• Journal of Biomedical Engineering Research
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• v.24 no.5
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• pp.401-410
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• 2003

This study investigates the biomechanical efficacies of various cement augmentation techniques with or without pressurization for varying degrees of osteoporotic femur. For this study, a biomechanical analysis using a finite element method (FEM) was undertaken to evaluate surgical procedures, Simulated models include the non-cemented(i.e., hip screw only, Type I), the cement-augmented(Type II), and the cemented augmented with pressurization(Type III) models. To simulate the fracture plane and other interfacial regions, 3-D contact elements were used with appropriate friction coefficients. Material properties of the cancellous bone were varied to accommodate varying degrees of osteoporosis(Singh indices, II∼V). For each model. the following items were analyzed to investigate the effect surgical procedures in relation to osteoporosis of varying degrees : (a) von Mises stress distribution within the femoral head in terms of volumetric percentages. (b) Peak von Mises stress(PVMS) within the femoral head and the surgical constructs. (c) Maximum von Mises strain(MVMS) within the femoral head, (d) micromotions at the fracture plane and at the interfacial region between surgical construct and surrounding bone. Type III showed the lowest PVMS and MVMS at the cancellous bone near the bone-construct interface regardless of bone densities. an indication of its least likelihood of construct loosening due to failure of the host bone. Particularly, its efficacy was more prominent when the bone density level was low. Micromotions at the interfacial surgical construct was lowest in Type III. followed by Type I and Type II. They were about 15-20% of other types. which suggested that pressurization was most effective in limiting the interfacial motion. Our results demonstrated the cement augmentation with hip screw could be more effective when used with pressurization technique for the treatment of intertrochanteric fractures. For patients with low bone density. its effectiveness can be more pronounced in limiting construct loosening and promoting bone union.

• The Journal of Korean Academy of Prosthodontics
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• v.42 no.5
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• pp.597-607
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• 2004

Purpose: This study was peformed to investigate the retrievability of the cemented crown from the cementation type implant abutment. Material and method: The cementation type implant abutments (NEOBIOTECH implant abutment regular, 3 degree taper, 10mm length, 4mm diameter, Ti grade III, machined surface. Hwasung, Kyunggi-do) and cemented crowns were divided into 3 groups, depending on their hole angles formed in the crowns for their retrievability. The abutments and crowns were luted with 4 kinds of cements and separation test using metal wedge was executed with Instron 4465 Universal Testing Machine and the maximum impact force of the modified crown ejector was measured. Results and conclusion : 1. All of the cementation type implant abutments and cemented crowns were separated with relatively small force by metal wedge. 2. The retrieving force was minimum when the metal wedge was applied perpendicular to the axis of abutment. 3. The force for retrieving crowns from abutments was maximum in resin cement group, and reduced in orders of zinc phosphate cement, glass ionomer cement and zinc oxide eugenol cement. 4. The maximum force obtained by the crown ejector was higher than the retrieval force in ZOE and GI cement and lower than that in ZPC and resin cement. 5. If it has similar conditions clinically, the cemented crowns luted with 2 types of cements (ZOE, GI cement) can be safely retrieved from the cementation type implant abutments by the modified crown ejector.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.224-227
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• 2004

The cement can be influenced by the temperature. Especially, when it is cold weather, it causes some problems in such properties as mixing, placing and curing of concrete. According to the Concrete Standard Specification(2003), in case of the average daily outdoor temperature below $4^{\circ}C$, it recommends to use the cold weather concrete. In this research, the on-site quality characteristics of the cold weather concrete using high early strength portland cement(Type III cement) were studied. As a result, the cold weather concrete using high early strength portland cement can obtain its excellent properties and benefit the cost of construction.

• Restorative Dentistry and Endodontics
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• v.12 no.2
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• pp.111-116
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• 1987

The experimental study was made to evaluate the influence of retentive grooves on the canal wall upon the retention of post, using different type of cements. Ninety periodontally involved anterior teeth were extracted and divided into six groups of 15 teeth. The groups were labeled as follows: Group I: Dentatus post cemented zincphosphate cement into post hole with smooth wall. Group II: Dentatus post cemented with zincphosphate cement into post hole with retentive grooves. Group III: Dentatus post cemented with glass-ionomer cement into post hole with smooth wall. Group IV: Dentatus post cemented with glass-ionomer cement into post hole with retentive grooves. Group V: Dentatus post cemented with composite resin adhesive into post hole with smooth wall. Group VI: Dentatus post cemented with composite resin adhesive into post hole with retentive grooves. The tensile strength was tested by an Instron type tester with cross-head speed of 5mm per minute. The results were as follows: In the group without retentive grooves, three kinds of cement have little effect upon retentive capacity of Dentatus post. The Dentatus post cemented on the canal wall with retentive grooves is more retentive than Dentatus post without retentive grooves.

• The Journal of Korean Academy of Prosthodontics
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• v.29 no.1
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• pp.13-22
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• 1991

This study investigated the effects of surface treatment on the tensile bond strength of resinbonded prosthesis. The Rexillium III specimens were treated with $50{\mu}m\;Al_2O_3$ blasting. Type IV gold alloy specimens were treated with $400^{\circ}C$ heating and tin plating method. All specimens were bonded with MBAS composite resin cement and followed by immersion test into the $37^{\circ}C$ water bath for 7 days. The specimens were debonded in tension with an Instron machine and observed with SEM. The modes of failure were recorded also. The following conclusions were obtained : 1. The tensile bond strength decreased in following order. $50{\mu}m\;Al_2O_3$ basted Resillium III group, Type IV gold alloy group treated with $400^{\circ}C$ heat and tin plating type IV gold alloy group, and statistical significant differences were observed(p<0.05). 2. The tensile bond strength decreased in all groups after 7 days immersion test, but statistical significant differences were observed in Rexillium III specimens only. 3. The sharp and irregular surface were observed in Rexillium III, but $400^{\circ}C$ heat treated and tin plated groups had round and broad surface in SEM. 4. The models of bond failure were cohesive-adhesive failure mainly.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05b
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• pp.485-488
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• 2006

