• Journal of the Korean Society for Precision Engineering
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• v.13 no.10
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• pp.36-45
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• 1996

The precise estimation of the reliability and life of the Ravigneaux planetary gear train used in an automatic transmission is necessary in order to enable accurate material and geometric properties to reliability distrobution and the number of load cycles at failure. These are critical for the proba- bilistic design of complex planetary gear system as Ravigneaux type particularly during various gear ratios. The Ravigneaux planetary gear train has five gears, such as a forward and a reverse sun gear, a short and a long pinion, and an annulus gear. In this paper, the Ravigneaux gear system is analyzed to figure out the reliablity distribution. i.e. the probability of survival in the system without its overhaul. First, the reliablity method based on the Weibull distribution is used in conjuction with the Palmgren's model to predict both the individual reliabilities of its components and the nimber of load cycles when the system failed. Then using the presented method, the life of the Ravigneaux gear system can be determined. Alwo the different design parameters such as tooth face width, material property, and Weibull exponent are applied and reached to optimal ones. Thus, the precise evaluation of the reliability and life of the Ravigneaux planetary gear train used in an automatic transmission can be effectively carried out.

• Journal of Korean society of Dental Hygiene
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• v.12 no.5
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• pp.1029-1038
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• 2012

Objectives : This study was examine a relationship those variables with health-related quality(HRQOL) of life in the elderly and provide basic information on HRQOL and evidence for establishing effective health policies for old ages ultimately. Methods : This research was conducted through individual interviews using a structured questionnaire and oral status examinations of 600 residents The data have been analyzed using $X^2$-test through PASW Statistics 18.0.0(SPSS Korea Datasolution Inc.) and Structural Equation Modeling through LISREL ver8.8. Results : According to the Structural Equation Modeling, independent variables which influence the health-related quality of life are as follows: sex the highest, followed by existence of chronic diseases, perceived health, age, perceived oral health the lowest. Parameters are as follows: oral health-related quality of life the highest, followed by subjective oral symptoms, and oral health status the lowest. Conclusions : In order to improve the quality of life of olds, it is not only necessary to improve perceived health through reduce of chronic diseases, but is also required to regular tooth check-up to reduce subjective oral symptoms for increase oral health-related quality of life.

• Journal of Technologic Dentistry
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• v.22 no.1
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• pp.13-20
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• 2000

This experiment was done to find out how the length and the diameter of the sprue effects the porosity created during the moduling process, which is caused by the metal's shrinking and stretching action. the experiment was done in two groups(A and B), using experimental gold, and made 10 copings for both groups. 1. In group A, The length of the sprues were given the same, but the diameter of the sprue were 6, 8, 10, 12, 18 gauge. As a result, the porosity came out big with 12 and 18 gauge and for 10, 8, 6 gauge, the porosity was hardly seen or none was noticeable. 2. In group B, the diameter was given the sam for the sprues, but the length of the sprues were 5, 10, 15, 20, 25mm. As a result, the porosity came out big with 25, 20, 15mm the porosity was hardly seen or none was noticeable. 3. The diameter needs to be big and the length, short. 4. The appropriate sized sprue must be chosen for each individual tooth, according to it's shape and size.

• The korean journal of orthodontics
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• v.2 no.1
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• pp.47-52
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• 1971

Serial extraction procedure, when cautiouly practiced in severe discrepancy case, can be a good clinical approach, but the treatment planning must always be based on accurate analysis of all conditions, especially patient's individual growth pattern and his family development. It is most difficult to determine the timing and selection of most effective sequence of deciduout extraction. It is the best candidate that patient is with class I malocclusion with harmony of the skeletal and muscular system and severe discrepancy of the tooth system. The authors have observed a female, who has complained of the malalignment of mandibular permanent incisor teeth. Serial extraction has been performed to relieve it through adequate various informations and resulted in a fairly good prognosis.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.33 no.2
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• pp.173-180
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• 2007

