• The korean journal of orthodontics
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• v.28 no.5 s.70
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• pp.813-823
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• 1998

The frictional force has been considered as an harmful factor in an active unit where tooth movement occurs, but as an advantageous factor in anchor unit that resist tooth movement. That is, efficient tooth movement is planned by using ligation methods that have low levels of bracket-wire frictional force and the anchorage control can be achieved by using ligation methods that have high levels of bracket-wire frictional force that result in binding of the bracket accompanied by little or no tooth movement. The purpose of this study was to evaluate the frictional force generated between bracket and wire in accordance with the methods of ligation, the material of ligation and the passage of time under artificial saliva. Tested were 0.017x0.022 inch stainless steel wires in standard edgewise twin brackets for upper central incisors in a 0.018-inch slot. The wires were ligated into the brackets with elastomeric modules and stainless steel ligatures. Whole tie, half tie, twisting tie and double overlay tie were done with elastomeric modules. With 0.009-inch stainless steel ligature whole tie and half tie were done by needle holder and whole tie by ligature tying plier. With 0.012-inch stainless steel ligature whole ties were done by needle holder. Whole tie groups of elastomeric module were kept in artificial saliva bath at $37^{\circ}C$ for 28 days. The frictional force was recorded by means of an Instron universial testing instrument (4202 INSTRON, Instron Co., U.S.A.) at initial, 7, 14, 21, and 28 days. The results for ligated samples in a simulated oral environment revealed the fellowing : ${\cdot}$In elastomeric module whole tie, 28 days group was significantly greater mean static frictional force than any other group but there were no significant differences among any other group (p>0.05). ${\cdot}$Elastomeric module twisting ties were significantly greater mean static frictional forces than any other ligation method but there were no significant differences between twisting tie and double overlay tie (p>0.05). Twisting tie, double overlay tie, whole tie, half tie showed differences in decreasing order. ${\cdot}$Stainless steel half tie produced lower mean static frictional force than whole tie, ligation by ligature tying plier produced greater mean static frictional force than by needle holder and ligation with 0.012-inch stainless steel ligature produced greater mean static frictional force than with 0.009-inch stainless steel ligature (p<0.05). ${\cdot}$There were no significant differences between the mean static frictional forces of elastomeric whole tie and stainless steel whole tie (p>0.05).

• The Journal of Korean Academy of Prosthodontics
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• v.55 no.2
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• pp.144-150
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• 2017

Purpose: The aim of this in vitro study is to investigate load bearing capacity of esthetic abutments according to the type of material and wall thickness. Materials and methods: 70 specimens equally divided into seven groups according to their abutment wall thicknesses. The abutments prepared with titanium 0.5 mm wall thickness were used as a control group (Ti-0.5), whereas zirconia abutments and resin nano ceramic abutments with wall thickness 0.5 mm, 0.8 mm and 1.0 mm were prepared as test groups (Zir-0.5, Zir-0.8, Zir-1.0 and RNC-0.5, RNC-0.8, RNC-1.0). All specimens were tested in a universal testing machine to evaluate their resistance to fracture and all of them underwent thermo-cycling before loading test. Mean fracture values of the groups were measured and statistical analyses were made using two-way ANOVA. Results: Zir-1.0 showed the highest mean strength ($2,476.3{\pm}342.0N$) and Zir-0.8 ($1,518{\pm}347.9N$), Ti-0.5 ($1,041.8{\pm}237.2N$), Zir-0.5 ($631.4{\pm}149.0N$) were followed. The strengths of RNC groups were significantly lower compared to other two materials (RNC-1.0 $427.5{\pm}72.1$, RNC-0.8 $297.9{\pm}41.2$) and the strengths of all the test groups decreased as the thickness decreases (P < .01). RNC-0.5 ($127.4{\pm}35.3N$) abutments were weaker than all other groups (P < .05). Conclusion: All tested zirconia abutments have the potential to withstand the physiologic occlusal forces in anterior and posterior regions. In resin nano ceramic abutments, wall thickness more than 0.8 mm showed the possibility of withstanding the occlusal forces in anterior region.

