• Restorative Dentistry and Endodontics
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• 제12권2호
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• pp.45-53
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• 1987

The purpose of this study was to evaluate the tensile bond strength between composite resin and the human enamel. Three composite resin systems, two chemical (Clearfil Posterior, and Clearfil Posterior-3) and one light cure (Photo Clearfil-A), used with and without an intermediate resin (clearfil bonding agent), were evaluated under different amounts of load (10g, 200g and 200g for a moment) for in vitro tensile bond strength to acid-eched human enamel. Clinically intact buccal or lingual surfaces of 144 freshly extracted human permanent molars, embedded in acrylic were flattened with No #600 carborundum discs. Samples were randomly assigned to the different materials and treatments using a table of random numbers. Eight samples were thus prepared for each group(Table 2) these surfaces were etched with an acid etchant (Kurarey Co. Japan) in a mode of etching for 30 seconds, washing for 15 seconds, and drying for 30-seconds. During the polymerization of composite resin on the acid-etched enamel surfaces with and without bonding agent 10-gram, 200 gram and temporary 200 gram of load were applied. The specimens were stored in 50% relation humidity at $37^{\circ}C$ for 24 hours before testing. An universal Testing machine (Intesco model No. 2010, Tokyo, Japan) was used to apply tensile loads in the vertical directed (fig 5), and the force required for separation was recorded with a cross head speed of 0.25 mm/min and 20 kg in full scale. The results were as follow: 1. The tensile bond strength was much greater in applying a bonding agent than in not doing that. 2. The tensile bond strength of chemical cure composite resin was higher than that of light cure composite resin with applying on bonding agent on the acid-etched enamel. 3. In case of not applying a bonding agents on the acid-etching enamel, the highest tensile bond strength under 200 gram of load was measured in light cure composite resin. 4. The tensile bond strength under 200-gram of load has no relation with applying the bonding agent. 5. Under the load of 10-gram, There was significant difference in tensile bond strength as applying the bonding agent.

• Composites Research
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• 제23권4호
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• pp.21-27
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• 2010

대부분의 구조물 파괴는 피로에 의해서 발생한다. 따라서 지금까지 모드 혼합비가 피로 특성에 어떤 영향을 미치는지에 대한 수많은 연구가 수행되어 오고 있다. 하지만 대부분의 연구가 금속/금속 계면이나 복합재료 층간 분리에 관한 연구이다. 따라서 본 연구에서는 이종재료인 복합재료/금속 계면의 피로 특성에 대한 기초 자료를 얻고자 하였다. 이를 위하여 복합재료와 탄소강을 동시 경화법을 이용하여 접합한 SLB(single leg bending) 시편을 이용하여 피로 실험을 수행하였다. 특히, 피로 특성에 모드 혼합비$(G_{II}/G_T)$가 어떠한 영향을 미치는지에 대해 알아보고자 하였다. 전체적으로 모드 II 하중 성분 이 많을수록 균열진전속도가 빨라진다는 결과를 얻었다.

• 비파괴검사학회지
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• 제36권3호
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• pp.211-216
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• 2016

에폭시 수지는 여러 산업분야에서 다양한 구조물의 접합과 제조에 사용된다. 구조물의 안전성과 접합재료의 최적 성능 확보를 위해서는 에폭시 수지의 경화 과정 모니터링 기반의 공정 제어가 요구된다. 광섬유 센서는 실과 같은 형태적 특징으로 인해 에폭시 수지의 경화 모니터링에 적합한 센서이다. 본 연구에서는 광섬유 브래그 격자 센서(fiber Bragg grating, FBG)를 이용하여 에폭시 수지의 경화 모니터링 연구를 수행하였다. 실제 실험을 통해, FBG를 기반으로 에폭시 수지의 경화과정에서 에폭시의 부피 수축에 의해 센서에 가해지는 변형률을 측정하고 온도의 변화에 의한 신호 변화를 보정하여 경화과정에서 발생하는 변형률의 정확한 모니터링이 가능함을 확인하였다. 추가적으로, 두 가지 에폭시 수지의 경화도 과정을 비교 분석하여 에폭시 종류에 따른 경화과정의 차이를 확인하였다. 결론적으로 FBG 센서가 에폭시 수지의 경화도 모니터링에 유용하다는 점을 확인하였다.

