• Korean Journal of Materials Research
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• v.29 no.2
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• pp.129-135
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• 2019

A powder mixture of 70 wt% $Al_2O_3$ and 30 wt% hydroxyapatite (HA) is sintered at $1300^{\circ}C$ or $1350^{\circ}C$ for 2 h at normal pressure. An $MgF_2$-added composition to make HA into fluorapatite (FA) is also prepared for comparison. The samples without $MgF_2$ show ${\alpha}$ & ${\beta}$-tricalcium phosphates (TCPs) and $Al_2O_3$ phases with no HA at either of the sintering temperatures. In the case of $1,350^{\circ}C$, a $CaAl_4O_7$ phase is also found. Densification values are 69 and 78 %, and strengths are 156 and 104 MPa for 1,300 and $1,350^{\circ}C$, respectively. Because the decomposition of HA produces a $H_2O$ vapor, fewer large pores of $5-6{\mu}m$ form at $1,300^{\circ}C$. The $MgF_2$-added samples show FA and $Al_2O_3$ phases with no TCP. Densification values are 79 and 87 %, and strengths are 104 and 143 MPa for 1,300 and $1,350^{\circ}C$, respectively. No large pores are observed, and the grain size of FA ($1-2{\mu}m$) is bigger than that of TCP ($0.7{\mu}m{\geq}$) in the samples without $MgF_2$. The resulting $TCP/Al_2O_3$ and $FA/Al_2O_3$ composites fabricated in situ exhibit strengths 6-10 times higher than monolithic TCP and HA.

• Microbiology and Biotechnology Letters
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• v.43 no.2
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• pp.164-168
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• 2015

Citric acid is produced via submerged fermentation using yeasts. Among eight different strains of yeast, Candida zeylanoides was chosen as the strain for producing citric acid and optimized for various C/N ratios and effects of phosphate or Fe²⁺ ions in a clean carbon source medium (glucose: fructose, 1:1). The yield of citric acid was maximized at a C/N ratio of 40/1, a phosphate addition of 1.0 g/l, and an Fe²⁺ ion concentration of less than 50 mg/l, yielding up to 91 g/L in the broth with 18.5 g/l of isocitric acid in a six-day fermentation period using a pre-treated molasses medium. The yield of batch culture was 0.51 (Y_p/s, g/g) in a 5 L-Jar fermenter.

• Journal of Periodontal and Implant Science
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• v.46 no.5
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• pp.350-359
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• 2016

Purpose: The purpose of the present study was to evaluate the effectiveness of a minimal concentration of bone morphogenetic protein-2 (BMP-2) in terms of quantitative and qualitative analyses of newly formed bone in a rabbit maxillary sinus model. Methods: In 7 rabbits, sinus windows were prepared bilaterally. Biphasic calcium phosphate (BCP) loaded with 0.05 mg/mL BMP-2 was grafted into one sinus (the BMP group) and saline-soaked BCP was placed into the other (the control group) in each animal. The animals were allowed an 8-week healing period before being sacrificed. Specimens including the augmented area and surrounding tissues were then removed and evaluated both radiographically and histologically. Results: There was a difference in the mineralization of new bone between the groups. In the BMP group, the greater part of the new bone consisted of mature lamellar bone with an evident trabecular pattern, whereas the control group showed mostly woven bone, consisting only partially of lamellar bone. Histometrically, the area of new bone was significantly greater ($4.55{\pm}1.35mm^2$ vs. $2.99{\pm}0.86mm^2$) in the BMP group than in the control group (P<0.05); however, the total augmentation volumes were not significantly different between the groups. Conclusions: Within the limitations of this study, it can be suggested that a minimal concentration of BMP-2 (0.05 mg/mL) had an osteoinductive effect with accelerated mineralization in a rabbit sinus model using a BCP carrier.

• Journal of Periodontal and Implant Science
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• v.47 no.6
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• pp.381-387
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• 2017

Purpose: The aim of this study was to evaluate volumetric and histologic changes in edentulous alveolar ridge areas after ridge preservation using basic fibroblast growth factor-2 (bFGF-2) in combination with collagenated biphasic calcium phosphate (BCP). Methods: The experiments were performed in 6 adult male beagle dogs. The following 3 groups were created: 1) ridge preservation with bFGF-2 and collagenated BCP (experimental group), 2) ridge preservation with collagenated BCP (positive control group), and 3) a negative control group in which no ridge preservation procedure was performed. Volumetric change analysis was performed using an optical scanner and casts. Histological observations were made using light microscopy. Results: After the initial swelling subsided, the magnitude of the volumetric change in the experimental group and positive control group was smaller than in the negative control group. In the experimental group, a distinct trend was observed for the resorption of residual bone and collagen fibers at 4 weeks and for more mature bone and faster healing at 12 weeks. Conclusions: Based on the findings of the present study, bFGF-2 may be considered for use as a therapeutic molecule in ridge preservation procedures.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.40
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• pp.3.1-3.8
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• 2018

