Key Engineering Materials Vols. 309-311

Abstract: Titanium dental implant screws were implanted into the pearl sacs of a fresh water bivalve (hyriopsis cumingii Lea) by replacing the pearls. After 45 days of cultivation, the implant surfaces were deposited with a nacre coating with iridescent luster. The coating was about 200-600 µm in thickness and composed of a laminated nacreous layer and a transitional non-laminated layer that consisted mainly of vaterite and calcite polymorphs of calcium carbonate. The transitional layer was around 2-10 µm thick in the convex and flat region of the implant surface and could form close contact with titanium surface; while the transitional layer was much thicker in the steep concave regions and could not form close contact with the titanium surface. The improvement to the design of the dental implant with respect to this coating method was suggested in the paper. The results suggest that it is possible to fabricate a biologically active and degradable, and mechanically tough and strong nacre coating on titanium dental implant by this novel coating technology.

Abstract: Nacre powder suspensions in alcohol added with acetic acid (Suspension I) or calcium chloride (Suspension II) were prepared. Titanium substrates were coated with nacre powder by EPD in the suspensions. The result shows that Suspension II is more stable than Suspension I, and deposition rate in Suspension II is much higher than that in Suspension I. XRD and FTIR results show that the nacre coatings exhibit the same characteristics as the raw nacre powder. SEM morphologies show that uniform coatings are achieved. Scratch test shows that bonding strength of coatings from Suspension I is much higher than that of Suspension II. The higher bonding strength from Suspension I was confirmed to be closely related to the concurrent deposition of organic molecules dissolved in the suspension.

Abstract: A part of the titanium dental implant surface, which will meet connective tissue after being inserted in mandibular bone, was coated with calcium phosphate by ion beam assisted deposition (IBAD). Twenty-four implants of coated and uncoated group were randomly placed in mandibles after 3 months of premolars extraction in beagle dogs. All the implants were firmly anchored in the bone and had no clinical signs of peri-implant inflammation after 3-month insertion. The probing depth in calcium phosphate coated group is 1.9±0.2 mm, less than in control group (2.1±0.2 mm) (p<0.05). Most of the probing sites tended to bleed upon probing in two groups. It might indicate that the calcium phosphate coating has the potential to promote soft tissue integration.

Abstract: This work aims to study the effect of incorporating proteins with different isoelectric points (pI) on the structure, composition and morphology of biomimetic calcium-phosphate (Ca-P) coatings. For that, bovine serum albumin (BSA) and lysozyme, having respectively acidic and basic pIs, were used as model proteins. It was observed that the incorporation of positively charged proteins, such as lysozyme, was able to significantly change the structure of the coatings, possibly due to the preferential interactions between the protein and negatively charged phosphate ions. These results indicated that proteins with different characteristics can be incorporated into biomimetic Ca-P coatings in order to obtain a hybrid coating and at the same tailoring their properties.

Abstract: Previously, the properties of room temperature processed silica sol gel (also called xerogels) as resorbable and biocompatible controlled release systems were described. It was demonstrated that drugs and macromolecules with a variety of properties and characteristics could be released in a controlled manner. In this study, we focus on the synthesis of antibacterial thin solgel films on intramedullary nails and fracture fixation materials. We determine the effect of processing parameters on the in vitro properties and demonstrated a time- and load- dependent release of vancomycin from the film. This study suggests that thin sol-gel films hold great promise for the prevention and treatment of bone infections.

Abstract: A FGF-2-apatite composite layer was formed on hydroxyapatite (HAP) ceramics using supersaturated calcium phosphate solutions containing various amounts of potassium chloride. The optimum conditions for the formation of the composite layer were determined by using cytochrome C (cyt C), one of the dummy proteins of FGF-2, and an immersion solution with a Ca/P molar ratio of 0.19 and a potassium chloride concentration of 8 mM. The amounts of cyt C and FGF-2 immobilized in the composite layer were 1.28±0.30 and 3.18±0.01 µg cm-2, respectively. The release of FGF-2 from the composite layer continued for at least 3 days. It was considered that the release period of FGF-2 could be extended to day 10 because the release of cyt C continued for at least 10 days. When the composite layer is formed on commercial bone substitutes, it is expected that the promotive effect on bone formation around the bone substitutes will continue for at least 10 days.

Abstract: Fibronectin (FN) and type I collagen (Col), which are kinds of extracelluar matrices, were coprecipitated with calcium phosphate to form a composite layer on a hydroxyapatite (HAP) ceramic using a supersaturated calcium phosphate solution (CP solution). The amounts of protein immobilized in the layers were determined to be 20.97±3.04 µg·cm-2 for FN, 5.26±0.19 µg·cm-2 for Col and 21.72±2.30 µg·cm-2 for simultaneously immobilized FN and Col. When osteoblastic MC3T3-E1 cells were cultured on the HAP ceramics with the composite layer containing FN and/or Col, calcified tissue was formed through the activity of the cells. The result showed that the composite layer accelerated the differentiation of MC3T3-E1 to bone-forming cells. It is assumed that osteoblastic cells in alveolar bone migrated and differentiated on the surface of the tooth roots when the artificial tooth roots were covered with the composite layer.

Abstract: Poly methyl methacrylate(PMMA) with mar resistant or poly ethtylene(PE) substrates were surface-treated by applying plasma discharge or alkaline solution. Ceramic thin film comprised of silicon oxide, titanium oxide and zirconium oxide was formed on these surface treated substrates respectively from an aqueous solution, and after the formation of ceramic thin film, titanium oxide thin film was also coated on them from aqueous solution at ordinary temperature and pressure. The thin film coated polymer material was tested in mechanical property. The thin film was hard and the adhesion strength to the organic polymer substrate was very high. The substrate was soaked in SBF and apatite was formed on the substrate. This method is promising for developing hard and soft tissue implants with various mechanical properties as well as high bioactivity.

Abstract: A novel poly(lactic acid) (PLA)/calcium carbonates hybrid membrane containing silica was prepared using aminopropyltriethoxysilane (APTES) for biodegradable bone guided regeneration. Carboxy groups in PLA made a chemical bond with amino groups in APTES, resulting in the formation of the hybrid membrane. The silica-hybridized PLA was an amorphous phase. The membrane formed hydroxycarbonate apatite (HCA) on its surface after 3 d of soaking in simulated body fluid (SBF). After soaking the membrane in SBF, almost no Si was present in SBF. X-ray energy dispersive spectroscopy showed the HCA layer includes Si with Ca and P. A result of osteoblast-like cellular proliferation on the membrane showed no cell-toxicity.

Abstract: Silicon is one of the essential ions with a stimulating effect on bone formation. β- tricalcium phosphate ceramic (β-TCP) with a modified surface containing silica was prepared in order to accelerate the bone formation. Sintered β-TCP pellets were spin-coated with a prehydrolyzed silica sol, and subsequently laser-irradiated using CO2 laser at the power of 6.5W. Scanning electron microscopy attached with X-ray energy dispersive spectrometry (SEM-EDS) showed that the silica was doped into the β-TCP surface. The silicon ion was released into a trisbuffer solution at pH 7.4 at 37 oC during one week of soaking.