• 한국안전학회지
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• 제12권4호
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• pp.57-62
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• 1997

The combined structure of hybrid composite made through the bonding process of materials of different properties greatly defines its mechanical characteristics, as the results of the experiments on materials of different properties show much dissimilarity. When carbon/epoxy materials are applied to hybrid composite, the carbon materials helps to improve the mechanical properties of the hybrid composite, and the epoxy reduces its fracture strain and impact resistance. Carbon fiber which is now in general commercialization is classified as high modulus or high strength system, and its manufacturing methods are various. The study of the materials having combined structure is focused on the numerical analysis of the layers of bonding surface in materials with difference modulus. The hybrid composite made through the multilayered bonding of reinforced aluminium sheets with aramid fiber now faces the marketing phase, and especially its excellent fatigue resistance and mechanical properties promote active researches on the similar products of hybrid composite. This study aims to investigate the effects of CFRP volume ratio and fiber's orientation over the properties of mechanical strength and fatigue life of the hybrid composite, AI7075/CFRP. To carry out this study, static tensile and fatigue tests were given to some of the panels which, made through the co-cure processing in an autoclave, have different CFRP volume ratio and carbon fiber orientations.

• The Journal of Advanced Prosthodontics
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• 제12권4호
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• pp.189-196
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• 2020

PURPOSE. The aim of the present study was to investigate the effects of surface treatments on the bond strengths between polymer-containing restorative materials and two dual-cure resin cements. MATERIALS AND METHODS. In the present study, rectangular samples prepared from Lava Ultimate (LU) and Vita Enamic (VE) blocks were used. The specimen surfaces were treated using CoJet sandblasting, 50 ㎛ Al₂O₃ sandblasting, % 9 HF (hydrofluoric) acid, ER,Cr:YSGG laser treatment, and Z-Prime. Dual-cure resin cements (TheraCem and 3M RelyX U 200) were applied on each specimen's treated surface. A micro-tensile device was used to evaluate shear bond strength. Statistical analysis was performed using the SAS 9.4v3. RESULTS. While the bond strength using TheraCem with LU or VE was not statistically significant (P=.164), the bond strength using U200 with VE was statistically significant (P=.006). In the TheraCem applied VE groups, Z-Prime and HF acid were statistically different from CoJet, Laser, and Sandblast groups. In comparison of TheraCem used LU group, there was a statistically significant difference between HF acid and other surface treatments. CONCLUSION. The bonding performance between the restorative materials and cements were material type-dependent and surface treatment had a large effect on the bond strength. Within the limitations of the study, the use of both U200 and TheraCem may be suggested if Z-prime was applied to intaglio surfaces of VE. The cementation of LU using TheraCem is suitable after HF acid conditioning of the restoration surfaces.

• 대한치과교정학회지
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• 제41권2호
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• pp.121-126
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• 2011

Objective: The purpose of this study was to evaluate shear bond strength (SBS) and failure site location of brackets bonded to enamel with or without desensitizer application. Methods: Sixty-six freshly extracted human premolar teeth were randomly divided into 3 groups of 22. Group 1 served as the control. Desensitizer was applied to the remaining teeth at two time intervals (Group 2, bonded immediately after Pro-$Relief^{TM}$ (Colgate-Palmolive Co., New York, NY, USA) application and Group 3, bonded 30 days after Pro-$Relief^{TM}$ application with the teeth stored in artificial saliva during the 30 days). Orthodontic brackets were bonded with a light cure composite resin and cured with a halogen light. After bonding, the SBS of the brackets was tested using a universal testing device. Adhesive remnant index (ARI) scores were determined after the brackets failed. Data were analyzed with analysis of variance, Tukey's HSD, and G tests. Results: The SBS was significantly lower in Group 2 than in Groups 1 (p = 0.024) and 3 (p = 0.017). Groups 1 and Group 3 did not differ (p = 0.991). ARI scores did not differ significantly among groups. Conclusions: The Pro-$Relief^{TM}$ desensitizer agent applied immediately before bonding significantly reduces bond strength, but the SBS values still exceed the minimum 5.9 - 7.8 MPa required for adequate clinical performance. Immersing the teeth in artificial saliva for 30 days after applying the Pro-$Relief^{TM}$ desensitizer agent and before bonding increased the SBS to control levels.

