MACRO-SHEAR BOND STRENGTH AND MICRO-SHEAR BOND STRENGTH OF CEROMER BONDED TO METAL ALLOY AND FIBER REINFORCED COMPOSITE

Park Hyung-Yoon,Cho Lee-Ra,Cho Kyung-Mo,Park Chan-Jin The Korean Academy of Prosthodonitics 2004 대한치과보철학회지 Vol.42 No.6

Statement of problem. According to the fracture pattern in several reports, fractures most frequently occur in the interface between the ceromer and the substructure. Purpose. The aim of this in vitro study was to compare the macro shear bond strength and microshear bond strength of a ceromer bonded to a fiber reinforced composite (FRC) as well as metal alloys. Material and methods. Ten of the following substructures, type II gold alloy, Co-Cr alloy, Ni-Cr alloy, and FRC (Vectris) substructures with a 12 mm in diameter, were imbedded in acrylic resin and ground with 400, and 1, 000-grit sandpaper. The metal primer and wetting agent were applied to the sandblasted bonding area of the metal specimens and the FRC specimens, respectively. The ceromer was placed onto a 6 mm diameter and 3 mm height mold in the macro-shear test and 1 mm diameter and 2 mm height mold in the micro-shear test, and then polymerized. The macro- and micro-shear bond strength were measured using a universal testing machine and a micro-shear tester, respectively. The macro- and micro-shear strength were analyzed with ANOVA and a post-hoc Scheffe adjustment ($\alpha$ = .05). The fracture surfaces of the crowns were then examined by scanning electron microscopy to determine the mode of failure. Chi-square test was used to identify the differences in the failure mode. Results. The macro-shear strength and the micro-shear strength differed significantly with the types of substructure (P<.001). Although the ceromer/FRC group showed the highest macroand micro-shear strength, the micro-shear strength was not significantly different from that of the base metal alloy groups. The base metal alloy substructure groups showed the lowest mean macro-shear strength. However, the gold alloy substructure group exhibited the least micro-shear strength. The micro-shear strength was higher than the macro-shear strength excluding the gold alloy substructure group. Adhesive failure was most frequent type of fracture in the ceromer specimens bonded to the gold alloys. Cohesive failure at the ceromer layer was more common in the base metals and FRC substructures. Conclusion. The Vectris substructure had higher shear strength than the other substructures. Although the shear strength of the ceromer bonded to the base metals was lower than that of the gold alloy, the micro-shear strength of the base metals were superior to that of the gold alloy.

Research Trends in Hybrid Cross-Laminated Timber (CLT) to Enhance the Rolling Shear Strength of CLT(CLT의 rolling shear 향상을 위한 hybrid cross laminated timber 연구 동향)

( Seung Min YANG ),( Hwa Hyung LEE ),( Seog Goo KANG ) 한국목재공학회 2021 목재공학 Vol.49 No.4

