Biomedical subjects

Joo L Ong

Publications and source records attributed to Joo L Ong.

At least 19 recordsLinked to original sources

PubMed2006

Properties and cyclic fatigue of glass infiltrated tape cast alumina cores produced using a water-based solvent.

OBJECTIVE: The purpose of this study was to investigate the properties of tape cast alumina composite produced using a water-based solvent and its possible clinical use as an all ceramic crown system in a fixed partial denture. Durability of the system will be measured by fatigue test to simulate the masticating conditions of the oral cavity. METHODS: The optimal weight ratio of water-based alumina tape was determined by tensile strength, shrinkage ratio and durability. The coefficient of thermal expansion, fracture toughness, biaxial flexural strength and flexural strength after fatigue test of a composite produced from alumina tape at optimal weight ratios were determined and compared to In-Ceram alumina core (control). RESULTS: The weight ratio of alumina/(alumina+binder+plasticizer) of 0.84 and binder/(binder+plasticizer) of 0.5 was observed to be the optimal composition for achieving excellent composite properties. Coefficient of thermal expansion of the sintered alumina tape was observed to be 7.3x10(-6)/degrees C, and this value was increased to 7.5x10(-6)/degrees C after infiltrating the sintered tape with glass. The fracture toughness and biaxial flexural strength of glass infiltrated alumina tape was observed to be 4.6 MPa m(1/2) and 498 MPa, respectively. After cyclic loading for 10(2)-10(6) cycles, no significant change in the biaxial flexural strength was observed between the glass infiltrated alumina core and the In-Ceram alumina core (p>0.05). SIGNIFICANCE: The observed properties provide evidence that the water-based tape cast alumina-glass composite is suitable for clinical use as an all ceramic crown system in a fixed partial denture.

Aluminum Oxide↗

PubMed2006

Effects of applied voltages on hydroxyapatite coating of titanium by electrophoretic deposition.

Hydroxyapatite (HA) coatings were deposited on titanium substrates by electrophoretic deposition (EPD) at constant voltage and dynamic voltage, respectively. Various surface morphologies were observed under different type of voltages. Under a constant voltage of 20 V, a dense HA coating could be prepared. Under a constant voltage of 200 V, big HA particles were deposited and the coating was porous. Under a dynamic voltage, a continuous gradient HA coating could be obtained. HA coatings were characterized with a field emission-scanning electron microscopy (FE-SEM) and an X-ray diffraction (XRD). XRD indicated no significant HA decomposition when the coatings were sintered for 2 h at 800 degrees C.

Coated Materials, Biocompatible↗

PubMed2006

Preparation and characterization of anodized titanium surfaces and their effect on osteoblast responses.

In this study, titanium (Ti) surface was modified by anodizing with a mixture of beta-glycerophosphate sodium and calcium (Ca) acetate, and the anodized surfaces were characterized by scanning electron microscopy, X-ray diffraction, and electron probe microanalysis. In vitro osteoblast response to anodized oxide was also evaluated. The anodic oxide produced was observed to have interconnected pores (0.5-2 microm in diameter) and intermediate roughness (0.60-1.00 microm). In addition, anodic oxide was observed to have amorphous and anatase oxide. Calcium and phosphorus ions were deposited on the Ti oxide during anodization. Osteoblast differentiation, as indicated by alkaline phosphatase production, was enhanced on anodized surfaces. It was thus concluded from this study that Ca phosphate can be deposited on Ti surfaces by anodization. It was also concluded that the phenotypic expression of osteoblast was enhanced by the presence of Ca phosphate and higher roughness on anodized Ti surfaces.

Acetates↗

PubMed2005

A review on calcium phosphate coatings produced using a sputtering process--an alternative to plasma spraying.

