Bioceramic Coatings Research Articles

Histomorphometric Evaluation of Alumina-Blasted/Acid-Etched and Thin Ion Beam-Deposited Bioceramic Surfaces: An Experimental Study in Dogs

In an attempt to overcome the potential long-term limitations observed with plasma-sprayed hydroxyapatite-coated implants, nanothickness bioceramic coatings have been processed onto previously grit-blasted/acid-etched surfaces. Our objective was to evaluate the bone response to alumina-blasted/acid-etched and a thin ion beam-deposited bioceramic (Test) implant surfaces at 2 and 4 weeks in vivo with a dog tibia model. Plateau root form implants (5 x 6 mm) were placed bilaterally along the proximal tibia of 6 Doberman dogs and remained for 2 and 4 weeks in vivo (n=6 per implant type and time in vivo). After euthanization, the implants were processed in a nondecalcified form and reduced to approximately 30 mum-thickness plates. Transmitted light optical microscopy at various magnifications was used to qualitatively evaluate the bone healing patterns. Bone-to-implant contact (BIC) was determined and 1-way ANOVA at 95% level of significance with Tukey's post-hoc multiple comparisons was used for statistical analysis. Histomorphology showed new bone formation filling the spaces between the plateaus at both in vivo time intervals through large quantities of woven bone formation. A higher degree of bone organization was observed between the plateaus of Test implants at 4 weeks in vivo than the alumina-blasted/acid-etched implants. No significant differences in BIC were observed for the different groups (P> .86). Despite nonsignificant differences between BIC for the different implant surfaces and times in vivo, higher degrees of bone organization were observed for the Test implants at 4 weeks, and biomechanical testing is suggested to verify its biomechanical fixation effectiveness.

Experiment, thermal simulation, and characterizations on transmission laser coating of hydroxyapatite on metal implant

Coating of bioceramic material, Hydroxyapatite (HAp), on metal implant has attracted many attentions in biomedical industry recently because its combination of good mechanical property and biocompatibility. However, most of current HAp coatings lack coating/substrate interfacial strength, and/or biocompatibility. The cell-tissue attachment is affected by the degraded biocompatibility due to decomposition of HAp during high temperature processing. In this article, an innovative method, transmission laser coating (TLC), is investigated to coat HAp on Ti substrate with low temperature processing. This process enhances the HAp/Metal interfacial property of current coatings, while maintaining good biocompatibility. Experiments are conducted using a continuous neodymium-doped yttrium aluminium garnet (Nd-YAG) laser. Multiphysics simulation is conducted to simulate the temperature distribution in coatings and substrates during TLC processing. X-ray energy dispersion spectrum is used to measure the chemical composition of HAp coatings after TLC process. Pull-out tests are conducted to measure the interfacial strength between the HAp coating and Ti substrate. Cell culture study is conducted to qualitatively evaluate the biocompatibility after TLC of HAp particles. These results show that TLC processing will open new ways of producing biocompatible bioceramic coatings with controlled thickness, and at low processing temperature.

Gradient Rare-Earths Bioceramic Composite Coating Fabricated by Wide-Band Laser Cladding and its Bioactivity

A gradient bioceramic composite coating was prepared by wide-band laser cladding technique on TC4 alloy surface. The influence of rare earths oxide CeO2 on microstructure of bioceramic coating was studied. The experimental results indicated that CeO2 plays an important role in inducing HA + β-TCP formation. There is almost no HA+β-TCP in bioceramic coating without CeO2. When CeO2 content is higher than 0.2 wt.%, the amount of HA+β-TCP catalyzed by CeO2 gradually increases. The amount of HA+β-TCP becomes largest when CeO2 content is up to 0.4wt%. However, when CeO2 content ranges from 0.6 wt.% to 0.8 wt.%, the amount of synthesizing HA+β-TCP conversely goes down. Through cell culture experiment in vitro, the effect of bioceramic coating with different CeO2 contents on the expression of characteristic protein is investigated. The results show that the largest amount of expression of hydroxyproline(Hyp) at 2d and alkaline phosphatase(ALP) at 6d on coating is complied with 0.4wt.% CeO2, The result indicates that bioactivity of bioceramic coating is dependent on the amount of HA + β-TCP catalyzed by different CeO2 contents.