Background: In this research article, we evaluate the use of sub-periosteal tunneling (tunnel technique) combined with alloplastic in situ hardening biphasic calcium phosphate (BCP, a compound of β-tricalcium phosphate and hydroxyapatite) bone graft for lateral augmentation of a deficient alveolar ridge. Methods: A total of 9 patients with deficient mandibular alveolar ridges were included in the present pilot study. Ten lateral ridge augmentation were carried out using the sub-periosteal tunneling technique, including a bilateral procedure in one patient. The increase in ridge width was assessed using CBCT evaluation of the ridge preoperatively and at 4 months postoperatively. Histological assessment of the quality of bone formation was also carried out with bone cores obtained at the implant placement re-entry in one patient. Results: The mean bucco-lingual ridge width increased in average from 4.17 ± 0.99 mm to 8.56 ± 1.93 mm after lateral bone augmentation with easy-graft CRYSTAL using the tunneling technique. The gain in ridge width was statistically highly significant (p = 0.0019). Histomorphometric assessment of two bone cores obtained at the time of implant placement from one patient revealed 27.6% new bone and an overall mineralized fraction of 72.3% in the grafted area 4 months after the bone grafting was carried out. Conclusions: Within the limits of this pilot study, it can be concluded that sub-periosteal tunneling technique using in situ hardening biphasic calcium phosphate is a valuable option for lateral ridge augmentation to allow implant placement in deficient alveolar ridges. Further prospective randomized clinical trials will be necessary to assess its performance in comparison to conventional ridge augmentation procedures.

• Journal of Periodontal and Implant Science
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• v.49 no.1
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• pp.47-57
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• 2019

Purpose: This study was designed to observe the resorption pattern of biphasic calcium phosphate (BCP) used for maxillary sinus augmentation over a 3- to 6-year healing period, and to investigate factors affecting the resorption of BCP. Methods: A total of 47 implants placed in 27 sinuses of 22 patients were investigated. All patients had residual bone height less than 5 mm at baseline. The modified Caldwell-Luc approach was used to elevate the maxillary sinus membrane, and the sinus cavity was filled with BCP (70% hydroxyapatite and 30% ${\beta}$-tricalcium phosphate). Implant placement was done simultaneously or in a staged manner. Serial radiographic analysis was performed up to 6 years postoperatively. Results: During the follow-up period, no implant loss was reported. The mean reduced height of the augmented sinus (RHO) was $0.27{\pm}1.08mm$ at 36 months, and $0.89{\pm}1.39mm$ at 72 months postoperatively. Large amounts of graft material (P=0.021) and a long healing period (P=0.035) significantly influenced the amount of RHO. In particular, there was a significant relationship between a healing period longer than 40 months and RHO. Conclusions: BCP can achieve proper dimensional stability with minimal reduction of the graft height in a 3- to 6-year healing period after maxillary sinus augmentation. The healing period and the amount of graft material influenced the resorption of BCP.

• Korean Journal of Dental Materials
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• v.44 no.3
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• pp.263-272
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• 2017

In this study, antibacterial chlorhexidine (CHX)-containing hydroxyapatite (HAp) was coated on titanium and investigated its characteristics. Ti-mSBF-CHX group was prepared by soaking titanium disks in the modified simulated body fluid (mSBF) mixed with CHX. Ti-mSBF group was coated using mSBF without CHX. Ti-mSBF-adCHX group was prepared by soaking Ti-mSBF specimen in CHX-containing solution. The crystallines clusters composed with nano-shaped crystallites were coated on the surface of the Ti-mSBF specimen. The ribbon-shaped crystallites were observed with the crystalline clusters on the Ti-mSBF-CHX specimen. The content of CHX chemical compositions was high in ribbon-shaped crystallites. HAp crystalline structure was dominant for all prepared specimens, and ${\beta}-TCP$ (tricalcium phosphate) and OCP (octacalcium phosphate) crystalline structures were observed in the Ti-mSBF-CHX specimen. FT-IR spectra showed the strong peaks of CHX in Ti-mSBF-adCHX and Ti-mSBF-CHX groups. However, after immersing in a phosphate buffered saline (PBS), CHX was rapidly released in Ti-mSBF-adCHX group, while it was slowly released in Ti-mSBF-CHX. We expect that the coating method of Ti-mSBF-CHX group could be used for protecting inflammation of titanium implant by incorporating antibacterial agent CHX into HAp layer.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.34 no.1
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• pp.1-11
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• 2012

