• Restorative Dentistry and Endodontics
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• v.36 no.4
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• pp.300-305
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• 2011

Objectives: The aim of this study was to evaluate the various NiTi rotary instruments regarding their ability to provide a circular apical preparation. Materials and Methods: 50 single canal roots were selected, cut at the cementodentinal junction and the coronal 1/3 of the canals was flared using Gates Glidden burs. Samples were randomly divided into 5 experimental groups of 10 each. In group I, GT files, Profile 04 and Quantec #9 and #10 files were used. In Group II Lightspeed was used instead of Quantec. In Group III, Orifice shaper, Profile .06 series and Lightspeed were used. In Group IV, Quantec #9 and #10 files were used instead of Lightspeed. In Group V, the GT file and the Profile .04 series were used to prepare the entire canal length. All tooth samples were cut at 1 mm, 3 mm and 5 mm from the apex and were examined under the microscope. Results: Groups II and III (Lightspeed) showed a more circular preparation in the apical 1mm samples than the groups that used Quantec (Group I & IV) or GT files and Profile .04 series.(Group V)(p < 0.05) There was no significant difference statistically among the apical 3, 5 mm samples. In 5 mm samples, most of the samples showed complete circularity and none of them showed irregular shape. Conclusions: Lightspeed showed circular preparation at apical 1 mm more frequently than other instruments used in this study. However only 35% of samples showed circularity even in the Lightspeed Group which were enlarged 3 ISO size from the initial apical binding file (IAF) size. So it must be considered that enlarging 3 ISO size isn't enough to make round preparation.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.14 no.2
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• pp.14-18
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• 2015

In recent years, world is faced with a transportation energy dilemma, and the transportation is almost dependent on a single fuel - petroleum. However, Hybrid Electric Vehicle (HEV) technology holds more advantages to reduce the demand for petroleum in the transportation by efficiency improvements of petroleum consumption. Therefore, there is a trend that lower gear noise levels are demanded in HEV for drivers to avoid annoyance and fatigue during operation. And meshing transmission error (T.E.) is the excitation that leads to the tonal noise known as gear whine, and radiated gear whine is also the dominant source of noise in the whole gearbox. In this paper, the analysis of gear tooth profile and lead modification is firstly presented, and then, the different transmission error of no mesh misalignment and mesh misalignment under one loaded torque for the 1st gear pair of HEV gearbox was investigated and compared. At last, the appropriate tooth modification was used to minimize and compare the transmission error of the gear pair with mesh misalignment under the loaded torque.

• Journal of Ocean Engineering and Technology
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• v.28 no.4
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• pp.314-323
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• 2014

In this study, a gearbox and blade were modeled in the MASTA program, and the housing and carrier components were modeled using a finite element method. Using substructure synthesis, all the components were combined and used to establish a vibration model of a 2.5-MW wind turbine gearbox. In addition, the safety displacement factor was evaluated using an AGMA data sheet about bearing's outer race for the input shaft and output shaft. As a result, the bearing's outer race for the input shaft, and the radial and axial responses were satisfied by the $1^{st}$ and $2^{nd}$ planetary gears and the $3^{nd}$ helical gear transmission error(TE), respectively. However, the output shaft support bearing's outer race responses were not satisfied with the radial response by the $2^{nd}$ TE and axial response by the $3^{rd}$ TE. To reduce the vibration, tooth modification was needed. After profile tooth modification, at the outer race of the output shaft support bearing, the radial response was reduced by approximately $20{\mu}m$, and the axial response was reduced by approximately $6{\mu}m$.

• Journal of Periodontal and Implant Science
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• v.31 no.3
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• pp.531-542
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• 2001