The shrinkage properties of the high strength concrete using the cement of Type I, Type III and Type IV was examined, and the following results were obtained. (1) Consideration of the autogenous shrinkage when evaluating appropriately the shrinkage properties of the high strength concrete is indispensable. (2) The autogenous shrinkage prediction expression of JSCE can estimate the properties of autogenous shrinkage of the cement made from korea with in general sufficient accuracy. (3) It is necessary to advance examination which used Korean aggregate about dry shrinkage from now on, and to attain highly accuracy of the autogenous shrinkage prediction expression.

• Journal of the Korea Concrete Institute
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• v.21 no.6
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• pp.729-735
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• 2009

In this study, it is experimentally verified a feasibility of the wasted phosphogypsum ($CaSO_4/H_2O$) that is a byproduct from the phosphoric acid process of manufacturing fertilizers can be applied as an admixture in slag cement. For the test, phosphogypsum is modified as dihydrate, hemihydrate, type III anhydrite, and type II anhydrite, and then chemical characteristics and mechanical properties of various slag cements containing above mentioned gypsum materials were analyzed. The test results show that the gypsum made at high temperature has better quality with decrease of water-soluble phosphoric acid ($S-P_2O_5$) which has an effect on the quality of cement. And type II anhydrite shows superior quality in terms of drying shrinkage and the compressive strength of cement paste with hemihydrate at 56 days is higher than other gypsum material.

• Journal of the Korea institute for structural maintenance and inspection
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• v.11 no.6
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• pp.143-151
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• 2007

This study presents the experimental results of frost durability including resistance to freezing-thawing and surface scaling of concrete. Mixing design was proportioned with the various water-binder ratio between 0.37 and 0.47 and three different binder compositions corresponding to Type I cement without any supplementary cementitious materials(OPC), Type II cement with 50% blast-furnace slag replacement(BFS50), and ternary cement with Type III cement, 15% fly ash, and 35% slag replacement (BFS35%+FA15%). Test results showed that the mixing design with BFS50% and BFS35%+FA15% exhibited higher durability factor than that made with OPC only. Finally, the use of blend cement containing slag can be used effectively in terms of frost durability of the concrete exposed to severe condition under coastal environment like as flying salt, sea water spray, etc.

• Restorative Dentistry and Endodontics
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• v.12 no.1
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• pp.119-129
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• 1986

The purpose of this study was to evaluate the marginal leakage of glass ionomer cement with different cavosurface margins. 192 class V cavities were prepared on freshly extracted non-carious teeth and glass ionomer cement were inserted according to the manufacturer's instructions. Cavity preparations for this investigation were performed in four groups. The experimental specimens were made by packing the glass ionomer cement (Fuji Ionomer Type II G-C Co. Japan) into the prepared 192 cavities of four groups with different modes: Group I. - The 48 cavities with $90^{\circ}$ butt-joint cavosurface preparation and restored with glass ionomer cement. Group II. - The 48 cavities with butt-joint preparation modified by $135^{\circ}$ beveling the cavosurface in the dentin and restored with glass ionomer cement. Group III. - The 48 cavities with butt-joint preparation modified by cutting a chamfer in the dentin and restored with glass ionomer cement. Group IV. - The same 48 cavities as group I, and overfilled with glass ionomer cement beyond the cavosurface angle. And four groups above described divided into three subgroups by means of conditioning the cavity walls: Control group. - Glass ionomer cement filled in the prepared 64 cavities after being cleaned with a stream of tap water. Phosphoric acid treatment group. - Glass ionomer cement filled in the prepared 64 cavities after being conditioned with a 50% phosphoric acid. Citric acid treatment group. - Glass ionomer cement filled in the prepared 64 cavities after being conditioned with a 50% citric acid. All 192 specimens were immersed in the 2.0% basic fuchsin solution and subjected to thermal stress at one-minute intervals ($4{\pm}2^{\circ}C$ to $60{\pm}2^{\circ}C$) for 70 minutes before exposure to the dye. The specimens were sectioned ecclesiologically through the center of the restorations for different periods of immersion time, 24 hours, 7 days, 14 days 30 days. The sections were examined under a stereoscopic microscope. The results were as follows: 1. The degree of marginal leakage in group II and III was greater than that in group I and IV. 2. The degree of marginal leakage in phosphoric acid treatment group was similar with that in control group. 3. The degree of marginal leakage in citric acid treatment group was less than that in control group. 4. In all groups, the degree of marginal leakage in phosphoric acid treatment group was greater than that in citric acid treatment group. 5. There is no statistical difference of the degree of marginal leakage according to the immersion time in the dye solution.

• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.3
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• pp.144-151
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• 2010

In this study, it is investigated the mechanical chemical properties of cement matrix using phosphogypsum and kaolin as a admixture for the substitutive materials to silica fume which is so expensive. For the test, phosphogypsum is modified as dihydrate, hemihydrate, type III anhydrite, and type II anhydrite, respectively and furnaced kaolin at $900^{\circ}C$ was also manufactured into meta kaolin by air cooling and water cooling method. The chemical characteristic and mechanical properties of various type of blended cements contained above mentioned gypsum and meta kaolin materials analyzed and compared with those characteristics of cement matrix with silica fume. From the test, the cement mixed meta kaolin made in water cooling has more excellent quality than other material.