• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2002.10a
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• pp.462-467
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• 2002

New methods for screw and spline production has been developed recently by Japan and other developed countries in the basis of Rolling Dies work to cut down the production cost. These methods give us high precision of the products. But we in Korea mostly import Dies for manufacturing forming products. It is thought that if we don't develop our own technology for Rolling Dies, we will have to spend much money for importing Forming concerned equipments. In this paper, we designed the rolling dies based on the diameter of material and calculated the proper number of teeth of gear to establish desirable method for Rolling dies. And the result is shown after manufacturing Involute spline with the rolling dies.

• Journal of Species Research
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• v.8 no.3
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• pp.283-287
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• 2019

Pardosa pseudolaevitarsis n. sp. and Hygrolycosa umidicola Tanaka, 1978 belonging to Lycosidae are described from Korea. To date, fourteen species in the genus Pardosa C. L. Koch, 1847 have been described from Korea. H. umidicola belongs to Hygrolycosa Dahl, 1908 was once described from Korea, but the previous description of this species could not provide adequate scientific evidence for adding H. umidicola to the Korean spider fauna. Pardosa pseudolaevitarsis n. sp. is similar to P. laevitarsis Tanaka & Suwa, 1986 in the shape of its epigyne and palp, but can be distinguished by the followings: epigynal atrium small; spermathecae extending to the end of atrium; shape, location and orientation of fertilization duct in epigyne and internal genitalia; blunt basal spur of median apophysis in palp; number, shape and arrangement cheliceral teeth on both margins. Both species were collected using pitfall traps on a ridge between rice fields and seem to prefer habitats with relatively high humidity.

• The Journal of the Korean dental association
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• v.22 no.11 s.186
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• pp.979-989
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• 1984

The purpose of this study was to obtain the basic data for oral health program planning of the totally blind persons. The author had surveyed oral health status and dental needs of 268 totally blind persons aged from 7 years old to 29 in Seoul, Korea, Thereafter, the toothbrushing frequency, df rate, dft index, DMF rate, DMFT index, restorative treatment requirement, bridge status, periodontal status, and periodontal requirement were calculated and discussed. The obtained results were as follows: 1. The average toothbrushing frequency was 2.53 times a day, and the average toothbrushing frquency after eating was 2.12 times a day. 2. DMF rate was 53.73%, and DMFT index was 2.12. 3. the average number of teeth required restorative treatment due to dental caries was 1.95. 4. Oral hygiene instruction was required in 15.30%, oral porphylaxis and oral hygiene instruction in 58.58%, periodontal therapy in 10.14%. %. Incremental dental care system was recommended to improve dental health status of the totally blind persons.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.16 no.5
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• pp.205-210
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• 2007

The integration method of binary and real encoding in genetic algorithm is proposed to deal with design variables of various types in gear drive design. The method is applied to optimum design of multi-stage gear drive. Integer and Discrete type design variables represent the number of teeth and module, and continuous type design variables represent face width, helix angle and addendum modification factor etc. The proposed genetic algorithm is applied for the gear ratio optimization and the volume optimization(minimization) of multi-stage geared motor which is used in field. In result, the proposed design optimization method shows an effectiveness in optimum design process and the new design has a better results compared with the existing design.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1993.10a
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• pp.224-230
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• 1993

Closed-die forging of spur gears with hollow cylindrical billet has been analysed by using the upper-bound method. A kinematically admiccible velocity field has been developed. wherein, an involute curve has been introduced to represent the forging die profile. In the analysis, the deformation regions have been divided into nine zones. A constant frictional stress has been assumed on the contacting surfaces. Utilizing the formulated velocity field, numerical calcuations have been carried out to investigate the effects of various parameters, such as module, number of teeth and friction factor,on the forging of spur gears.

• Animal Systematics, Evolution and Diversity
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• v.29 no.2
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• pp.175-178
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• 2013

The Fraser's dolphin, Lagenodelphis hosei has a pantropical distribution. Only several stranding or catch data were available from Japan and Taiwan in the north-west Pacific region. An adult female L. hosei stranded in Jeju-do, Korea. The specimen was identified by external features and skull measurements. It showed the same external appearance ratio and range in the number of teeth with L. hosei former described. The cranial measurements also well corresponded to condylobasal length proportions given in the previous descriptions of the holotype. This is the first record of the species in Korean waters. We report the information on external and osteological characters of the specimen.