New promising techniques for depositing hydroxyapatite (HA) and calcium phosphate (CaP) coatings on medical devices are continuously being investigated. Given the vast number of experimental deposition process currently available, this review will focus only on CaP and/or HA coatings produced using the sputtering process. This review will discuss the characterization of sputtered CaP coatings before and after post-deposition treatments and tissue responses to some of the characterized coating surfaces. From the studies observed in the literature, current research on sputtered CaP coatings has shown some promises that may eliminate some of the problems associated with the plasma-spraying process. It has been generally accepted that sputtered HA and CaP coatings improve bone strength and initial osseointegration rate. However, optimal coating properties required to achieve maximal bone response are yet to be reported. As such, the use of well-characterized sputtered CaP and/or HA surfaces in the evaluation of biological responses should be well documented to avoid controversial results. In addition, future investigations of the sputtering process should include clinical trials, to continue the understanding of bone responses to coated-implant surfaces of different properties, and the possibility of coupling sputtered HA and CaP coatings with growth factors.

Animals↗

PubMed2005

Ectopic osteoinduction and early degradation of recombinant human bone morphogenetic protein-2-loaded porous beta-tricalcium phosphate in mice.

The present study investigated the ectopic osteoinduction and early degradation of recombinant human bone morphogenetic protein-2 (rhBMP-2)-loaded porous beta-tricalcium phosphate (beta-TCP) in mice. The porous beta-TCP with 50 microg of rhBMP-2 (n = 25) and porous beta-TCP (control group, n = 25) were implanted into muscle pouches in the right and left thigh of 28-day-old mice (n = 25), respectively. At every time point (3, 7, 14, 21 and 28 days after implantation), five mice were euthanized and the histological examinations of implantation sites were performed. In addition, the alkaline phosphatase (ALP) activity was also quantitatively analyzed. For the rhBMP-2-loaded group, blood vessel formation and immature cartilage was observed within the porous beta-TCP 3 days after implantation. Mature cartilage was observed 7 days after implantation of rhBMP-2-loaded porous beta-TCP. Newly formed woven bone, lamellar bone as well as marrow were observed 14 and 21 days after implantation of the rhBMP-2-loaded porous beta-TCP. Lamellar bone and marrow were observed 28 days after implantation of the rhBMP-2-loaded porous beta-TCP. For the control group, no bone or cartilage was observed at all time points. However, multinucleated giant cells and fibrous tissues were observed in the control group at 7 and 28 days after implantation, respectively. At 21 and 28 days after implantation, porous beta-TCP was observed to fragment indicating early degradation of the porous beta-TCP in both groups. In addition, ALP was observed to be significantly higher in the rhBMP-2-loaded beta-TCP as compared to the control beta-TCP. It was concluded from this study that the rhBMP-2-loaded porous beta-TCP induced blood vessel and ectopic bone formation.

Absorbable Implants↗

PubMed2005

Effect of heat-treated titanium surfaces on protein adsorption and osteoblast precursor cell initial attachment.

The clinical success of dental implants is governed in part by surface properties of implants and their interactions with the surrounding tissues. The objective of this study was to investigate the effect of heat-treated titanium surfaces on protein adsorption and osteoblast precursor cell attachment in vitro. Passivated titanium samples used in this study were either non heat treated or heat treated at 750 degrees C for 90 minutes. It was observed that the contact angle on heat-treated titanium surfaces was statistically lower compared with the non-heat-treated titanium surfaces. The non-heat-treated titanium surface was also observed to be amorphous oxide, whereas heat treatment of titanium resulted in the conversion of amorphous oxide to crystalline anatase oxide. No significant difference in albumin and fibronectin adsorption was observed between the heat-treated and non-heat-treated titanium surfaces. In addition, no significant difference in initial cell attachment was observed between the two groups. It was concluded that heat treatment of titanium resulted in significantly more hydrophilic surfaces compared to non-heat-treated titanium surfaces. However, differences in oxide crystallinity and wettability were not observed to affect protein adsorption and initial osteoblast precursor cell attachment.

Adsorption↗

PubMed2005

The effect of sputtered calcium phosphate coatings of different crystallinity on osteoblast differentiation.