Periodontal debridement is most important procedure in periodontal treatment, because periodontal disease is the biofilm infection. The use of ultrasonic instrument has many clinical advantages compared to classical hand instrument. The introduction of newly developed ultrasonic scaler tips made the use of ultrasonic scaler popular. However the study of tooth substance removal according to the working parameters of ultrasonic scaler with newly developed tips is not sufficient. The purpose of this study is to evaluate the effects of working parameters of piezoelectric ultrasonic scaler with curette tip on casting gold removal. The working parameters was standardized by the sledge device which controls lateral force(0.5 N, 1.0 N, 2.0 N) and power setting was adjusted 2, 4, 8 in P mode and S mode and instrumentation time was 5 seconds. The defect depth and width were measured with profile meter and defect surface was examined by SME. The depth of defect was significantly large in S mode( $39.58{\pm}19.35{\mu}m$) compared to P mode( $8.37{\pm}6.98{\mu}m$). There was significant decrease of depth of defect between 1.0N($32.87{\pm}27.18{\mu}m$) and 2.0N( $14.86{\pm}15.04{\mu}m$). The area of defect was also significantly large in S mode($4482.42{\pm}3551.71{\mu}m^2$) compared to P mode( $922.06{\pm}960.32{\mu}m^2$). There was significant decrease of area of defect between 1.0N($3889.12{\pm}3936.00{\mu}m$) and 2.0N( $974.66{\pm}986.01{\mu}m$). The change of mode did not effect on the width of the defect. The change of power setting did not effect on the depth, width, and area of defect. In spite of limitation of this study it could be concluded that the use of piezoelectric ultrasonic scaler with curette tip on S mode could make significant tooth substance loss.

• Journal of Dental Rehabilitation and Applied Science
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• v.35 no.3
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• pp.170-179
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• 2019

The prosthodontic treatments in maxillary anterior teeth focus on achieving esthetic appearances. It is possible to improve the esthetic appearance by adjusting the shape, arrangement, and color of the maxillary anterior teeth. For anterior teeth restoration, it is necessary to evaluate the relationship of teeth, lip and gingival architecture with the facial profile of patient. Also, clinician needs to fully understand what the patient wants to. DSD (digital smile design) concept can be applied as a tool to improve communication with the clinician, technician and patient. In addition, DSD can help to meet the needs of the patient. In this case, it was impossible to achieve symmetry due to congenital missing of maxillary central incisor. The definitive treatment goal was to get the harmony of maxillary anterior teeth, lip and the patient's face. This case report describes that the patient and clinician got the satisfying esthetic outcome by using DSD.

• Journal of Oral Medicine and Pain
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• v.46 no.4
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• pp.131-135
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• 2021

Purpose: Depression is a condition that weakens psychosocial functioning and reduces quality of life. In Korea, the prevalence of depression among the elderly is 29.2% and depression is a considerable public health concern for the elderly. Depression has a statistically significant relationship with oral conditions such as number of teeth and salivary flow rate. Oral health-related quality of life (OHRQoL) is the concept including subjective evaluations of psychological, physical and social aspects of oral health. Tooth loss and hyposalivation can affect mental health and quality of life. Our study was designed to identify the relationship among the number of teeth, salivation, OHRQoL, and depressive symptoms in the elderly in Korea. Methods: We recruited 100 participants, aged over 65 years, and assessed their number of teeth, unstimulated salivary flow rate. All participants filled out oral health impact profile 14 (OHIP-14) and Zung self-rating depression score (SDS) for checking OHRQoL and depressive symptoms. Statistical analysis was done by R program. Results: We found that the positive relationship between OHIP-14 and SDS after Mann-Whitney test (p=0.03). The lower SDS group had an OHIP-14 median score of 4. On the other hand, the higher SDS group had a median value of 7.5. The other factors (number of teeth and salivary flow rate) did not show correlations with OHIP-14 or SDS. Conclusions: OHRQoL and depressive symptoms have significant correlation.

• Journal of Periodontal and Implant Science
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• v.36 no.2
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• pp.461-471
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• 2006

In order to achieve a satisfactory esthetic result of periodontal surgery or implant in maxillary anterior area, periodontists must be aware of normal alveolar bone anatomy. The purpose of this study was to evaluate the relationship of alveolar bone morphology to tooth shape and form. 78(mean age : 25 yrs) periodontally healthy volunteers participated in this study. Two maxillary central incisor and one lateral incisor were selected to study. With minimal local anesthesia, gutta-percha cone inserted to labial gingival sulcus of selected teeth just after bone sounding with periodontal probe. Metal ball (4mm diameter) attached to palatal fossa of central incisor. Then, periapical radiograph was taken according to long cone paralleling technique. After film scan, labial alveolar bone profile reproduced along interproximal bone and apical ends of gutta-percha cones on computer screen. By utilizing computer program, the distance from height of interproximal bone to the labial bone crest in central incisor-central incisor and central incisor-lateral incisor area was measured and converted to real distance by using vertical length of metal ball on film. After measuring crown length & width of central incisor, the 10 individuals ranked lowest GW/L ratio (crown width/length ratio) and the 10 ranked highest were selected as having a long-narrow(group N), or a short-wide(group W) form of the central incisors. Means of the distance from height of interproximal bone to the labial bone crest of group N, W were calculated and compared by means of independent t-test. The results were as follows: 1. Mean distance from the height of the interproximal bone to the labial bone crest was $3.5{\pm}0.7mm$ between two central incisor, and $2.8{\pm}0.6mm$ between central and lateral incisor. 2. Mean GW/L ratio of group N was 0.57, and group W was 0.8. Mean distance from the height of the interproximal bone to the labial bone crest of group N was higher than group W in both measured area(measurements of group N, W were $3.9{\pm0.2mm$ and $3.5{\pm}0.2mm$ between two central incisor, $3.0{\pm}0.2mm$ and $2.8{\pm}0.2mm$ between central and lateral incisor), but there were no statistically significant differences when the groups were compared. Within the limits of the present study, there was a tendency that subjects with long-narrow teeth have more scalloped alveolar bone profile than subjects with short-wide teeth in upper anterior area, but no statistically significant differences were found.

