• Restorative Dentistry and Endodontics
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• v.33 no.5
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• pp.419-427
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• 2008

This study analyzed the influence of dental adhesive/primer on the bond strength between indirect resin composite and the resin cement. Seventy disc specimens of indirect resin composite (Tescera Dentin, Bisco) were fabricated. And bonding area of all specimens were sandblasted and silane treated for one minute. The resin cements were used with or without application of adhesive/primer to bonding area of indirect resin restoration, Variolink-II (Ivoclar-Vivadent) : Exite DSC, Panavia-F (Kuraray) : ED-Primer, RelyX Unicorn (3M ESPE) Single- Bond, Duolink (Risco) : One-step, Mulitlink (Ivoclar-Vivadent) : Multilinh Primer. Shear bond strength was measured by Instron universal testing machine. Adhesive application improved shear bond strength (p<0.05) But Variolink II and Panavia-F showed no statistically significant difference according to the adhesive application. With the above results, when resin inlay is luted by resin cement it seems that application of dental adhesive/primer is necessary in order to improve the bond strength.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.8 no.3
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• pp.401-406
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• 1998

For the applications in optical waveguides and devices, LiNbO_3$ single crystals need to overcome the weakness of optical damage due to the inhomogeneities of laser-induced refractive index. This problem can be solved by doping of Mg in LiNbO_3$ and proton exchange of LiNbO_3$. In this study, to understand the mechanism of optical damage resistance in LiNbO_3$, the changes of lattice defects in LiNbO_3$ caused by MgO doping and acid treatment were observed indirectly by $OH^-$ absorption bands using a FT-IR spectrophotometer. The effect of lattice defects on temperature, heat-treatment and polishing were also investigated. It is shown that MgO doping increases optical damage resistance by generating the defects of $Mg_{Nb}^{2+}$ in the lattice of LiNbO_3$, and that proton exchange by implantation of $H^+$ ion in the hexagonally closest packed oxygen layers on the surface of LiNbO_3$, makes lattice defects, which diffuse into the crystal after heat-treatment above $400^{\circ}C$.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.4
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• pp.93-99
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• 2019

The purpose of this study was to investigate the bond strength between PEKK(Polyetherketoneketone) and Sinfony(3M ESPE, Seefeld, Germany) the dental composite resin by proposing the three representative surface treatment methods and evaluate to see if they affect the bond strength between two materials. A total of 30 PEKK($Pekkton^{(R)}$ Ivory, $Cendres+M{\acute{e}}taux$, Bienne, Switzerland) specimens were prepared, embedded in acrylic resin, polished(P 1200 grid) to surface, and each group was divided into 10 specimens. After then, by the surface treatment method, it classified into three groups(n=10) such as Air abrasion group(PN), applying Single Bond Universal(3M ESPE) after Air abrasion(PB), applying OPAQUE(3M ESPE) after Air abrasion(PO). Then, veneering was performed by using Sinfony(3M ESPE, Seefeld, Germany). All completed specimens were allowed to rest in a $37^{\circ}C$ water bath for 24 hours. Shear bond strength of each group was measured and fracture patterns were classified. Statistic analysis was performed with One-way ANOVA followed by post hoc Scheffe tast (p<.05). Statistical analysis was performed using the SPSSWIN 21.0 program. As a result of one-way ANOVA, the average value of PB group was $27.67{\pm}4,18MPa$ and it was shown as the highest bond strength, PN and PO were $20.43{\pm}1.70$ and $19.8{\pm}4.77MPa$ each, and these were relatively low(F=18.4, P<.001), and as the post-test the Scheffe test was conducted and verified (p<.05). After examining the scheffe test, it was showed significant differences as PB>PO, PB>PN(p<.001). Through this study, in order to enhance the bonding force between PEKK and the composite resin, perform the Air abrasion and surface treatment by using Single Bond Universal(3M ESPE) is recommended, and as coMPared with other studies. And it is assumed that the increase of the application time of the Air abrasion affects the increase of the shear bond strength. Thus, further research is required.

• Design & Manufacturing
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• v.13 no.1
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• pp.13-18
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• 2019

The size and prospects of the domestic semiconductor equipment market are increasing every year. In the case of various parts used inside semiconductor equipments, high durability such as high strength and abrasion resistance is demanded. Particularly, the gases used in semiconductor production processes are toxic. In order to prevent such toxic gas leakage, a precision processing technique and a surface treatment technique for preventing corrosion are required. Electro-polishing is an electro-chemical method of polishing a metal surface to make it smooth and polished. Electro-polishing is mainly used in the finishing process of metal surface. Unlike mechanical polishing, electro-polishing is used in many fields, such as fine chemical etching equipment, since no damaged layer or burr, fine polishing groove and particles are generated. However, in order to withstand the gas used in the semiconductor equipment, the parts must have high corrosion resistance. However, the surface hardness generally become lowered through electro-polishing. Therefore, in this study, surface hardness were experimentally observed before and after electro-polishing. Then, a method of improving hardness by preparing a nitrided layer by plasma ion nitriding treatment.

