• 대한기계학회논문집A
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• 제31권7호
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• pp.732-738
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• 2007

Effects of melt-mixing conditions on fracture properties of hydroxyapatite filled bioabsorbable poly(L-lactic acid)(HA/PLLA) composites was investigated by measuring the firacture toughness value of HA/PLLA composites prepared under different mixing time and rotor speed. The fracture surface morphology was also examined by profile measurement and scanning electron microscopies. It was found that the fracture toughness of HA/PLLA composites decreases due to decrease of ductile deformation of PLLA matrix and debonding of interfaces with increase of the rotor speed and mixing time. Effect of mixing process on neat PLLA was also assessed, and it was found that the fracture toughness of PLLA decreases due to disappearance of multiple craze formation and increase of defects. Such thermal and shear-stress degradation were found to be the primary mechanisms of the degradation of HA/PLLA composites during melt-mixing process.

• 대한치과보철학회지
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• 제33권2호
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• pp.317-334
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• 1995

The purpose of this study was to compare the bone formation, maturation around HA-and titaniumcoated dental implants in dog. 5 hydroxyapatite coated IMZ implants and 5 titanium coated IMZ implants were placed into the previously extracted site in the mandible of 5 adults dogs. All dogs were injected intravenously Tetracycline, Alizalin red S, and Calcein for bone fluorescent labelling, After the experimental period of 16weeks, the dogs were sacrificed and tissue samples around the implants were obtained. Microscopic observations(ligth, polariged and fluorescence microscope), morphometric analysis, line profile with EPMA, and quantitative analysis for Ca,P, and Ti were performed. The results were as follows ; 1. Bone maturations around the implants were relatively lower than those of natural teeth. No significant differences in bone maturation and remodeling patterns were observed between the two implants groups. 2. Calcification of bone surrounding the implants was initiated in 8-11 weeks for HA-coated implants, while it took 11 weeks or more for Ti-coated implants. 3. Bone-to-implants contact ratio of 82.63% was recorded for HA-coated group and 72.25% for titanium coated group, with no significant difference between the two groups. 4. Bone around the implants exhibited reduced quantity of Ca and P in the $100{\mu}m$ region relative to natural teeth, while the rest of the regions showed no statistical differences. No significant differences were found between the two implant groups. 5. There was a separation of HA layer from the implant core and subsequent infiltration of inflammatory cells into the resulting space in the HA-coated implants, and evidences of phagocytosis of HA particles by macrophages. Bone calcification was more rapid around HA-coated implants compared to titanium-coated implants, but HA coated implants did not show any significant differences either in the degree of calcification or the bone-to-implant contact ratio over Ti coated implants. HA coated implants may have complications associated with HA absorption and separation of HA layer from the implant core.

• 한국세라믹학회지
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• 제52권3호
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• pp.204-208
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• 2015

Synthesis of hydroxyapatite (HA) was attempted through a room-temperature reaction of calcined eggshell with phosphoric acid. Ball-milled, calcined eggshell powder, which has a specific surface area of $31.6m^2/g$, was mixed with various concentrations of phosphoric acid at room temperature. The mixtures showed high reactivity and a vigorous exothermic reaction ; the reacted samples showed both $Ca(OH)_2$ and $CaHPO_4$ crystal phases. After heating at temperatures above $400^{\circ}C$, an HA crystal phase was observed in all samples. The calcined eggshell showed a pure CaO single phase, while the $Ca(OH)_2$ phase was only observed in the wet, ball-milled calcined powder. The degree of formation of the HA crystal phase increased as the phosphoric acid concentration and the heating temperature were increased. A mixture with 50 wt% phosphoric acid concentration showed a well-developed HA crystal phase after heat treatment at $800^{\circ}C$, while the formation of a more intensive amorphous phase was observed in the products of the room-temperature reaction.

• 한국세라믹학회지
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• 제52권5호
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• pp.374-379
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• 2015

Mullite-matrix and $Al_2O_3$-matrix composites were fabricated with 30 wt% hydroxyapatite (HA) and tricalcium phosphate (TCP), respectively, as additives to give bioactivity. A diphasic gel process was employed to lower the densification temperature of the mullite matrix to $1320^{\circ}C$. A polymer complexation process was used to synthesize a TCP powder that was fully densified at $1250^{\circ}C$, for application to the matrix. For the HA/mullite composite, HA decomposed during sintering by reactions with the matrix components of $Al_2O_3$ and $SiO_2$, resulting in a mixture of $Al_2O_3$, TCP, and other minor phases with a low densification of less than 88% of the theoretical density (TD). In contrast, the TCP/$Al_2O_3$ composite was highly densified by sintering at $1350^{\circ}C$ to 96%TD with no reaction between the components. Different from the TCP monolith, the TCP/$Al_2O_3$ composite also showed a fine microstructure and intergranular fracture, both of which characteristics are advantageous for strength and fracture toughness.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제38권
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• pp.2.1-2.9
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• 2016