BACKGROUND: Coating titanium implants with hydroxyapatite (HA) has been suggested to increase osseointegration by stimulating early osteoblast function. The goal of this study was to determine the extent to which the crystalline content of the HA surface affected osteoblast function in vitro. METHODS: Osteoblasts were isolated from fetal rat calvaria. Titanium coupons were sputter coated and analyzed. Mineralized nodule formation on plastic using von Kossa staining was compared to tetracycline and procion dye labeling. Cell proliferation, adhesion, alkaline phosphatase activity, morphology and spreading, and cytoskeletal arrangement were analyzed. Reverse transcription-polymerase chain reaction (RT-PCR) was used to determine the expression of mRNA for specific proteins. RESULTS: The percent crystallinity of coatings was 0% (HA1), 1.9% +/- 0.4% (HA2), and 66.4% +/- 2.8% (HA3). The nodule formation and cell number were greatest on titanium and HA3 compared to HA1 and HA2 (P < 0.01). At weeks 2 to 4, all samples showed strong alkaline phosphatase, osteocalcin, monocyte-colony stimulating factor (M-CSF), and receptor activator of nuclear factor kappa B ligand (RANKL) expression, but the specific activity of alkaline phosphatase decreased. Cell adherence was greater than 60% of applied cells for all surfaces except HA3. The cells were significantly more elongated on titanium, with no difference on the HA-coated surfaces. Actin filaments were arranged peripherally at 5 hours but arranged parallel to the long axis of the cell at 20 hours. CONCLUSIONS: Procion labeling is a valid method for evaluating mineralized nodule formation on opaque surfaces. There were no major differences in osteoblast function using titanium or high-crystalline coatings, and most functions were decreased on amorphous or low-crystalline coatings.

Animals↗

PubMed2004

Diffusion in musculoskeletal tissue engineering scaffolds: design issues related to porosity, permeability, architecture, and nutrient mixing.

The field of tissue engineering continues to advance with the discovery of new biomaterials, growth factors and scaffold fabrication techniques. However, for the ultimate success of a tissue engineered construct the issue of nutrient transport to the scaffold interior needs to be addressed. Often, the requirements for adequate nutrient supply are at odds with other scaffold design parameters such as mechanical properties as well as scaffold fabrication techniques, leading to incongruities in finding optimal solutions. The goal of this review article is to provide an overview of the various engineering design factors that promote movement of nutrients, waste and other biomolecules in scaffolds for musculoskeletal tissue engineering applications. The importance of diffusion in scaffolds and how it is influenced by porosity, permeability, architecture, and nutrient mixing has been emphasized. Methods for measuring porosity and permeability have also been outlined. The different types of biomaterials used, scaffold fabrication techniques implemented and the pore sizes/porosities obtained over the past 5 years have also been addressed.

Animals↗

PubMed2004

Interaction of hydroxyapatite-titanium at elevated temperature in vacuum environment.

In this study, the interaction between hydroxyapatite (HA) and titanium (Ti) at elevated temperature in vacuum environment was investigated. The 80 wt% HA-20 wt% Ti powder mixtures and 90 wt% HA-10 wt% Ti powder mixtures were dry pressed and heat-treated at 1100 degrees C in vacuum environment. HA powders and the commercially pure Ti powders were used as controls. The heat-treated samples were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy, scanning electron microscope (SEM) and energy disperse spectra. XRD and SEM indicated densification of metallic Ti specimens during the in-vacuum heat treatment. Heat treatment of HA specimens in vacuum resulted in the loss of hydroxyl groups as well the formation of a secondary beta-tricalcium phosphate phase. Metallic Ti was not observed in the in-vacuum heat-treated HA-Ti specimens. However, alpha-tricalcium phosphate, tetracalcium phosphate and calcium titanium oxide were observed for the in-vacuum heat-treated HA-Ti specimens. It was concluded that the in-vacuum heat-treatment process completely converted the metal-ceramics composites to ceramic composites.

Coated Materials, Biocompatible↗

PubMed2004

Evaluation of titanium plasma-sprayed and plasma-sprayed hydroxyapatite implants in vivo.