激光快速成形工艺参数对生物陶瓷复合涂层物相组成的影响

激光快速成形工艺参数对生物陶瓷复合涂层物相组成的影响

Histomorphometrical Comparison of Alumina-Blasted/Acid-Etched and a Thin Ion Beam Deposited Bioceramic Surfaces at Early Implantation Times. An Experimental Study in Dogs.

Among surface modifications commercially available for dental implants, the incorporation of bioceramic coatings is one of the most popular. However, concerns regarding the effectiveness of the bond between the metallic surface and the coating have led to the development of thin-film Ca- and P- based bioceramic coatings. The purpose of this study was to evaluate the early bone response to a thin ion bean deposited (Test) bioceramic implant surface compared to an alumina-blasted/acid-etched (Control) surface in a canine model. Results showed that although no difference in bone-to-implant (BIC) could be noted between the two different surfaces, more organized bone architecture was present around the Test implants in 4 weeks. Based on this observation, the incorporation of a thin- film bioceramic coating positively influenced bone healing around dental implants at early times.

In situ synthesis of hydroxyapatite coating by laser cladding

HA bioceramic coatings were synthesized on titanium substrate by laser cladding using cheap calcium carbonate and calcium hydrogen phosphate. The thermodynamic condition for synthesizing HA was calculated by software Matlab 5.0, the microstructure and phase analysis of laser clad HA bioceramic coatings were studied by electron probe microanalyser (EPMA), X-ray diffractometer (XRD) and transmission electron microscopy (TEM). The theoretical results show that the Gibbs free enthalpy for the synthesis of HA phase is satisfied, and the presence of HA phase in the clad coatings was then further verified by XRD and the selected area diffraction patterns. When the laser power is 600 W and the scanning speed is 3.5 mm/s, the compact HA bioceramic coatings were obtained, which have cellular dendritic structure and consist of the phases of HA, α-Ca 2P 2O 7, CaO and CaTiO 3.

Bioceramic Coatings on Biomorphic SiC by Electrophoretic Deposition

In this research, bioactive glass powders were electrophoretically deposited on biomorphic SiC ceramic substrates. A post-deposition thermal treatment was carried out to improve the properties of the coatings. Particle size, surface morphology, composition and thickness of the coatings have been studied by Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS) and interferometric profilometry respectively. The analysis demonstrated that the electrophoresis parameters, such as the voltage, the distance between the electrodes and the deposition time, play an important role on the thickness of the coatings. The post-deposition thermal treatment produces glass particles cohesion and leads to obtaining a homogeneous microstructure. The excellent coverage of the porous SiC surface morphology is also demonstrated. Finally, in order to assess the bioactive character of the glass coatings, in vitro test by immersion in simulated body fluid (SBF) was carried out.

Bone growth is enhanced by novel bioceramic coatings on Ti alloy implants

Calcium phosphate ceramics are widely used as coating materials to orthopedic implants and are found to enhance initial bony ingrowth by stimulating osseous apposition to the implant surface. In this study, two novel calcium orthophosphate materials were selected for coating onto the commonly used orthopedic implant material Ti-6Al- 4V. One was calcium alkali orthophosphate with the crystalline phase Ca10[K/Na](PO4)7 with a small addition of SiO2 (AW-Si) and the other was calcium orthophosphate composed of 70 mol % fluorapatite, Ca10(PO4)6F2 and 30 mol % CaZr4(PO4)6 (FA7Z). The coated implants were placed in cortical and cortico-cancellous bone of sheep femur for six weeks. Retrieved samples were tested for osseointegration and mechanical strength. It was found that both coatings produced enhanced bone/implant contact rate compared to the control when implanted in cortico-cancellous bone. This study demonstrates that the two coatings have the capability of encouraging bone growth, and hence the potential for being used as coating materials on Ti implants.

Physico/chemical characterization and in vivo evaluation of nanothickness bioceramic depositions on alumina‐blasted/acid‐etched Ti‐6Al‐4V implant surfaces

The objective of this study was to physico/chemically characterize and evaluate the in vivo performance of two nanothickness ion beam assisted depositions (IBAD) of bioceramic coatings on implants in a beagle model. Alumina-blasted/acid-etched (AB/AE) Ti-6Al-4V implants were subjected to two different IBAD depositions (IBAD I and IBAD II), which were physico/chemically characterized by SEM, EDS, XPS, XPS + ion-beam milling (depth profiling), XRD, AFM, and ToF-SIMS. A beagle dog tibia model was utilized for histomorphometric and biomechanical (torque) comparison between AB/AE, IBAD I, IBAD II, and plasma-sprayed hydroxyapatite (PSHA) coated implants that remained in vivo for 3 and 5 weeks. The coatings were characterized as amorphous Ca-P with high Ca/P stoichiometries with thicknesses of an order of magnitude difference (IBAD I = 30-50 nm and IBAD II = 300-500 nm). The histomorphometric and biomechanical testing results showed that the 300-500 nm thickness deposition (IBAD II) and PSHA positively modulated bone healing at early implantation times.

