Alp) staining. RESULTS. The cellular morphology of MC3T3-E1 pre-osteoblasts was more stretched on a smooth surface than on a rough surface, regardless of the material. Cellular proliferation was higher on smooth surfaces, but there were no significant differences between 3Y-TZP, YN4533, and YN4533/Al20. Osteoblast differentiation patterns on YN4533 and YN4533/Al20 were similar to or slightly higher than seen in 3Y-TZP. Although there were no significant differences in bone marker gene expression (alkaline phosphatase and osteocalcin), Alp staining indicated better osteoblast differentiation on YN4533 and YN4533/Al20 compared to 3Y-TZP. CONCLUSION. Based on these results, niobium oxide containing Y-TZPs have comparable osteogenic potential to 3Y-TZP and are expected to be suitable alternative ceramics dental implant materials to titanium for aesthetically important areas.

• 대한치과기공학회지
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• 제20권1호
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• pp.99-120
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• 1998

The objective of this study is to research the job spirits of Korea Dental Technisians, Then to figure out the reality of Dental Laboratory Technology field. So to provide data for improving the working condition in which they can with the proper value and pride and be of help in the development of Dental Laboratory Technology field. 1. Before entering school, 121(59.1%) scarcely knew about Dental Technisians, which show its perception is fairly low. The reason for choosing their job, 93(45.4%) answered the most it has a rosy future. 2. About the job satsfaction, 77.5% was satisfied counting the "so-so"s as contentment. About the channel for getting their jobs, 81(39.5%) the most made it through their own efforts. 3. The most influential factor when choosing their jobs, character and aptitude is answered the most by 115(56.1%). The working period they want is the time when they can't work for health problem, 76(37.1%) answered. 4. The most favored job condition of Dental Technitians is opening their own office(69, 33.7% and the most favored work is dental ceramics 62.9%, 129) 5. About their desires on changing jobs, about 52.2% was considering it and the reason for it they are treated improperly in spite of their academic background.(57.1%, 117ppl) 6. About the events for improvement of their job knowledge, 75(36.6%) answered participation in seminars. For the present, the most interesting part is to take new skills via the seminars(33.7%, 69ppl) 7. On the future of the Dental Laboratory Technology field, 80.4% said would be better. On the claims for the Dental Laborotory Technology Association, 152(74.1%) said they wanted their reights and interests protected.

• 대한의용생체공학회:의공학회지
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• 제11권1호
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• pp.5-12
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• 1990

Calcium phosphate ceramics have been applied intensively to orthopaedic and dental implants by virtue of their osteoconductive nature. In an attempt to enhance the bone implant intergrity and Eta utility, these ceramics are deposited onto the porous surface of metallic implants. The coating procedure and the ensuing phase transformations of the ceramic alter the mechanical properties and surface chemistry of the ceramic layers as well as those of the substrate. These structural and compositional differences are directly related to the interaction mechanisms at the surface-active ceramicbone interface. Material and processing induced influences on dissolution, electrokinetic behavior, ceramic-metallic substrate interface and boRe growth enhancement are presented.

• 대한치과보존학회:학술대회논문집
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• 대한치과보존학회 2001년도 춘계학술대회
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• pp.235-237
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• 2001

;Dentistry has benefited from tremendous advances in technology with the introduction of new techniques and materials, and patients are aware that esthetic approaches in dentistry can change one's appearance. Increasingly. tooth-colored restorative materials have been used for restoration of posterior teeth. Tooth-colored restoration for posterior teeth can be divided into three categories: 1) the direct techniques that can be made in a single appointment and are an intraoral procedure utilizing composites: 2) the semidirect techniques that require both an intraoral and an extraoral procedure and are luted chairside utilizing composites: and 3) the indirect techniques that require several appointments and the expertise of a dental technician working with either composites or ceramics. But, resin restoration has inherent drawbacks of microleakage. polymerization shrinkage, thermal cycling problems. and wear in stress-bearing areas. On the other hand, Ceramic restorations have many advantages over resin restorations. Ceramic inlays are reported to have less leakage than resin restoration and to fit better. although marginal fidelity depends on technique and is laboratory dependent. Adhesion of luting resin is more reliable and durable to etched ceramic material than to treated resin composite. In view of color matching, periodontal health. resistance to abrasion, ceramic restoration is superior to resin restorationl. Materials which have been used for the fabrication of ceramic restorations are various. Conventional powder slurry ceramics are also available. Castable ceramics are produced by centrifugal casting of heat-treated glass ceramics. and machinable ceramics are feldspathic porcelains or cast glass ceramics which are milled using a CAD/CAM apparatus to produce inlays (for example, Cered. They may also be copy milled using the Celay apparatus. Pressable ceramics are produced from feldspathic porcelain which is supplied in ingot form and heated and moulded under pressure to produce a restoration. Infiltrated ceramics are another class of material which are available for use as ceramic inlays. An example is $In-Ceram^{\circledR}$(Vident. California, USA) which consists of a porous aluminum oxide or spinell core infiltrated with glass and subsequently veneered with feldspathic porcelain. In the 1980s. the development of compatible refractory materials made fabrication easier. and the development of adhesive resin cements greatly improved clinical success rates. This case report presents esthetic ceramic inlays for posterior teeth.teeth.

