• The korean journal of orthodontics
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• v.36 no.5
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• pp.339-348
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• 2006

Objective: With development of the skeletal anchorage system, orthodontic mini-implant (OMI) assisted on masse sliding retraction has become part of general orthodontic treatment. But compared to the emphasis on successful anchorage preparation, the control of anterior teeth axis has not been emphasized enough. Methods: A 3-D finite element Base model of maxillary dental arch and a Lingual tipping model with lingually inclined anterior teeth were constructed. To evaluate factors influencing the axis of anterior teeth when OMI was used as anchorage, models were simulated with 2 mm or 5 mm retraction hooks and/or by the addition of 4 mm of compensating curve (CC) on the main archwire. The stress distribution on the roots and a 25000 times enlarged axis graph were evaluated. Results: Intrusive component of retraction force directed postero-superiorly from the 2 mm height hook did not reduce the lingual tipping of anterior teeth. When hook height was increased to 5 mm, lateral incisor showed crown-labial and root-lingual torque and uncontrolled tipping of the canine was increased.4 mm of CC added to the main archwire also induced crown-labial and root-lingual torque of the lateral incisor but uncontrolled tipping of the canine was decreased. Lingual tipping model showed very similar results compared with the Base model. Conclusion: The results of this study showed that height of the hook and compensating curve on the main archwire can influence the axis of anterior teeth. These data can be used as guidelines for clinical application.

• The korean journal of orthodontics
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• v.28 no.1 s.66
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• pp.17-27
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• 1998

Study on growth change of dental arch is considered to both an important data in orthodontic diagonsis and treatment planning as well as analysis of treatment results , also, arch form is important in anthropology and dentistry, even more so in prosthodontics and orthodontics. In the field of orthodontics, studies on the functional aspect of upper and lower teeth and maintenance of stability of dentition and occlusion were carried out from the early days. Some of the early studies include explanation of growth change in dental arch from measuring directly fom human stroll, and afterwards, cephalometrics x-rays were introduced; accordingly, studies using cephalometric measurement and linear measurements of study models were often performed. By this method, arch width, arch depth and perimeters were measured, and growth change or dental arch was studied. The subject ror this study were sn children(boys and girls or ages from 3 yens to 12 years from Kang-won district and Seoul, who has no history of orthodontic treatment and who show healthy status and normal growth and development. Cephalometric x-ray, panoramic x-ray, and study model were taken for each subject consecutively for 2 years, and the subjects are still followed up. 400 pairs of study models from the past two years were used in this study; mesio-distal diameater of each tooth, intercanine width, intermolar width, canine depth, molar depth and arch perimeters were measured. Afterwards, mean value and each standard deviation of each age group and each gender were obtained, and representation graph were drawn. The following conclusion were obtained. 1. Intercanine width showed gradual increase until the age of 10-years and after that, showed no increase. 2. Intermolar width in upper arch showed gradual increase : intermolar width in lower arch showed no significant chang, and after the age of 9-years, showed increase. 3. Cainine arch depth showed relatively rapid increase after the age of 6-years, and this pattern was more obvious in lower arch. 4. Molar arch depth increased gradually in both archs and it decrease after the age of 10-years : this phenomenon was more prominent in the lower arch. 5. Arch perimeter showed gradual inerease and convert to plateau at the age of 10-years, after that, it decreased. this pattern was more prominent in lower arch.

• Journal of the korean academy of Pediatric Dentistry
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• v.44 no.2
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• pp.154-163
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• 2017

This study aims to investigate the utilization status of dental services by foreign children living in Seoul and their level of satisfaction with the treatments. We developed a structured questionnaire with 35 questions, which comprised 14 questions (demographic characteristics) and 21 questions (oral hygiene and dental experience of the child). In this study, the distribution of nationality of 391 participants differed from the actual statistics in Korea. It consisted of high percentage of participants from African countries (23.6%), as well as North American countries (24.1%). In addition, the education status of most parents was above the level of college graduate. Despite the relatively high socioeconomic status of the participants, they showed minimal dental health knowledge regarding the aspect of oral hygiene. Utilization of dental health services and the types of dental clinics visited by them were similar before and after coming to Korea. The participants showed overall satisfaction with the care, but many of them expressed the need for improvement with regard to treatment fee and communication. In conclusion, foreign children living in Seoul require appropriate dental health education and governmental support to promote regular dental check-ups, to improve their overall oral health, and prevent the incidence of dental caries.