• The korean journal of orthodontics
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• v.25 no.3 s.50
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• pp.341-353
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• 1995

Previous study had shown the diversities in the propriety for optimal bond strength on the concentration of the etchant. The aim of present study in vitro was to evaluate and compare the shear bond strength of orthodontic brackets to enamel and to measure the depth of etch on the phosphoric acid concentrations. A hundred and seventy six extracted bovine lower centrals were ground to yield flat surfaces and etched by the concentration $0%,\;5%,\;10%,\;20%,\;30%,\;40%,\;50%,\;60%,\;70%,\;80%\;and\;85\%$ of phosphoric acid respectively during 60 seconds. The shear bond strength of orthodontic brackets, the depth of etch and surface roughness of the enamel were measured, and scanning electron microscopic observations on the etched enamel surfaces were carried out. The data obtained from the very experiments were processed and statistically analyzed and evaluated. The gradual increase in the depth of etch to enamel as the accretion of the concentration of the phosphoric acid upto $40-50\%$ and decline henceforth were manifested. The surface roughness showed no correlation with the depth of etch, yet moderate correlation with the shear bond strength of brackets. Scanning electron microscopic investigation revealed that morphological patterns of the etched enamel surfaces for $5\%\;to\;40\%$ of concentrations were even and homogenous, and those for $50\%$ as well as $60\%$ exhibited the overetched and unhomogenous. The shear bond strengths kom $10\%\;to\;60\%$ of concentration showed no statistically significant differences. It was suggested that the shear bond strengths at $5\%\;and\;70\%$ were sufficient to tolerate the force levels of the ordinary orthodontic treatment notwithstanding to be significantly lower than those from $10\%\;to\;60\%$ phosphoric acid solution.

• Restorative Dentistry and Endodontics
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• v.27 no.4
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• pp.363-369
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• 2002

최근에 많이 사용되어지고 있는 치과용 접착제는 산 부식 후 수분이 있는 상태에서 적용하는 wet-bonding 술식을 많이 추천하고 있다. 하지만 self-etching primer의 경우 산부식과 priming 과정이 동시에 시행되고, 제조자들은 건조된 치아표면에 적용할 것을 추천하고 있다. 그러나 건조된 정도에 대하여서는 별다른 추천사항이 없으며. 수분이 self-etching primer에 어떤 영향을 미치는지에 대하여서는 별다른 연구가 이루어져 있지 않은 상태이다. 이에 본 연구에서는 치질 삭제 후 남아있는 수분이 self-etching primer의 레진 접착 강도에 어떤 영향을 미치는 지를 알아보고자 하였다. 발거한 대구치 96개를 이용하여 물기가 있는 상태에서 #600 사포로 표면을 연마하고, 법랑질 면을 노출시킨 군과 상아질을 노출시킨 군으로 분류 후, 30분 공기 중 방치 군 (1군), 5초 공기 건조 군 (2군), 1초 공기 건조 군 (3군), 솜으로 약간의 물기를 제거한 군(blot dry) (4군) 등 총 8개의 군으로 나누었다. Self-etching adhesive system인 Clearfil SE Bond primer를 20초간 적용하고, bonding제 도포 후 10초간 광중합 시행하였다. 접착제 처리한 치아면에 몰드를 고정한 후 Clearfil AP-X 복합레진을 2mm 충전하고, 40초간 광중합을 시행하였다. 24시간 후 전단 응력 결합강도를 측정하였으며, 그 결과는 다음과 같이 나타났다. 법랑질과 상아질 모두에서, 30분 건조군과 5초 공기건조군이 1초와 blot drying 군보다 높은 결합강도를 보였으며 통계학적으로 유의한 차이를 보였다(p＜0.05). 본 실험 결과에 의하면 self-etching adhesive system을 사용함에 있어서 법랑질과 상아질군 공히 건조된 상태에서 사용하여야 하며 수분의 존재시 치아와의 결합력이 감소하는 것으로 나타났다. 따라서 임상에서 접착제의 적용시 수분의 조절에 주의하여야 할 것으로 사료된다.