• Journal of Dental Rehabilitation and Applied Science
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• v.18 no.3
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• pp.157-170
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• 2002

The purpose of this study is to analyze the shear bond strength according to kinds of surface treatment agents and resin cements after acid etching of IPS Empress 2. For this purpose, test groups were classified into silane-treated bonding groups, silica-coated group and Targis link applied group. Then, nine bonding groups in total, each three groups per kind, were prepared by using three kinds of resin cements-Panavia F, Variolink II and Rely-X ARC, and thirty test specimens per group were prepared. To examine any changes in the oral environment, the shear bond strength of each test specimen was measured after dipping test for 24 hours and for five weeks, respectively, in distilled water at $37^{\circ}C$ and performing heat cycle 10,000 times in total, each 2,000 times per week, during a five weeks of dipping, under the condition similar to the oral environment. The bond failure modes were also observed by means of a scanning electron microscope. The results are summarized as follows 1. Statically significant differences between the surface conditioning materials were observed. The shear strength of the silane treatment was the highest of all three types of surface treatments(p<0.001). 2. Shear strengths varied significantly for different types of resin luting agents. But bond strength of Targis link surface treatments were not significantly different(p<0.05). 3. No significant difference of bonding strengths was found between storage time conditions(24 hours and 5 weeks). Only group II, IV, VII, IX were significantly different(p<0.05). 4. After thermocycling, the shear bond strengths of all groups were significantly decreased (p<0.05). Group III, V, VI were no significantly different. 5. On the SEM observation of fractured surfaces, all groups were shown complex failure.

• Journal of Life Science
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• v.26 no.11
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• pp.1320-1329
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• 2016

The present study examined the cytotoxic effects of 1, 2, 3, 4, 6-penta-O-galloyl-${\beta}$-D-glucose (PGG), known as the pentahydroxy gallic acid ester of glucose, in the various human cancer cell lines (A-549, MDA-MB-231, U87-MG, MCF-7 and PANC-1), normal MRC-5 fetal fibroblasts, and dental papilla tissue- derived mesenchymal stem cells (DPSCs). Significantly (p<0.05) lower half maximal inhibitory concentration ($IC_{50}$) values were observed in the A-549 and MDA-MB-231 cells showing a high proliferation capacity, compared with other cancer and normal cell lines with a relatively low proliferation capacity. The population doubling time (PDT) was significantly (p<0.05) higher in the $10{\mu}M$ PGG-treated cell lines than those of untreated control cell lines. The present study demonstrated that the $IC_{50}$ value increases proportionally to the extending PDT. A high cell number with senescence-associated ${\beta}-galactosidase$ activity was also observed in the $10{\mu}M$ PGG-treated cells compared with those of untreated control cells. Moreover, the level of telomerase activity was significantly (p<0.05) decreased with $10{\mu}M$ PGG treatment, especially in A-549 and MDA-MB-231 cells showing a high proliferation capacity. Based on these observations, PGG could serve as a potent agent for cancer chemotherapy, as its treatment was more effective in cells with a high proliferation capacity.

• Journal of Life Science
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• v.21 no.5
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• pp.631-646
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• 2011

Mesenchymal stem cells (MSC) are multipotent and can be isolated from diverse human tissues including bone marrow, fat, placenta, dental pulp, synovium, tonsil, and the thymus. They function as regulators of tissue homeostasis. Because of their various advantages such as plasticity, easy isolation and manipulation, chemotaxis to cancer, and immune regulatory function, MSCs have been considered to be a potent cell source for regenerative medicine, cancer treatment and other cell based therapy such as GVHD. However, relating to its supportive feature for surrounding cell and tissue, it has been frequently reported that MSCs accelerate tumor growth by modulating cancer microenvironment through promoting angiogenesis, secreting growth factors, and suppressing anti-tumorigenic immune reaction. Thus, clinical application of MSCs has been limited. To understand the underlying mechanism which modulates MSCs to function as tumor supportive cells, we co-cultured human adipose tissue derived mesenchymal stem cells (ASC) with cancer cell lines H460 and U87MG. Then, expression data of ASCs co-cultured with cancer cells and cultured alone were obtained via microarray. Comparative expression analysis was carried out using DAVID (Database for Annotation, Visualization and Integrated Discovery) and PANTHER (Protein ANalysis THrough Evolutionary Relationships) in divers aspects including biological process, molecular function, cellular component, protein class, disease, tissue expression, and signal pathway. We found that cancer cells alter the expression profile of MSCs to cancer associated fibroblast like cells by modulating its energy metabolism, stemness, cell structure components, and paracrine effect in a variety of levels. These findings will improve the clinical efficacy and safety of MSCs based cell therapy.

