• The korean journal of orthodontics
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• v.41 no.4
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• pp.280-287
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• 2011

Objective: This study compared the stability of cylindrical miniscrews (Cy, 7 mm in length) with that of tapered miniscrews (Ta, 5 mm in length), using torque values to determine if the healing time before loading affects the stability of the miniscrew and if the insertion torque is associated with the removal torque measured after a few weeks of healing. Methods: Ta and Cy with different thread lengths were placed in the tibias of 12 female New Zealand white rabbits (body weight: 3.0 - 3.5 kg), and the maximum insertion torque values (ITV) were measured. No orthodontic forces were applied so as to allow us to determine the pure effects of the different shapes. After 3 different healing periods (2, 4, and 6 weeks), maximum removal torque values (RTV) were measured immediately before the rabbits were sacrificed. Results: No miniscrews were loosened. There were no significant differences in ITV or RTV between the Ta and Cy nor were there any significant differences in the ITV and RTV between the 3 groups, which had different healing periods. There was a correlation between the ITV and RTV. Conclusions: Shorter Ta showed similar stability as Cy, as determined by torque values. This result strongly suggests that the tapered shape is more advantageous than the cylindrical shape. The RTV did not increase significantly over time. It is recommended that a miniscrew be loaded immediately; waiting a few weeks before loading should be avoided. The correlation between the ITV and RTV suggests that the ITV can be used to estimate a screw's future stability.

• Journal of the korean academy of Pediatric Dentistry
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• v.36 no.4
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• pp.575-579
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• 2009

Behcet's disease(BD) is a multisystem vasculitis that almost any organ in the body may be involved. Its diagnosis bases on clinical criteria in the absence of any specific laboratory test to confirm it. The clinical criteria proposed for the diagnosis for BD include recurrent oral and genital ulceration, skin lesion, ocular changes, and positive response to pathergy test. Besides these essential features, BD may manifest itself on the gastrointestinal tract, central nervous system, and other systemic involvements. Among these clinical features, recurrent oral ulcers are present in most BD patients, often as the initial symptom, preceding other manifestations by many years. Therefore, dentists are in the important position for the early detection and diagnosis of BD. In this case report, we are presenting a case of 6 year-old girl, who came to the pediatric dentistry department for evaluation and treatment of pain and dysphagia caused by severe recurrent oral ulcers. Through taking detailed dental and medical history and clinical examination, we reported the possibility of BD to the medical team and prescribed topical lidocaine to relief pain during swallowing. The medical team, which involved pediatrics, ophthalmology, dermatology, and gastroenterology, finally confirmed BD through various examinations. Detection of the possibility of BD in the dental field helped early diagnosis and proper management by the medical team.

• International Journal of Oral Biology
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• v.33 no.4
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• pp.205-211
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• 2008

Gingival overgrowth can cause dental occlusion and seriously interfere with mastication, speech, and dental hygiene. It is observed in 25 to 81% of renal transplant patients treated with cyclosporine A (CsA). CsA-induced gingival overgrowth (CIGO) is caused by quantitative alteration of the extracellular matrix components, particularly collagen. However, the molecular mechanisms involved in the pathogenesis of CIGO remain poorly understood, despite intense clinical and laboratory investigations. The aim of the present work is to identify differentially expressed genes closely associated with CIGO. Human gingival fibroblasts were isolated by primary explant culture of gingival tissues from five healthy subjects (HGFs) and two patients with the CIGO (CIGO-HGFs). The proliferative activity of CsA-treated HGFs and CIGO-HGFs was examined using the MTT assay. The identification of differentially expressed genes in CsA-treated CIGO-HGF was performed by differential display reverse transcriptase-polymerase chain reaction (RT-PCR) followed by DNA sequencing. CsA significantly increased the proliferation of two HGFs and two CIGO-HGFs, whereas three HGFs were not affected. Seven genes, including the beta subunit of prolyl 4-hydroxylase (P4HB) and testican 1, were upregulated by CsA in a highly proliferative CIGO-HGF. The increased P4HB and testican-1 mRNA levels were confirmed in CsA-treated CIGO-HGFs by semiquantitative RT-PCR. Furthermore, CsA increased type I collagen mRNA levels and suppressed MMP-2 mRNA levels, which are regulated by P4HB and testican-1, respectively. These results suggest that CsA may induce gingival overgrowth through the upregulation of P4HB and testican-1, resulting in the accumulation of extracellular matrix components.

