• Korean Journal of Ecology and Environment
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• v.35 no.3 s.99
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• pp.237-246
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• 2002

Tamjin Dam is built in the upper reaches of the Tamjin River which flows through the Janghung-gun and Gangjin-gun of the Jeollanamdo, Korea. In order to map out a preservation strategy of the fish community from dam construction, We studied the distribution of fish distribution and changes of the habitat environment. we found 49 fish species inhabiting in the downstream and upstream of the Tamjin Dam. Among them, migratory fish were two species sweet smelt, Plecoglossus altivelis and freshwater eel, Anguilla japonica. The Coreoperca kawamebari which designated as a species to be protected by The Ministry of Environment of Korea was also observed. After the dam construction, reservoir would be filled with water and running water system will change to standing water system. Then the habitat and spawning space for mountain torrent fish will be reduced and the migration of migratory fish to upstream will be blocked. Through our study, we proposed several ways to protect fish community. In order to preserve the reduced habitat and spawning area of mountain torrent fish, a fishway has been diagnosed to be built in the shallow reservoir in the entrance of the upriver. The establishment of artificial spawning ground on the riverside has been recommended. In addition, We propose a creation of a shelter for fresh water eel, Anguilla japonica in areas where the depth of the water is about l0m by laying rocks. Since it is difficult for a spawning ground to be formed naturally in the reservoir due to the year-round changes in water level, We suggested a floating spawning facility using an artificial fixture. In the downstream of the dam, a waterway-style habitat and spawning ground in the river and increasing the diversity and abundance of fish fauna in the Tamjin River. A low-cost and highly efficient operational fishway has been recommended so that migratory fish such as Plecoglossus altivelis (sweetfish) can migrate from the lower reaches to the upper reaches of the river.

• The Journal of Korean Academy of Prosthodontics
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• v.59 no.2
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• pp.173-180
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• 2021

Purpose: The purpose of this study was to evaluate the retentive characteristics of the additional attachments used with implant bar attachment under repeated insertion/removal cycles. Materials and methods: The newly developed attachment and the commercially available attachment were investigated: ADD-Lock (AL), Locator blue (LB). Two fixtures were placed parallel to each other on the custom lower mounting, and patrix of each attachment was fixed to the fixture. Also, the matrix of each attachment was placed on the opposing upper mounting. A universal testing machine was used to measure the retentive force during initial, 100, 250, 500, 1000, 2000, and 2500 repeated insertion/removal cycles. Wear and deformation of the attachment s were observed by scanning electron microscopy (SEM). Mann-Whitney U test (α=.05) and wilcoxon signed-rank test (α=.05) were performed to compare retentive force between each group and before and after 2500 repeated insertion/removal cycles. Results: In terms of initial retentive force and retentive force after 2500 repeated insertion/removal cycles, the AL group (15.24 ± 1.46 N and 9.74 ± 1.16 N) showed significantly smaller values than the LB group (43.53 ± 12.39 N and 22.99 ± 4.77 N) (P<.05). Also, in the loss of retentive force, the AL group (5.50 ± 1.08 N, 36.08%) showed a smaller value than the LB group (20.54 ± 11.89 N, 47.19%) (P<.05). Based on SEM analysis, The AL group showed noticeable wear and deformation in the patrix and the LB group in the matrix. Conclusion: Locator showed a higher initial retentive force than newly developed attachment, while the loss of retentive force was also higher. Both additional attachments are considered to have sufficient retentive force after repeated insertion/removal cycles.

• The Journal of Korean Academy of Prosthodontics
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• v.61 no.2
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• pp.101-112
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• 2023

Purpose. This retrospective study was to investigate the survival and complication rates of posterior single implant according to the implant diameters, lengths and position. Materials and methods. Patients who had been restored single implant prosthesis in the posterior area by the three prosthodontists in the department of prosthodontics, Daejeon dental hospital of Wonkwang university, in the period from February 2014 to May 2018 were selected for the study. A total of 505 patients with 697 implants were observed. The survival and complications of implants were investigated using electronic medical records and radiographs. Fixture diameters, lengths, position, patient's sex and age were assessed as possible factor affecting the survival and complications of implants. Results. 3-year cumulative survival rates of posterior single implants were 98.5% and 5-year cumulative survival rates were 94.4%. 5-year cumulative survival rates were higher in implants with diameter > 4.0 mm (97.0%) than implants with diameter ≤ 4.0 mm (89.5%), and in females (98.8%) than males (92.4%). There were statistically significant differences (P < .05). The mechanical complication rate was 20.1% and the biological complication rate was 4.7%. Complications occurred in order of abutment screw loosening (7.5%), decementation (6.3%), proximal contact loss (3.7%) and so on. Abutment screw loosening occurred more frequently in the lower molar region (10.5%), in males (9.5%) than females (5.1%), and in patients aged < 65 years (9.4%) than patients aged ≥ 65 years (5.1%). There were statistically significant differences (P < .05). Conclusion. The 5-year cumulative survival rates were higher in implants with diameter > 4.0 mm than implants with diameter ≤ 4.0 mm and in females than males. Abutment screw loosening which was the most commonly occurring complication occurred more frequently in the lower molar region, in males than females, and in patients aged < 65 years than patients aged ≥ 65 years. There were statistically significant differences.