• Korean Chemical Engineering Research
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• v.59 no.4
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• pp.508-513
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• 2021

In order to improve the durability of a proton exchange membrane fuel cells (PEMFC), it is essential to improve the durability of the polymer membrane. In order to improve the durability of the membrane, an e-PTFE support and a radical scavenger are added. In this study, the chemical durability of the reinforced membrane with ePTFE support and the non-reinforced membrane was compared by Fenton reaction. In the Fenton experiment of the polymer membrane without the addition of a radical scavenger, the absorption rate of hydrogen peroxide solution and iron ions through the cross section of the specimen cut into small pieces was higher in the reinforced membrane, so that the fluorine outflow concentration was higher. According to the type and amount of radical scavenger added, the fluorine outflow concentration of the reinforced membrane has a large difference of more than 3 times, indicating that the effect of the radical scavenger was stronger than that of the support.

• Journal of Periodontal and Implant Science
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• v.36 no.2
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• pp.289-303
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• 2006

This study was performed to evaluate the effect of bone graft materials including demineralized freeze-dried bone, freeze-dried bone, deproteinized bovine bone on space-making capacity and bone formation in guided bone regeneration with titanium reinforced ePTFE membrane(TR-ePTFE). Adult male rabbits(mean BW 2kg) were used in this study. Intramarrow penetration defects were surgically created with round bur on calvaria of rabbits. TR-ePTFE membrane was adapted to calvarial defect and bone graft materials were placed. Animals were sacrificed at 2, 8, 12 weeks after surgery. Non-decalcified specimens were processed for histologic analysis and prepared with Villaneuva bone stain. The results of this study were as follows: 1. TR-ePTFE membrane was biocompatible and capable of maintaining the space-making. 2. Tissue integration was not good at TR-ePTFE membrane. Fixation was not enough. so, wound stabilization was not good. 3. In animals using deproteinized bovine bone, demineralized freeze-dried bone, bone formation was little. 4. In animals using freeze-dried bone, bone formation was better. Within the above results, bone formation may be inhibited when wound stabilizafion was not good.

• Journal of Periodontal and Implant Science
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• v.25 no.2
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• pp.301-320
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• 1995

The purpose of this study was to evaluate a new biodegradable membrane - atelocollagen as a guided tissue regeneration barrier on the dehiscence defects adjacent to the dental implants. 3 beagle dogs were selected for this study and all the mandibular premolars($P_1,P_2,P_3&P_4$) were extracted. Twelve weeks after the extraction, the edentulous ridges were formed to be placed the titanium plasma-sprayed IMZ implants. Four implant osteotomies were performed on each side of the mandible. The osteotomies were placed facially in the edentulous ridges to approximate an actual dehiscence defect as closely as possible, The standardized dehiscence defects were created 3 mm in width and 4 mm in height by osteotomy. A total 24 implants were placed. e-PTFE, ateloco11agen and $Collatape^{(R)}$ were placed to cover the defects and the one defect served as a control, not covered any membrane. By random selection, three dogs were sacrificed at 2 weeks, 4weeks and 8 weeks after fixation with 3% glutaraldehyde. A week before sacrificing, 8-week dog was infused intravenously with oxy-tetracycline 30mg/kg. The left mandibular blocks were used for full decalcified histologic preparation and the right mandibular blocks were selected for undeca1cified preparation, At 2 weeks, the regenerated bone of e-PTFE and atelocollagen groups appeared to be more dense than other groups and the percentage of bone defect fill was highest for e-PTFE and follwed by ateloco1lagen group. However, the $Collatape^{(R)}$ and control groups showed a little new bone formation. $Collatape^{(R)}$ was almost degraded within 2 weeks. At 4 weeks, the regenerated new bone were much greater and denser than at 2 weeks for e-PTFE and ateloco11agen group. Although a part of atelocollagen bagan to be degraded at the margin and surrounded by foreign body giant cells related to foreign body reaction, it was generally intact and the regenerated new bone was shown much more than at 2 weeks. The amount of new bone in $Collatape^{(R)}$ and control groups at 4 weeks were similar to that of 2 weeks group. At 8 weeks, the regenerated bone was matured and observed along the implant fixture. Direct new bone formation and calcium deposits beneath the e-PTFE were observed. No further bone growth was seen in the $Collatape^{(R)}$ and control groups. In reflected fluoromicrcocopic observation, the osteogenic activity was pronounced between e-PTFE membrane and the old bone. High osteogenic activity was also observed in atelocol1agen group. This study suggested that the ateloco11agen as well as e-PTFE could be used for guided tissue regeneration on dehiscence defects adjacent to the dental implants. But the $Collatape^{(R)}$ was completely resorbed within 2 weeks and was not a suitable membrane for guided bone regeneration.