• The korean journal of orthodontics
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• v.28 no.4 s.69
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• pp.533-546
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• 1998

A Skeletal Class III malocclusion may be the result of a large mandible, a small maxilla or combination of the two. Protraction devices for the maxilla are used to promote the growth of a deficient maxilla by applying extraoral force to actively growing patients. This study has been performed to determine whether there are significant differences in skeletal and dental changes between FH/Pal 1 and FH/Pal 2 group, SNA 1 and SNA 2 group, SNB 1 and SNB 2 group, and LFH 1 and LFH 2 group after RME and facial mask therapy. The results of this study can be summarized and concluded as follows ; 1. In all patients after maxillary protraction, the maxilla and maxillary dentitions moved forward, and the mandible rotated backward and downward. In most of them, palatal plane is tends to have an upward inclination. 2. The FH/Pal group 1, having an upward inclination of the palatal plane as a result of Facial mast showed statistically significant maxillary forward movement compared to the FH/Pal group 2. 3. The SNA group 1 showed significantly less mandibular backward movement and there was a tendency for the palatal plane to upward inclination compared to SNA group 2. 4. The SNB group 1 showed significantly less maxillary forward movement, but the vertical dimension, especially the lower facial height increased by mandibular downward rotation compared to SNB group 2. 5. LFH group 1, which had large saddle angle and posterior positioned mandible in the pre-treatment stage, showed maxillary protraction effect without significant increase in lower facial height compared to LFH group 2.

• Journal of the korean academy of Pediatric Dentistry
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• v.34 no.4
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• pp.560-568
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• 2007

This study was performed to compare the shear bond strength of primary enamel & dentin treated by AQ Bond $Plus^{TM}$ and G $Bond^{TM}$, recently developed 6th generation dentin bonding system, to that of Single $Bond^{TM}$ being widely used. Also by observing the resin tag under scanning electron microscope, Resin tags of each material were also observed under scanning electron microscope and compared to one another. The possibility of clinical application of All-in-One system which has an advantage to reduce chair-time for children with difficult behavior pattern was evaluated. The results obtained are as follows: 1. No statistically significant difference between groups was found in shear bond strength of primary enamel. 2. In primary dentin, the shear bond strength of AQ Bond $Plus^{TM}$ was $1.15\;{\pm}\;0.37\;MPa$, G $Bond^{TM}$ was $1.69\;{\pm}\;0.74\;MPa$ and Single $Bond^{TM}$ was $0.56\;{\pm}\;0.11\;MPa$. There were no statistical difference between AQ Bond $Plus^{TM}$ and G $Bond^{TM}$ and between G $Bond^{TM}$ and Single $Bond^{TM}$, whereas statistically significant difference was found between AQ Bond $Plus^{TM}$ and Single $Bond^{TM}$. 3. Under scanning electron microscope, resin tags observed in AQ Bond $Plus^{TM}$ and G $Bond^{TM}$ were very weak and tangled while strong and thick tags were shown with many lateral branches in Single $Bond^{TM}$. The result of the present study coupled with the advantages of less working time over the previous generation suggests that All-in-One system might be effectively used in adhesive dental procedures for primary teeth.

• Journal of Dental Rehabilitation and Applied Science
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• v.24 no.2
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• pp.213-230
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• 2008

