• The korean journal of orthodontics
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• v.28 no.1 s.66
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• pp.143-153
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• 1998

Platelet-derived growth factor(PDGF) and lipopolysaccharide(LPS) may be the important regualtors of bone metabolism Exogenous PDGF is recognized to have a stimulating effect on bone resorption in organ culture but to stimulate the formation of new bone ultimately. LPS is known to be a stimulating agent on the osteoclastic activity. The purpose of this study was to evaluate the effects and the interaction of PDGF and LPS on periodontal ligament(PDL) cells which have important roles in bone remodeling. Cultured human periodontal ligament cells were tented with various concentration or PDGF and/or LPS. The cellular viability was measured by Microtitration(MTT) assay according to the lapse time of culture. The obtained results were as follows: 1. The viability of PDL cells was not different from the con01 in 0.1ng/ml of PDGF, but was significantly increased to be over the level of control in 1ng/ml of PDGF at the second day of culture, and in 10ng/m1 of PDGF at the second and the third day of culture. 2. The cellular viability was decreased in $0.5{\mu}g/ml$ or $5{\mu}g/ml$ LPS at the third day of culture. 3. Incubation with both 1ng/ml or 10ng/ml of PDGF and $0.5{\mu}g/ml$ of $5{\mu}g/ml$ of LPS resulted in the increased cellular viability at the third day, which was greater than LPS only treated group. It was greater than even the control group in 10ng/m1 of PDGF. From the above findings, we could summarize that the admixture of PDGF and LPS could not less increase the viability of the human periodontal ligament cells than PDGF only.

• Journal of Periodontal and Implant Science
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• v.41 no.1
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• pp.10-16
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• 2011

Purpose: Avulsed tooth can be completely recovered, if sound periodontal ligament (PDL) of tooth is maintained. Although a lot of storage solutions have been explored for the better storage of avulsed tooth, there is a shortcoming that the preservation time is much short. On the other hand, there has been studies that (-)-epigallocatechin-3-gallate (EGCG), the most abundant polyphenol in green tea, which is related to the anti inflammatory, antioxygenic, and antibacterial effects, allows the successful preservations of tissues and cells. This study evaluated the effect of EGCG on avulsed-teeth preservation of Beagle dogs for a period of time. Methods: The atraumatically extracted teeth of Beagle dogs were washed and preserved with 0/10/$100\;{\mu}M$ of EGCG at the time of immediate, period 1 (4 days in EGCG-contained media and additional 1 day in EGCG-free media), period 2 (8 days in EGCG-contained media and additional 2 days in EGCG-free media) and period 3 (12 days in EGCG-contained media and additional 2 days in EGCG-free media). Then, the cell viabilities of preserved teeth was calculated by dividing optical density (OD) of 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay with OD of eosin assay to eliminate the measurement errors caused by the different tissue volumes. Results: From the results, the immediately analyzed group presented the highest cell viability, and the rate of living cells on teeth surface decreased dependent on the preservation period. However, the $100\;{\mu}M$ of EGCG-treated group showed statistically significant positive cell activity than EGCG-free groups throughout preservation periods. Conclusions: Our findings showed that $100\;{\mu}M$ EGCG could maintain PDL cell viability of extracted tooth. These results suggest that although EGCG could not be a perfect additive for tooth preservation, it is able to postpone the period of tooth storage. However, further in-depth studies are required for more plausible use of EGCG.

• The korean journal of orthodontics
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• v.24 no.4 s.47
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• pp.871-883
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• 1994

This experiment was designed to study possible roles of $interleukin-1\beta$, interleukin-6 and tumor necrosis $factor-\alpha$ in bone remodeling by measuring their effects on $PGE_2,\; LTB_4$ and collagenase production when they were administered to human periodontal ligament fibroblasts. Human periodontal ligament fibroblasts were collected from first premolars extracted for orthodontic treatment. They were incubated in the environment of $37^{\circ}C,\;5\%\;Co^2,\;and\;100\%$ humidity. They were treated with $0.25\%$ trypsin-EDTA solution and centrifuged. PDL cells in the fifth to seventh passage were used for the experiment. Cells were seeded onto the culture dishes and when they were successfully attached, human recombinant $interleukin-1\beta$, interleukin-6, and tumor necrosis $factor-\alpha$ were administered, alone or in combination. They were incubated for 4, 8 and 24 hours and the levels of $PGE_2,\;LTB_4$ and collagenase released into the culture media were assessed by enzymeimmunoassay and collagenase activity assay. The conclusions are as follows: 1. $IL-1\beta\;and\;TNF-\alpha$ were very active in stimulating the production of $PGE_2$ and collagenase by human periodontal ligament fibroblasts, while IL-6 increased $LTB_4$ production. 2. $IL-1\beta$ significantly increased $PGE_2$, but $LTB_4$ Production was not increased. $IL-1\beta$ is thought to act mainly via the cyclooxygenase pathway of arachidonic acid metabolism. 3. IL-6 tended to inhibit $IL-1\beta$ in the production of $PGE_2$ and collagense whereas IL-6 and $TNF-\alpha$ showed auditive effect in the level of $PGE_2$. The above cytokines increased the release of at least one of $PGE_2,\;LTB_4$ and collagenase. It suggests that cytokines are involved in bone remodeling process by stimulating PDL fibroblasts to produce various bone-resorptive agents. The roles of cytokines in bone remodeling as a whole would need further study.

