• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2012.05a
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• pp.126-126
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• 2012

In this study, adhesion of plasma spray coated hydroxyapatite film on the two-step anodized dental implant was investigated. The plasma spray was carried out on the dental implant after two step anodization. The adhesion of coated HA film was investigated by FE-SEM after fatigue test. In the case of two-step anodized implant showed a good adhesion between implant and coated film.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2003.10a
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• pp.59-59
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• 2003

In recent, various functional coatings on artificial tooth implants have been conducted to enhance the bonding strength between implants and bones. Despite of these efforts, some previous reports argued that an adhesion strength between titanium implant and the final coatings like hydroxyapatite(HA) is weaker than the strength between coating and bone. In order to increase the adhesion force between the final coating and implant surface, TiN/DLC based functionally graded coating, which has higher mechanical strength than the titanium implant, was applied as a middle layer between titanium implant and final coating. Particularly we finally coated a biocompatible hydroxyapatite film on the DLC layer and examined the mechanical properties. As a result, TiN/DLC based functionally graded coating showed the higher adhesion strength compared with hydroxyapatite single layer coating on the titanium implant.

• Restorative Dentistry and Endodontics
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• v.15 no.1
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• pp.33-43
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• 1990

Reactions of polyacrylic acid with hydroxyapatite, enamel and dentin were examined using infrared spectroscopy for the detection of $COO^-$ ions bonded to substrates. And also atomic aboscorption spectrophotometry and visible spectrophotometry were used to analyze the concentrations of calcium and phosphorus in the filtered solutions. The results were as follows. 1. Chemical adhesion of poly acrylic acid to hydroxyapatite, enamel and dentin was observed by infrared spectroscopy. 2. More calcium and phosphorus were detected in the filtered solutions of sodium polyacrylate-reacted specimens than in the filtered solutions of deionized Water-reacted specimens. 3. Mechanism of adhesion of polyacrylate to substrates is postulated that the bond is ionic in nature by displacement of $Ca^{2-}$ and ${PO_4}^3$ ions from the surface of substrates.

• Journal of the Korean Ceramic Society
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• v.33 no.9
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• pp.1003-1011
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• 1996

Hydroxyapatite powder was synthesized by a citrate method, . Char-like precursor composed of Ca8(HPO4)2(PO4)4.5H2O (OCP) and CaCo3 was found via viscous resin-like intermediate by heating the mixed aqueous solution of Ca(NO3)2.4H2O(NH4)2HPO4 and citric acid. Resulted powder was transformed into hydroxyapatite phase by firing over 120$0^{\circ}C$-135$0^{\circ}C$ for 4 hr using the powder calcined at 90$0^{\circ}C$ for 10 hr composed of mostly single hydroxyapatite phase. The sintered densities increased with firing temperature up to 130$0^{\circ}C$ but the highest relative density was about 94% of theoritical value. indicating the presence of closed pores. The maximum 96 MPa of flexural strength was obtained at 120$0^{\circ}C$ firing but the flexural strength showed lower values over the above sintering condition. Vitro test was performed by immersing of two jointed specimens in SBF for seven days and adhesion was observed between two specimens.

• Biomaterials and Biomechanics in Bioengineering
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• v.1 no.2
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• pp.81-93
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• 2014

An in vitro cell study evaluating cell adhesion to hydroxyapatite (HA) coated prosthetic Ti-6Al-4V alloy via laser treatment is presented in comparison with uncoated alloy. Based on our previous in vitro biocompatibility study, which demonstrated higher cell attachment and proliferation with MC3T3-E1 preosteoblast cells, the present investigation aims to reveal the effect of laser coating Ti alloy with HA on the adhesion strength of bone-forming cells against centrifugal forces. Remaining cells on different substrates after centrifugation were visualized using fluorescent staining. Semi-quantifications on the numbers of cells were conducted based on fluorescent images, which demonstrated higher numbers of cells retained on HA laser treated substrates post centrifugation. The results indicate potential increase in the normalized maximum force required to displace cells from HA coated surfaces versus uncoated control surface. The possible mechanisms that govern the enhancing effect were discussed, including surface roughness, chemistry, wettability, and protein adsorption. The improvement in cell adhesion through laser treatment with a biomimetic coating could be useful in reducing tissue damage at the prosthetic to bone junction and minimizing the loosening of prosthetics over time.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.37 no.3
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• pp.214-224
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• 2011

Objective: This study examined the potential of the in vitro osteogenesis of microtopographically modified surfaces, RBM (resorbable blasting media) surfaces, which generate hydroxyapatite grit-blasting. Methods: RBM surfaces were modified hydroxyapatite grit-blasting to produce microtopographically modified surfaces and the surface morphology, roughness or elements were examined. To investigate the potential of the in vitro osteogenesis, the osteoblastic cell adhesion, proliferation, and differentiation were examined using the human osteoblast-like cell line, MG-63 cells. Osteoblastic cell proliferation was examined as a function of time. In addition, osteoblastic cell differentiation was verified using four different methods of an ALP activity assay, a mineralization assay using alizarin red-s staining, and gene expression of osteoblastic differentiation marker using RT-PCR or ELISA. Results: Osteoblastic cell adhesion, proliferation and ALP activity was elevated on the RBM surfaces compared to the machined group. The cells exhibited a high level of gene expression of the osteoblastic differentiation makers (osteonectin, type I collagen, Runx-2, osterix). imilar data was represented in the ELISA produced similar results in that the RBM surface increased the level of osteocalcin, osteopontin, TGF-beta1 and PGE2 secretion, which was known to stimulate the osteogenesis. Moreover, alizarin red-s staining revealed significantly more mineralized nodules on the RBM surfaces than the machined discs. Conclusion: RBM surfaces modified with hydroxyapatite grit-blasting stimulate the in vitro osteogenesis of MG-63 cells and may accelerate bone formation and increase bone-implant contact.