• Korean Journal of Materials Research
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• v.2 no.2
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• pp.119-125
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• 1992

Oxygen segregation in horizontal-magnetic-field-applied Czochralski (HMCZ) silicon crystals has been studied as a function of magnetic field strength (B) and crucible rotation rate (C). Along the axis of 57mm din. <100> crystals grown under B=2, 3, 4 kG and C=4-15rpm, the oxygen distribution was usually saw-tooth shaped and fluctuated unevenly. Compared to the conventional CZ method, this result seems to indicate that the horizontal magnetic field, at levels used in the present experiment, had a destabilizing influence on oxygen transport to the growth interface. On the other hand, as C increased, the oxygen fluctuation lessened, and [0] increased overall. At B=2 kG, an oxygen profile in a level of 27-36 ppma was achieved by a programmed ramp of C. Oxygen precipitation behavior of the HMCZ silicon during a simulated device manufacturing process was compared and found to be inferior to that of typical CZ silicon. The uneven oxygen profile in the as-grown state was identified as the major source of poor precipitation uniformity in the HMCZ silicon.

• Journal of Dental Rehabilitation and Applied Science
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• v.30 no.4
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• pp.339-349
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• 2014

If the maxillomandibular relationship is unstable or requires treatment for improved function and esthetics, the first treatment objective is to provide stable occlusal contacts. The patient has moderate mental retardation. Due to inadequate vertical overjet, horizontal arch malrelation and excessive tooth loss, full mouth rehabilitation was required. The purpose of treatment planning is to establish physiologic maxillomandibular relation. Using cephalometrics for occlusal analysis is an aid to make a decision. The amount of horizontal bone reduction was calculated with evaluating soft tissue profile. After provisional denture placement, healing of the surgical site and newly adapted arch relationship was evaluated. The patient satisfied with esthetics and showed stable holding contacts. Periodic examination is needed to exclude occlusal disharmony.

• Journal of Korean society of Dental Hygiene
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• v.13 no.5
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• pp.759-767
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• 2013

Objectives : The purpose of this study was to investigate the relationship between the oral health status of elderly people and their oral health-related quality of life. Methods : The subjects were the elderly people over 65 years old in Busan. A total of 479 elderly people participated in the study from general hospital, two research institutes, eight dental clinics, six welfare institutions, sixteen senior centers, and three nursing homes. The oral health impact profile-14 (OHIP-14) was used in the routine dental checkups of the elderly people. Results : Those who had no oral symptoms had a better oral health-related quality of life. Among the subfactors of the OHIP-14, significant differences were shown in functional limitation(p=0.001), physical pain(p<0.001), emotional discomfort(p<0.001), physical disability(p=0.001), emotional disability (p=0.001), social disability(p=0.005), physical handicap(p=0.003) and total OHIP-14(p<0.001). Those who had 18 sound teeth(natural teeth) or more had a better oral health-related quality of life. Among the subfactors of the OHIP-14, significant differences were shown in functional limitation(p<0.001), physical pain(p=0.007), emotional discomfort(p=0.019), physical disability(p=0.018), Emotional disability(p=.032) and total OHIP-14 (p=0.006). Conclusions : The results revealed a close relationship between oral health status and oral health-related quality of life. The number of sound teeth(natural teeth) and frequency of toothbrushing had a more positive influence. Therefore oral health programs for the elderly people can preserve remaining teeth. Toothbrushing is the best way to improve the quality of life in the elderly people.