• The korean journal of orthodontics
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• v.25 no.3 s.50
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• pp.333-339
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• 1995

The hormonally active vitamin D metabolite, 1,25-dihydroxy vitamin $D_3[1.25-(OH)_2D_3]$ is one of the several humoral factors that may regulate osteoblast differentiation. The purpose of this study was to evaluate the effects of $1,25-(OH)_2D_3$ on the PDL cells. Human PDL cells were prepared from the first premolar tooth extracted for the orthodontic treatment and they were incubated in the environment of $37^{\circ}C,\;5\%\;CO_2\;and\;95\%$ humidity. $[{^3}H]$-thymidine incorporation as a measure of proliferation potential and alkaline phosphatase activity were evaluated at 10nM, 100nM $1,25-(OH)_2D_3$. The observed results were as follows. 1. $1,25-(OH)_2D_3$ was significantly enhanced $[{^3}H]$-thymidine incorporation at 100nM, But did not affect by 10nM. 2. $1,25-(OH)_2D_3$ was significantly increased alkaline phosphatase activity at 1 day and 6 days in a dose-dependent manner.

• The korean journal of orthodontics
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• v.28 no.3 s.68
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• pp.419-429
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• 1998

This study was carried out in order to study early histologic changes and repair reaction appling to extrusive force for 3rd premolar of adult dogs. After 1 week of extrusive force with elastic chain, one of dogs was sacrified and after 3 weeks retention period, another dog was sacrified. The paraffin sections of samples were stained with Hematoxylin - Eosin and Masson's Trichrome and were examed by light microscopy . The obtained results as follows 1. In Hematoxylin - Eosin and Masson Trichrome stain of control group , the periodontal ligament width was constant from apical third to cervical third of the root and periodontal fiber arrangement was horizontal or oblique in cervical third. oblique in middle third, oblique in apical third of root. in alveolar bone, smooth appearance was shown 2. In Group 1, all periodontal fiber arrangement was oblique toward tooth, and the periodontal ligament width increased Partially PDL was ruptured in apex. In MT stain, immature bone formation was seen at alveolar crest area. Active bone formation was observed along the one side of alveolus, and apical portion of pulp was involved with blood vessel rupture , vacuolization of pulp tissue and hyperemia 3. In Group 2, most periodontal ligament arrangement and PDL width was repaired and fiber density increased. In MT stain, mineralization of immature bone on the alveolar crest was progressed. In pulp, vacuole and hyperemia was diminished and fibrotic change was diminished 4. After 3 week periodontal ligament has more repair ability than pulp tissue. pulp was involved with vacuolization and fibrosis, so it takes more time for repair.

• Journal of the korean academy of Pediatric Dentistry
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• v.34 no.2
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• pp.192-203
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• 2007

This study histologically assessed the effect of topical alendronate application on periodontal healing in replanted teeth in fifty four SD Rats. Upper first molars in rat were extracted and replanted after dried during 15 minutes or 60 minutes in the air. In Group I, all teeth were replanted after 15 minutes of dry storage without any other treatment. In Group II and III, the pulps were removed and all teeth were replanted after soaking 10 min in Hank's balanced salt solution with/without alendronate, followed by 60 minutes of dry storage. the rats were sacrificed after 7, 15 and 30 days. The histological parameters studied were healed PDL, surface inflammatory and replacement resorption, and inflammatory severity. The following conclusions could be drawn from the present investigation. 1. Group I showed lower inflammatory root resorption and inflammation severity rate, compared to Group II and Group III. In Group I there showed effective for reattachment and regeneration of PDL. 2. In Group II, inflammatory root resorption were more severe and faster than other groups. There were extensive root resorption in the rats sacrificed after 30 days. 3 In Group III, there were localized inflammatory resorption in several areas, but extensive resorption did not occur Group III showed increase in root resorption rate, compared to Group I. However this difference was not statistically significant. 4. There were no difference between sacrificed days in replacement root resorption in all groups.

• Journal of Periodontal and Implant Science
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• v.27 no.4
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• pp.883-908
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• 1997