• Korean Chemical Engineering Research
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• v.58 no.4
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• pp.524-529
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• 2020

To increase the mechanical durability of the proton exchange membrane fuel cells, a reinforced membrane in which a support is placed in the polymer membrane is used. The support mainly uses e-PTFE, which is hydrophobic and does not transfer ions, which may cause performance degradation. In this study, we investigated the effect of e-PTFE support on PEMFC performance and electrochemical durability. In this study, the reinforced membrane with the support was compared with the single membrane (non-reinforced membrane). Due to the hydrophobicity of the support, the water diffusion coefficient of the reinforced membrane was lower than that of the single membrane. The reinforced membrane had a lower water diffusion coefficient, resulting in higher HFR, which is the membrane migration resistance of ions, than that of a single membrane. Due to the low hydrogen permeability of the support, the OCV of the reinforced membrane was higher than that of the single membrane. The support was shown to reduce the hydrogen permeability, thereby reducing the rate of radical generation, thereby improving the electrochemical durability of the reinforced membrane.

• Journal of Periodontal and Implant Science
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• v.26 no.4
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• pp.967-987
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• 1996

The present study was to evaluate the healing patterns of guided tissue regeneration( GTR) using resorbable $Vicryl^{(R)}$(polyglactin 910) mesh and nonresorbable expanded polytetrafluoroethylene(ePTFE) membrane with or without bone grafting using autogeneous bone and demineralized freeze-dried bone allograft(DFDBA) in the grade II furcation defects. Mucoperiosteal flaps were reflected buccally in the mandibular 2nd, 3rd and 4th premolar areas and furcation defects were created surgically by removing $5{\times}6mm$ alveolar bone in 4 dogs. Root surfaces were thoroughly debrided of periodontal ligament and cementum, and notches were placed on root surface at the most apical bone level. In the right and left mandibular quadrant, each tooth was received $Vicryl^{(R)}$ mesh(ACE Surgical Supply Co., USA) only, $Vicryl^{(R)}$ mesh with DFDBA, $Vicryl^{(R)}$ mesh with autogeneous bone grafts, ePTFE membrane($Core-tex^{(R)}$ membrane, W.L. Gore & Associates Inc., USA) only, ePTFE membrane with DFDBA or ePTFE membrane with autogeneous bone grafts. For the fluorescent microscopic examination, fluorescent agents were injected at 2, 4 and 8 weeks after surgery. Four weeks after surgery, 2 dogs were sacrificed and ePTFE membranes were removed from remaining 2 dogs, which were sacrificed at 12 weeks after surgery. Undecalcified tissues were embedded in methylmethacrylate and $10{\mu}m$ thick sections were cut in a buccolingual direction. These sections were stained with hematoxylin-eosin stain and Masson's trichrome stain, and evaluated by descriptive histology and linear measurements. The results were as follows : 1) $Vicryl^{(R)}$ mesh group showed less connective tissue attachment than ePTFE membrane group. 2) The combination of GTR using $Vicryl^{(R)}$ mesh and osseous grafts resulted in new attachment and new bone formation more than GTR using $Vicryl^{(R)}$ mesh only. 3) GTR using ePTFE membrane, with or without osseous grafts, enhanced periodontal regeneration. 4) Root resorption and dentoalveolar ankylosis were observed in the areas treated with the combination of GTR and DFDBA. It was suggested that the effect of adjunctive bone grafting in GTR procedure depends on the materials and the physical properties of barrier membranes. $Vicryl^{(R)}$ mesh performed a barrier function and the use of adjunctive bone grafting may enhance the periodontal regeneration.