• The Journal of Advanced Prosthodontics
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• 제5권2호
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• pp.161-166
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• 2013

PURPOSE. This study aimed to identify the effects of the sintering conditions of dental zirconia on the grain size and translucency. MATERIALS AND METHODS. Ten specimens of each of two commercial brands of zirconia (Lava and KaVo) were made and sintered under five different conditions. Microwave sintering (MS) and conventional sintering (CS) methods were used to fabricate zirconia specimens. The dwelling time was 20 minutes for MS and 20 minutes, 2, 10, and 40 hours for CS. The density and the grain size of the sintered zirconia blocks were measured. Total transmission measurements were taken using a spectrophotometer. Two-way analysis of variance model was used for the analysis and performed at a type-one error rate of 0.05. RESULTS. There was no significant difference in density between brands and sintering conditions. The mean grain size increased according to sintering conditions as follows: MS-20 min, CS-20 min, CS-2 hr, CS-10 hr, and CS-40 hr for both brands. The mean grain size ranged from 347-1,512 nm for Lava and 373-1,481 nm for KaVo. The mean light transmittance values of Lava and KaVo were 28.39-34.48% and 28.09-30.50%, respectively. CONCLUSION. Different sintering conditions resulted in differences in grain size and light transmittance. To obtain more translucent dental zirconia restorations, shorter sintering times should be considered.

• Imaging Science in Dentistry
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• 제51권3호
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• pp.261-269
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• 2021

Purpose: The aim of this study was to evaluate the radiopacities of various types of restorative materials with different thicknesses compared with enamel, dentin, and aluminum. Materials and Methods: Four bulk-fill resins, 2 hybrid ceramics, 2 micro-hybrid resin composites, 6 glass ionomer-based materials, 2 zinc phosphate cements, and an amalgam were used in the study. Twelve disk-shaped specimens were prepared from each of 17 restorative materials with thicknesses of 1 mm, 2 mm, and 4 mm (n=4). All the restorative material specimens with the same thickness, an aluminum (Al) step wedge, and enamel and dentin specimens were positioned on a phosphor storage plate and exposed using a dental X-ray unit. The mean gray values were measured on digital images and converted to equivalent Al thicknesses. Statistical analyses were performed using 2-way analysis of variance and the Bonferroni post hoc test(P<0.05). Results: Radiopacity was significantly affected by both the thickness and the material type (P<0.05). GCP Glass Fill had the lowest radiopacity value for samples of 1 mm thickness, while Vita Enamic had the lowest radiopacity value for 2-mm-thick and 4-mm-thick samples. The materials with the highest radiopacity values after the amalgam were zinc phosphate cements. Conclusion: Significant differences were observed in the radiopacities of restorative materials with different thicknesses. Radiopacity was affected by both the material type and thickness.

• 대한치과기공학회지
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• 제42권4호
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• pp.307-312
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• 2020

Application of ceramic materials for fabrication of dental restoration materials has been a focus of interest in the field of esthetic dentistry. The ceramic materials of choice are glass ceramics, spinel, alumina, and zirconia. The development of yttrium tetragonal zirconia polycrystal (YTZP)-based systems is a recent addition to all-ceramic systems that have high strength and are used for crowns and fixed partial dentures. Computer-aided design/computer-aided manufacturing (CAD/CAM)-produced, YTZP-based systems are popular with respect to their esthetic appeal for use in stress-bearing regions. The highly esthetic nature of zirconia and its superior physical properties and biocompatibility have enabled the development of restorative systems that meet the demands of today's patients. Many in vitro trials have been performed on the use of zirconia; however, relatively fewer long-term clinical studies have been published on this subject. The use of zirconia frameworks for long-span fixed partial dentures is currently being evaluated; in the future, more in vivo research and long-term clinical studies are required to provide scientific evidence for drawing solid guidelines. Further clinical and in vitro studies are required to obtain data regarding the long-term clinical use of zirconia-based restorations.