Purpose: The purpose of this study was to evaluate the bone regeneration capacity of silk fibroin (SF) when combined with beta tricalcium phosphate (${\beta}$-tricalcium phosphate [TCP]) and rh-bone morphogenetic protein (BMP) in vivo by micro-computed tomography (CT), soft x-ray, and histological analysis. Methods: A total of 56 critical size defects formed by a trephine bur made on 28 adult female Spague-Dawley rats were used for this study and the defect size was 5.0 mm in diameter. The defects were transplanted with (1) no graft material (raw defect), (2) autogenous bone, (3) SF ($10{\mu}g$), (4) SF-BMP ($10{\mu}g$, $0.8{\mu}g$ each), and (5) SF+${\beta}$-TCP ($10{\mu}g$). At 4 and 8 weeks after operation, the experimental animals were sacrificed. Samples were evaluated with soft x-ray, histological examinations and 3-dimensional micro-CT analysis. Results: In the 3-dimensional micro-CT evaluation, bone volume and bone surface data were higher in the SF-BMP ($12.8{\pm}1.5$, $138.6{\pm}45.0$ each) (P<0.05) and SF-TCP ($12.3{\pm}1.5$, $144.9{\pm}30.9$ each) group than in the SF group ($6.1{\pm}3.3$, $77.2{\pm}37.3$ each) (P<0.05), except for the autogenous group ($15.0{\pm}3.0$, $190.7{\pm}41.4$ each) at 4 weeks. At 8 weeks, SF-BMP ($16.8{\pm}3.5$, $173.9{\pm}34.2$ each) still revealed higher (P<0.05) bone volum and surface, but SF-TCP ($11.3{\pm}1.5$, $1132.9{\pm}52.1$ each) (P=0.5, P=0.2) revealed the same or lower amount compared with the SF group ($13.8{\pm}2.7$, $127.5{\pm}44.8$ each). The % of bone area determined by radiodensity was higher in the SF-TCP ($31.4{\pm}9.1%$) and SF-BMP ($36.2{\pm}16.2%$) groups than in the SF ($19.0{\pm}10.4$) group at the period of 4 weeks. Also, in the histological evaluation, the SF-BMP group revealed lower inflammation reaction, lower foreign body reaction and higher bone healing than the SF group at postoperative 4 weeks and 8 weeks. The SF-TCP group revealed lower inflammation at 4 weeks, but accordingly, as the TCP membrane was absorbed, inflammatory and foreign body reaction are increased at 8 weeks. Conclusion: The current study provides evidence that the silk fibrin can be used as an effective grafted material for tissue engineering bone generation through a combination of growth factor or surface treatment.

• Korean Journal of Microbiology
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• v.49 no.4
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• pp.398-402
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• 2013

This study was to investigate beneficial effects of microbial mixture on red pepper which was capable of promoting plant growth by solubilizing insoluble phosphate as well as protecting plants from pathogenic attack. Saccharomyces sp. L13 was isolated for phosphate solubilizing activity on aluminium phosphate, tricalcium phosphate, calcium hydrophosphate, and magnesium hydrophosphate. On the other hand, Bacillus sp. L32 was isolated for antagonistic activity against Phytophthora capsisi and Colletotrichum gloeosporioides, causing Phytophthora blight and Anthracnose disease in pepper, respectively. The strain L32 exhibited antagonistic activities both under dual culture assays and detached leaves assays. The each strain under the condition of mixed cultivation exhibited the same growth rates as one under pure cultivation. In greenhouse study, the mixed culture showed the both effect of plant growth promotion and reduction of disease symptom development against P. capsisi and C. gloeosporioides providing a potential as effective microbial agent for plant husbandry.

• Journal of Periodontal and Implant Science
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• v.32 no.3
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• pp.489-500
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• 2002

The purpose of this study was to evaluate newly fabricated tricalcium phosphate(TCP)/chitosan microgranuls as bone substitutes. TCP/chitosan microgranules were fabricated by dropping TCP-chitosan suspension into the NaOH/ethanol solution. The size of microgranules could be controllable via airflow rate. PDGF-BB was loaded into the fabricated granules via freeze-drying methods(300 ng/20 mg). To evaluate cell proliferation, cultured osteoblasts cell lines(MC3T3-El) was dropped on the BioOss(R), chitosan microgranules, TCP/chitosan microgranules and cultured for 1, 7 , 14, and 28 days. Scanning electron microscopic observation was done after 7 days of culture and light microscopic examination was done after 28 days of culture. PDGF-BB release from the microgranules was tested. Rabbit calvarial defects(8 mm in diameter) were formed and chitosan, TCP/chitosan, PDGF-TCP/chitosan microgranules, and BioGran(R) were grafted to test the ability of new bone formation. At SEM view, the size of prepared microgranules was 250-1000 um and TCP powders were observed at the surface of TCP/chitosan microgranules. TCP powders gave roughness to the granules and this might help the attachment of osteoblasts. The pores formed between microgranules might be able to allow new bone ingrowth and vascularization. There were no significant differences in cell number among BioOss(R) and two microgranules at 28 day. Light and scanning electron microscopic examination showed that seeded osteoblastic cells were well attached to TCP/chitosan microgranules and proliferated in a multi-layer. PDGF-BB released from TCP/chitosan microgranules was at therapeutic concentration for at least 1 week. In rabbit calvarial defect models, PDGF-TCP/chitosan microgranules grafted sites showed thicker bone trabeculae pattern and faster bone maturation than others. These results suggested that the TCP/chitosan microgranules showed the potential as bone substitutes.