• 대한화학회지
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• 제46권3호
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• pp.233-240
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• 2002

본 연구에서는 잠재성 양이온 개시제 (N-benzyl pyrazinium hexafluoroantiminate, BPH)를 이용한 에폭시/폴리우레탄 블랜드계의 혼합조성에 따른 경화거동과 유변학적 특성 그리고 기계적 물성 변화에 대하여 연구하였다. 블랜드계의 반응성은 DSC를 이용하여 반응 온도에 따른 전환률을 구하여 측정하였으며, 유변학적 특성은 레오미터를 이용한 등온 실험을 통하여 측정하였고, 가교 활성화에너지(Ec)는 겔화 시간과 경화 온도를 이용하여 Arrhenius 방정식으로 구하였다. 한편, 경화된 시편의 기계적 물성은 충격강도 실험을 통하여 측정하였다. 실험결과, 블랜드계의 열잠재성 촉매로 사용된 BPH는 어떤 공개시제 없이도 우수한 촉매 특성을 나타내었다. 본 블랜드계의 가교 활성화에너지 및 충격강도는 PU가 30 wt% 첨가되었을 때 최대를 나타내었는데, 이는 EP와 PU간의 수소결합으로 인한 치밀한 가교밀도의 증가 때문이라고 사료된다.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2004년도 춘계학술대회 논문집
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• pp.404-409
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• 2004

To maximize the productivity in machining molds and dies, machine tools should operate at high speeds. During the high speed operation of moving frames or spindles, vibration problems are apt to occur if the machine tool structures are made of conventional steel materials with inferior damping characteristics. However, self-excited vibration or chatter is bound to occur during high speed machining when cutting speed exceeds the stability limit of machine tool. Chatter is undesirable because of its adverse effect on surface finish, machining accuracy, and tool life. Furthermore, chatter is a major cause of reducing production rate because, if no remedy can be found, metal removal rates have to be lowered until vibration-free performances is obtained. Also, the resonant vibration of machine tools frequently occurs when operating frequency approaches one of their natural frequencies because machine tools have several natural frequencies due to their many continuous structural elements. However, these vibration problems are closely related to damping characteristics of machine tool structures. The polymer concrete has high potential for machine tool bed due to its good damping characteristics with moderate stiffness. This paper presents the use of polymer concrete and sandwich structures to overcome vibration problems. Also, co-cure bonding method for functional part mounting was exhibited experimentally, by which manufacturing time and cost for polymer concrete bed will be remarkably reduced.

• Restorative Dentistry and Endodontics
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• 제15권1호
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• pp.107-119
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• 1990