본 연구는 고층 목조건축에 사용되는 대형 목재 패널인 CLT의 낮은 rolling shear strength를 개선하기 위해 hybrid CLT의 연구 개발 동향을 분석하였다. 이를 통해 CLT의 국산화를 위한 연구개발 방향에 활용 가능한 기초자료를 마련하고자 하였고, 낮은 rolling shear strength를 향상시키기 위한 방안으로 활엽수 층재 사용, 층재 배열 각도 변화, 구조용 목질복합체의 사용이 주를 이루고 있다. 활엽수 층재는 침엽수 보다 rolling shear strength와 shear modulus 모두 2배 이상의 높은 값을 나타내므로 활엽수 층재 사용 및 미이용 수종의 활용이 가능함을 확인하였다. 층재 배열 각도 변화에 따라 rolling shear stength 1.5배, shear modulus 8.3배, bending stiffness 4.1배 향상되어 층재 배열 각도를 감소시킴으로써 CLT 강도 향상을 확인하였다. 구조용 목질재료는 기존에 강도성능이 확보된 재료로 층재로 사용하였을 때 최대 MOR 1.35배, MOE 1.5배, rolling shear strength 2배 향상되었고, 층재 간의 접착강도 또한 집성재 블록전단강도 기준인 7.0 N/mm²을 확보할 수 있었다. 선행연구 결과를 통해 MOE 7.0 GPa, MOR 40.0 MPa 이상의 휨 특성을 가진 구조용 목질재료를 사용하였을 때 강도성능이 향상됨을 확인하였다. 이를 통해 구조용 목질재료 층재 강도 기준으로 판단하였다. rolling shear strength 개선하기 위한 최적의 방법은 기존 규격에 의한 강도값을 가진 구조용 목질재료의 적용이 가장 유리할 것으로 판단하나, 구조용 목질재료의 섬유 배열에 따른 CLT 층재 배열 방향, 층재 간 접착 강도 등에 대한 추가적인 연구가 필요하다. In this study, hybrid CLT research and development trends were analyzed to improve the low rolling shear strength of CLT, a large wooden panel used in high-rise wooden buildings. Through this, basic data that can be used in research and development directions for localization of CLT were prepared. As a way to improve the low rolling shear strength, the use of hardwood lamina, the change of the lamina arrangement angle, and the use of structural composite materials are mainly used. Rolling shear strength and shear modulus of hardwood lamina are more than twice as high as softwood lamina. It confirmed that hardwoods can be used and unused species can be used. Rolling shear strength 1.5 times, shear modulus 8.3 times, bending stiffness 4.1 times improved according to the change of the layer arrangement angle, and the CLT strength was confirmed by reducing the layer arrangement angle. Structural wood-based materials have been improved by up to 1.35 times MOR, 1.5 times MOE, and 1.59 times rolling shear strength when used as laminas. Block shear strength between the layer materials was also secured by 7.0 N/㎟,which is the standard for block shear strength. Through the results of previous studies, it was confirmed that the strength performance was improved when a structural wood based materials having a flexural performance of MOE 7.0 GPa and MOR 40.0 MPa or more was used. This was determined based on the strength of layered materials in structural wood-based materials. The optimal method for improving rolling shear strength is judged to be the most advantageous application of structural wood based materials with strength values according to existing specifications. However, additional research is needed on the orientation of CLT lamina arrangement according to the fiber arrangement of structural wood-based materials, and the block shear strength between lamina materials.

A Study on the Block Shear Strength according to the Layer Composition of and Adhesive Type of Ply-Lam CLT(Ply-Lam CLT의 층재 구성 및 접착제 종류에 따른 블록전단강도에 관한 연구)

( Gyu Woong Choi ),( Seung Min Yang ),( Hyun Jae Lee ),( Jun Ho Kim ),( Kwang Hyeon Choi ),( Seog Goo Kang ) 한국목재공학회 2020 목재공학 Vol.48 No.6

