• The Journal of Advanced Prosthodontics
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• v.10 no.1
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• pp.1-7
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• 2018

PURPOSE. The aim of this study was to evaluate the effects of abutment diameter, cement type, and re-cementation on the retention of implant-supported CAD/CAM metal copings over short abutments. MATERIALS AND METHODS. Sixty abutments with two different diameters, the height of which was reduced to 3 mm, were vertically mounted in acrylic resin blocks with matching implant analogues. The specimens were divided into 2 diameter groups: 4.5 mm and 5.5 mm (n=30). For each abutment a CAD/CAM metal coping was manufactured, with an occlusal loop. Each group was sub-divided into 3 sub-groups (n=10). In each subgroup, a different cement type was used: resin-modified glass-ionomer, resin cement and zinc-oxide-eugenol. After incubation and thermocycling, the removal force was measured using a universal testing machine at a cross-head speed of 0.5 mm/min. In zinc-oxide-eugenol group, after removal of the coping, the cement remnants were completely cleaned and the copings were re-cemented with resin cement and re-tested. Two-way ANOVA, post hoc Tukey tests, and paired t-test were used to analyze data (${\alpha}=.05$). RESULTS. The highest pulling force was registered in the resin cement group (414.8 N), followed by the re-cementation group (380.5 N). Increasing the diameter improved the retention significantly (P=.006). The difference in retention between the cemented and recemented copings was not statistically significant (P=.40). CONCLUSION. Resin cement provided retention almost twice as strong as that of the RMGI. Increasing the abutment diameter improved retention significantly. Re-cementation with resin cement did not exhibit any difference from the initial cementation with resin cement.

• The Journal of Advanced Prosthodontics
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• v.14 no.3
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• pp.162-172
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• 2022

PURPOSE. The present study aims to analyze the effect of abutment neck taper and types of cement on the amount of undetected remnant cement of cement-retained implant prostheses. MATERIALS AND METHODS. Three neck taper angles (53°, 65°, 77°) and three types of cement (RMGI: resin-modified glass ionomer, ZPC: zinc phosphate cement, ZOE: zinc oxide eugenol cement) were used. For each group, the surface percentage was measured using digital image and graphic editing software. The weight of before and after removing remnant cement from the abutment-crown assembly was measured using an electronic scale. Two-way ANOVA and Duncan & Scheffe's test were used to compare the calculated surface percentage and weight of remnant cement (α = .05). RESULTS. There were significant differences in remnant cement surface percentage and weight according to neck taper angles (P < .05). However, there were no significant differences in remnant cement surface percentage and weight on types of cement. No interaction was found between neck taper angles and types of luting cement (P > .05). The wide abutment with a small neck taper angle showed the most significant amount of remnant cement. And the types of luting cement did not influence the amount of residual cement. CONCLUSION. To remove excess cement better, the emergence profile of the crown should be straight to the neck taper of the abutment in cement-retained implant restoration.

• Journal of Dental Rehabilitation and Applied Science
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• v.22 no.4
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• pp.329-340
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• 2006

Statement of problem: Damping of the peak force transmitted to implants has been reported by in vitro studies using impact forces on resin-veneered superstructures. Theoretical assumptions suggest that use of acrylic resin for the occlusal surfaces of a prosthesis would protect the connection between implant and bone. Therefore, the relationship between prosthesis materials and the force transmitted through the implant system also needs to be investigated under conditions that resemble the intraoral mechanical environment. Purpose: The purpose of this study was to analyze the fracture strength and modes of temporary prosthesis when a flange or occlusally extended structure were connected on the top of the abutment. Material and method: Modified abutments of winged and bulk design were made by casting the desired wax pattern which is made on the UCLA type plastic cylinder. Temporary crowns were made using templates on the modified abutments, and its fracture toughness and strain were compared to the traditional temporary prosthesis. To evaluate the effect of aging, 5.000 times of thermocycling were performed, and their result was compared to the 24hours specimen result. Results: The following conclusions were drawn from this study: 1. In the fracture toughness test, temporary crown's fracture line located next to the screw hole while modified designs with metal support showed fracture line on the metal and its propagation along the metal-resin interface. 2. Wing and bulk structure didn't show significant difference in the fracture toughness (p>0.05), but wing structure showed stress concentration on the screw hole area compared to bulk structure which showed even stress distribution. 3. In the fracture toughness test after thermocycling, wing and bulk structure showed increased or similar results in metal supported area while off-metal area and temporary crown showed decreased results. 4. In the strain measurement after thermocycling, its value increased in the temporary and bulk structure. However, wing structure showed decreased value in the loading point while increased value in the screw hole area. Conclusion: Wing type design showed compatible result to the bulk type that its application with composite resin prosthesis to the implant dentistry is considered promising.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.1090-1097
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• 2008

