Papers by Author: Seong Ho Choi

Abstract: We developed new calcium phosphate bone substitute material, amorphous calcium polyphosphate. The new material is synthesized by a cement-like slif-setting reaction with calcium phosphate glass, basic materials and water. In this study, we prepared with CPG, Na2CO3 and NaOH solution. When they are mixed together, amorphous phase was precipitated. The precipitated amorphous phase consisted of polyphosphate chains condensed with Na ions released from Na2CO3 and NaOH. When the amorphous calcium polyphosphate dissolves, inorganic polyphosphates are released into the medium. The inorganic polyphosphates as the dissolution product inducted the calcification of the osteoblast cells. Therefore, in animal test, the new bone formation in rat calvarial defects treated with the new material was significantly higher than sham-surgery control group, especially in the initial stage. The amorphous calcium polyphosphate was biocompatible and bioresorbable and promoted the new bone formation.

Abstract: Calcium sulfate used in this study is newly fabricated to overcome its disadvantages; brittleness, difficult handling properties, rapid resorption and reaction heating. Especially when calcium sulfate is used in the graft procedure, it is difficult to control the setting time, solubility into blood and body fluid. To improve the handling properties, Calcium sulfate is mixed with Carboxylmethylcellulose (CMS). The putty type calcium sulfate used in the present study presented lower values in cementum formation and new bone formation than the control group. This may be due to use of poor osteoinductive calcium sulfate alone in the defect, limiting new bone formation. In addition, complete resorption of calcium sulfate after 8 weeks presents that addition of polymer failed to delay the resorption rate of calcium sulfate. Rather, it seemed to disturb the natural healing of the defect when compared with the findings in the control group. But the favorable result of calcium sulfate is shown when used with alloplast. The material used in the present study was developed for easier formability and manipulation avoiding scattering or dissolving of the material with blood or body fluid. However, the results reveal that further studies on effect of calcium sulfate with various other bone graft materials and ideal ratios in mixing the two should be determined in the future.However, the results reveal that further studies on effect of calcium sulfate with various other bone graft materials and ideal ratios in mixing the two should be determined in the future.

Abstract: The purpose of this study was to evaluate the osteogenesis of tetracycline blended chitosan membranes on the calvarial critical size defect in Sprague Dawley. An 8 mm surgical defect was created with a trephine bur in the area of the midsagittal suture. Forty rats were divided into four groups: negative control group, positive control group and two experimental groups. Three types of membranes were made and a comparative study was done. One type of non-woven membrane was made by chitosan for positive control. The other two types of non-woven membranes were made by immersing non-woven chitosan into either the tetracycline solution or the chitosan-tetracycline solution. Histologic analysis was done at 2 weeks and 8 weeks of healing periods. We concluded that that the use of tetracycline blended chitosan membrane on the calvarial defects in rats has a significant effect on the regeneration of bone tissue in itself. In addition it implicates that tetracycline blended chitosan membrane may be useful for guided tissue regeneration.

Abstract: This study evaluated periodontal repair and biomaterial reaction following implantation of a newly fabricated calcium phosphate chitosan block bone and chitosan membrane on the regeneration of 1- wall intrabony defects in the beagle dogs. The surgical control group received a flap operation only, while experimental group was treated with calcium phosphate chitosan block bone and/or chitosan membrane. All dogs were uneventful healing without any complication. The subjects were sacrificed 8 weeks after the experimental surgery, and a comparative histological and histometric examination was done. Chitosan membrane group significantly enhanced bone regeneration compared to control, CaP-chitosan block bone and combination group. Chitosan membrane remnants were observed in chitosan and combination group, while CaP-chitosan bone materials were resorbed completely. These results suggest that Chitosan membrnae significantly enhanced bone and cementum formation in advanced periodontal defects.

Abstract: The aim of this study was to evaluate the regenerative effects of chitosan membranes containing tetracycline (TC) applied to surgically created one-wall intrabony defects in beagle dogs. The defects either received chitosan membrane (CH), chitosan membrane containing 0.5%, 1% TC (CH-TC0.5, CH-TC1.0) or flap operation only. The animals were sacrificed 8 weeks after the experimental surgery, and comparative histological and histometric examinations were done. The amount of junctional epithelium migration and connective tissue adhesion did not show any statistically significant differences among the groups. The amount of new cementum regeneration, and new bone regeneration were significantly greater in CH-TC1.0 group than the control (P<0.05). The results suggest that chitosan membrane combined with 1.0% TC may have beneficial effect on the regeneration of bone and cementum in intrabony periodontal defects.

Abstract: The purpose of this study was to evaluate the effects of collagen membrane coated with PLGA on bone regeneration in rat calvarial defect. Five groups of 10 animals each received either collagen membrane coated with 0.5%, 1%, 3% concentration of PLGA, collagen membrane only or surgical control. Each group of animals was healed into 2 healing periods of 2(5 animals) and 8(5 animals)weeks and histologic and histomorphometric analysis were done. The results of the following study revealed that surgical implantation of collagen membranes coated with PLGA enhanced local bone formation at both 2 and 8 weeks independent of different PLGA concentrations. In conclusion, collagen membrane coated with PLGA shows a significant bone formation behavior irrespective of their concentration.

Abstract: The purpose of this study was to evaluate histologically the effect of LiF-maleic acid added calcium aluminate (LM-CA) bone cement and calcium aluminate-polymethylmethacrylate (CA-PMMA) composite bone cement on bone regeneration in rat calvarial defect. After calvarial defects in 8 mm in diameter were created, three groups of 10 animals, a total of 30, each either received LM-CA bone cement, CA-PMMA composite bone cement or a sham-surgery control. Histologic analysis was done at 2 weeks and 8 weeks of healing periods. We concluded that LM-CA bone cement can be used as a bioactive bone graft material due to ability of bonding to the existing bone and CA-PMMA can be used as a graft material for augmentation of bone-volume due to dimensional stability.

Abstract: The aim of this study is to evaluate the effects of coating implants with hydroxyapatite (HA) by an ion beam-assisted deposition (IBAD) method and to compare them with implants prepared with machined and anodized surfaces. Twenty-four implants in this study were divided into three groups; machined, anodized, anodized plus IBAD surface implants. Implant stability and osseointegration were assessed by resonance frequency analysis (RFA) and histologic analysis. We can conclude that implants coated by HA by IBAD demonstrate characteristics of contact osteogenesis, but the research design does not permit conclusions regarding long-term treatment outcome with implants. Further studies are needed.

Abstract: The purpose of this study was to compare the bone regenerative effect of calcium phosphate glass according to the particle size in vivo. We prepared two different sizes, that is 400 μm and 40 μm, of calcium phosphate glass powder using the system CaO-CaF2-P2O5-MgO-ZnO. Critical-sized calvarial defects were created in 60 male Sprague-Dawley rats. The animals were divided into 3 groups of 20 animals each. Each defect was filled with a constant weight of 0.5 g calcium phosphate glass powder mixed with saline. As controls, the defect was left empty. The rats were sacrificed 2 or 8 weeks after postsurgery, and the results were evaluated using histological as well as histomorphometrical studies. The particle size of the calcium phosphate was crucial; 400 μm particles promoted new bone formation, while 40 μm particles inhibited it because of severe inflammation.