• The Korean Journal of Pesticide Science
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• v.20 no.1
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• pp.1-6
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• 2016

In order to obtain efficient control effect of the pesticide, it is important to ensure uniform adhesion to the desired plant parts at the right time. Pesticide spray method (application technology) is an important factor affecting the efficacy and crops persistent expression. The aim of this study was to develop an efficient system to investigate the coating weight distribution of citrus leaves due to the difference between the nozzle and spray sprinkler system using dithianon used in citrus scab. Other An, engine type sprayer was used as the control. Speed sprayer and different sprinklers were wsed to way the deposit amounts of dithianon on citrus leaves. The test was conducted at the National Institute of Horticultural Herbal Science Citrus Research Station, located in the circle citrus Jeju Island. In order to examine whether the citrus orchard spray and the evenl on the whole, dithianon (43% flowable 1000-fold dilution) was sprayed, filter paper and leaves were analyzed by the height as top, middle, bottom. Speed sprayer the was most effective on depositing at the middle position, of the leaves. All other sprays the leaces except the dry mist sprinkler were not effective enough to deposit on the back sides. To achieve more deposits on the high position leaves, an improve ment in the nozzle and an efficient power system of sprayer were needed.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.2
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• pp.202-209
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• 2018

This study analyzed the effects of the nutrient intake on oral health and chewing difficulty according to the age group. The subjects were 5,855 participants of the third Korea National Health and Nutrition Examination Survey(KNHANES VI), 2015, Korea Centers for Disease Control and prevention and aged 20 years and over. The data were analyzed using SPSS Ver 21.0, classified as the difficulty in chewing group (DC) and no difficulty in chewing group (NDC). As a result, the DC rates were 5 times higher in the 60+ year age group (39.5%) than in the 20-39 year age group (8.1%). The DC group were experience periodontal disease (33.4%), dental caries (30.1%), diabetes (41.8%), myocardial infarction (57.3%), arthritis (44.0%), asthma (48.0%), and depression (41.9%). In addition, 86% of the DC group were experiencing speech problems. The DC group had significantly lower intakes (1446.59g), than the NDC group (1666.62g), and the protein, carbohydrate, dietary fiber and other dietary intake were significantly lower. These findings suggest that the chewing difficulty is related to the nutrient intake, and psychological status in the elderly DC group. Therefore, the care of chewing difficulties is essential for the elderly to maintain a healthy lifestyle. Accordingly, oral care and myofunctional therapy are needed to maintain oral health.

• Journal of the korean academy of Pediatric Dentistry
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• v.32 no.1
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• pp.49-54
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• 2005

Shell teeth, a rare dysplastic condition of dentin, was first described by Rushton in 1954. It is characterized by normal enamel, extremely thin dentin, correspondingly large pulp chambers, and shortened roots. This case report is of a male 3 years old. He is refered to the Chosun University dental hospital Pediatric Dentistry because of dental caries and dentin hypoplasia. Intra-oral examination showed attrition of all primary teeth. Radiographic examination showed that the pulps were extremely large with only a shell of surrounding hard tissue. The permanent premolars were missed congenitally. The diagnosis was shell teeth. Because of behavior problem, all dental treatment was undertaken with general anaesthesia. Extration, endodontic treatment and SS crown were performed. The patient has now been wearing the space maintainer and manages it well. The patient is seen intervals for supervision and follow-up care.