Early healing of nanothickness bioceramic coatings on dental implants. An experimental study in dogs

Thick bioceramic coatings like plasma sprayed hydroxyapatite have been shown to increase the overall tissue response and biomechanical fixation of dental implants. However, the presence and potential fracture of a bone-coating-metallic substrate interface at long times after implantation led these implants to fall from favor in clinical practice. The purpose of this study was to evaluate the biomechanical fixation and biological response of Ca- and P-based, 20-50 nm thickness bioceramic deposition on a previously alumina-blasted/acid-etched Ti-6Al-4V implant surface in a dog model. Cylindrical alumina-blasted/acid-etched (AB/AE) (Control, n = 16), and Nanothickness bioceramic coated AB/AE(Nano, n = 16) implant surfaces were surgically placed in dogs proximal tibia and remained for 2 and 4 weeks in vivo. Following euthanization, the implants-in-bone were mounted in epoxy and pullout at a 0.5 mm/min rate. Following mechanical testing, the specimens were decalcified and processed (Hematoxylin and Eosin) for standard transmitted light microscopy evaluation. Percent bone-to-implant contact (BIC) to the pulled out implant surface was determined through computer software. Statistical analyses were performed by one-way ANOVA at 95% level of significance and Tukey's post-hoc multiple comparisons. No significant differences in pullout force were observed (p > 0.88): 2W Control (212.08 +/- 42.96 N), 2W Nano (224.35 +/- 42.97 N), 4W Control (207.07 +/- 42.97 N), and 4W Nano (190.15 +/- 45.94 N). No significant differences in %BIC were observed (p > 0.94): 2W Control (72.66 +/- 8.51), 2W Nano (69.44 +/- 8.51), 4W Control (70.44 +/- 8.51), and 4W Nano (69.11 +/- 9.09). It is shown that 20-50 nm thickness bioceramic depositions onto previously alumina-blasted/acid-etched substrates did not improve the biomechanical fixation and the BIC at early implantation times, and studies concerning shorter and longer implantation times are recommended for confirmation or before a conclusion can be made.

Microstructure and Thermal Behavior of Gradient Bioceramic Coatings Fabricated by Laser Cladding on Titanium Alloy

Based on a high power CO2 laser beam passing by an integral mirror, the bioceramic coatings of gradient composition were designed and fabricated on titanium alloy substrate (Ti-6Al-4V). The relations among laser processing parameters, microstructure and thermal behavior of the gradient bioceramic coatings were investigated. The morphology of the composites was observed by scanning electron microscope (SEM). Phase composition of the coatings was analyzed by X-ray diffraction (XRD). And the thermal behavior of raw powders was evaluated through thermal gravimetry and differential scanning calorimetry (TG-DSC) test. The results demonstrated that the bioceramic coatings were metallurgically bonded to the titanium alloy substrate. The bioceramic coatings contained such bioactive phases as HA and β-TCP, which offered an advantageous condition for osseo-connection. The DSC thermograms showed the endothermic peaks at different temperature, which resulted from the different transitions process, respectively. Furthermore, the DSC results were in accordance with TG data of the powders and showed that with the increasing temperature the weight of sample accordingly decreased.

Fabrication and Biocompatibility of Gradient Bioceramic Coatings on Titanium Alloy Substrate by Laser Cladding

Based on a high power CO2 laser beam passing by pyramid polygon mirror, the bioceramic coatings of gradient composition were fabricated on titanium alloy substrate (Ti-6Al-4V). The relations among laser processing parameters, microstructure and biocompatibility of the gradient bioceramic coatings were investigated. The results indicated that the contents of rare earth oxide additions had an immediate effect on the formation of bioactive phases. The gradient bioceramic coatings showed favorable biocompatibility in vivo after they were implanted into canine femur for 45, 90, and 180 days, respectively. The bioceramic coatings of Ca/P=1.4 and 0.6wt.% Y2O3 totally combined with new bones merely implanted for 45 days. Furthermore, the MTT (Methyl Thiazolyl Tetrazolium) colorimetry results of cell proliferation demonstrated that the cell growth distinctly increased on the gradient bioceramic coatings by laser cladding compared with the un-treated titanium alloy substrate.