• The Journal of Korean Academy of Prosthodontics
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• v.36 no.2
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• pp.302-322
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• 1998

This study was accompolished to analyze and compare the number and area of the occlusal contact points in healthy volunteers and athletes with normal occlusion. For this study, 15 athletes(13 amles and 2 females with average age 20) and 21 healthy volunteers(14 mles and 7 females with average age 20.09) were selected. The visual display acquired by scanning of occlusal record in maximal intercuspation was converted into 16 gray value image. Then, using computer program(J & Lee Occlusal Analyser), the pixel which was in definite range of the gray value was recognized, and the numbers of recognized pixel were calculated to area. The results were as follows ; 1. The average numbers of total occlusal contact feints were 31.05 in control group, and 34.67 in athlete group. The average area of total occlusal contacts was $100.25mm^2$ in control group, and $127.78mm^2$ in athlete group. 2. In control group, the average numbers of occlusal contact points were revealed in order as follows ; the first molar(8.48), the second molar(8.24), the second premolar(4.71), the lateral incisor(2.90), the first premor(2.43), the central incisor(2.19), and the canine(2.1). The least average in canine(2.1) was similar to the average(2.19) in central incisor and (2.09) in lateral incisor. In athlete group, the average numbers of occlusal contact points were revealed in order as follows ; the first molar(8.97), the second molar(8.47), the second premolar(5.60), the canine(3.80), the lateral incisor(3.33), the first premolar(2.67), and the central incisor(1.93). 3. In control group, the average areas of occlusal contact surface were revealed in order as follows ; the first molar($39.47mm^3$), the second molar($37.54mm^3$), the second premolar($9.54mm^3$) the first premolar($6.18mm^3$), canine($3.49mm^3$), the central incisor($2.76mm^3$), and the lateral incisor($1.28mm^3$). In athlete group, the average areas of occlusal contact surface were revealed in order as follows ; the first molar($44.11mm^3$), the second molar($40.69mm^3$), the second premolar($16.50mm^3$), the first premolar($9.39mm^3$), the canine($5.08mm^3$), the lateral incisor($3.7mm^3$), and the central incisor($2.25mm^3$). 4. With aging in both control and athlete group, there was a decreasing tendancy in average number of occlusal contact point, and was an increasing tendancy in average area of occlusal contact surface. In comparison at each age, both the numbers and area of occlusal contact were greater in athlete group than in control group. It was not significant in the numbers of occlusal contact points beween athlete and control group(p>0.1), but significant in the area of occlusal contact surface(p<0.03). 5. In comparision as to the kind of sports(Gymnastics : 2, Rugby : 3, Soccor : 5, Ice hocky : 5), the numbers of occlusal contact points were the most in ice hocky, and the area of occlusal contact surface was the greatest in gymnastics. With increasing a career in athlete group, there was a decreasing tendancy in average numbers of occlusal contact points and was an increasing tendancy in average area of occlusal contact surface. 6. By T-scan analyzing, the contact numbers on the anterior teeth were greater in control group than in athlete group, and on the posterior teeth were greater in athlete group than in control group. And the results acquired by T-scan were lesser than that caquired by the silicone bite records. It was not significant in the posterior teeth, but significant in the anterior teeth. In T-scan records, the numbers of occlusal contact points on second molar were the greatest, but in the silicone records, the numbers on first molar were the greatest.

• The Journal of the Korean dental association
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• v.56 no.5
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• pp.263-276
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• 2018