According to the increase in use of implants in clinical dentistry, new kinds of complications happen. Complications that can happen during implant placement are bleeding, nerve injury, jaw fracture, fenestration of maxillary sinus or nasal cavity, dehiscence, fenestration, injury of adjacent tooth. And complications that can happen after implant operation are infection, bleeding, hematoma, chronic sinusitis, peri-implantitis. Problems that are confronted during implant placement happen by inadequate preoperative treatment plan, inadequate consideration about individual anatomic difference, inadequate operation process and lack of experience of clinician. It is important that clinicians consider possible complications in advance and make a comprehensive treatment plan. We report the patient who was happened ramus fracture during block bone harvesting from ramus of severely atrophic mandible, the patient who came to emergency ward due to postoperative swelling and bleeding and the patient whose implant was migrated to maxillary sinus with a review of literature.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.23 no.2
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• pp.303-314
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• 1993

The purpose of this study was to find out the prevalence of dental anomalies in 600 normal persons (male:363, female:237) at age 14 to 39 years, through history taking, oral examination, and radiographic observations of subjects. The obtained results were as follows: 1. The prevalences of individual dental anomalies were as follows; Congenitally missing teeth 7%; supernumerary teeth 1.33%; ectopic eruption; 8.50%, transposition;0.33% rotation; 23.67%, microdontia;11.16%(peg lateralis;5.33%, third molar;5.83%), prolonged retention of deciduous teeth;1.33%, crowding 49.83%, and spacing;15.17%. 2. Alterations in numbers of teeth : The most frequently missing teeth were mandibular lateral incisors, followed by mandibular second premolars and maxillary second premolars. In numbers of congenitally missing teeth per person, 52.38% had one missing tooth and 30.95% had two missing teeth. In supernumerary teeth, there was higher rate in male than in female. Most supernumerary teeth were mesiodens of median area in maxilla and the eruption pattern of that teeth generally was unerupted state. 3. In transposition, exchange of position of teeth involved the canine and first premolar. 4. Congenital missing rate of permanent successors in prolonged retention of deciduous teeth was 69.23%. 5. Crowing and spacing had respectively higher rate in mandible and in maxilla.

• Journal of Periodontal and Implant Science
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• v.35 no.4
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• pp.975-989
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• 2005

Periodontal disease is caused by accumulation of bacterial plaque. For the reason, plaque control is essential to control and prevent periodontal disease. Among the plaque control methods, mechanical plaque removal, tooth brushing is common and reliable. But it depends on individual habituation and their manner. To catch up the gap of effectiveness, lots of oral hygiene appliances have been developing. Powered toothbrush is the most interesting field and is showing on the market with various motion type. This study was performed to compare clinical effects of plaque removal between powered toothbrush and manual toothbrush. The results were as follows : 1. Plaque index was decreased statistically after the brushing than before the brushing in every group.(p<0.05) 2. Comparing plaque index among the three groups before and after brushing, there were no statistically significant differences. 3. Interproximal plaque index was decreased statistically after the brushing than before the brushing in every group.(p<0.05) 4. Comparing interproximal plaque index among the three groups before and after brushing, there were no statistically significant differences.

• Journal of Periodontal and Implant Science
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• v.38 no.2
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• pp.199-206
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• 2008

Purpose: Variation in the morphology of gingival papilla may be determined by the shape and position of anatomic crown as well as contact area and embrasure form of individual teeth. However, periodontal biotype classification is regarded to be subjective because of the lack of definite criteria. In this study, we defined the objective parameters which constitute the periodontal biotype and measured their relationship. Materials and Methods: 109 of dental casts were prepared using three dimensional scanner and specialized reconstruction software, then acquiredvirtual models were sent to the 20 professional dentists to define the specific periodontal biotypes. Several parameters around periodontal structures were measured from the virtual models; facial surface area of the anterior tooth (AT), anterior papillary area (AP), proportion of the dento-papillary complex, clinical papillary length (PL), and clinical papillary angle (PA). Statistical analysis was performed to confirm the relationship among parameters. Results: Coincidence rate of periodontal biotype within observers was $63.77{\pm}16.05%$. Coincidence rate between observers was $76.15{\pm}16.43%$. Among the parameters measured, PL showed the most positive correlations and PA presented the most negative correlations. The parameter of the AP and PL of six maxillary anterior teeth showed significant correlation coefficient. Conclusion: Anterior papillary area and clinical papillary length would be objective parameters for determining the consistent periodontal biotypes.

