Biomedical subjects

Hyoun-Ee Kim

Publications and source records attributed to Hyoun-Ee Kim.

42 records · Page 3Linked to original sources

PubMed2003

Enhanced performance of fluorine substituted hydroxyapatite composites for hard tissue engineering.

Dense fluorine (F) substituted hydroxyapatite composites with yttria-doped zirconia (Y-TZP) and/or alumina (Al(2)O(3)) were successfully fabricated without applying pressure at 1400 degrees C for 3 h. The suppression of decomposition via the formation of a fluor-hydroxyapatite (FHA) solid solution allowed the sintered body to reach full density. Such fully densified FHA-composites exhibited improved mechanical properties, such as strength, toughness, and hardness, having values of more than approximately 2-4 times higher than those of pure HA or HA-composites. The proliferation behavior of osteoblast-like cells on the FHA-composites showed no cytotoxicity and comparable cell viability to that observed in pure HA for up to 10 days.

Journal Article↗

PubMed2002

Hydroxyapatite-based composite for dental implants: an in vivo removal torque experiment.

Screw-shaped dental implants were fabricated from commercially pure Ti (c.p. Ti) and HA-based composites. The HA-based composites were fabricated by mixing HA with Al(2)O(3)-coated ZrO(2) powders. The mechanical properties of these composites were enhanced by a factor of 3. These were implanted into the rabbit tibiae and the removal torque to loosen the implants in vivo was measured in order to investigate the osteointegration. After a healing period of 6 weeks, the implants were retrieved with a torque gauge instrument. The HA-based composite implants showed an almost 2-times-higher removal torque when compared to the Ti implants (ANOVA, p < 0.05), indicating excellent biocompatibility to bone. Thus, HA-based composites had not only better mechanical properties but also similar bioactivity as HA itself. It is believed that a HA-based composite is suitable for artificial dental implants.

Aluminum Oxide↗

PubMed2002

Biological performance of calcium phosphate films formed on commercially pure Ti by electron-beam evaporation.

Thin and defect-free calcium phosphate films with a Ca/P ratio of 1.62 were formed by electron-beam evaporation. The as-deposited films had average bonding strengths to the metal implants of 64.8 MPa and the dissolution rates of 47.5 nm/h in isotonic saline solutions. The interface mechanical characteristics and histology of the as-machined, as-blasted, and calcium phosphate coating on the machined surfaces of commercially pure titanium were investigated. After a healing period of 12 weeks, the implants were unscrewed with a torque gauge instrument at the day of sacrifice. The coated sample showed a removal torque of 48.5 Ncm (SD 5.4) compared to 32.3 Ncm (SD 2.91) for the uncoated implant with the same surface roughness, and 47.3 Ncm (SD 5.8) for the grit blasted screw. The histomorphometric analyses of the calcium-phosphate-coated implants revealed a mean of 52.4% (SD 6.3) as the highest bone to implant contact.

Animals↗

PubMed2002

Effect of CaF2 on densification and properties of hydroxyapatite-zirconia composites for biomedical applications.

Hydroxyapatite (HA) composites with zirconia (ZrO2) up to 40 vol% were fabricated with the addition of CaF2. The sinterability of the composites was found to be enhanced markedly by the addition of small amounts of CaF2 (< 5 vol%). Decomposition of HA to beta-TCP was suppressed due to the substitution of F- for OH-, consequently forming fluor-hydroxyapatite (FHA) solid solution. This suppression of decomposition allowed the production of a fully dense body, which retained both high flexural strength and fracture toughness. The osteoblast-like cell (MG63) response to these F- ion-containing composites displayed comparable cell viability to pure-HA by in vitro proliferation test.

Biocompatible Materials↗

PubMed2002

Effect of calcinations of starting powder on mechanical properties of hydroxyapatite-alumina bioceramic composite.

The effect of calcinations of starting powder on the mechanical properties of hydroxyapatite (HA)-based bioceramic composite was investigated. The calcinations of HA powder in air at 900 degrees C increased the crystallinity as well as the size of the powder. Ball milling after the calcinations was effective in eliminating large agglomerates in the powder. When the powder was mixed with reinforcing Al(2)O(3) powder, the mixture became fine and homogeneous. The flexural strength of HA-Al(2)O(3) composite was increased by the calcinations processes at all the Al(2)O(3) concentration. However, the fracture toughness was not much influenced by the calcinations. These results lead to the conclusion that the calcinations process effectively reduced the critical flaw size in the body by removing the agglomerates in the HA powder.

Journal Article↗

PubMedDate not supplied

Hydroxyapatite/poly(epsilon-caprolactone) composite coatings on hydroxyapatite porous bone scaffold for drug delivery.

Hydroxyapatite (HA) porous scaffold was coated with HA and polycaprolactone (PCL) composites, and antibiotic drug tetracycline hydrochloride was entrapped within the coating layer. The HA scaffold obtained by a polymeric reticulate method, possessed high porosity ( approximately 87%) and controlled pore size (150-200 microm). Such a well-developed porous structure facilitated usage in a drug delivery system due to its high surface area and blood circulation efficiency. The PCL polymer, as a coating component, was used to improve the brittleness and low strength of the HA scaffold, as well to effectively entrap the drug. To improve the osteoconductivity and bioactivity of the coating layer, HA powder was hybridized with PCL solution to make the HA-PCL composite coating. With alteration in the coating concentration and HA/PCL ratio, the morphology, mechanical properties, and biodegradation behavior were investigated. Increasing the concentration rendered the stems thicker and some pores to be clogged; as well increasing the HA/PCL ratio made the coating surface be rough due to the large amount of HA particles. However, for all concentrations and compositions, uniform coatings were formed, i.e., with the HA particles being dispersed homogeneously in the PCL sheet. With the composite coating, the mechanical properties, such as compressive strength and elastic modulus were improved by several orders of magnitude. These improvements were more significant with thicker coatings, while little difference was observed with the HA/PCL ratio. The in vitro biodegradation of the composite coatings in the phosphate buffered saline solution increased linearly with incubation time and the rate differed with the coating concentration and the HA/PCL ratio; the higher concentration and HA amount caused the increased biodegradation. At short period (<2 h), about 20-30% drug was released especially due to free drug at the coating surface. However, the release rate was sustained for prolonged periods and was highly dependent on the degree of coating dissolution, suggesting the possibility of a controlled drug release in the porous scaffold with HA+PCL coating.

Absorbable Implants↗