• The Journal of Korean Academy of Prosthodontics
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• v.42 no.6
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• pp.628-640
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• 2004

Statement of problem. Wear as a result of repeated closing/opening cycles may decrease the friction coefficient of screw head, threads, and other mating components and, consequently, resistance to opening gradually decreases. It may cause screw loosening, which is one of the most common failures in implant prosthesis. Purpose. The purpose of this study is to evaluate the changes on the head and thread surface of the abutment screws after repeated closing and opening through the examination of tested screws in SEM(scanning electron microscope). Materials and methods. Five species of abutments were selected (3i-three, Avana-two) respectively by two pieces. The implant fixtures were perpendicularly mounted in liquid unsaturated polyesther(Epovia, Cray Valley Inc.) with dental surveyor. Each abutment was secured to the implant fixture by each abutment screw with recommended torque value using a digital torque controller. The abutment screws were repeatedly tightened and removed 20 times with a digital controller. FESEM (field emission scanning electron microscope, Netherland, Phillips co., model:XL 30 SFEG) was used to observe changes of each part caused by repeatedly closing/opening expeiment. First, the Photomicrographs of pre-test screws provided by each manufacturer were taken. The changes of each screw were investigated after every fifth closing and opening experiment with FESEM. Scaning electron microscope photomicrographs of each screw were taken four times. Results. As the number of closing and opening was increased, the wear or distortion of hexed or squared slot that contacted with the driver tip was more severely progressed. Wear or distortion of hexed slot was more severe than that of squared slot and it was more remarkable in the titanium screw than in the gold screw. All the tested screws showed that the width in the crest of their screw thread decreased gradually as the test was proceeded. Conclusions. Conclusively, we recommend the clinical use of gold screw, a periodic exchanges of abutment screws and avoiding repeated closing/opening unnecessarily. We also suggest a more careful manipulation of the abutment screw and screw-driver and using of abutment screw with an acute-angled slot design rather than an obtuse-angled one. Finally, it is suggested that the new slot design and the surface treatment for enduring wear or distortion should be devised.

• Journal of Technologic Dentistry
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• v.35 no.2
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• pp.145-155
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• 2013

Purpose: The recent proliferation of the aging population, oral health care is closely related to the mental health of the elderly is very important being recognized. Provide basic data for improving the quality of life for the elderly, to determine whether the oral health of the elderly whether oral self-perception of health and any related wish. Methods: Surveys to May 20 from April 15, 2011, subjects were elderly and living in Daejeon and Chungnam 277 people were examined. All the statistics using SPSS 18.0 for the determination of statistical significance, and the significance level was 0.05. Results: 1. Recognized, the most common oral health, self-aware bad the state (46.2%) there was no significant difference in the general characteristics according to self-Oral health status, remaining natural dimensions or the intra-oral prosthetic, there was no significant difference. More teeth, residual phase, in accordance with intra-oral prosthetic mandibular Not all dentures, partial dentures, full dentures net self-perception of oral health status better recognized. 2. According to the type of partial dentures, oral health status self-phase, mixed mandibular removable, fixed, fixed, removable partial dentures in order to recognize that good oral health, self-aware state, showed between them, there was no significant difference. 3. Of variable dimension that has nothing to do with the remaining natural maxillary and mandibular prosthetic maxillary prosthetic mandibular partial dentures, age income, a positive correlation was negatively correlated. The case of the mandible, the mandibular prosthetic mandibular partial denture, maxillary prosthetic, the amount of income were correlated. 4. Intra-oral Prosthetics correlation variables in the maxillary, mandibular prosthesis, the positive correlation between income, age was negatively correlated, if the income of the mandible. Maxillary partial denture has nothing to do with the variable portion of the mandibular denture, age was a negative correlation was found. Conclusion: Satisfaction and how now it is important simply to live as long, but you need to pay attention to the quality of life, sometimes with an aging population and the increase of soybean To buy the loss of teeth causes the typical health problems of the elderly. Elderly people of any relevant oral health and the oral cavity by the state to determine whether to provide the basic data for oral health education was more residual value, intra-oral prosthetics there is no more self-aware, the oral health status is good to recognize that appeared. Strengthen the oral health education to improve the quality of life of the elderly, and is thought to be necessary to increase the number of residual.