In this study, bone interfacial strength and bone contact length at the plasma-sprayed hydroxyapatite (HA) and titanium plasma-sprayed (TPS) implants were evaluated in vivo. Non-coated titanium (Ti) implants were used as controls. Cylindrical coated or non-coated implants (4.0mm diameter by 8mm long) were implanted in the dogs' mandibles. Loading of the implants was performed at 12 weeks after implantation. At 12 weeks after implantation (prior to loading) and 1 year after loading, implants were evaluated for interfacial bone-implant strength and bone-implant contact length. No significant differences in interfacial bone-implant strength for all groups at 12 weeks after implantation and after 1 year loading in normal bone were found. However, bone contact length for HA implants was significantly higher than the TPS and Ti implants for both periods tested (12 weeks after implantation and 1 year after loading). It was concluded that TPS implants exhibited similar pull-out strength compared to the HA implants. In addition, the lower bone contact length on the TPS surface compared to HA surfaces did not affect the interfacial bone-implant strength for both implants.

Aerosols↗

PubMed2004

Osteoblast response and calcium deposition on phospholipid modified surfaces.

In this study, the effect of calcium phosphate complexed phospholipid (Ca-PL-PO4) coatings on solid surfaces on the in vitro calcium (Ca) deposition and on the osteoblast responses was evaluated. Commercially available phospholipids were converted to their Ca-PL-PO4, and were coated on glass Petri dishes. The coated dishes were immersed in the simulated body fluid for up to 14 days under sterilized conditions at 37 degrees C, and the amount of calcium (Ca) deposited was quantified. Similarly, by measuring the alkaline phosphatase specific activity, the differentiation of osteoblast precursor cells were evaluated after seeding the cells on Ca-PL-PO4 coated cell culture plastics. It was observed that all Ca-PL-PO4 enhanced Ca deposition on coated surfaces. The, polar head group of phospholipids in coated surfaces was observed to have an influence on the Ca deposition as well as the osteoblast differentiation. Among the phospholipids evaluated, phosphatidylserine (Ca-PS-PO4) exhibited the strongest calcium deposition and more enhanced alkaline phosphatase specific activity. It was therefore concluded from this study that Ca-PS-PO4 surface modification may be an alternative method for enhancing bone-implant interactions.

Body Fluids↗

PubMed2003

Protein adsorption on titanium surfaces and their effect on osteoblast attachment.

The objective of this study was to investigate the adsorption of albumin and fibronectin on titanium (Ti) surfaces and the effect of preadsorbed albumin and fibronectin on osteoblast attachment in vitro. Bovine serum albumin and bovine fibronectin were used in this study. Maximum adsorption of bovine serum albumin and fibronectin on Ti surfaces was observed to occur after 180-min incubation. In the presence of preadsorbed proteins, osteoblast attachment on Ti surfaces was observed to be enhanced compared to control Ti surfaces. However, cell attachment was affected by the types of protein adsorbed. Preadsorbed albumin was observed to have no significant effect on the amount of osteoblast cells attached. In comparison to control Ti surface and Ti surfaces preadsorbed with albumin, Ti surfaces preadsorbed with fibronectin for 15 min was observed to significantly increase osteoblast cell attachment, whereas Ti surfaces preadsorbed with fibronectin for 180 min did not affect cell attachment. In addition, cell morphology of the attached cells on protein preadsorbed Ti surfaces was not affected by the type of protein used in this study. It was concluded from this study that the concentration of fibronectin adsorbed on Ti surfaces was higher compared to albumin. In addition, it was also concluded that the concentration of fibronectin on Ti surfaces plays a role in governing cell attachment.

Adsorption↗

PubMed2003

In vivo histological response to anodized and anodized/hydrothermally treated titanium implants.