• Composites Research
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• v.22 no.4
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• pp.41-49
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• 2009

Natural fiber reinforced composites are emerging as low-cost, lightweight, recyclable, and eco-friendly materials. These are biodegradable and non-abrasive. Due to eco-friendly and biodegradable characteristics of natural fibers, they are being considered as potential candidates to replace the conventional fibers. The chemical, mechanical, and physical properties of natural fibers have distinct features depending upon the cellulose content of the fibers which varies from fiber to fiber. The mechanical properties of composites are influenced mainly by the adhesion between matrix and fibers. Several chemical and physical modification methods of fiber surface were incorporated to improve the tiber-matrix adhesion resulting in the enhancement of mechanical properties of the composites. This paper outlines the works reported on natural tiber reinforced composites with special reference to the type of fibers, polymer matrix, processing techniques, treatment of fibers, and fiber-matrix interface.

• The korean journal of orthodontics
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• v.26 no.5 s.58
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• pp.591-599
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• 1996

This study was undertaken to investigate the cytotoxicity of orthodontic wires after doing various treatments to the wires. 018x025 inch Stainless steel(A) and Co-Cr(B) wires were used and each of them were divided into 4 groups. A-1 and B-1 groups were as received state, and A-2 and B-2 groups were heat treated. A-3 and B-3 groups were electropolished after heat treatment, and A-4 and B-4 groups were soldered with Ag-solder. Each group had 3 wires and these were sterilized with Ethylene Oxide gas. We used human gingival fibroblast cell culture and agar overlay technique to investigate the cytotoxicity of each group of wires. The cytotoxicity of wire was assessed using reaction index (zone index/lysis index). The findings of this study were as follows. 1. Both of the stainless steel wire and Co-Cr wire showed no cytotoxicity in as received state. 2. Heat treatment or electropolishing of the wires had no effect on the cytotoxicity of the wires 3. Soldered stainless steel wires showed a little wider zone of discoloration than soldered Co-Cr wires, but the zone index and cytotoxicity(reaction index) was not different. 4. Soldered wires showed moderate cytotoxicity in both of the wires.

• Journal of Dental Rehabilitation and Applied Science
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• v.37 no.4
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• pp.177-185
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• 2021

Clinical applications of translucent zirconia as well as traditional zirconia (3 mol% yttria stabilized tetragonal zirconia polycrystal, 3Y-TZP) are increasing. For this reason, studies on factors affecting the optical properties of dental zirconia have been continuously reported. The optical effect of dental zirconia may vary depending on the yttria content, the thickness of the prosthesis, the sintering process, polishing, glazing and cementation in laboratory and clinical procedures. Increasing the yttria concentration can reduce the masking effect. Translucency decreases as the thickness of the restoration increases, but the required thickness may vary depending on the properties of the zirconia block. The high-speed sintering method can shorten the manufacturing time, but in some cases, the translucency of the prosthesis may decrease. In addition, the optical properties can be affected by the surface roughness of zirconia and the polishing process. The use of an appropriate colored cement can help with the masking effect of zirconia and can be useful for color matching for more esthetic results.

• Journal of Dental Rehabilitation and Applied Science
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• v.24 no.1
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• pp.113-127
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• 2008

The purpose of this study was to evaluate effect of application of $ZirLiner^{(R)}$ and blasting treatments on shear bond strength of zirconia-veneered porcelain interface. 60 uncolored zirconia plates and 30 colored zirconia plates were fabricated and divided into nine groups of 10 according to blasting treatment such as as-ground, glass blasting and alumina blasting and zirliner application. Veneering porcelains were built up over the center of the treated zirconia ceramic surface using jig and fired according to the manufacturers' instructions. Each specimen was completely embedded in acrylic resin. The specimens were placed in a mounting jig and subjected to shear force by a universal testing machine. Load was applied at a crosshead speed of 0.5㎜/min until failure. Average shear strengths were analyzed with two-way analysis of variance and one-way analysis of variance and the Duncan's post-hoc test. The fracture surfaces of the failed specimens were examined by SEM. The obtained results were as follows: 1. Depending on surface treatment by blasting, the degree of roughness is revealed in the order of Glass-blasted, As-ground, and Alumnia-blasted. The roughness average of uncolored and colored zirconia ceramic were not significantly different from blasting treatments. 2. In uncolored zirconia ceramic, the shear bond strength were not significantly different from blasting treatments. However, the shear bond strength were significantly different from Zirliner application. 3. Used ZirLiner, mean shear bond strength of colored zirconia was lower than uncolored zirconia. Especially, mean shear bond strength of colored zirconia was quite low with alumina-blasting treatment. 4. SEM analysis showed that veneered porcelain failed in zirconia ceramic interface and there was no cohesive failure.