Characterization and In Vivo Studies of Nanothickness Ca- and P-Based Coatings

Objective: This series of laboratorial and in-vivo studies describe the characterization, evolution, and in-vivo performance of various Ca- and P-based nanothicknesses and microstructures ion beam assisted depositions (IBAD) onto Ti-6Al-4V implants. Materials and Methods: Characterization- The 4 mm in diameter and 10 mm in length implant rods (Ti-6Al-4V) with IBAD I, IBAD II, and control (alumina-blasted/acid-etched, AB/AE) surfaces were provided by an implant manufacturer. The in-vitro characterization comprised the following techniques: (1) SEM/EDS, (2) XPS/Depth Profiling (3) Thin-film XRD (4) AFM + ToF-SIMS for coating thickness determination (5) AFM- Ra determination. In-vivo- Three animal experiments were carried out for evaluation of the nanothickness bioceramic coatings. All experiments comprised a proximal tibia model with 4-6 implants placed along the bones. Times in-vivo ranged from 2-5 weeks. Static (bioactivity, bone to implant contact) and dynamic (mineral apposition rates- MAR) histomorphometric measurements were recorded. Biomechanical testing was performed by pullout and torque to interfacial failure testing. Results: Combination of the characterization techniques showed that all bioceramic coatings were Ca- and P-based bioceramics of amorphous microstructure. AFM +ToF-SIMS showed that IBAD II coatings were thicker (300-500 nm) compared to IBAD I coatings (30-50 nm). Surface roughness did not change significantly for the IBAD implant groups compared to control. The in-vivo results showed higher degrees of osseoactivity, torque to failure, and MAR for the coated implants at different times in-vivo. IBAD II had higher biomechanical fixation at early implantation times compared to other groups. Conclusions: The results obtained in the in-vitro part this study support that both IBAD I and IBAD II coatings are Ca- and P- based amorphous bioceramics in the nanothickness range with theoretical high dissolution rates. The increased osseoactivity observed for IBAD coated and the high MAR values observed for IBAD coated compared to AB/AE implants support the effect of the bioceramic coating presence in the overall bone healing. A thickness effect was reveled through biomechanical testing where IBAD II (300-500nm thickness) presented higher performance.

Mechanical properties of sol–gel calcium titanate bioceramic coatings on titanium

We discuss the mechanical properties and wear characteristics of sol–gel CaTiO 3 nanocrystalline ceramic coatings on titanium substrates. The structure and surface morphology of the coatings were investigated by X-ray diffraction, optical profilometry, and atomic force microscopy. The mechanical properties of CaTiO 3 coatings were characterized by using nanoindentation, scratch- and microwear-tests. The effect of titanium nitride intermediate layer on the improvement of the coating properties has been investigated. The best CaTiO 3 coatings with a TiN intermediate layer demonstrated the bonding strength up to 70 MPa, stability and low linear wear rate (∼ 1 μm per million cycles) during ball-on-disc reciprocal wear tests in micromotion (50–500 μm amplitude) with Ti6Al4V-alloy static partner at contact pressures up to 500 MPa in both dry and simulated body fluid environments.

Production of microscale particles from fish bone by gas flow assisted laser ablation

Recycled wastes from fish and seafood can constitute a source of precursor material for different applications in the biomedical field such as bone fillers or precursor material for bioceramic coatings to improve the osteointegration of metallic implants. In this work, fish bones have been used directly as target in a laser ablation system. A pulsed Nd:YAG laser was used to ablate the fish bone material and a transverse air flow was used to extract the ablated material out of the interaction zone. The particles collected at a filter were in the micro and nanoscale range. The morphology as well as the composition of the obtained particles were characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and transmission electron microscopy (TEM). The results reveal that the composition of the analyzed particles is similar to that of the inorganic part of the fish bone.