Bone remodeling is characterized by the coupling of osteoclast-mediated bone resorption and osteoblast-mediated bone formation. The process is tightly regualted at the local level by an incompletely known netwotk of peptide and non-peptide fators. Nitric oxide(NO), synthesized by nitric oxide synthetase(NOS) from L-arginine, is becoming recognized as an important bioregualtory molecule in a variety of tissue, but little is known about its possible role in periodontal tissue. The purpose of this study is to investigate the expression of nitric oxide synthetase(NOS) in inflamed gingiva and the effects of cytokine on the expression of NOS protein. The expression of NOS in gingival tissue was evaluated by immunohistochemical staining for $NOS_1$, $NOS_2$, $NOS_3$. The effect of cytokine on the expression of NOS in human periodontal ligament cells and osteoblast-like HOS cells by western blot analysis. Further, we studied that NO functions in periodontal ligament cells as a regulatory molecule. PDL cells incubated with NOS inhibitor and donor. The protein expression, type I collagen & non-collagenous protein, nitrate production and cell proliferation were evaluated The results were as follows. 1. $NOS_1$, $NOS_2$, $NOS_3$ was rarely distributed in healthy gingiva, but stronger stained in gingival epithelium, endothelial cells, and mononuclear cells of inflammed gingiva. 2. The cytokine stimulated $NOS_1$, and $NOS_3$ protein were not inducing or inhibitory effect to compared with control in PDL and HOS cells. 3.Incubation of cells with combination of $TNF-{\alpha}$, $IFN-{\gamma}$, LPS result in a time dependant increase in $NOS_2$ expression, reaching a maximal level after 24 hours of stimulation. 4. The osteonectin protein inhibitory effect of NMA, inhibitor of NOS, was reversed by Larginine in dose dependant manner. 5. NMA decreased cell poliferation and nitrate production, but the inhibitory efffect of NMA was also prevented by the NO donor, sodium nitropruiside. These results suggest that exogenously synthesized NO was playing a stimulating effect on cell proliferation or on non-collagenous protein expression. Therefore NO have an important role in mediation of localized bone destruction associated inflammatory bone disease such as periodontitis.

• Journal of the korean academy of Pediatric Dentistry
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• v.32 no.3
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• pp.395-402
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• 2005

In considering the healing process of injured periodontal tissue, healing rate would be influenced by the cellular activity of periodontal fibroblasts(PDLFs). In addition, the reattachment among PDLFs should be induced for healing process. The purpose of this study was to evaluate the effects of epidermal growth factor(EGF) on the proliferation and attachment of PDLFs and to verify the efficacy of EGF as a storage media or a pre-replantation conditioner of traumatically avulsed tooth. Human recombinant epidermal growth factor(hrEGF) and human periodontal fibroblasts from first premolar were prepared. At first, MTT assay was done to evaluate the toxic effect on human periodontal fibroblast and the maximum cellular growth of EGF. Cellular proliferation rate was then compared between control group and 10ng/ml EGF added group. Also, western blot was done to evaluate the expression of fibronectin in both groups. The results were as follows: 1. From MTT assay, EGF showed no toxic effect on PDL fibroblasts. The highest proliferation was shown at 10ng/ml EGF. 2. In 10ng/ml EGF added group, the degree of proliferation of PDLFs was significantly higher than that in control group. 3. Fibronectin expression of EGF added group was also significantly higher than that of control group. From this study we could conclude that EGF enhanced the regeneration rate of periodontal fibroblast, which could be used as a pretreatment agent or a storage media for traumatically avulsed teeth.

• Journal of the Optical Society of Korea
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• v.8 no.2
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• pp.83-89
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• 2004

A variable optical attenuator with a bending-sensitive fiber (BSF) that can be used in optical networks is developed. The refractive index profile of the BSF is divided into four regions which are inner core, center dip of inner core, outer core and clad. The 3-dimensional finite difference beam propagation method (3D FD-BPM) is utilized to find the characteristics of the BSF, so the mode profile of the BSF and optical power attenuation according to the bending are investigated, and the equivalent model of the BSF is made. By using this equivalent model of the BSF, the BSF is fabricated, and the refractive index profile of the BSF is measured, which is similar to refractive index profile of the proposed BSF. The fabricated variable optical fiber attenuator (VOFA) consists of the BSF in a rectangular rubber ring with a fixed bend radius (BR) in a steady state. The VOFA using the proposed BSF was able to attenuate the optical power by more than about －38 ㏈ at certain wavelengths (1540∼1560 nm) based on adjusting the mechanical pressure applied to the upper surface of the rectangular rubber ring with the bent BSF. In addition, the proposed VOFA produced an insertion loss of 0.68 ㏈, polarization dependent loss (PDL) of about 0.5 ㏈, and return loss of less than －60 ㏈.

• Journal of Dental Rehabilitation and Applied Science
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• v.20 no.1
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• pp.57-70
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• 2004

The significance of occlusion has regained its popularity in dentistry with the introduction of implant therapy. Literature has reported that the clinical success and longevity of dental implants can be achieved by biomechanically controlled occlusion. Occlusal overload is known to be one of the main causes for implant failure. Evidences have suggested that occlusal overload contribute to early implant bone loss as well as deosseointegration of successfully integrated implants. Unlike natural teeth, osseointegrated implants are ankylosed to surrounding bone without the periodontal ligament (PDL) which provides mechanoreceptors as well as shock-absorbing function. Moreover, the crestal bone around dental implants may act as a fulcrum point for lever action when a force (bending moment) is applied, indicating that implants/implant prosthesis could be more susceptible to crestal bone loss by applying force. Hence, it is essential for clinicians to understand inherent differences between teeth and implants and how force, either normal or excessive force, may influence on implants under occlusal loading. The purposes of this paper are to review the importance of implant occlusion, to establish the optimum implant occlusion with biomechanical rationale, to provide clinical guidelines of implant occlusion and to discuss how to manage complications related to implant occlusion.