• The Journal of Korean Academy of Prosthodontics
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• v.48 no.2
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• pp.111-121
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• 2010

Purpose: This 3D-FEA study was performed to investigate the influence of marginal bone loss pattern around the implant to the stress distribution. Material and methods: From the right second premolar to the right second molar of the mandible was modeled according to the CT data of a dentate patient. Teeth were removed and an implant ($\Phi\;4.0{\times}10.0mm$) was placed in the first molar area. Twelve bone models were created; Studied bone loss conditions were horizontal bone loss and vertical bone loss, assumed bone loss patterns during biologic width formation, and pathologic vertical bone loss with or without cortification. Axial, buccolingual, and oblique force was applied independently to the center of the implant crown. The Maximum von Mises stress value and stress contour was observed and von Mises stresses at the measuring points were recorded. Results: The stress distribution patterns were similar in the non-resorption and horizontal resorption models, but differed from those in the vertical resorption models. Models assuming biologic width formation showed altered stress distribution, and weak bone to implant at the implant neck area seams accelerates stress generation. In case of vertical bone resorption, contact of cortical bone to the implant may positively affect the stress distribution.

• Archives of Craniofacial Surgery
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• v.10 no.1
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• pp.49-54
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• 2009

Purpose: Inevitably, Maxillary structural defect follows maxillary cancer extirpation. Maxillary reconstruction is over every surgeon's head. Every physician tried to overcome limited donor site of craniofacial defect. We considered to suggest optimal method of inferior orbital wall defect in functional point as well as esthetic point. Methods: We performed wide excision of maxilla and vascularized partial thickness calvarial bone flap to reconstruct the defect from cancer extirpation in three cases. We select ipsilateral superficial temporal artery, vein and outer cortex of parietal bone flap as donor. And we applied bone flap as inferior orbital wall structure. The bony surface was wrapped with fascia to prevent direct contact between orbital contents and rough bony flap surface. Computed tomography image was checked during follolw up period. Results: We can observe these patients for over two years. In all three cases, We can get fair inferior orbital wall structure. Even though they got radiation therapy, there was no limitation of extraocular movements, no diplopia. no enophthalmos. Also there was minimal donor site morbidity. Conclusion: We suggest vascularized calvarial bone flap is practically excellent strategy for inferior orbital wall reconstruction.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.34 no.4
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• pp.233-238
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• 2012

Purpose: To evaluate the effect of silvernanopartilce treated implants on the bone formation and osseointegration. Methods: Silvernanoparticle was produced using an anodic oxidation method. The size of silvernanoparticle ranged from 3.5 nm to 5.9 nm. To check the effect of the capability of osseointegration of silvernanoparticle coated Implant, 32 implants (16 piece of Implant treated with nanoparticle, and 16 piece of Implant was not treated for control) were placed at both the tibia of 8 New Zealand white rabbits. After 4 weeks, 4 rabbits were sacrificed and the removal torque was measured for comparison of the osseointagration ability. Further, 4 rabbits were sacrificed and sliced samples were made. H&E stain was done for microscopic finding. Results: The removal torque of the experimental group was $102.37{\pm}30.54$ N/cm, and the control group was $73.30{\pm}19.97$ N/cm. It was statistically significant (P<0.001). Microscopic finding also shows extinguish results in silvernanoparticle treated implants. Bone formation rate of the experimental group was 43.94% and the control group was 7.58%. It was observed to be statistically significant (P=0.017). Bone to implant contact rate of the experimental group was 58.09%, and the control group was 19.43%. It was found with statistical significance (P<0.001). Conclusion: The silvernanopartilce treated implant shows a better capability of bone regeneration and osseointegration than the non-treated one. Technology to produce smaller particles would make silver more useful and safer.

• Journal of Periodontal and Implant Science
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• v.50 no.2
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• pp.121-131
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• 2020

Purpose: Dental implant-associated medication-related osteonecrosis of the jaw has been frequently reported in patients administered bisphosphonates (BPs) to prevent osteoporosis. The aim of this study was to investigate the effect of intermittent administration of parathyroid hormone (PTH) on peri-implant bone in the maxillae of ovariectomized rats systemically administered BPs. Methods: Thirty 8-week-old female Sprague-Dawley rats were randomly divided into 3 groups. The OVX-ZP group included ovariectomized rats administered 60 ㎍/kg of zoledronate once a week for 6 weeks and 30 ㎍/kg PTH after implant installation. The OVX-Z group included ovariectomized rats administered 60 ㎍/kg of zoledronate once a week for 6 weeks and saline after implant installation, and the control group included rats that underwent a sham operation and were then administered saline. Rats were sacrificed 4 weeks after implant placement for histomorphometric and micro-computed tomography (CT) analyses. Results: The average bone area percentage was greater in the OVX-ZP group than in the OVX-Z group (53.4%±4.0% vs. 28.9%±9.5%, P=0.01). The bone-to-implant contact ratio was 50.8%±1.4% in the OVX-ZP group and 16.9%±2.4% in the OVX-Z group (P=0.012). The average bone volume ratio as shown on micro-CT was 31.3%±19.8% in the OVX-ZP group and 19.4%±9.3% in the OVX-Z group (P=0.045). The OVX-ZP and OVX-Z groups displayed similar trabecular thickness (0.06±0.004 mm vs. 0.06±0.002 mm) (P>0.05) and trabecular separation (0.21±0.02 mm vs. 0.29±0.13 mm) (P>0.05). However, the number of trabeculae in the OVX-ZP group was significantly higher than that in the OVX-Z group (4.3±1.33/㎣ vs. 2.2±0.19/㎣) (P=0.024). Conclusions: The present findings indicate that intermittently-administered PTH can promote peri-implant bone formation and suggest that PTH administration may aid in effective treatment for medication-related osteonecrosis of the jaw after dental implantation.

