• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2003.04a
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• pp.454-459
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• 2003

The paper will present chip formation mechanism and surface integrity generation mechanism based on the systematical experimental tests. Some basic factors such as the end milling cutter tooth number, cutting forces, cutting temperature, cutting vibration, the chip status, the surface roughness, the hardness distribution and the metallographic texture of the machined surface layer are involved. the chip formation mechanism is typical thermal plastic shear localization at high cutting speed with less number og shear ribbons and bigger shear angle than at low speed, which means lack of chip deformation. The high cutting speed with much more cutting teeth will be beneficial to the reduction of cutting forces, enlarge machining stability region, depression of temperature increment, auti-fatigability as well as surface roughness. The burrs always exists both at low cutting speed and at high cutting speed. So the deburr process should be arranged for milling titanium alloy in any case.

• Animal Systematics, Evolution and Diversity
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• v.40 no.3
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• pp.258-262
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• 2024

Abludomelita rotundactyla (Ren, 2012), belonging to the family Melitidae Bousfield, 1973 has been collected from Baengnyeongdo Island and Yangyang in Korea. This species was previously known from Yellow Sea, China and Sakhalin Island, Russia. Abludomelita rotundactyla is morphologically distinguished from congeners by gnathopod 2, palm excavate, defined by midventral acute process; gnathopod 2 with prominently plump dactylus; pleonites and urosomites dorsal formulae 7-9-9-5-4; and epimeron 3 with posterior serrations. The newly recorded species in Korea, A. rotundactyla is well accorded with the original description except for the number of pleonites dorsal teeth. The newly recorded species is described and fully illustrated in the present study. A key to the Abludomelita species in Korea is also provided. This additional record now brings the total recorded number of abludomelitid species to three in Korea.

• Restorative Dentistry and Endodontics
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• v.32 no.4
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• pp.377-384
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• 2007

Present tooth bonding system can be categorized into total etching bonding system (TE) and self-etching boding system (SE) based on their way of smear layer treatment. The purposes of this study were to compare the effectiveness between these two systems and to evaluate the effect of number of themocycling on microleakage of class V composite resin restorations. Total forty class V cavities were prepared on the single-rooted bovine teeth and were randomly divided into four experimental groups: two kinds of bonding system and another two kinds of thermocycling groups. Half of the cavities were filed with Z250 following the use of TE system, Single Bond and another twenty cavities were filled with Metafil and AQ Bond, SE system. All composite restoratives were cured using light curing unit (XL2500, 3M ESPE, St. Paul, MN, USA) for 40 seconds with a light intensity of $600mW/cm^2$. Teeth were stored in distilled water for one day at room temperature and were finished and polished with Sof-Lex system. Half of teeth were thermocycled 500 times and the other half were thermocycled 5,000 times between $5^{\circ}C$ and $55^{\circ}C$ for 30 second at each temperature. Teeth were isolated with two layers of nail varnish except the restoration surface and 1 mm surrounding margins. Electrical conductivity (${\mu}A$) was recorded in distilled water by electrochemical method. Microleakage scores were compared and analyzed using two-way ANOVA at 95% level. From this study, following results were obtained: There was no interaction between variables of bonding system and number of thermocycling (p = 0.485). Microleakage was not affected by the number of thermocycling either (p = 0.814). However, Composite restoration of Metafil and AQ Bond, SE bond system showed less microleakage than composite restoration of Z250 and Single Bond, TE bond system (p = 0.005).

• The Journal of Korean Academy of Prosthodontics
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• v.46 no.4
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• pp.381-395
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• 2008

Purpoose: For decades dental implants have been used widely in the field of prosthetic dentistry. However there is confusion when establishing treatment plans in cases where some teeth are remained but an insufficient number of implants can be used due to limited anatomical status and ecomomical problems. Many clinicians have tried to connect natural teeth and implants, and it still has controversy. But, there have been few studies on mechanical analysis of connecting natural teeth and implants with konus telescopic removable partial dentures. The purpose of this study was to analyze the stress distribution of prosthesis, abutment and alveolar bone when teeth and implants were connected with the konus telescopic denture, by means of 3-dimensional finite element analysis. Material and methods: The assumption of this study was that there were 2 mandibular canine (11 mm in length, 4 mm in diameter) and 2 implants(10 mm in length, 4 mm in diameter) which are located in the second premolar region. The mandible, teeth, implants, abutments, and connectors are modeled, and analyzed with the commercial software, ANSYS Version 8.1(Swanson, Inc., USA). The control group used implants instead of natural teeth. 21038 elements, 23544 nodes were used in experimental group and 107595 elements, 21963 nodes were used in control group, Stress distribution was evaluated under 150 N vertical load on 3 experimental conditions - between teeth and implants (Load case 1), posterior to implants (Load case 2), between natural teeth (Load case 3). Results: 1. In all load cases, higher von mises stress value was observed in the experimental group. 2. Maximum von miss stress observed in all load cases and all locations were as follows ; a. 929.44 Mpa in the experimental group, 640.044 Mpa in the control group in outer crown and connector - The experimental group showed 1.45 times high value compared with the control group. b. 145,051 Mpa in the experimental group, 142.338 Mpa in the control group in abutment - The experimental group showed 1.02times high value compared with the control group. c. 32.489 Mpa in the experimental group, 25.765 Mpa in the control group in alveolar bone - The experimental group showed 1.26times higher value compared with the control group. 3. All maximum von mises stress was observed in load case 2, and maxim von mises stress in alveolar bone was 32.489 Mpa at which implant failure cannot occur. 4. If maximum von mises stress is compared between two groups, the value of the experimental group is 1.02 times higher than the control group in abutment, 1.26 times higher than the control group in alveolar bone. Conclusion: If natural teeth and implants are connected with the konus telescopic denture, maximum stress will be similar in abutment, 1.26 times higher in alveolar bone than the control group. With this result, there may be possible to make to avoid konus telescopic dentures where natural teeth and implants exist together.