Background: We reviewed the biological and mechanical properties of porous hydroxyapatite (HA) compared to other synthetic materials. Computer-aided design/computer-aided manufacturing (CAD/CAM) was also evaluated to estimate its efficacy with clinical and radiological assessments. Method: A systematic search of the electronic literature database of the National Library of Medicine (PubMed-MEDLINE) was performed for articles published in English between January 1985 and September 2013. The inclusion criteria were (1) histological evaluation of the biocompatibility and osteoconductivity of porous HA in vivo and in vitro, (2) evaluation of the mechanical properties of HA in relation to its porosity, (3) comparison of the biological and mechanical properties between several biomaterials, and (4) clinical and radiological evaluation of the precision of CAD/CAM techniques. Results: HA had excellent osteoconductivity and biocompatibility in vitro and in vivo compared to other biomaterials. HA grafts are suitable for milling and finishing, depending on the design. In computed tomography, porous HA is a more resorbable and more osteoconductive material than dense HA; however, its strength decreases exponentially with an increase in porosity. Conclusions: Mechanical tests showed that HA scaffolds with pore diameters ranging from 400 to $1200{\mu}m$ had compressive moduli and strength within the range of the human craniofacial trabecular bone. In conclusion, using CAD/CAM techniques for preparing HA scaffolds may increase graft stability and reduce surgical operating time.

• 한국세라믹학회지
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• 제41권3호
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• pp.202-209
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• 2004

침전법 및 솔젤법에 의하여 10- l5 nm 및 500 nm 크기의 구형 TiO$_2$ 분말을 제조하고 수열합성법으로 50-70 nm 및 120-250 nm 크기의 침상 hydroxyapatite(이하 HA라 표기) 입자를 각각 제조한 다음, 두 분말의 조성비를 달리한 세 종류(HA/TiO$_2$비; 75/25, 50/50, 25/75wt%)의 HA/TiO$_2$ 복합분말을 planetary 볼밀로 혼합하여 각각 제조하였다. 복합분말을 탄소몰드에 넣고 hot-press를 사용하여 가압소결로 치밀체를 제조하였는데, 가압도중 대부분의 HA가 tricalcium phosphate(이하 TCP라 표기)로 분해되면서 $\beta$-TCP/TiO$_2$ 복합체가 제조되었다. 제조된 복합체의 미세구조와 소결밀도는 복합분말의 형태와 조성에 따라 변화하였는데, 입자가 균질하게 분산되어 있는 미세구조를 갖는 복합분말을 소결한 경우, 치밀한 소결체를 얻을 수 있었으며, 소결온도가 증가할수록 균질한 미세구조를 나타내었다. 또한 복합분말 내 HA 함량이 증가하면서 소결체의 입자크기가 증가한 반면, 소결밀도가 감소하고, 미세구조는 불균질하였다. 반대로 HA분말에 비하여 TiO$_2$분말의 함량이 큰 시편은 전체적으로 작은 입자크기와 균질한 미세구조를 나타냈으며, 소결밀도 또한 증가하였다.

• Journal of Korean Neurosurgical Society
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• 제52권1호
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• pp.27-31
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• 2012

Objective : Although hydroxyapatite (HA) spacer has been used for laminoplasty, there have been no reports on factors associated with fusion and on the effects of HA shape. Methods : During January 2004 and January 2010, 45 patients with compressive cervical myelopathy underwent midline-splitting open door laminoplasty with winged (33 cases) and wingless (12 cases) HAs by a single surgeon. Minimal and mean follow up times were 12 and 28.1 months, respectively. Japanese Orthopedic Association (JOA) score was used for clinical outcome measurement. Cervical X-rays were taken preoperatively, immediately post-operatively, and after 3, 6, and 12 months and computed tomography scans were performed preoperatively, immediately post-operatively and after 12 months. Cervical lordosis, canal dimension, fusion between lamina and HA, and affecting factors of fusion were analyzed. Results : All surgeries were performed on 142 levels, 99 in the winged and 43 in the wingless HA groups. JOA scores of the winged group changed from $10.4{\pm}2.94$ to $13.3{\pm}2.35$ and scores of the wingless group changed from $10.8{\pm}2.87$ to $13.8{\pm}3.05$. There was no significant difference on lordotic and canal dimensional change between two groups. Post-operative 12 month fusion rate between lamina and HA was significantly lower in the winged group (18.2 vs. 48.8% p=0.001). Multivariate analysis showed that ossification of the posterior longitudinal ligament, male gender, and wingless type HA were significantly associated with fusion. Conclusion : Clinical outcome was similar in patients receiving winged and wingless HA, but the wingless type was associated with a higher rate of fusion between HA and lamina at 12 months post-operatively.