• Journal of Periodontal and Implant Science
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• v.46 no.6
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• pp.362-371
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• 2016

Purpose: The increasing demand for esthetically pleasing results has contributed to the use of ceramics for dental implant abutments. The aim of this study was to compare the biological response of epithelial tissue cultivated on lithium disilicate ($LS_2$) and zirconium oxide ($ZrO_2$) ceramics. Understanding the relevant physicochemical and mechanical properties of these ceramics will help identify the optimal material for facilitating gingival wound closure. Methods: Both biomaterials were prepared with 2 different surface treatments: raw and polished. Their physicochemical characteristics were analyzed by contact angle measurements, scanning white-light interferometry, and scanning electron microscopy. An organotypic culture was then performed using a chicken epithelium model to simulate peri-implant soft tissue. We measured the contact angle, hydrophobicity, and roughness of the materials as well as the tissue behavior at their surfaces (cell migration and cell adhesion). Results: The best cell migration was observed on $ZrO_2$ ceramic. Cell adhesion was also drastically lower on the polished $ZrO_2$ ceramic than on both the raw and polished $LS_2$. Evaluating various surface topographies of $LS_2$ showed that increasing surface roughness improved cell adhesion, leading to an increase of up to 13%. Conclusions: Our results demonstrate that a biomaterial, here $LS_2$, can be modified using simple surface changes in order to finely modulate soft tissue adhesion. Strong adhesion at the abutment associated with weak migration assists in gingival wound healing. On the same material, polishing can reduce cell adhesion without drastically modifying cell migration. A comparison of $LS_2$ and $ZrO_2$ ceramic showed that $LS_2$ was more conducive to creating varying tissue reactions. Our results can help dental surgeons to choose, especially for esthetic implant abutments, the most appropriate biomaterial as well as the most appropriate surface treatment to use in accordance with specific clinical dental applications.

• The Journal of Korean Academy of Prosthodontics
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• v.41 no.3
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• pp.300-318
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• 2003

Statement of problem: The success of implants depends on intimate and direct contact of implant material on bone tissue and on functional relationship with soft tissue contact. Creation and maintenance of osseointegration depend on the understanding of the tissue's healing, repairing, and remodeling capacity and these capacities rely on cellular behavior. Altering the surface properties can modify cellular responses such as cell adhesion, cell motility, bone deposition, Therefore, various implant surface treatment methods are being developed for the improved bone cell responses. Purpose: The purpose of this study was to evaluate the responses of osteoblast-like cells to surface-modified titanium. Materials and Methods: The experiment was composed of four groups. Group 1 represented the electropolished surface. Group 2 surfaces were machined surface. Group 3 and Group 4 were anodized surfaces. Group 3 had low roughness and Group 4 had high roughness. Physicochemical properties and microstructures of the discs were examined and the responses of osteoblast-like cells to the discs were investigated. The microtopography was observed by SEM. The roughness was measured by three-dimension roughness measuring system. The microstructure was analyzed by XRD, AES. To evaluate cell responses to modified titanium surfaces, osteoblasts isolated from calvaria of neonatal rat were cultured. Cell count, morphology, total protein measurement and alkaline phosphatase activities of the cultures were examined. Results and Conclusion: The results were as follows 1. The four groups showed specific microtopography respectively. Anodized group showed grain structure with micropores. 2. Surface roughness values were, from the lowest to the highest, electropolished group, machined group, low roughness anodized group, and high roughness anodized group. 3. Highly roughened anodized group was found to have increased surface oxide thickness and surface crystallinity. 4. The morphology of cells, flattened or spherical, were different from each other. In the electropolished group and machined group, the cells were almost flattened. In two anodized groups, some cells were spherical and other cells were flattened. And the 14 day culture cells of all of the groups were nearly flattened due to confluency. 5. The number of attached cells was highest in low roughness anodized group. And the machined group had significantly lower cell count than any other groups(P<.05). 6. Total protein contents showed no difference among groups. 7. The level of alkaline phosphatase activities was higher in the anodized groups than electropolished and machined groups(P<.05).