The aim of this study was to analyze the initial movement and the stress distribution of each tooth and periodontal ligament during the lingual lever-arm retraction of 6 maxillary incisors using FEA. Two kinds of finite element models were produced: 2-properties model (simple model) and 24-properties model (multi model) according to the material property assignment. The subject was an adult male of 23 years old. The DICOM images through the CT of the patient were converted into the 3D image model of a skull using the Mimics (version 10.11, Materialise's interactive Medical Image Control System, Materialise, Belgium). After series of calculating, remeshing, exporting, importing process and volume mesh process was performed, FEA models were produced. FEA models are consisted of maxilla, maxillary central incisor, lateral incisor, canine, periodontal ligaments and lingual traction arm. The boundary conditions fixed the movements of posterior, sagittal and upper part of the model to the directions of X, Y, Z axis respectively. The model was set to be symmetrical to X axis. Through the center of resistance of maxilla complex, a retraction force of 200g was applied horizontally to the occlusal plane. Under this conditions, the initial movements and stress distributions were evaluated by 3D FEA. In the result, the amount of posterior movement was larger in the multi model than in the simple model as well as the amount of vertically rotation. The pattern of the posterior movement in the central incisors and lateral incisors was controlled tipping movement, and the amount was larger than in the canine. But the amount of root movement of the canine was larger than others. The incisor rotated downwardly and the canines upwardly around contact points of lateral incisor and canine in the both models. The values of stress are similar in the both simple and multi model.

• Journal of Dental Rehabilitation and Applied Science
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• v.26 no.3
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• pp.221-239
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• 2010

Bone loss may occur depending on the loading conditions. careful treatment planning and prosthetic procedures are very important factors for the proper distribution of stress. Evaluate the stress distributions according to numbers and location of implants in three-unit fixed partial dentures. A mandible missing the right second premolar, first molar and second molar was modeled. Using the CT data. we modeled a mandible with a width of 15mm, a height of 20mm and a length of 30mm, 2mm-thickness cortical bone covering cancellous bone mallow. An internal type implant and A solid type abutment was used. A model with 3 implants placed in a straight line, offset 1.5 mm buccally, offset 1.5 mm lingually and another model with 3 implants offset in the opposite way were prepared. And models with 2 implants were both end support models, a mesial cantilever model and a distal cantilever model. Three types of loading was applied; a case where 155 N was applied solely on the second premolar, a case where 206 N was applied solely on the second molar and a case where 155 N was applied on the first premolar and 206 N was applied on the first and second molar. For all the cases, inclined loads of 30 degrees were applied on the buccal cusps and vertical loads were applied on the central fossas of the teeth. Finite element analysis was carried out for each case to find out the stress distribution on bones and implants. This study has shown that prostheses with more implants caused lower stress on bones and implants, no matter what kind of load was applied. Furthermore, it was found out that inclined loads applied on implants had worse effects than vertical loads. Therefore, it is believed that these results should be considered when placing implants in the future.

• Journal of agricultural medicine and community health
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• v.25 no.2
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• pp.427-440
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• 2000

A comparative study was made about health resources, medical care service statistics and public health service statistics by health subcenters at Jangdong and Jangpyung townships, Jangheung County, Chollanamdo before and after the unification of two health subcenter to improve their function. 1. While two general physicians, one dentist, 4 nurse aids arid one oral hygienist were working at two health subcenters with simple facility with examination room and public health office in 1997 prior to the unification, in 1999 after the unification of two health subcenters 14 staff including a specialist physician, a general physician, a dentist, a herb hygienist, a radiology technician and a physical therapist were working in the new health subcenters equipped with appropriate facilities in two storey building. 2. In 1997 before the unification the yearly total income of two health subcenters was 78,815 thousand won(about 14,000 won per capita) and the amount was 140,376 thousand won(about 25,000 won per capita) in 1999 after the unification. And the income was used for operation of health subcenters excluding personnel expense. 3. While 90.5% of visitors to the health subcenters came for general medical care, and 91.6% came for the revisit before the unification, after the unification 71.2% came for general medical care, 10.8% for dental care, 16.5% for oriental physician's care, 29.7% for the first visit and 70.3% for revisit. Most common problem cared for was musculoskeletal disorder like arthralgia. Average treatment cost per person per month was 9,363 won before the unification and 8,309 won after the unification. 4. Through the comparison of execution rate of public health services before and after the unification. the practice rate of most health service among target population including visiting service for chronic illness, maternal and child health service and immunization service increased after the unification. The practice rate of tuberculosis control service, hypertension control and diabetes management was a little decreased. In conclusion, continuous effort to satisfy all persons in two townships and evaluation are necessary to coincide with the spirit of unification of two health subcenters.