본 연구에서는 공학목재로 목구조건축에 주로 사용되는 집성재 및 CLT 그리고 Ply-lam CLT의 블록전단시험을 실시하여 강도 및 파괴 유형을 비교 분석하였다. 이를 통해 Ply-lam CLT의 라미나 및 합판의 수종, 접착제의 종류 및 Layer구성 등 최적생산을 위한 제조조건을 구명하고자 하였으며 그 결과는 다음과 같다. 블록전단시험을 통해 집성재, Ply-lam CLT, CLT 순으로 높은 강도를 나타냈다. 특히, 낙엽송 합판과 낙엽송 라미나의 복합구조로 제조되는 Ply-lam CLT의 전단강도는 집성재 전단강도 기준인 7.1 N/mm²을 통과하였다. 아울러 본 연구에서는 집성재, CLT, Ply-lam 접착에 사용된 접착제 종류에 따른 전단강도의 차이는 나타나지 않았다. 그러나 Ply-lam CLT의 경우에는 라미나와 합판의 수종에 따라 Ply-lam CLT의 전단강도의 차이를 나타냈다. 그 결과는 낙엽송 > 남양재 ≒ 육송 합판 순으로 높은 강도를 나타났다. Ply-lam CLT의 최적구성은 낙엽송 합판과 낙엽송 라미나를 사용하는 경우이며 접착제는 용도에 따라 PRF, PUR을 선정하여 사용하면 될 것으로 판단된다. 목질재료 유형에 따른 전단강도 파괴 양상 결과 분석을 통하여 집성재는 shear parallel-to-grain, CLT는 rolling shear, Ply-lam CLT는 shear parallel-to-grain과 rolling shear가 복합적으로 나타났다. 이는 전단강도 결과와 밀접한 관련이 있으며 rolling shear로 인하여 CLT보다 Ply-lam CLT에서 더 높은 전단 강도를 나타내는 것으로 판단된다. In this study, a block shear strength test was conducted to compare and analyze the strength and failure mode on the glued laminated timber, CLT, and Ply-lam CLT, which are mainly used for the construction of wood construction as engineering wood. Through this, the Ply-lam CLT manufacturing conditions for optimum production, such as the type of lamina, plywood, adhesive, and layer composition, were investigated. The results are as follow. Through block shear strength test, it showed high strength in the order of glued laminated timber, Ply-lam CLT and CLT. In particular, the shear strength of Ply-lam CLT, which is made of a composite structure of larch plywood and larch lamina, passed 7.1 N/mm², which is a Korean industrial standards for block shear strength of structural glued laminated timber. In addition, in this study, there was no different in shear strength according to the adhesive type used for glulam, CLT, and Ply-lam CLT adhesion. However, in the case of Ply-lam CLT, the difference in shear strength of Ply-lam CLT was shown according to the type of lamina and plywood. The results showed high strength in the order of Larix kaempferi > Mixed light hardwood ≒ Pinus densiflora, sieb, et, Zucc plywood. The optimal configuration of Ply-lam CLT is when larch plywood and larch lamina are used, and it is decided that the adhesive can be used by selecting PRF and PUR according to the application. The results of block shear strength failure mode by type of wood based materials were analyzed. The failure mode showed shear parallel-to-grain for glulam, rolling shear for CLT, and shear parallel-to-grain and rolling for ply-lam CLT. This is closely related to shear strength results and is decided to indicate higher shear strength in Ply-lam CLT than in CLT due to rolling shear.

Perfobond rib 전단연결재의 전단강도 및 잔류강도 평가

안진희(Ahn Jin Hee),김상효(Kim Sang Hyo),구현본(Koo Hyun-Bon),강균희(Kang Gyun Hee) 대한토목학회 2007 대한토목학회논문집 A Vol.27 No.2A

본 논문에서는 실험적 연구를 통해 perfobond 전단연결재의 전단거동 특성과 피로하중에 따른 잔류강도 변화를 평가하였다. 이를 위해 총 18개의 perfobond 전단연결재 시험체를 제작하였으며, 이들 시험체에 대한 정적 및 피로 직접전단실험을 실시하여 홀 관통철근콘크리트 다웰효과반복하중 작용 등이 전단강도에 미치는 영향을 분석하였다. 실험결과, perfobond 전단연결재의 전단강도에서 콘크리트 다웰효과는 최대전단강도의 약 65%를 차지하고, perfobond 전단연결재 홀에 배치된 관통철근은 전단강도를 100% 이상 증가시키는 것으로 나타났다. 특히, 홀 관통철근은 전단연결부 파괴시 하중-슬립 거동의 연성을 현저히 향상시키는 것으로 나타났다. 두 종류의 피로하중(도로교설계기준에 명시된 설계하중과 설계하중의 50%)을 일정횟수 반복재하한 후 정적 직접전단실험을 통해 측정한 perfobond 전단연결재의 잔류강도는, 홀 관통철근이 없는 시험체의 잔류강도는 최대전단강도의 약 65% 수준으로 저하되었으나, 홀 관통철근이 설치된 시험체의 잔류강도는 반복재하하중에 의하여 크게 감소되지 않음을 확인할 수 있었다. 따라서, 교량과 같이 피로하중이 빈번히 작용하는 구조물에 perfobond 전단연결재를 사용할 경우, 전단강도의 저하를 방지하기 위해 홀 관통철근 배근이 필요한 것으로 나타났다. This paper deals with the static shear strength and residual strength after cyclic loading of perfobond rib shear connectors. A total of eighteen push-out specimens with perfobond rib shear connectors were fabricated and a series of static and residual push-out tests were conducted. Then, the influences of hole crossing bars, concrete dowel, and cyclic loading on the shear strength were evaluated experimentally. As a results of this study, it is proved that the concrete dowel action is charge of 65% in ultimate shear strength of perfobond shear connectors, and the hole crossing bars increase the shear strength of that in two times. Especially, at the time of failure of shear connectors, the hole crossing bars significantly increase ductility of load-slip behavior. According to the residual push-out tests applying two types of cyclic loadings, design load and 50% of design load specified in Korean Highway Bridge Design Code, the residual strength, which was drawn by static push-out test after cyclic loadings, of the specimens without hole crossing bars were reduced to 65% of ultimate strength. However, the residual strength of the hole crossing bars were not reduced significantly. Therefore, as the perfobond shear connectors are applied to the Bridges which are frequently subjected to the fatigue loadings, it is designable to install hole crossing bar in order to prevent reducing of shear strength by fatigue loadings.