• The Journal of the Korean dental association
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• v.55 no.8
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• pp.528-536
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• 2017

Treatment with removable partial denture is effective for partially edentulous patients who are unable to obtain sufficient retention and stability for functional and esthetic restoration. There are several cases reporting the improvement of retention and stability of the partial denture using a small number of implants. However, there are limited studies on the implant-assisted removable partial denture using a small number of remaining teeth and the bar locator system. The bar locator system has an advantage in that it could compensate the angle of insertion of removable prosthesis on implant with inconsistent placement angle due to anatomical constraints compared to when using the locator only. This case report describes the patient with $Parkinson^{\circ}$Øs disease who was treated with the Locator bar system using two previously placed implants and two remaining teeth on maxilla. No additional implants could be placed because of the medical and economic condition of the patients, and the angle of one of two implants could not be matched with the direction of the removable partial denture insertion. Considering the angle of the implants, the patient was treated with implant-assisted RPD using the Locator bar system and had satisfactory results in the aspect of esthetics, masticatory function, and oral hygiene maintenance.

• Journal of the Korean Society of School Health
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• v.14 no.1
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• pp.73-81
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• 2001

The purpose of this study was to collect basic data for the development of effective oral health education program in elementary school. The subjects in this study Were 604 fourth-year, fifth-year and sixth-year students of an elementary school in Seoul, Oral health awareness and behaviors were surveyed and analyzed. The findings of this study were as follows: 1. The most common time for toothbrushing was after dinner(62.0%) and before bedtime(62.3%). By school year, the largest number who brushed their teeth after dinner were fourth and fifth graders while the greatest number who did so after breakfast were sixth graders. Seventy-four percent of respondents brushed the teeth twice or more a day. By school year, the fifth-year students brushed their teeth the least while girls outperformed the boys in daily toothbrushing frequency(p<0.05). Regarding the intake of cariogenic food, 62.1% took that kind of food once or more a day. By school year, the fifth graders took the most (p<0.05), and girls took more cariogenic food than the boys(p<0.05). 2. Ninety percent of the respondents had visited a dental clinic. By grade, the sixth-year students had visited a dental clinic more frequently and girls more frequently than boys. Eighty percent of the respondents visited a dental clinic to receive treatment but just 12.3% visited a dental clinic to prevent oral diseases. Concerning the fear of dental treatment, only 14.4% expressed fear. School year made no difference, yet the percentage of girls who experienced fear was higher than that of boys(p<0.05). Regarding preventive treatment, 39.7% experienced pit and fissure sealing and 24.2% experienced the application of fluorides. All the students hadn't much experience in preventive treatment regardless of school year -- gender didn't make a difference. 3. Fourty-six percent of respondents had a preference for the fluoride mouth rinsing program; 38.4% wanted that program to continue. As to the reason for preference, 38.2% preferred it because of the prevention of dental caries, 43.0%, the largest percentage, didn't favor it because they found it too much trouble to do(some of the respondents gave two different answers). 4. Despite an increase in the frequency of toothbrushing at the right time, they still took cariogenic food frequently. Their visit to a dental clinics also aimed at treatment more than at prevention, and they had very narrow experience of preventive treatment Furthermore, the fluoride mouth rinsing program failed to draw their interest Therefore, it is recommended that a successful oral health education program should be developed.