• Biomaterials and Biomechanics in Bioengineering
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• 제4권1호
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• pp.21-32
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• 2019

Eggshell is a waste material after the usage of egg. In this work, biowaste chicken eggshells were used for preparing carbonated hydroxyapatite (HA) nanoparticles of high purity through aqueous precipitation method at room temperature. The eggshell-derived HA will be a cost-effective bioceramics for biomedical applications and an effective material-recycling technology. Additionally, mulberry leaf extract was used as a template to regulate the morphology, size and crystallinity of HA, and the effects of pH value were also examined. Characterization of the samples was performed by X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) spectroscopy. Scanning electron microscopy (SEM) was used to determine the size, shape and morphology of HA. The results indicate that only one phase of HA were synthesized in the both absence and presence of mulberry leaf extract at pH of 7 and above, while DCPD or DCPA/DCPD phase was observed at pH 4 condition. The crystallite sizes of the HA samples obviously decreased when adding mulberry leaf extract as a template, while they decreased gradually as the solution pH levels increased. With increasing pH level from 7 to 14, the rod-like HA nanoparticles gradually changed to spherical shape at pH 14. Note that, the obtained product is Mg and Sr containing A- and B-type carbonate HA at alkaline pH and it can be a potential material for biomedical applications.

• Journal of Industrial and Engineering Chemistry
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• 제67권
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• pp.244-254
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• 2018

Surface modified poly ${\text\tiny{L}}$-lactic acid (PLLA) samples with hydroxyapatite (HA), heparin and bone morphogenetic protein-2 (BMP-2) mediated by polydopamine (pDA) coating (PLLA/pDA/HA/Hep/BMP-2) were prepared, and their effects on the enhancements of bone formation and osseointegration were evaluated in vitro and in vivo as compared to PLLA, PLLA/pDA/HA, and PLLA/pDA/Hep/BMP-2. The changes in surface chemical compositions, morphologies and wettabilities were observed by X-ray photoelectron spectroscopy (XPS), field-emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM) and water contact angle measurements. Pre-coating of HA particles with pDA provided uniform and homogeneous anchoring of particles to PLLA surface. In addition, the strong ionic interaction between heparin and pDA led PLLA surface readily heparinized for loading of BMP-2. In vitro experiments revealed that the levels of alkaline phosphatase (ALP) activity, calcium deposition, and osteocalcin (OCN) gene expression were higher in MG-63 human osteosarcoma cell lines grown on PLLA/pDA/HA/Hep/BMP-2 than on control PLLA, PLLA/pDA/HA, and PLLA/pDA/Hep/BMP-2. In vivo studies using micro-computed tomography (micro-CT) also showed that PLLA/pDA/HA/Hep/BMP-2 screw exhibited greatest value of bone volume (BV) and bone volume/tissue volume (BV/TV) among samples. Histological evaluations with H&E and Von Kossa staining demonstrated that a combination of HA and BMP-2 contributed to the strong osseointegration.

• 대한화학회지
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• 제57권4호
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• pp.493-498
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• 2013

리포솜은 표적 약물을 봉입하여 병소에 안전하게 전달할 수 있는 약물전달체로서 연구되고 있다. 그러나 일반적인 리포솜은 표적부위에서 약물방출이 제한적인 문제점이 있다. 따라서 본 연구에서는 리포솜의 안정성을 향상시키고 표적부위에서 외부 초음파로부터 약물의 방출을 극대화시키기 위하여 하이드록시아파타이트(hydroxyapatite, HA)가 코팅된 리포솜을 개발하였다. 대조군 리포솜은 인지질과 콜레스테롤을 이용하여 제조하였고, 대조군 리포솜의 표면에 칼슘 아세테이트, 포스포릭에시드, 그리고 25% 암모니아용액을 이용하여 HA를 코팅하였다. 모델 약물로는 독소루비신을 사용하였다. HA코팅 리포솜의 크기는 120 nm 이었고, 약물봉입효율은 95% 이상이었다. 30% 혈장용액 내에서 HA코팅 리포솜의 입자크기는 일정한 상태를 유지하였으며, 대조군 리포솜은 크기가 1.4배 증가하였다. 외부 초음파 자극에 의한 리포솜으로부터 약물 방출을 유도한 후, 방출된 약물의 세포 이입율은 HA 코팅된 리포솜이 3배 이상 대조군 리포솜에 비하여 증가하였다. 본 연구에서는 외부 초음파 자극에 의하여 리포솜으로부터 약물의 방출을 극대화시키기 위한 초음파 민감형 리포솜을 개발하였고, 본 제형은 표적부위에서 약물의 방출을 효과적으로 제어하기 위한 분야에 활용이 가능할 것이다.