• Journal of the korean academy of Pediatric Dentistry
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• v.32 no.4
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• pp.604-610
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• 2005

This study was to evaluate the effects of several light curing units on the microleakage of composite resin restorations in primary teeth. The types of curing units were traditional low intensity halogen light(Optilux 360), plasma arc light(Filpo) low heat plasma arc light(Aurys) and high intensity LED(Freelight 2). After preparing cavities on sound primary teeth, cavities were filled with composite resin(Z100) using the same resin bond agent(Scotchbond Multi-Purpose) and were cured with each curing light system. After storing each specimen in sterile water for 24 hours, thermal circulation was done 1,000 times followed by pigmentation using 2% methylene blue solution. Each specimen was sliced and the degree of pigmentation was graded. When microleakage is graded, the average of Aurys was 0.95 which was the lowest and Freelight 2(1.05), Filpo(1.25), Optilux 360(1.30) followed. But values were not shown statistically significant difference (P>0.05). The results suggest that the newly developed curing units which has advantage in children by decreasing discomfort and procedure time can increase the microleakage of the composite resin.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.22 no.1
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• pp.70-75
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• 2000

The cemento-ossifying fibroma is a well-demarcated and occasionally encapsulated neoplasm composed of fibrous tissue that contains varying amounts of calcified tissue resembling bone, cementum, or both. The greatest number of cases are encountered during the third and fourth decades of life and there is a definite female predilection, with female-to-male ratios as high as 5 : 1 being reported. The mandible is involved far more than the maxilla, and 90 percent of all cases are located in the mandible. The mandibular premolar-molar area is the most common site. Radiographically, the lesion is most often well defined and unilocular. Depending on the amount of calcified produced in the tumor, it may appear as completely radiolucent ; more often it shows varying degrees of radiopacity. Some lesions may be largely radiopaque with a radiolucent halo. On microscopic study, the tumor is composed of fibrous tissue of varying degrees of cellularity containing calcified material. This may be in the form of trabeculae of osteoid and bone or basophilic ovoid calcifications that resemble cementum-like material. Admixture of the two types of calcifications are commonly seen. On this case, large cemento-ossifying fibroma has grown in the mandible and this lesion was treated by complete surgical excision and posterior iliac bone graft. A review of literature and a report of a case of cemento-ossifying fibroma are presented.

• Journal of Dental Rehabilitation and Applied Science
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• v.36 no.3
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• pp.168-175
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• 2020

Purpose: The purpose is to test and evaluate the physical properties of commonly used temporary restoration materials and newly emerged materials. Materials and Methods: Four groups of polymer materials were evaluated: Polymethyl methacrylate (PMMA) 2 groups, Polyetheretherketone (PEEK), Polycarbonate. Four physical properties were tested: surface hardness, bending strength, abrasion resistance during wear, wear behavior. The 3-axis bending strength and Vickers hardness test were measured using a universal testing machines respectively. The microstructure was observed with a scanning electron microscope and weight comparison was evaluated after 100,000 chewing tests using a chewing simulator. Kruskal wallis test was performed to evaluate statistical significance. Results: The four groups showed the highest flexural strength and Vickers hardness of PEEK, followed by PC, PMMA-H, PMMA-T. Microstructure observation also showed the least surface roughness in the PEEK group, followed by PC, PMMA-H, PMMA-T. Conclusion: PC is considered to have sufficient mechanical properties that can be applied to the manufacture of temporary teeth. However, further studies, such as biocompatibility, are considered to be necessary for practical clinical applications.

• Restorative Dentistry and Endodontics
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• v.35 no.6
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• pp.429-435
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• 2010

Objectives: The aim of this study was to investigate average working lengths of Korean posterior teeth and evaluate validity of endodontic file length. Materials and Methods: The endodontic working length of the posterior teeth of 670 Korean patients were measured than each mean value and standard deviation were investigated than the frequency deviation and standard deviation per each length were calculated. Results: Among the canals of premolar, 66.5% of canal length was marked under 20 mm by endodontic working length and 95.4% could be measured under 22 mm and Among the canals of molars, 95.5% of canal length was marked under 20 mm endodontic working length. Conclusions: With the result of measurement of endodontic working length of premolars of Korean, it suggested that 23 mm endodontic file is more proper than the 21 mm and 25 mm file on the market.