• Journal of Periodontal and Implant Science
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• v.26 no.1
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• pp.117-132
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• 1996

The purpose of this study was to evaluate the bacterial adherence on e-PTFE membrane immersed in whole saliva from subjects with different periodontal status. Experiment involved 3 subject groups: 5 persons with healthy periodontium(probing depth below 3mm and no signs of gingival inflammation including bleeding on probing), 10 patients with gingivitis(probing depth below 3mm and apparent signs of gingival inflammation), and 10 patients with advanced periodontitis(probing depth over 7mm and apparent signs of gingival inflammation). Each disease group was included before and after scaling and root planing treatment. After obtaining whole saliva from each subject, e-PTFE membrane(Gore-Tex periodontal membrane : $GTPM^{(R)}$, W.L. Gore & Associates, Flagstaff, USA) specimens were immersed at room temperature in the saliva aliqouts for 1, 3, 7 days. The weight between pre - and post - immersion in saliva was measured with the analytical balance and the difference was recorded. The specimens were processed for SEM observation. The bacterial adherence on the membrane specimens was evaluated using the scanning electron microscope images. The obtained results were as follows : 1. There was no difference in the weight of bacteria adherent to e-PTFE membrane specimens according to the periodontal status and the immersion periods. 2. As the exposure time to saliva increased, the bacterial adherence to the membrane specimen significantly increased in all groups(P<0.005). 3. As the severity of periodontal disease increased, the bacterial adherence to the membrane specimens significantly increased(p<0.001). 4. After scaling and root planing, the bacterial adherence to the membrane specimens significantly decreased in gingivitis and periodontitis patient group(P<0.001). These results suggest that bacterial contamination on exposed barrier membrane surface be reduced through improvement of periodontal status and oral health environment before and after GTR procedure for the successful outcome.

• Journal of Periodontal and Implant Science
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• v.30 no.3
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• pp.569-584
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• 2000

In order to evaluate the effects of the early exposure of e-PTFE membrane on the periodontal regeneration, 21 cases of 21 patients diagnosed as the chronic adult periodontitis were evaluated. All were class II furcation involvement cases. The control group was composed of 7 cases treated only by the flap operation. 14 cases were treated by the e-PTFE membrane as the experimental group, the membranes of 7 cases were exposed more than 1mm during healing period, which were named as the experimental group I, and the others, experimental group II. Clinical parameters such as probing pocket depth, clinical attachment level, bone probing depth, and gingival recession were recorded before the treatment and 6 months after the treatment. The results were as follows. 1. Significant probing depth reductions were observed for all groups(p<0.05), but no group shows significantly greater reductions than another. 2. Significant clinical attachment gains were observed for the experimental group II(p<0.05), no significant gains were observed in the other groups. 3. Significant bone probing depth reductions were observed for the experimental group II(p<0.05), no significant reductions were observed in the other groups. 4. All but the experimental group II exhibited a significant increase in gingival recession(p<0.05). The result suggested that is case of the e-PTFE membrane is exposed, the result is similar to that of flap operation without membrane. Therefore selecting the proper treatment case, intricate surgical procedure and infection control are essential for minimizing the chance of membrane exposure and finally for the good treatment results.