Flexural behavior of high-strength steel hybrid composite beams

Jun, Su-Chan,Lee, Cheol-Ho,Han, Kyu-Hong,Kim, Jin-Won Elsevier 2018 Journal of constructional steel research Vol.149 No.-

<P><B>Abstract</B></P> <P>In this study, hybrid utilization of high-strength steel in composite beams was proposed in order to maximize their flexural capacity and full-scale testing was conducted in two phases to investigate their flexural behavior. In fabricating specimens, high-strength steels were utilized for the bottom flange while normal-strength steels were used for the top flange and the web. In Phase I testing, however, all the high-strength steel bottom flange specimens were not able to reach their plastic moment by about 10–15% due to unexpected longitudinal shear failure along the beam axis, although sufficient shear studs were provided for full composite behavior and the plastic neutral axis location was limited within 15% of the total depth of the composite beam section. The specimens in Phase II testing designed with additional shear reinforcements showed no longitudinal shear cracking and developed their plastic capacity with reasonable deformability as intended in design. This implies that, different from the design of conventional composite beams, checking the longitudinal shear strength of composite concrete slab is crucial when designing hybrid composite beams utilizing high-strength steels. The nominal longitudinal shear strength was well predicted by the shear-friction based models in ACI 318-14 and AASHTO LRFD. The test results of this study show that when the limitation on the depth of the plastic neutral axis set forth by Eurocode 4 is satisfied along with sufficient longitudinal shear strength, the plastic stress design method can still be applied to the design of hybrid composite beams utilizing high-strength steels whose nominal yield strength is as high as 650 MPa.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Hybrid utilization of high-strength steel in composite beams to maximize their flexural capacity is presented. </LI> <LI> The longitudinal shear failure of the concrete slab is one of the critical limit states in hybrid composite beams. </LI> <LI> The reliability of the design equations for the longitudinal shear strength among representative standards is evaluated. </LI> <LI> The plastic stress design method can still be applied to high-strength hybrid composite beams. </LI> </UL> </P>

Evaluation of punching shear strength of voided slabs considering the effect of the ratio b₀/d

Chung, Joo-Hong,Bae, Baek-Il,Choi, Hyun-Ki,Jung, Hyung-Suk,Choi, Chang-Sik Elsevier 2018 ENGINEERING STRUCTURES Vol.164 No.-

<P><B>Abstract</B></P> <P>Voided slabs have been used as an effective technique to replace the heavy reinforced-concrete solid slabs. In voided slabs, the punching shear strength varies according to the arrangement of voids around the column because voids intersecting a failure surface anywhere along its radial length can directly reduce the punching shear strength and voids outside a failure surface can also reduce the punching shear strength by making the variation of shear stress around its perimeter. In this study, the punching shear strength of voided slabs was evaluated according to the arrangement of voids through experimental tests and numerical simulations. As a result, the factors on influencing the punching shear strength of voided slabs were determined as the void-based reduction of the cross-sectional area at the control perimeter and the ratio of the length of the control perimeter to the effective depth of the slab. Based on these influencing factors, a new method was developed to determine that the control perimeter section produces the smallest shear strength. This method can estimate the punching shear strength of voided slab systematically by assuming the location of the control perimeter at the solid region or voided region.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Test results of punching shear strength of voided slabs. </LI> <LI> Numerical investigation of the punching shear strength of voided slab. </LI> <LI> Punching shear strength evaluation of voided slabs which have affected by the arrangement of voids. </LI> <LI> Newly developed control perimeter calculation method for punching shear. </LI> </UL> </P>