• Journal of the korean academy of Pediatric Dentistry
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• v.39 no.3
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• pp.249-256
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• 2012

Cone beam computed tomography (CBCT) has become widely available in recent years and is recognized as an important diagnostic tool for varies disease and condition of the orofacial structure. Clinician is easy to determine adequate treatment plan for pediatric patients by using CBCT. CBCT is used in Chonbuk National University Dental Hospital since 2005. This research presents clinical application of CBCT on patients visiting department of pediatric dentistry in Chonbuk National University Dental Hospital from Jan, 2005 to July, 2011. 1. Total number of patients taken CBCT is 252, and total number of area taken CBCT is 279. 2. An age group form 9 years to 12 years showing 53% was highest and percentage of 6~8 years showed 24%. 3. Chief complaints for CBCT taking are position and shape of impacted teeth (49.1%), mesiodens (19.4%), supernumerary teeth (7.9%), position and root canal shape of erupting teeth (7.2%), cyst (5.4%), inflammatory lesion (3.9%), odontoma (3.9%), tumor (2.2%), and et al. 4. Treatments are extraction (29.7%), orthodontic traction and leveling (24.0%), follow up (16.5%), refer to other professional part (11.5%), endodontic treatment (3.9%), surgical removal (2.9%), malsupialization (3.9%), enucleation (1.1%), and fail to follow up (5.0%), and et al.

• Journal of the korean academy of Pediatric Dentistry
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• v.49 no.2
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• pp.170-179
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• 2022

This study aimed to evaluate the masticatory performance of Korean children and adolescents and to investigate related factors. Early loss of primary molars, degree of occlusion of first molars, occlusal relationship of first molars, and presence of anterior crossbite were considered. From March 2020 to July 2021, 56 children and adolescents between the ages of 6 and 12 were included. The mixing ability index (MAI) was calculated to evaluate the masticatory efficiency of children and adolescents. The subjects were classified into three groups according to the number of early lost primary molars; normal dentition, 1 - 2 teeth lost, more than 3 teeth lost. The number of participants are 23, 18, and 15, respectively. There was no difference in the MAI values between the normal dentition group and the group has 1 - 2 teeth lost. However, when 3 or more primary molars were lost, the MAI value decreased and a significant difference was observed. This study is the first study to evaluate the masticatory performance of children and adolescents in Korea, and it will be helpful to pediatric dentists who evaluate the masticatory performance of children and adolescents and strive to improve the masticatory efficiency of children and adolescents in clinical practice.

• Restorative Dentistry and Endodontics
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• v.22 no.2
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• pp.546-559
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• 1997

The purposes of this study were to evaluate the efficiency of cavity preparation and to determine the incidence of tooth crack when root-end retrograde cavity preparation was done with ultrasonics. 91 distobuccal root-ends of extracted human maxillary first molars were cut by 3 mm perpendicularly to the long axis of tooth using a slow speed diamond saw, retrocavities were prepared using a slow-speed no. 2 round bur as controls, and stainless steel ultrasonic tips of power settings of 1 through 10 as experimentals. Time consumed and the number of strokes used for the cavity preparation were measured and evaluated, and the incidence of tooth cracks was observed under a stereomicroscope. The results were as follows : For the retrograde cavity preparation, time and number of strokes used were decreased as the ultrasonic power setting increased (p<0.001). High power setting of ultrasonics induced significantly more tooth cracks than did the slow-speed bur or low- and medium power setting of ultrasonics (p<0.05). Teeth with previous crack induced significantly more tooth cracks than those without previous one when high power setting of ultrasonics were used for the retrograde cavity preparation (p<0.001). Teeth with initial apical canal size of no. 10 induced significantly more crack than did those with size of no. 15 when low power setting of ultrasonics were used for the retrograde cavity preparation (p<0.05).

• Journal of Periodontal and Implant Science
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• v.31 no.3
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• pp.565-571
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• 2001

The purpose of this study is to determine if a relationship exists among osteoporosis, alveolar bone density and periodontal disease in postmenopausal osteoporotic women and postmenopausal healthy women. Twenty-two women were evaluated for this study. They were attending the postmenopausal clinic, Seoul National University Hospital and generally healthy except osteoporosis. They had experienced menopause not less than one year when we began to examine them. Bone densities of lumbar area(L2-L4) was determined by DEXA(LUNAR-expert Co,. U.S.A). We diagnosed osteoporosis when T-score was below -2.5 and healthy state when T-score was over -1. Osteoporotic(10 female), not hormone-treated group and healthy control group(12 female) were asked for their age, menopausal age, menopausal period and the number of remaining teeth and examined clinically for plaque index(PI), gingival index(GI), clinical attachment loss(CAL) on their 6 Ramfjord index teeth. Intraoral radiographs were taken in maxillary anterior zone. All films were equally exposed and developed. Each films was digitized and analysed using image processing software, Scion image. Alveolar bone regions of interest were selected and Intensity of each pixel was quantized in the array ranging from 0(white) to 255(black). The two groups were comparable with respect age, menopausal age, menopausal period and number of remaining teeth. The osteoporotic women had significantly lower alveolar bone density than controls in maxilla. But no significant difference was found with respect clinical attachment loss, plaque index and gingival index. Supported by the Ministry of Public Health and Welfare, Korea (HMP-00-CH-10-0009).