Long-term survival and prognosis of narrow-diameter implants have been reported to be adequate to consider them a safe method for treating a deficient alveolar ridge. The objective of this study was to perform case report of narrow-diameter implants with a trapezoid-shape in anterior teeth alveolar bone. A 50-year-old male patient presented with discomfort due to mobility of all of the maxillary teeth and mandibular incisors. Due to destruction of alveolar bone, four anterior mandibular teeth were extracted. Soft tissue healing was allowed for approximately 3 months after the extraction, and a new design of implant placement was planned for the mandibular incisor area, followed by clinical and radiological evaluation. Implant placement was determined using an R2GATE surgical stent. The stability of the implants was assessed by ISQ measurements at the first and second implant surgery and after prosthetic placement. At 1 and 3 months and 1 year after implantation of the prosthesis, clinical and radiological examinations were performed. Another 50-year-old male patient presented with discomfort due to mobility of the mandibular central incisors. For the same reason as in the first patient, implant placement was carried out in the same way after extraction. ISQ measurements and clinical and radiological examinations were performed as in the previous case. In these two clinical cases, 12 months of follow-up revealed that the implant remained stable without inflammation or additional bone loss, and there was no discomfort to the patient. In conclusion, computer-guided implant surgery was used to place an implant in an optimal position considering the upper prosthesis. A new design of a narrow-diameter implant with a trapezoid-shape into anterior mandibular alveolar bone is a less invasive treatment method and is based on the contour of the deficient alveolar ridge. Through all of these procedures, we were able to reduce the number of traumas during surgery, reduce the operation time and total treatment period, and provide patients with more comfortable treatment.

• The Journal of the Korean dental association
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• v.53 no.11
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• pp.855-869
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• 2015

The purpose of this study was to evaluate the oral health promotion of the disabled persons by voluntary dental services in Ulsan Metropolitan City. Two dentists taken a calibration training for national oral health survey examined the oral health status of 473 disabled persons from two special schools for the disabled children and adolescents, a residential facility and a gymnasium for the disabled persons in 2009-2010. The surveyed disabled persons in the age range was from 7 to 74 years old. Voluntary dentists, oral hygienists and other civilian volunteers had supplied with the oral health care services to the disabled persons at dental clinics of special schools for the disabled children and adolescents, and a dental clinic supported from Nam-Gu Public Health Center in Ulsan Metropolitan City since 1997. The obtained data from these surveys were analyzed with the SPSS statistical package. Among subjects aged 12-14 years, subjects with decayed, missing and filled teeth (DMFT) in permanent dentition was 46.9%; subjects with untreated decayed teeth, 17.2%. The number of decayed, missing and filled teeth in permanent dentition was 1.36. The proportion of decayed components of DMFT score was 28.00%; proportion of missing components of DMFT score, 1.43%; proportion of filled components of DMFT score, 70.57%. The proportion of filled components of DMFT score among disabled persons of all age group in Ulsan were evaluated to be a similar level to non-disabled citizens in Ulsan from 2010 Korean National Survey. The oral health care programs for disabled persons by voluntary services of dental professionals and other civilians are evaluated to be effective for the oral health promotion of disabled persons in Ulsan.

• Journal of Korean Dental Science
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• v.16 no.2
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• pp.128-148
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• 2023

Dementia is an umbrella term that describes the loss of thinking, memory, attention, logical reasoning, and other mental abilities to the extent that it interferes with the activities of daily living. More than 50 million individuals worldwide live with dementia, which is expected to increase to 131 million by 2050. Recent research has shown that poor oral health increases the risk of dementia, while oral health declines with cognitive decline. In this narrative review, the literature was based on the "hypothesis" that dementia and oral health have a close relationship, and appropriate oral health and occlusal rehabilitation treatment can improve the quality of life of patients with dementia and prevent progression. We conducted a literature search in PubMed and Google Scholar databases, using the search terms "dementia," "major neurocognitive disorder," "dentition," "occlusion," "tooth loss," "dental prosthesis," "dental implant," and "occlusal rehabilitation" in the title field over the past 30 years. A total of 131 studies that scientifically addressed dementia, oral health, and/or oral rehabilitation were included. In a meta-analysis, the random effect model demonstrated significant tooth loss increasing the dementia risk 3.64-fold (pooled odds ratio=3.64, 95% confidence interval [2.50~5.32], P-value=0.0348). Tooth loss can be an important indicator of cognitive function decline. As the number of missing teeth increases, the risk of dementia increases. Loss of teeth can lead to a decrease in the ascending information to the brain and reduced masticatory ability, cerebral blood flow, and psychological atrophy. Oral microbiome dysbiosis and migration of key bacterial species to the brain can also cause dementia. Additionally, inflammation in the oral cavity affects the inflammatory response of the brain and the complete body. Conversely, proper oral hygiene management, the placement of dental implants or prostheses to replace lost teeth, and the restoration of masticatory function can inhibit symptom progression in patients with dementia. Therefore, improving oral health can prevent dementia progression and improve the quality of life of patients.