• Journal of the Korean Ceramic Society
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• v.55 no.2
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• pp.145-152
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• 2018

Although many bone graft materials have been developed, powder graft materials are somewhat difficult to use in surgery. To solve this problem, a bone graft material in the form of a viscous paste was prepared. Hydroxyapatite was used as a bone graft material, and methyl cellulose was used to impart viscosity. Three cases of samples were prepared, and freeze-dried block type and sintered specimens were made from the paste. The recrystallization of the graft material in a simulated body fluid and the degree of graft adhesion with a tooth were observed by scanning electron microscopy (SEM). The test for cytotoxicity was carried out and the sample was grafted into the back of a mouse to confirm the presence or absence of side effects in the animal's body. Based on these investigations, composites of this type are expected to be applicable for bone grafts.

• Korean Journal of Materials Research
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• v.22 no.4
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• pp.211-214
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• 2012

Optimal conditions for HA plasma spray-coating on Ti6Al4V alloy were investigated in order to obtain enhanced bone-bonding ability with Ti6Al4V alloy. The properties of plasma spray coated film were analyzed by SEM, XRD, surface roughness measurement, and adhesion strength test because the film's transformed phase and crystallinity were known to be influential to bone-bonding ability withTi6Al4V alloy. The films were formed by a plasma spray coating technique with various combinations of plasma power, spray distance, and auxiliary He gas pressure. The film properties were analyzed in order to determine the optimal spray coating parameters with which we will able to achieve enhanced bone-bonding ability with Ti6Al4V alloy. The most influential coating parameter was found to be the plasma spray distance to the specimen from the spray gun nozzle. Additionally, it was observed that a relatively higher film crystallinity can be obtained with lower auxiliary gas pressure. Moderate adhesion strength can be achievable at minimal plasma power. That is, adhesion strength is minimally dependent on the plasma power. The combination of shorter spray distance, lower auxiliary gas pressure, and moderate spray power can be recommended as the optimal spray conditions. In this study, optimal plasma spray coated films were formed with spray distance of 70 mm, plasma current of 800 A, and auxiliary gas pressure of 60 psi.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.21 no.4
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• pp.70-76
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• 2022

Calcium-phosphate-based bioceramics are promising biomaterials for scaffolds because they can assist in bone regeneration. In this study, a laser sintering deposition system was developed, and 3D hydroxyapatite (HA) scaffolds were fabricated. The main process conditions of the HA scaffolds were laser power, table velocity, and laser focal distance. As the laser power increased, the line width, line height, and layer thickness also increased. Further, the line width, line height, and layer thickness decreased as the table velocity increased. As the laser focal distance increased, the line width increased, but the line height and layer thickness decreased. The fabricated green scaffolds were sintered at 1050 ℃ and 1150 ℃. The sintered scaffolds had a uniform and continuous interconnected shape, with pore sizes ranging from 850 to 950 ㎛ having 53% porosity. The compressive strength of the scaffolds decreased from 0.72 MPa (1050 ℃) to 0.53 MPa (1150 ℃). The biocompatibility of the scaffolds was investigated by analyzing the adhesion of osteoblast-like MG-63 cells cultured on the surfaces of the scaffolds. The results indicate that the scaffold sintered at 1050 ℃ had good mechanical and biological properties compared to that at 1150 ℃.

• Archives of Plastic Surgery
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• v.36 no.3
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• pp.247-253
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• 2009

Purpose: Hydroxyapatite(HA) has been widely used due to its chemical similarity to bone and good biocompatibility. HA is composed of macropores and micropores. Too much irregularities of the micropores are ineffective against the adhesion and proliferation of osteoblast. Many efforts have been tried to overcome these drawbacks. HA crystal coating on the irregular surface of HA scaffold, crystallized HA, is one of the method to improve cell adhesion. Meanwhile, the collagen has been incorporated with HA to create composite scaffold that chemically resembles the natural extracellular matrix components of bone. The authors proposed to examine the effect of collagen - coated crystallized HA on the adhesion and proliferation of osteoblast. Method: HA powder containing $10{\mu}m$ pore size was manufactured as 1 cm pellet size. For the making crystallized HA, 0.1 M EDTA solution was used to dissolve HA powder and heated $100^{\circ}C$ for 48 hours. Next, the crystallized HA pellets were coated with collagen (0.1, 0.5, and 1%). The osteoblasts were seeded into HA pellets and incubated for the various times (1, 5, and 9 days). After the indicating days, methylthiazol tetrazolium (MTT) assay was performed for cell proliferation and alkaline phosphatase (ALP) activty was measured for bone formation. Result: In SEM study, the surface of crystallized HA pellet was more regular than HA pellet. MTT assay showed that the proliferation of osteoblasts increased in a collagen dose - dependent and time - dependent manner and had a maximum effect at 1% collagen concentration. ALP activity also increased in a collagen dose - dependent manner and had a highest effect at 1% collagen concentration. Conclusion: These data showed that crystallization and collagen coating of HA was effective for osteoblast proliferation and ALP activity. Therefore, our results suggest that crystallized - HA scaffold with collagen coating is may be a good strategy for tissue engineering application for bone formation.