In the study, characterization of the anodized titanium surface was performed. In addition, histological evaluation and interfacial strength at the bone-implant interface of the characterized surfaces were then evaluated with the use of a rabbit model at 6 and 12 weeks after implantation. Surface treatments consisted of either anodization or anodization followed by hydrothermal treatments. Nontreated titanium surfaces were used as controls in this study. Using scanning-electron microscopy, porous oxide layers were observed on surfaces of anodized titanium implants, whereas porous oxide layers and HA needles were observed on anodized titanium implants following hydrothermal treatments. X-ray diffraction analysis showed the oxide layers were consisted mainly of anatase and a little of rutile. By the hydrothermal treatment on the anodizing surface, HA peaks, as well as the peaks of anatase and trace amounts of rutile peaks were observed. In EPMA analysis, the Ca/P ratio for the anodic oxide was 1.54 for anodized surfaces, whereas the Ca/P ratios for HA needles and the anodic oxide were 1.64 and 0.57, respectively, for anodized surfaces following hydrothermal treatments. Although no significant difference was observed for the percent bone contact on all implants evaluated in the in vivo study, the removal torque strength was significantly higher for anodized implants (48.02+/-5.92 N/cm) than the untreated implants (controls) (27.83+/-1.78 N/cm) at 6 weeks after implantation. As such, it was concluded that the surface anodized implants resulted in a high interfacial strength at an early implantation period as compared to the nontreated titanium implants.

Animals↗

PubMed2003

Efficacy of glow discharge gas plasma treatment as a surface modification process for three-dimensional poly (D,L-lactide) scaffolds.

Gas plasma surface modification of three-dimensional poly (D,L-lactide) scaffolds fabricated by a novel vibrating particle fabrication technique was demonstrated to enhance cell adhesion, proliferation, and differentiation over 10 days in culture using human embryonic palatal mesenchyme cells. Characterization of corresponding two-dimensional treated surfaces revealed decreased contact angle measurements of 54.2 +/- 0.6 degrees for treated surfaces compared to 72.3 +/- 0.7 degrees for control surfaces (p < 0.05). SEM of treated surfaces revealed increased surface roughness combined with marked pitting and erosion. This may contribute to increased cell adhesion. WST-1 cell proliferation assay measurements as an index of cell numbers revealed a statistically significant increase in proliferation activity on treated surfaces on days 1 and 4 compared with controls. There was a fivefold increase in WST-1 activity for both control and treated groups over 10 days. Confocal laser micrographs revealed increased cell numbers on treated specimens throughout all layers of the scaffold, indicating that the glow discharge process enhanced cell proliferation throughout the entire scaffold architecture. Scanning electron micrographs demonstrated increased cell adhesion for treated specimens at the polymer surface most evident after days 1 and 4 of culture. Alkaline phosphatase (ALP)-specific activity peaked by day 7 for control and treated surfaces, indicating cellular differentiation. There was a trend for increased protein production on the treated specimens compared with controls at the initial time points although the differences were not statistically significant. These results demonstrated that gas plasma surface modification enhances osteoblast-like cell function in a three-dimensional scaffold model.

Absorbable Implants↗

PubMed2003

In vitro osteoblast response to anodized titanium and anodized titanium followed by hydrothermal treatment.

In this study, Titanium (Ti) surfaces were modified using anodization. The electrolyte used for anodization was a mixture of calcium glycerophosphate and calcium acetate. The anodized surfaces were divided into three groups. Hydrothermal treatments were performed on two of the anodized groups for either 2 or 4 h. In vitro osteoblast response to anodized oxide and the hydrothermal treated oxide after anodization was evaluated in this study. Calcium and phosphorus ions were deposited on the Ti oxide during anodization. Anodized surfaces following a 4-h hydrothermal treatment were observed to promote the growth apatite-like crystals as compared with anodized surfaces after a 2-h hydrothermal treatment. Cellular function and onset of mineralization, as indicated by protein production and osteocalcin production, respectively, also were observed as enhanced on hydrothermal-treated surfaces. It was thus concluded from this study that calcium phosphate and apatite-like crystals could be deposited on Ti surfaces using anodization and a combination of anodization and hydrothermal treatment. It was also concluded that the phenotypic expression of osteoblast was enhanced by the presence of calcium phosphate or apatite-like crystals on anodized or hydrothermally treated Ti surfaces.

Alkaline Phosphatase↗

PubMed2003

Bond strength, compositional, and structural properties of hydroxyapatite coating on Ti, ZrO2-coated Ti, and TPS-coated Ti substrate.