전단철근으로 보강되지 않은 강섬유보강 초고강도콘크리트의 전단강도에 대한 실험적 연구

배백일(Bae, Baek-Il),최현기(Choi, Hyun-Ki),최창식(Choi, Chang-Sik) 대한건축학회 2017 大韓建築學會論文集 : 構造系 Vol.33 No.3

In this study, fiber reinforced ultra high strength concrete beams were tested defining the shear behavior of fiber reinforced ultra high strength concrete and evaluating the previously suggested equations for shear strength of concrete members. The main variables of test are compressive strength of concrete(100, 200 MPa), volume fraction of steel fiber(0, 2%), shear-span to depth ratio(3.4, 2.0). According to the test results, specimens without fiber experienced the abrupt shear failure. In the case of fiber reinforced specimen with shear span ratio of 3.4, failure mode of test specimen is changed into flexural failure. And specimen with shear span ratio 2.0 experienced shear-compression failure mode. However, shear strength increase caused by the increase of compressive strength of concrete is not higher than effect of steel fiber inclusion. In order to make safe design of fiber reinforced ultra high strength concrete under shear, shear strength estimation equations are evaluated. Comparing estimated value with test results, shear strength contribution of matrix is over-estimated and shear strength contribution of steel fiber is under-estimated. Among all equations, equation of AFGC-Setra is most accurate.

Interfacial shear behavior of a high-strength pile to sleeve grouted connection

Lee, Jeong-Hwa,Won, Deok-Hee,Jeong, Youn-Ju,Kim, Seong-Hwan,Kang, Young-Jong Elsevier 2017 ENGINEERING STRUCTURES Vol.151 No.-

<P><B>Abstract</B></P> <P>A grouted connection is a type of structural composite connection member produced from two different-sized steel tubes and a grout annulus between them. The grouted connection has been widely used in offshore oil and gas platforms and wind turbine structures by simply grouting between the pile and sleeves. In general, the axial compression strength of the connection is known to be affected by the grout strength, shear-key spacing and radial stiffness parameters of the composite section. In this study, concentric and eccentric loading tests were performed to investigate the interfacial shear behavior of the high-strength grouted connections according to the shear-key spacings. The interface shear behaviors, focusing on the strength, failure mode, and strain of the grout and steel tubes, were evaluated by tests and finite element (FE) analysis. The test results showed that the primary strength of the connection was mainly affected by the grout strength, whereas the ultimate strength was affected by the yield strength of the sleeves and the friction coefficient between the steel tubes and grout. It was also concluded that the test results on the high-strength grouted connections were similar to those of previous studies on normal-strength grouted connections, and the eccentric loading did not reduce the axial capacity of the connection. Although the ultimate failure modes of the connections could not be considered in the current design equations, they may contribute to the safe design of high-strength grouted connections.</P> <P><B>Highlights</B></P> <P> <UL> <LI> This study investigated the interfacial shear behavior of high-strength grouted connections. </LI> <LI> Experimental studies were conducted to evaluate the strength and failure behavior of the connections. </LI> <LI> FE analysis was performed to elaborate upon the test results. </LI> <LI> The current design codes can enable the safe design of connections, although they do not consider the ultimate behavior of the sleeve and pile. </LI> <LI> The interfacial shear behavior of the connection was evaluated by the strength, failure mode, strains of the steel tubes and the grout annulus. </LI> </UL> </P>

A Study on Bracket-Adhesive Combinations in Aspect of Shear Bond Strength and Bond Failure