• Journal of Oral Medicine and Pain
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• v.37 no.2
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• pp.93-105
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• 2012

Let me introduce a teaching method to improve practice capacity in dental laboratary work. I applied theories of layers of modeling and reflection constituting cognitive apprenticeship and peer tutoring to my class. At internet uploading a file showing a practice procedure a week before the class of a course, I let students preview it. During the class I demonstrated the practice procedure in front of students. A superior student and an inferior student paired according to the previous practice grade and a feedback between a peer tutor and a peer tutee was activated. Late in the class, a student self-evaluated his own practice result and had a check of a professor. Finally he compared his own practice result with that in the file uploaded at internet and reflected. This teaching method led to improvement in students' satisfaction and efficiency of learning.

• The Journal of Korean Academy of Prosthodontics
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• v.38 no.4
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• pp.427-437
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• 2000

Recently the 2nd generation laboratory composite resins were introduced. Although the mechanical properties of these composite resins have been improved, there were some disadvantages such as discoloration, low abrasion resistance and debonding between metal and resin. The purpose of this study was to evaluate the tensile bond strength between non-pecious dental alloy(verabond) and four veneering reinforced composite resins ; Targis(Ivoclar Co., U.S.A.), Artglass(Kulzer CO., Germany), Sculpture(Jeneric Pentron Co., U.S.A.), and Estonia(Kurary Co., Japan). All test metal specimens were polished with #1,000 SiC paper, and sandblasted with $250{\mu}m$ aluminum oxide. After then. according to manufacturer's instructions metal adhesive primer and veneering resins were applied. All test specimens were divided into two groups. One group was dried in a desiccator at $25^{\circ}C$ for 3 days, the other group was subjected to thermal cycling($2,000{\times}$) in water($5/55^{\circ}C$). Tensile bond strength was measured using Instron Universal Testing machine and the fractured surface was examined under the naked eyes and scanning electron microscope. Within the limitations imposed in this study, the following conclusions can be drawn: 1. In no-thermal cycling groups, there were no significant differences between Estenia and VMK68 but there were significant differences between Targis, Artglass, Sculpture and VMK68(p<0.05). 2. In no-thermal cycling resin groups, the highest tensile bond strength was observed in Estenia and there were significant differences between Estenia and the other resins(p<0.05). 3. Before and after thermal cycling, there were significant differences in tensile bond strength of Targis and Artglass(p<0.05). The tensile bond strength of Artglass was decreased and that of Targis was increased. 4. In no-thermal cycling groups, Artglass showed mixed fracture modes(95%), but after thermal cycling, Artglass showed adhesive fracture modes(75%).

• The Journal of Korean Academy of Prosthodontics
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• v.57 no.4
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• pp.321-327
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• 2019

Purpose: To evaluate an effect of additional firing process after sintering of monolithic zirconia crown on marginal and internal fit through three-dimensional analysis. Materials and methods: Ten monolithic zirconia crowns were fabricated using titanium abutment model. Monolithic zirconia crowns were designed, milled, and sintered as a control group, and additional firing with coloring was performed as a test group. Three dimensional analysis were performed by using triple-scan protocol, and cross-section analysis on mesio-distal and disto-lingual section was evaluated to measure marginal and internal fitness. Then, three-dimensional surface difference on between two groups was evaluated (${\alpha}=.05$). Results: There was statistically significant difference between the control group ($32.0{\pm}24.3{\mu}m$) and the test group ($17.0{\pm}10.8{\mu}m$) in the mesial axial wall (P < .02) and the control group ($60.2{\pm}24.3{\mu}m$) and the test group ($71.8{\pm}21.5{\mu}m$) in the distal axial wall (P < .01). There was no statistically significant difference at the remaining point. Conclusion: There was no statistical significance on the deviation of inner surface of crown according to firing number, and the results of both group were considered clinically acceptable.