• Proceedings of the KACD Conference
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• 2003.11a
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• pp.546.1-546
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• 2003

Laser doppler flowmeter (LDF) has been applied to the measurement of pulpal blood flow (PBF) in human teeth. As far as we searched, the detection area of the pulp in the blood flow measurement has not been clarified, yet. Therefore, the purpose of this study was to obtain information of the detection area in PBF measurement using LDF. The experiments were performed on the artificial blood circulation in extracted human upper central incisors. The apical portions of examined teeth (n=6) were severed and root canals were enlarged from the apical end to the 2mm incisal to the level of enamel-cement junction. An individual resin cap of each tooth was prepared and a hole was drilled 2mm incisal to enamel-cement junction of the labial side of the cap. The measurement probe of LDF (MBF3D, Moor Instrument, UK) was plugged into the hole of the cap. Heparinized human peripheral blood, which was in advance collected and diluted 3 times with physiological saline, was pumped through the apical foramen of the teeth via a silicone tube and a disposable needle (o.d. 0.7mm) and blood flow signals were monitored. The flux signal significantly increased with the enlargement of the root canal to incisal direction (p<0.01, Friedman analysis). The result indicates that the performance of LDF in PBF with human teeth is limited.

• The korean journal of orthodontics
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• v.30 no.3 s.80
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• pp.317-333
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• 2000

The purpose of this study was to determine the proliferative activity of the osteoblasts and fibroblasts in the midpalatal area and to investigate the adjacent periodontal tissues of individual tooth following rapid expansion of the palate. Ten young adult dogs, aged approximately ten months, were used in the experiment. The experimental design was consisted of 1 week expansion group(Group E1, 3 dogs), 2 week expansion group(Group E2, 3 dogs), 2 week expansion and 2 week retention group(Group E3, 3 dogs), and control group(Group C, 1 dog). For each group, expansion screw was activated one time per day(1/4 turn;$90^{\circ}$) following Hyrax-screw application. The experimental animals in each group were sacrificed at 1, 2 and 4 weeks following palatal expansion. Maxillary tissue blocks were obtained and prepared ior the histomorphologic and immunohistochemical studies. Light mcroscope, polarizing microscope, and soft X-ray apparatus were used in this study, and following results were obtained. 1. In polarizing microscopic study, the expansion groups(E1 & E2) showed blue color representing bone resorption and new bone formation in midpalatal suture area. E3 groups skewed less blue color compared to the E1 and E2 group. But yellow color increased by calcification in the E3 groups. 2. Immunohistochemical study revealed that positive responses of the osteoblasts to PCNA and undifferentiated fibroblasts to EGF in E1 group were somewhat increased. Positive response to PCNA and EGF were increased in fibroblasts and the osteoblasts forming new bone in E2 group. In E3 group, the positive response cell concentrated the periphery of edge of palatal process in both PCNA and EGF. 3. Throughout the expansion period(E1 & E2), light microscopic study showed the edges of the extensive resorption and new palatal processes, indicating bone remodeling within the suture. E3 group exhibited less remodeling of midpalatal suture area. E2 group and E3 group showed cementum formation and resorption at the apex of 3rd premolar and 1st molar E3 group exhibited extensive hyalinized zone on the cervical portion of buccal side of 1st molar. 4. Soft X-ray analysis of E1 group showed hypomineralized defect and microfractures in various parts of the suture areas when compared with control animals. There was no significant difference in the degree of mineralization in the midpalatal suture region between the C and E3 groups. Tooth axis showed tipping of 3rd premolar and 1st molar in the E2 group and E3 group. Based upon these experimental results, it is concluded that the undifferentiated mesenchymal cells always presented in midpalatal suture area following RPE. Differentiated osteoblasts and fibroblasts possess proliferating cellular activity until the 2 week retention period. The posterior teeth are tend to tip buccally as RPE force applied. Retention group exhibited irreversible response with severe hyalinized zone on the buccal surface of the first molar.