This study conducted the decision method of lateral flow in abutment structures founded on the soft soils and the reliability analysis on the foundation pile for abutment. On the basis of the results, this study proposed the reliability design model. Reliability analysis was conducted by applying second moment method, point estimation method, and expected total cost minimization to lateral movement index, lateral movement decision index, modified lateral movement decision index, and circular failure safety factor for the decision criteria of lateral flow. The reliability index by analysis method had a similar tendency each other. Point estimation method was found as a practical method in the aspect of convenience because it could conduct the analysis only by mean and standard deviation as well as the partial derivative on random variables was not necessary. Optimum reliability index and optimum safety according to increasing in failure factors and load ratio were analyzed and loads and resistance factors of the design criteria of optimum reliability were estimated. It presented rational design model which can consider construction level and stability and economical efficiency overall.

• Geomechanics and Engineering
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• v.32 no.6
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• pp.601-613
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• 2023

Low liquid limit silt, widely distributed in the middle and down reaches of Yellow River, has the disadvantages of poor grading, less clay content and poor colloidal activity. It is very easy to cause vehicle jumping at the bridge-embankment transition section when the low liquid limit silt used as the backfill at the abutment back. In this paper, a series of laboratory tests were carried out to study the physical and mechanical properties of the low liquid limit silt used as back filling. Ground granulated blast furnace slag (GGBFS) was excited by active MgO and hydrated lime to solidify silt as abutment backfill. The optimum ratio of firming agent and the compaction and mechanical properties of reinforced soil were revealed through compaction test and unconfined compressive strength (UCS) test. Scanning electron microscope (SEM) test was used to study the pore characteristics and hydration products of reinforced soil. 6% hydrated lime and alkali activated slag were used to solidify silt and fill the model of subgrade respectively. The pavement settlement regulation and soil internal stress-strain regulation of subgrade with different materials under uniformly distributed load were studied by model experiment. The effect of alkali activated slag curing agent on curing silt was verified. The research results can provide technical support for highway construction in silt area of the Yellow River alluvial plain.

• The Journal of Korean Academy of Prosthodontics
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• v.42 no.2
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• pp.238-247
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• 2004

Statement of problem: Major objective in making on implant-supported prosthesis is the production of superstructure that exhibits a passive fit when connected to multiple abutments. One requirement to ensure passive fit is to make an accurate impression. Purpose : The purpose of this study was to compare the accuracy of master cast fabricated by using different impression methods at the different impression levels. Material and method: The master model used in this study was resin block having low implant analogs. Impression method studied were 1) direct method on fxiture level (Group FIX-D), 2) indirect method on fixture level(Group FIX-I), 3) modified indirect method on fixture level(Group FIX-M), 4) direct method on abutment level(Group AB-D) and 5) indirect method on abutment level(Group AB-I). Each of the five groups took 10 impressions. Fifty impressions were made for master cast by using Impregum $F^{(R)}$ impression material loaded on individual tray. Three dimensional measuring microscope was used to measure the inter-implant distance. Error rate of each inter-implant distance were calculated and evaluated. Results : The results were as follows. 1. Group FIX exhibited higher accuracy than group AB. 2. In group FIX, modified indirect method showed the highest accuracy, while indirect method showed the lowest accuracy. In group Ab, indirect method showed the higher accuracy than direct method. 3. Group FIX showed larger horizontal error than group AB. But, group AB showed the larger vertical error than group FIX. 4. Group Fix-M showed smallest vertical and horizontal error. Conclusion: An impression method have more effect on accuracy of master model than an impression level. A modified indirect method showed smallest vertical and horizontal error.

• Journal of the Korean Geotechnical Society
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• v.19 no.1
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• pp.21-29
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• 2003

In this study, practical guidelines to check the possibility of some lateral movement of piled abutment were investigated. In these tests, both the depth of soft clay and the rate of embankment construction are chosen to examine the effect on lateral soil movements. The depth of soft clay layer varies from 5.2 m to 11.6 m, and the rate of embankment construction has two types : staged construction(1m/30days, 1m/15days) and instant construction. Various measuring instruments such as LVDTs, strain gauges, pressure cells, and pore pressure transducers are installed in designed positions in ordo. to clarify the soil - pile interaction and the short and long term behavior f3. piled bridge abutments adjacent to surcharge loads. The validity of the proposed guidelines by centrifuge test was compared with the observed performance by lateral movement index, F(Japan Highway Public Corporation) and modified I index(Korea Highway Corporation). Based on the results obtained, the critical values off and modified I, as a practical guidelines, are proposed as 0.03 and 2.0, respectively.

