• 대한치과기공학회지
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• 제30권2호
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• pp.181-192
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• 2008

• 대한치과기공학회지
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• 제2권1호
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• pp.29-30
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• 1980

• The Journal of Advanced Prosthodontics
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• 제9권4호
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• pp.252-256
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• 2017

PURPOSE. This in vitro study aimed to analyze and compare the reproducibility of zirconia and lithium disilicate crowns manufactured by digital workflow. MATERIALS AND METHODS. A typodont model with a prepped upper first molar was set in a phantom head, and a digital impression was obtained with a video intraoral scanner (CEREC Omnicam; Sirona GmbH), from which a single crown was designed and manufactured with CAD/CAM into a zirconia crown and lithium disilicate crown (n=12). Reproducibility of each crown was quantitatively retrieved by superimposing the digitized data of the crown in 3D inspection software, and differences were graphically mapped in color. Areas with large differences were analyzed with digital microscopy. Mean quadratic deviations (RMS) quantitatively obtained from each ceramic group were statistically analyzed with Student's t-test (${\alpha}=.05$). RESULTS. The RMS value of lithium disilicate crown was $29.2\;(4.1){\mu}m$ and $17.6\;(5.5){\mu}m$ on the outer and inner surfaces, respectively, whereas these values were $18.6\;(2.0){\mu}m$ and $20.6\;(5.1){\mu}m$ for the zirconia crown. Reproducibility of zirconia and lithium disilicate crowns had a statistically significant difference only on the outer surface (P<.001). The outer surface of lithium disilicate crown showed over-contouring on the buccal surface and under-contouring on the inner occlusal surface. The outer surface of zirconia crown showed both over- and under-contouring on the buccal surface, and the inner surface showed under-contouring in the marginal areas. CONCLUSION. Restoration manufacturing by digital workflow will enhance the reproducibility of zirconia single crowns more than that of lithium disilicate single crowns.

• 대한치과기공학회지
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• 제45권3호
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• pp.67-73
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• 2023

Purpose: This in vitro study aimed to evaluate the clinical acceptability of precision of fit of the support thickness of Co-Cr alloy copings fabricated using selective laser melting (SLM). Methods: Thirty dental stone models of maxillary left molar abutments were manufactured, images were taken using a scanner, and a computer-aided design program was used to design the form of a conventional metal ceramic crown coping. Overall, 30 single copings were made from Co-Cr alloy using SLM and divided into three support radius groups (0.1, 0.25, and 0.35 mm) of 10 for each. Digitized data were superimposed with three-dimensional inspection software to quantitatively obtain the machinability of a ceramic crown coping, and visual differences were confirmed using a color map. The root mean square values of the ceramic crown coping group were statistically analyzed using one-way analysis of variance (α=0.05). Results: The precision of fit was superior with 0.25 mm compared with 0.1 mm and 0.35 mm, and the results exhibited significant differences (p<0.05). All specimens showed that various support thicknesses did not exceed the clinically permitted value of 120 ㎛, which mean that more than 0.1 mm and 0.35 mm of support radius for SLM was adequate. Conclusion: The support thickness of Co-Cr alloy restoration fabricated using SLM is shown to affect the adaptation.

• 한국산학기술학회논문지
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• 제15권1호
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• pp.21-26
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• 2014

치과에서 사용되는 구강 치료용 요오드 용기는 개폐 시 용기의 캡에 부착되어 있는 칼날에 의해 치료용 실은 절단이 된다. 금속의 칼날은 요오드 용액과 반응하여 단기간에 부식이 되는 문제로 인해 환자의 위생에도 영향을 준다. 이러한 문제를 해결하기 위해 최근 세라믹 칼날로 대체되어진 제품들도 개발되어 생산되는데, 이때 세라믹 칼날은 수작업과 기계가공을 통해 만들어 진다. 본 연구에서는 세라믹 칼날을 분말사출성형공정으로 대량 생산할 수 있도록 20Cavity의 균일 충전을 위한 유동 시스템을 제안하였다. Moldflow를 이용하여 20cavity 유동성에 대한 시뮬레이션을 진행하였고, 금형제작과 수정을 통해 금형을 완성하였다. 사출성형 후 탈지와 소결공정을 통해 완성하고, 금형에 세라믹 칼날을 인서트 사출하여 캡 제품을 완성하였다. 본 연구를 통해 유효한 절단 성능을 갖는 세라믹칼날 대량생산 가능성을 검증하였다.

• 한국전기전자재료학회논문지
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• 제30권10호
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• pp.656-664
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• 2017

This paper presents the design and fabrication of a high power piezoelectric ultrasonic surgery unit for multi-purpose dental implantation. A conventional piezoelectric ultrasonic surgery units consists of a transducer and a tip. However, the drawback of this simple structure is that the output performance of the transducer considerably changes with the change of the tips. An ultrasonic surgery unit that has an additional booster between the transducer and the tip can solve this problem to some extent; for this, an optimal structural design for the transducer is required. We used the Bolted Langevin Transducer (BLT) as the basic transducer; it consists of piezoelectric ceramics and a metal body. It's structure was optimized using mathematical methods to determine the length and radius of the tail and head masses. Additionally, the booster was also subjected to the same methods. Using these mathematical methods, optimal results in terms of the resonance frequency (24.96 kHz), displacement ($14.27{\mu}m$), and pressure (2.8 MPa), could be obtained. The validity of this proposed surgery unit was confirmed experimentally, exhibiting a cutting force of around 7% higher than that of a conventional surgery unit.