Han, Jae-Ik,Son, Woo-Sung 대한치과교정학회 1998 대한치과교정학회지 Vol.28 No.6

적절한 전단접착강도를 가지면서 법랑질손상과 브라켓파절을 적게 일으키는 브라켓-접착제의 그룹을 찾아내기 위하여 전단접착강도, 법랑질손상, 브라켓탈락양상, 브라켓 주위의 밀봉과 법랑질-접착제-브라켓 사이의 긴밀도를 연구하였다. 교정치료목적으로 발치한 240개의 치아를 각각 10개씩 24개 군으로 나누어서 브라켓을 접착한 후 48시간후에 전단접착강도를 측정하고 브라켓 탈락 양상을 조사하였다. 또한 브라켓주위의 밀봉과 법랑질-접착제-브라켓 사이의 긴밀도를 평가하기 위해서 브라켓이 접착된 치아를 반으로 자른후 주사전자현미경상에서 관찰하였다. 6종류의 브라켓과 4종류의 접착제가 사용되었으며 브라켓은 Image, Plastic, Crystaline, Fascination, Transcend, metal bracket을 사용하였으며 접착제로는 No-mix, Light-Bond, OrthoLC, Superbond C&B가 사용되었다. 이와같은 연구로 부터 다음과 같은 결론을 내렸다. 1. 전단접착강도는 Fascination-Light Bond 군에서 36.58Kg(410.07Kg/㎠)으로 가장 높았으며 Image-OrthoLC군에서 8.93Kg(75.51Kg/㎠)으로 가장 낮았다. OrthoLC를 접착제로 사용하였을 때 전단접착강도는 다른 접착제를 사용하였을 때 보다 비교적 낮았다. 2. 접착제의 종류에 관계없이 Fascination bracket의 전단접착강도는 비교적 높았으며 Image, Plastic bracket의 전단접착강도는 비교적 낮았다. Crystaline, Transcond bracket의 전단접착강도는 metal bracket의 전단접착강도와 비슷하거나 낮았다. 3. 전단접착강도와 법랑질 파절, 브라켓 파절은 상관관계가 있었으며, 접착강도가 증가할수록 법랑질 파절과 브라켓 파절은 증가하였다. 4. OrthoLC를 접착제로 사용하였을 때 법랑질 파절과 브라켓 파절은 일어나지 않았으나 Superbond C&B를 접착제로 사용하였을 때는 법랑질 파절과 브라켓 파절의 빈도가 높았다. 5. No-mix, Light-Bond를 접착제로 사용하였을 때 브라켓 주위의 밀봉과 법랑질-접착제-브라켓의 긴밀도는 양호하였다. 접착제의 종류에 관계없이 Ceramic bracket에서 접착제-브라켓의 긴밀도는 양호하였다. 6. 적절한 전단접착강도를 가지면서 법랑질 파절과 브라켓 파절을 일으키지 않은 군은 Crystaline-No mix, Crystaline-Light Bond, Crystaline-OrthoLC, metal-No mix, metal-Light Bond, metal-OrthoLC 군이였다. The purpose of the present study was to seek bracket-adhesive combinations which have adequate bond strength with no enamel and bracket fracture. The shear bond strengths were measured, the sites of failure and the enamel damage were investigated and the peripheral sealing and adaptation between enamel surface, bonging adhesive and bracket were evaluated, 240 noncarious human premolars were divided into twenty four groups of ten teeth. Shear bond strengths of each group were determined in an universal testing machine after two days passed and the debonded specimens were inspected to determine the predominant bond failure sites. To evaluate peripheral sealing and adaption between enamel surface adhesive and bracket, each specimen was cut longitudinally into two halves which included the midsection of the bracket, adhesive and enamel and examined in scanning electron microscope. Six different types of brackets were bonded to the tooth with four different type of adhesives. Six different types of brackets were Image, Plastic, Crystaline, Fascination, Transcend 2000 and metal bracket and four different adhesives were No-mix, Light-Bond, OrthoLC and Superbond C&B. From this study, it may be concluded that(1) The mean shear bond strength varied from a high of 36.58Kg(410.07Kg/㎠) with the Fascination-Light Bond combination group to a low 8.93Kg(75.51Kg/㎠) with the Image-OrthoLC combination group. When using OrthoLC as adhesive, the mean shear bond strength was significantly lower than that of other combination groups, (2) Regardless of adhesives, the mean shear bond strength of Fascination brackets was relatively high whereas Plastic and Image brackets had low shear bonding strength. The shear bond strength of Crystaline bracket and Transcend 2000 was relatively equal to or lower than that of metal bracket, (3) There was a correlation between bond strength, enamel damage and bracket fractrue. As the shear bond strength was increased, the rate of enamel damage and bracket fractrue were increased, (4) The combination groups that use OrthoLC as adhesive were debonded in shear stress without enamel fracture and bracket fracture, whereas the combination groups that use Superbond C&B as adhesive experienced a relative high enamel fracture rate and bracket fracture rate, (5) Peripheral sealing and adaptation between enamel-adhesive-bracket were relatively good when using Light-Bond or No-Mix as adhesive, Regardless of adhesives, adaptation between bracket-adhesive were relatively good in Ceramic brackets, (6) The combination groups which had adequate bonding strength with no enamel and bracket fracture were Crystaline-No mix, Crystaline-Light Bond, Crystaline-OrthoLC, metal-No mix, metal-Light Bond and metal-OrthoLC combination groups.