• Journal of Periodontal and Implant Science
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• v.34 no.1
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• pp.149-162
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• 2004

This study was performed to evaluate the effect of freeze-dried bone graft on space-making capacity and bone formation in the procedure of guided bone regeneration with titanium reinforced ePTFE membrane. After decortication in the calvaria, GBR procedure was performed on 8 rabbits with titanium reinforced ePTFE membrane filled with human FDBA(Rocky Mountain Tissue Bank,Aurora Co., USA). Decortication was performed to induce the effect of bone forming factor from bone marrow. The animals were sacrificed at 2 weeks, 4 weeks, 8 weeks and 12 weeks after the surgery. Non-decalcified specimens were processed for histologic analysis. πle results of this study were as follows: 1. Titanium reinforced-ePTFE membrane was biocompatable and capable of maintaining the space-making. 2. FDBA particle was surrounded with connective tissues but there was no evidence on new bone formation. 3. FDBA particle resorbed continuously but it remained until 12weeks after the surgery. Within the above results, TR-ePTFE membrane could be used effectively for Guided bone regeneration but It was assumed that FDBA does not appear to contribute to bone formation.

• Journal of Periodontal and Implant Science
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• v.38 no.2
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• pp.179-190
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• 2008

Purpose: In this study, the effect of micro-macroporous biphasic calcium phosphate(MBCP) incorporated with inorganic polyphosphate for bone regeneration in the calvaria of rabbit was evaluated. Materials and Methods: The procedure of guided bone regeneration was performed with titanium reinforced expanded polytetrafluoroethylene(TR-ePTFE) membrane. Four animal groups were compared : 1) TR-ePTFE membrane for negative control group, 2) TR-ePTFE membrane filled with MBCP for positive control group, 3) TR-ePTFE membrane filled with MBCP soaked in 4% inorganic polyphosphate for experimental group I, and 4) TR-ePTFE membrane filled with MBCP soaked in 8% inorganic polyphosphate for experimental group II. Results: 1. Negative control group showed the highest new bone formation at 16 weeks. 2. Positive control group showed the smallest new bone formation compared to other groups. 3. 8% inorganic polyphosphate induced more volume of bone formation, otherwise experimental group II did not show significant difference compared to negative control group. Conclusion: These results suggest that inorganic polyphosphate has a promoting effect on bone regeneration, possibly by enhancing osteoconductivity of the carrier and by increasing osteoinductivity of the defected alveolar bone tissue.

• Journal of Periodontal and Implant Science
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• v.27 no.1
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• pp.19-43
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• 1997

The barrier membranes for GTR procedure could be affected bY bacterial contamination after exposure to oral environment. This study was done to evaluate whether the tetracycline impregnated barrier membranes could inhibit bacterial attachment and penetration into membranes. The resorbable membrane(polylactic and polyglycolide copolymer, $Resolute^{(R)}$, W.L Gore and Associates, Inc..USA) and the non-resorbable membrane(e-PTFE; Gore-TexTM, W.L. Gore & Associates, Inc.,USA) were cut into 4mm discs and trated with 5% tridodecylmethylammonium chloride solution in ethanol and dried in air. The membranes were immersed in tetracycline(TC) solution (100mg/ml, pH 8.0) and dried. To the maxillary canine-premolar region in six periodontally healthy volunteers, removable acrylic devices were inserted, on which 8 cylindrical chambers were glued with TC impregnated and non-impregnated discs, the membrane discs were examined for bacterial attachment and penetration, and structural changes under SEM and LM. From the 1st day to the 7th day, membranes showed bacterial plaque formation composed of cocci and rods. Thereafter, filamentous bacteria appeared and the plaque thickness increased. The TC impregnated e-PTFE membranes showed less bacterial attachment and delayed in bacterial plaque maturation than non-treated membranes. As for bacterial penetration, the TC impregnated e-PTFE membranes showed superficial invasion and infrequent presence of bacteria in unexposed inner surface at the 4th week. while the non-treated e-PTFE membranes showed deep bacterial invasion at the 2nd week and frequent presence of internal bacteria at the 4th week. The resorbable membranes started to be resorbed at the 2nd week and were perforated at the 4th week, regardless of TC treatment. In conclusion, bacterial plaque formation and penetration was efficiently delayed in TC impregnated e-PTFE membranes, whereas resorbable membranes were similar in bacterial invasion due to membrane degradation and perforation, regardless of TC treatment.