• Journal of Technologic Dentistry
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• v.41 no.2
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• pp.63-69
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• 2019

Purpose: The purpose of this study is to evaluate the effect of CAD/CAM system milling tool wear on the marginal and internal fit of PMMA implant interim prosthesis three-dimensional manner. Methods: A total of 20 crowns were fabricated with CAD/CAM method. Their designs were unified to first molar of the left maxilla. The Customized abutments were prepared and scanned with on optical model scanner. Five crowns were milled by the newly replaced tool (1st milling), and 15 crowns were milled by 2nd, 3rd, 4th milling tool. The marginal and internal fit of 20 interim crowns were measured using the triple-scan protocol. Results: Statistically significant difference was found between the $1^{st}$ milling group ($51.8{\pm}14.6{\mu}m$) and the $3^{rd}$, $4^{th}$ milling group ($128.6{\pm}43.8{\mu}m$, $146.2{\pm}38.1{\mu}m$, respectively) at the distal margins. In the mesial margins, There was a statistically significant difference between the $1^{st}$ milling group ($63.6{\pm}25.9{\mu}m$) and the $3^{rd}$, $4^{th}$ milling group ($137.2{\pm}25.9{\mu}m$, $186.8{\pm}70.6{\mu}m$, respectively). In the distal line angle, significant difference was found between the $1^{st}$, $2^{nd}$, $3^{rd}$ milling groups and the $4^{th}$ milling group. In the mesial axial wall, significant difference was found between the $1^{st}$ milling group ($52.2{\pm}20.3{\mu}m$) and the $3^{rd}$, $4^{th}$ milling groups ($22.8{\pm}8.8{\mu}m$, $7.8{\pm}5.7{\mu}m$). Conclusion: As a result of the experiment, decrease of the marginal and internal fit was statistically significant as the number of machining cycles increased. In order to produce clinically excellent restorations, it is recommandable to consider the condition of the milling tool wear, when designing the restoration with CAD program.

• Journal of Microbiology and Biotechnology
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• v.26 no.10
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• pp.1817-1823
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• 2016

Areca nut (AN) chewing is a habit in many countries in Central, Southern, and Southeast Asia. It is strongly associated with the occurrence of oral, pharyngeal, and esophageal cancer as well as systemic inflammation. However, the association between AN intake and the development of gastric lesions has not yet been identified. The aim of this study was to investigate the effect of AN on gastric diseases using a mouse model for Helicobacter pylori infection. We studied four groups of mice: those fed a normal diet (ND), those fed a diet containing 2.5% AN (AD), those fed ND and infected with H. pylori PMSS1 strain (ND/HP), and those fed AD and infected with H. pylori PMSS1 strain (AD/HP). Food intake and body weight were monitored weekly during the experiments. At 10 weeks, the mice were sacrificed, and the stomach weight, H. pylori colonization, and gastric inflammation were evaluated. The stomach weight had increased significantly in the ND/HP and AD/HP groups along with increases in H. pylori colonization; however, there was no significant difference between these two groups with respect to stomach weight and colonization. On histological grading, mononuclear cell infiltration was severer in the AD/HP group than in the ND/HP group. These data suggest that chronic gastric inflammation was aggravated by AN treatment in the mice with H. pylori-induced gastric lesions. Furthermore, as previously suggested, this animal model is useful to determine the effect of potential carcinogens on gastric lesions induced by H. pylori infection.