The effect of titanium plasma-sprayed (TPS) and zirconia (ZrO(2))-coated titanium (Ti) substrates on the adhesive, compositional, and structural properties of plasma-sprayed hydroxyapatite (HA) coatings were evaluated. X-ray diffraction, Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy, energy dispersive spectroscopy, surface roughness, and adhesive strength were used to characterize the coatings. Apatite-type and alpha-tricalcium phosphate phases were observed for all HA coatings. A structural change due to the absence of a 960 cm(-1) peak during FTIR analysis was observed for all HA coatings. The coating surfaces appeared rough and melted, with surface roughness correlating to the size of the starting powder. No significant difference in the Ca/P ratio of HA on Ti and TPS-coated Ti substrates was observed. However, the Ca/P ratio of HA on ZrO(2)-coated Ti substrate was significantly increased. Interfaces between all coatings and substrates were observed to be dense and tightly bound, except for HA coatings on TPS-coated Ti substrate interface. However, an intermediate TPS or ZrO(2) layer between the HA and Ti substrate resulted in a lower adhesive strength as compared to HA on Ti substrate.

Adhesiveness↗

PubMed2003

Effect of hydrothermally treated anodic oxide films on osteoblast attachment and proliferation.

In this study, the effect of anodization following hydrothermal treatments on osteoblast cell attachment and proliferation were evaluated. The anodic oxide films produced in this study was observed to exhibit overlapping microporous structures with microprojections. In addition, the anodic oxide surfaces were significantly rougher in comparison to control untreated titanium (Ti) surfaces. Following hydrothermal treatments for 2 and 4 h, hydroxyapatite (HA) crystals were observed on anodic surfaces. Using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay, no significant difference in the biocompatibility of the treated and untreated Ti surfaces was observed. However, scanning electron micrographs indicated rounded osteoblast cells on control and anodized Ti surfaces, with numerous microvilli after 6 h. In contract, cells cultured on hydrothermally treated surfaces after 6 h incubation were observed to exhibit polygonal shape, flattened, and fully spread. In addition, more cells were observed on Ti surfaces that were hydrothermally treated for 4 h as compared to Ti surfaces that were hydrothermally treated for 2 h. After culturing the cells for 24 h and 4 days, no significant difference was observed for cells cultured on all surfaces. It was concluded from this study that hydrothermally treated surfaces exhibited an effect on early osteoblast attachment.

Animals↗

PubMed2003

Deposition of highly adhesive ZrO(2) coating on Ti and CoCrMo implant materials using plasma spraying.

ZrO(2) (4% CeO(2)) and ZrO(2) (3% Y(2)O(3)) coatings were deposited on titanium (Ti) and CoCrMo implants using plasma spraying and the adhesive, morphological and structural properties of the plasma-sprayed coatings were evaluated. Characterization of these coatings was performed using X-ray diffraction (XRD), scanning electron microscopy (SEM), surface roughness, hardness, and adhesive strength. XRD patterns showed that both the coatings appeared to be primitive tetragonal phase. SEM observations showed that both the ZrO(2) coatings appeared to be rough, porous and melted. The cross-section surface morphology of the coatings, coating-substrate interfaces and substrates without acid etching was very dense and smooth. After acid etching, as compared to the dense ZrO(2) coating-CoCrMo substrate interfaces, the thin gaps appeared within the ZrO(2) coating-Ti substrate interfaces. It is suggested that plasma spraying probably formed an amorphous Ti layer in the coating-Ti substrate interface that can be removed by acid etching. The average surface roughness of ZrO(2) (3% Y(2)O(3)) and ZrO(2) (4% CeO(2)) coatings was correlated to the starting powder size and substrates. No significant difference between the hardness of all coatings and substrates was observed. The adhesive strengths of ZrO(2) (4% CeO(2)) coating to Ti and CoCrMo substrates were higher than 68MPa and significantly greater than that of ZrO(2) (3% Y(2)O(3)) coatings.

Ceramics↗