• The Journal of Korean Academy of Prosthodontics
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• v.44 no.1
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• pp.112-123
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• 2006

Purpose: The biocompatibility and bio-adhesive property of a dental implant abutment are important for proper soft tissue healing and maintenance of osseointegration of implant. However, studies of soft tissue healing and mucosal attachment of various materials of implant abutment other than titanium are still needed. In this study, cell attachment, proliferation, cytotoxicity of human gingival fibroblast for ceramic, gold alloy, Ni-Cr alloy and, commercially available pure titanium as a control were evaluated, using MTS and scanning electron microscopy. Materials and Methods: Specimen was designed to disc, 4mm diameter and 1mm thickness, made of ceramic, gold alloy, Ni-Cr alloy and commercially available pure titanium. Primary culture of human gingival fibroblasts were grown in Dulbecco's modified Eagle's medium with 10% fetal bovine serum and 1% antibiotics. Cells were inoculated in the multiwell plates placed the specimen disc. Cell Titer 96 AQucous One Solution Cell Proliferation Assay were done after 1hour 3hours, 24hours, 3days, 5days of incubation. The discs were processed for scanning electron micrography to evaluate cell attachment and morphologic change. Results: The results were obtained as fellows. 1. The ceramic showed high cell attachment and proliferation and low cytotoxicity, which is as much bioadhesive and biocompatible as titanium. 2. The gold alloy represented limited proliferation of human gingival fibroblast and the highest cytotoxicity among tested materials (p<0.05). 3. The Ni-Cr alloy limited the proliferaion of the human gingival fibroblast compared to titanium(p<0.05) but cytotoxicity on the bottom of well was not so considerable, compared to titanium. 4. On the scanning electron micrographs , the ceramic showed good attachment and proliferation of human gingival fibroblast, which was similar to titanium. But gold alloy and Ni-Cr alloy showed the shrinkage of gingival fibroblast both after 24 hours and 3 days. On 5th day, small amount of the human gingival fibroblast proliferation was observed on the Ni-Cr alloy, while the shrinkage of gingival fibroblast was still observed on the gold alloy. Conclusions: These results suggest that the ceramic abutment is as biocompatible as titanium to make proper mucosal seal. The gold alloy has a high cytotoxicity to limit proliferation of gingival fibroblast, which suggest limited use on the anterior tooth where soft tissue healing is recommeded.

• The Journal of Korean Academy of Prosthodontics
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• v.44 no.1
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• pp.63-72
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• 2006

Purpose: The purpose of this study was to compare the accuracy of master cast fabricated by using different impression methods at the different impression levels. Material and Method: The master model used in this study was resin block having low implant analogs. Impression method studied were 1) direct method on future level (Group FIX-D), 2) Indirect method on fixture level(Group FIX-I), 3) Modified indirect method on fixture level(Group FD(-M), 4) Direct method on abutment level(Group AB-D) and 5) Indirect method on abutment level(Group AB-I). Each of the five groups took 10 impressions. Fifty impressions were made for master cast by using Impregum $F^(R)$ impression material loaded on individual tray. Three dimensional measuring microscope was used to measure the inter-implant distance. Error rate of each inter-implant distance were calculated and evaluated. Results: The results were as follows. 1. Group FIX exhibited higher accuracy than group AB. 2 In group FIX, modified indirect method showed the highest accuracy, while indirect method showed the lowest accuracy. In group Ab, indirect method showed the higher accuracy than direct method. 3. Group FIX showed larger horizontal error than group AB. But, group AB showed the larger vertical error than group FIX. 4. Group Fix-M showed smallest vertical and horizontal error.

• The Journal of Advanced Prosthodontics
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• v.8 no.2
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• pp.150-157
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• 2016

PURPOSE. The modified lateral-screw-retained implant prosthesis (LSP) is designed to combine the advantages of screw- and cement-retained implant prostheses. This retrospective study evaluated the mechanical and biological complication rates of implant-supported single crowns (ISSCs) inserted with the modified LSP in the posterior region, and determined how these complication rates are affected by clinical factors. MATERIALS AND METHODS. Mechanical complications (i.e., lateral screw loosening [LSL], abutment screw loosening, lateral screw fracture, and ceramic fracture) and biological complications (i.e., peri-implant mucositis [PM] and peri-implantitis) were identified from the patients' treatment records, clinical photographs, periapical radiographs, panoramic radiographs, and clinical indices. The correlations between complication rates and the following clinical factors were determined: gender, age, position in the jaw, placement location, functional duration, clinical crown-to-implant length ratio, crown height space, and the use of a submerged or nonsubmerged placement procedure. RESULTS. Mechanical and biological complications were present in 25 of 73 ISSCs with the modified LSP. LSL (n=11) and PM (n=11) were the most common complications. The incidence of mechanical complications was significantly related to gender (P=.018). The other clinical factors were not significantly associated with mechanical and biological complication rates. CONCLUSION. Within the limitations of this study, the incidence of mechanical and biological complications in the posterior region was similar for both modified LSP and conventional implant prosthetic systems. In addition, the modified LSP is amenable to maintenance care, which facilitates the prevention and treatment of mechanical and biological complications.