도재 수리시스템에 따른 도재와 복합레진의 전단결합강도

김경규,신상완,이정렬,김영수,Kim, Kyoung-Kyu,Shin, Sang-Wan,Lee, Jeong-Yeol,Kim, Young-Su 대한치과보철학회 2007 대한치과보철학회지 Vol.45 No.4

Purpose: This in vitro study evaluated shear bond strengths of surface treatment porcelains with four porcelain repair systems simulating intraoral bonding of composite resin to feldspathic porcelain or pressable porcelain. Material and methods: Eighty Porcelain disks were prepared. Group A: forty disk specimens were fabricated with Feldspathic Porcelain($Omega^{(R)}900$, Vident, Menlo Park, CA, USA). Group B: forty disk specimens were fabricated with Pressable Porcelain(IPS Empress 2 ingot, Ivoclar-Vivadent, Schaan, Liechtenstein, Germany). Each groups was divided into 4 subgroups and composite resin cylinders were bonded to specimen with one of the following four systems: Clearfil Porcelain Bond(L. Morita, Tustin, CA, USA), Ulradent Porcelain Etch. (Ultradent, Salt Lake City UT, USA), Porcelain Liner-M(Sun Medical Co., Kyoto, Japan), Cimara Kit(Voco, Germany). After surface conditioning with one of the four porcelain repair systems substrate surfaces of the specimen were examined microscopically(SEM). Shear bond strengths of specimens for each subgroup were determined with a universal testing machine (5mm/min crosshead speed) after storing them in distilled water at $37{\pm}1^{\circ}C$ for 24 hours. Stress at failure was measured in $MP_a$, and mode of failure was recorded. Differences among four repair systems were analyzed with two way ANOVA and Duncan test at the 95% significance level. Results: In the scanning electron photomicrograph of the treated porcelain surface, hydrofluoric acid etched group appeared the highest roughness. The shear bond strength of the phosphoric acid etched group was not significantly(p>0.05) different between feldspathic porcelain and pressable porcelain. But in no treatment and roughened with a bur group, the shear bond strength of the feldspathic porcelain was significantly higher than that of the pressable porcelain. In hydrofluoric acid etched group, the shear bond strength of the pressable porcelain was significantly higher(p<0.05). Conclusion: 1. Treatment groups showed significantly greater shear bond strengths than no treatment group(p<0.05). 2. Group with more roughened porcelain surface did not always show higher shear bond strengths. 3. In phosphoric acid etched group, there was no significant difference in shear bond strength between feldspathic porcelain and pressable porcelain(p>0.05). However in the other groups, there were significant differences in shear bond strengths between feldspathic porcelain and pressable porcelain(p<0.05).