The purpose of this study was to evaluate the marginal adaptability of the amalgam restorations in applying the cavity varnish (Copalite$^{(R)}$) and dentin bonding agent (Scotchbond 2$^{(R)}$) under the scanning electron microscope. For this study, eighteen sound extracted human molars were selected. Class I cavities in 12 teeth and class V cavities in 6 teeth were prepared using an air turbine with No. 701 tungsten carbide bur and finished using a low speed handpiece with No. 557 fissure bur. The prepared specimens were then divided into three groups including 4 class I cavities and 2 class V cavities in each group and restored as follows ; Group I. All the prepared cavities were restored with amalgam only (Control). Group II. Two layers of Copalite$^{(R)}$ cavity varnish were applied to the cavities with a gentle stream of air after each application and cavities were restored with amalgam. Group III. The enamel cavity margins were etched with 37% phosphoric acid gel for 60 sec., rinsed for 30 sec. and dried. One layer of visible lightcured Scotchbond Dental Adhesive$^{(R)}$ was applied and immediately cured for 20 seconds with visible light-cure unit and cavities were restored with amalgam. All the specimens were cut at the neck of the teeth and the occlusal halves of specimens were sectioned buccolingually in the longitudinal axis centering the amalgam restorations, using the disk. The cut specimens were ground with sandpapers (400, 600, 800, 1000 grit), and cleaned for 5 minutes in the ultrasonic cleaner (Brason Co. U.S.A.). In the cut surfaces, the amalgam - tooth interfaces were examined under the scanning electron microscope (JSM, 35C type, JEOL). The obtained results were as follows ; 1. The amalgam-tooth interfaces were reduced more significantly in the Copalite$^{(R)}$ and Scotchbond 2$^{(R)}$ application group than in the control group. 2. In the class I cavities, the Scotchbond 2$^{(R)}$ application group showed the findings similar to the Copalite$^{(R)}$ application group in the cavity floor, and the marginal adaptability was better in the side wall than in the cavity floor. 3. In the class I cavities, the Scotchbond 2$^{(R)}$ application group showed better marginal adaptability in the occlusal margin than in the gingival margin. 4. The marginal adaptability was in the order of the Scothbond 2$^{(R)}$ application group, the Copalite$^{(R)}$ application group and the control group.

• 대한치과교정학회지
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• 제38권4호
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• pp.275-282
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• 2008

본 연구는 포세린 표면에 $CO_2$ 레이저를 조사하여 세라믹 브라켓을 부착 후 전단결합강도를 측정하고, 산부식처리 및 샌드블라스트 등의 일반적인 방법을 시행하여 그 결과를 비교 분석하여 레이저 표면처리의 효과를 연구하고자 시행되었다. 90개의 포세린($8\;{\times}\;8\;{\times}\;4\;mm$) 시편을 제작하여 각각 10개씩 9개군으로 나누었다. 대조군(C)으로 아무런 표면처리를 하지 않은 글레이즈 표면을 사용하였으며, 실험군은 인산 처리군(OFA), 인산과 silane 처리군(OFA + S), 샌드블라스팅 처리군(SB), 샌드블라스팅과 silane 처리군(SB + S), 레이저 처리군(L), 레이저와 silane 처리군(L + S), 불산 처리군(HFA), 불산과 silane 처리군(HFA + S)으로 분류하였다. 만능시험기를 이용하여 전단결합강도를 측정하고 그 파절양상을 비교 분석한 결과 불산과 silane을 동시에 처리한 군에서 가장 높은 값($13.92\;{\pm}\;1.92\;MPa$)을 보였으며, 측정값은 SB + S ($10.16\;{\pm}\;1.27\;MPa$), HFA (10.09\;{\pm}\;1.07\;MPa$), L + S ($8.25\;{\pm}\;1.24\;MPa$), L ($7.86\;{\pm}\;0.96\;MPa$), OFA + S ($7.22\;{\pm}\;1.09\;MPa$), SB ($3.41\;{\pm}\;0.37\;MPa$), OFA ($2.81\;{\pm}\;0.37\;MPa$), 대조군($2.46\;{\pm}\;1.36\;MPa$) 순이었다. 브라켓 부착 시 치과용 레이저를 이용한 포세린의 표면처리 결과 전단결합강도의 값은 임상적으로 받아들여질 만한 수치를 보였으며 레이저와 silane을 동시에 처리한 군과는 통계적으로 유의할 만한 차이를 보이지 않았다(p > 0.05). 이상의 연구결과는 포세린 표면에 세라믹 브라켓 부착 시 2-watt의 $CO_2$ 레이저를 사용하여 전처리를 하는 방법은 시간절약의 관점에서 임상적으로 표면 전처리의 적절한 치료 대안이 될 수 있음을 보여주었다.