• The Journal of Advanced Prosthodontics
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• 제7권6호
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• pp.446-453
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• 2015

PURPOSE. To compare the push-out bond strength of feldspar and zirconia-based ceramic inlays bonded to dentin with different resin cements following simulated aging. MATERIALS AND METHODS. Occlusal cavities in 80 extracted molars were restored in 2 groups (n=40) with CAD/CAM feldspar (Vitablocs Trilux forte) (FP) and zirconia-based (Ceramill Zi) (ZR) ceramic inlays. The fabricated inlays were luted in 2 subgroups (n=20) with either etch-and-bond (RelyX Ultimate Clicker) (EB) or self-adhesive (RelyX Unicem Aplicap) (SA) resin cement. Ten inlays in each subgroup were subjected to 3,500 thermal cycles and 24,000 loading cycles, while the other 10 served as control. Horizontal 3 mm thick specimens were cut out of the restored teeth for push out bond strength testing. Bond strength data were statistically analyzed using 1-way ANOVA and Tukey's comparisons at ${\alpha}=.05$. The mode of ceramic-cement-dentin bond failure for each specimen was also assessed. RESULTS. No statistically significant differences were noticed between FP and ZR bond strength to dentin in all subgroups (ANOVA, P=.05113). No differences were noticed between EB and SA (Tukey's, P>.05) bonded to either type of ceramics. Both adhesive and mixed modes of bond failure were dominant for non-aged inlays. Simulated aging had no significant effect on bond strength values (Tukey's, P>.05) of all ceramic-cement combinations although the adhesive mode of bond failure became more common (60-80%) in aged inlays. CONCLUSION. The suggested cement-ceramic combinations offer comparable bonding performance to dentin substrate either before or after simulated aging that seems to have no adverse effect on the achieved bond.

• Restorative Dentistry and Endodontics
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• 제23권1호
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• pp.413-423
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• 1998

Dental ceramics exhibit excellent esthetic property, compressive strength, chemical durability, biocompatibility and translucency. This study evaluated the shear bond strength of composite resin to the new heat-pressed ceramic material (IPS-Empress System) depending on the surface treatments and bonding agents. The surface treatments were etching with 4.0% hydrofluoric acid, application of silane, and the combination of the two methods. Composite resin was bonded to ceramic with four kinds of dentin bonding agents(All-Bond 2, Heliobond, Scotch bond Multi-purpose and Tenure bonding agents). The ceramic specimen bonded with composite resin was mounted in the testing jig, and the universal testing machine(Zwick 020, Germany) was used to measure the shear bond strength with the cross head speed of 0.5 mm/min. The results obtained were as follows 1. The mean shear bond strength of the specimens of which the ceramic surface was treated with the combination of hydrofluoric acid and silane before bonding composite resin was significantly higher than those of the other surface treatment groups(p<0.05). 2. In the case of All-Bond 2 and Scotchbond Multi-purpose bonding agent group, the surface treatment methods did not influenced significantly on the shear bond(p>0.05). 3. Of the four bonding agents tested, the shear bond strength of Heliobond was significantly lower than those of other bonding agents regardless of the surface treatment methods(p<0.05). 4. The highest shear bond strength($12.55{\pm}1.92$ MPa) was obtained with Scotchbond Multipurpose preceded by the ceramic surface treatment with the combination of 4% hydrofluoric acid and silane.

• 치위생과학회지
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• 제9권2호
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• pp.153-160
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• 2009

본 연구는 금속-도재 수복물 제작에 사용되는 Ni-Cr alloy와 Co-Cr alloy, 그리고 티타늄에 gold bonding agent를 도포하여 Au coating 층을 형성하였다. 각 시편의 절단면을 전자현미경으로 Au coating 층과 porcelain bonder, 그리고 불투명 도재간의 결합을 관찰하였고, 각 계면의 상태를 SEM/EDS 방법으로 조사하였다. 실험에서 사용된 재료와 방법의 범위 내에서 다음과 같은 결론을 얻었다. 1. Gold bonding agent를 사용하여 형성한 Au coating 층은 미세다공성을 가진 구조로 판단되었다. 2. Au coating 층과 porcelain bonder 그리고 불투명 도재간의 결합은 잘 일어나 보였다. 3. Au coating 층은 도재 소성과정에서 발생하는 산화층의 확산을 제한하는 것으로 관찰되었다.

• 대한치과재료학회지
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• 제43권4호
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• pp.317-322
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• 2016

The effect of ice-quenching after degassing on the hardness change during simulated porcelain firing in a metal-ceramic Pd-Au-Ag alloy was investigated by means of hardness test, field emission scanning electron microscopic observations, and X-ray diffraction analysis. The hardness decreased by ice-quenching after degassing, which was induced by the homogenization of the ice-quenched specimen. The decreased hardness by ice-quenching after degassing was recovered from the 1st opaque stage which was the first stage of the remaining firing process for bonding porcelain. The microstructural change showed that the increase in hardness during the remaining firing process was caused by precipitation. The ice-quenching after degassing did not affect the hardness change during the subsequent porcelain firing process.