• Molecules and Cells
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• v.28 no.6
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• pp.515-520
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• 2009

Applications of bone marrow-derived mesenchymal stem cells in gene therapy have been hampered by the low efficiency of gene transfer to these cells. In current transduction protocols, retrovirus particles with foreign genes make only limited contact with their target cells by passive diffusion and have short life spans, thereby limiting the chances of viral infection. We theorized that mechanically agitating the virus-containing cell suspensions would increase the movement of viruses and target cells, resulting in increase of contact between them. Application of our mechanical agitation for transduction process has increased the absorption of retrovirus particles more than five times compared to the previous static method without changing cell growth rate and viability. The addition of a mechanical agitation step increased transduction efficiency to 42%, higher than that of any other previously-known static transduction protocol.

• The Journal of the Korean dental association
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• v.54 no.3
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• pp.198-205
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• 2016

The purpose of this paper was to investigate the significance of splinted and non-splinted implant-supported restorations with an internal connection for multiple consecutively missing teeth. Upon examination of the effects of fixture-abutment connection, the distribution of occlusal load was favorable in splinted implant-prosthesis with an external connection, but effect of strain distribution was not significant in splinted implant-prosthesis with an internal connection. In splinted implant-prostheses for short implants, strain distribution was not affected by the method of retention. For cement-retained prostheses, the effect of strain distribution due to splinting was not significant. In clinical studies, non-splinted prostheses with an internal connection for multiple consecutively missing teeth showed high survival rate, mild marginal bone loss, and stable periodontal condition. However, failure to achieve optimal proximal contact between single-unit prostheses may lead to food impaction, and veneer fracture may be inevitable when the framework provides inadequate support in the proximal region. In conclusion, splinted implant-prosthesis is not an indication in all cases, and clinical consideration of its use should be based on the patient's oral condition, such as location and number of implants, formation of proximal contact, canine guidance, existence of parafunctional habit, and oral hygiene, when multiple consecutively missing teeth are replaced by internal connection type implant.

• The Journal of Korean Academy of Prosthodontics
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• v.42 no.5
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• pp.556-571
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• 2004

Statement of problem: Surface texture of the implant is one of the important factors of the implant success, especially in the immediate implant loading. Many methods of the surface treatment of implant have developed and introduced. Purpose : This study was to evaluate the effects of the Ca-P coating implant crystallized the hydroxyapatite on the surface by the removal torque test and the histomorphometric analysis in vivo. Material and methods: 135 screw type implants, 4.0mm in length and 3.75mm in diameter were used in this study. Implants were divided into 3 groups and treated in the different mothods. Group I was not treated, Group II was treated in the SLA method, and Group III was treated in the Ca-P coating with the anodizing method and the hydroxyapatite was crystallized on the surface with the hydrothermal treatment. Firstly, the surface roughness of each group was measured, 45 rabbits were used in this experiment. Two implants were inserted on right tibial metaphysis and one implant was inserted on left side with the alternating order. After the healing periods of 3, 5, and 12 weeks, the rabbits were sacrificed to evaluate the osseointergration by the removal torque test and the histomorphometric analysis. Results : 1. In the analysis for the surface roughness, Group II showed the highest roughness. And Group III showed higher secondly. There was a significant difference one another statistically 2. In the removal torque test, Group III and II were significantly higher than Group I. There was no statistical difference between Group III and Group II. 3. For all Groups, the removal torque values at 12th week were significantly higher than at 3rd and 5th week. 4. In histomorphometric analysis, the bone implant contact rates of Group III and II were higher than that of Group I at 3rd and 5th week. There was a significant difference at 5th week. 5. In histomorphometric analysis, the bone implant contact rate of Group III and II increased from 3rd week to 5th week, but decreased at 12th week. In Group I, the contact rate at 12th week was significantly higher than at 3rd week and 5th week.

• The korean journal of orthodontics
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• v.17 no.2
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• pp.185-200
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• 1987

This paper was undertaken to observe the displacement of craniofacial complex with cervical headgear and to compare narrowing or widening effect of palate by use of contraction or expansion face-bow, respectively. The 3-dimensional finite element method(FEM) was used for a mathematical model composed of 597 nodes and 790 elements and an electrical resistance strain gauge investigation was performed to validate the finite element model. The outer bow of cervical headgear was adjusted to be placed below the occlusal plane by $25^{\circ}$ and met the midsagittal plane by $40^{\circ}$, and was loaded 1kg on each right and left hook toward posterior direction. The results were as follows 1. Generally, the maxillary teeth and facial bone were displaced in posterior, medial and downward direction. 2. It was the maxillary 2nd bicuspid that moved bodily. 3. The craniofacial complex rotated in a clockwise direction around the rotating axis which lay from the most posterior and lowest point connecting nasal crest of maxillary bone and vomer, progressively toward a more posterior, lateral and upward direction, anterior and upper area of pterygomaxillary fissure, base of medial pterygoid plate and laterally to the contact area of zygomatic arch with squamous part of temporal bone. 4. No contraction effect was observed by contraction face-bow when compared to the standard face-bow. 5. In case of expansion face-bow, the areas of maxillary 2nd bicuspid, molars and palate were expanded remarkably.