Characterization and in vitro evaluation of biphasic calcium pyrophosphate–tricalciumphosphate radio frequency magnetron sputter coatings

The objective of this study was to characterize the physicochemical, dissolution, and osteogenic properties of radio frequency magnetron sputtered dicalcium pyrophosphate/tricalciumphosphate (Pyro/TCP) and hydroxylapatite (HA) coatings. Therefore Pyro/TCP and HA coatings were deposited on grit-blasted titanium discs. The results showed that the deposited coatings were amorphous and changed into a crystalline structure after IR heat-treatment of 550 degrees C for HA and 650 degrees C for Pyro/TCP. Heat-treated HA coatings appeared to be stable during immersion in simulated body fluid (SBF), that is no changes in the XRD pattern were observed. Also, no dissolution of the coating was observed by scanning electron microscopy (SEM). Energy dispersive spectroscopy (EDS) revealed that the Ca/P ratio of the HA coatings remained constant during SBF immersion. On the other hand, the heat-treated Pyro/TCP coatings showed a surface reaction of calcium pyrophosphate into a beta-tricalcium phosphate phase during SBF immersion. This was confirmed by EDS analysis. Rat bone marrow-derived osteoblast-like cells cultured on the heat-treated substrates showed that cell proliferation and differentiation occurred on both types of bioceramic coatings. No significant differences for proliferation and early differentiation were observed between cells cultured on heat-treated Pyro/TCP and HA at individual time points. However, osteocalcin expression, a late marker for osteoblast-like cell differentiation, was significantly increased after 12 days of culture on HA-coatings. These results were confirmed by SEM observations and suggest increased osteogenic properties for HA-coatings over Pyro/TCP-coatings. Additional research is necessary to obtain conclusive evidence on the in vivo osteogenic capacity of Pyro/TCP coatings.

Evaluation of adhesion strength and toughness of fluoridated hydroxyapatite coatings

Adhesion strength and fracture toughness are two crucial mechanical properties for bioceramic coatings on metal implants directly affecting successful implantation and long-term stability. In this study, the adhesion strength of sol–gel derived FHA coatings on Ti6Al4V substrates was measured by pull-out tensile test, and the toughness was assessed by energy release method. With increase of the degree of fluoridation, the adhesion strength increases up to about 40% and the fracture toughness increases about 200 to 300%. Contrary to the wide-spread belief, it is interesting to note that after soaking in the Tris-buffered physiological saline solution (for 21 days), the adhesion strength increases about 60% as compared with the as-deposited coating, instead of decreasing. The mechanism of the increase is discussed.

APPLICATION OF SURFACE MODIFICATION IN BIOMEDICAL MATERIALS RESEARCH

In this paper, the applications and qualifications of biomedical materials are introduced. In regard to the hard tissue implants, the biocompatibility can be improved by preparing various bio-ceramic and bio-glass coatings. In view of this, the principles, characteristics, and applications of surface modification (plasma spraying, electrostatic spray deposition, micro-arc oxidation, pulsed laser deposition, sol–gel deposition, and magnetron sputtering) in biomedical materials are reviewed. In addition, the research direction of improving biocompatibility by surface modification is presented.

Structure of calcium titanate/titania bioceramic composite coatings on titanium alloy and apatite deposition on their surfaces in a simulated body fluid

In this study, TiO 2-based coatings containing Ca and P ions were prepared on titanium alloy surfaces by microarc oxidation (MAO). After soaking in aqueous NaOH solution and subsequent heat treatment at 700 and 800 °C, calcium titanate/titania bioceramic composite (CTBC) coatings were obtained. The results show that the outer layers (0–1.5 μm) of the CTBC coatings are mainly composed of Ca, Ti, O and Na constituents with a uniform distributions with increasing the depth near the surfaces. The surface phase compositions of the CTBC coating formed at 700 °C are anatase, rutile and CaTi 21O 38 phases, as well as a few CaTiO 3, while those of the CTBC coating formed at 800 °C are anatase, rutile and CaTiO 3. When incubated in a simulated body fluid (SBF), apatite was deposited on the CTBC coatings probably via formation of hydroxyl functionalized surface complexes on the CTBC coating surfaces by ionic exchanges between (Ca 2+, Na +) ions of the CTBC coatings and H 3O + ions in the SBF. The CTBC coating formed at 800 °C seems to facilitate the deposition of Ca and P probably due to the good crystallographic match between perovskite CaTiO 3 and HA on specific crystal planes.

Development and Characterization of Nano-TiO<sub>2</sub>/HA Composite Bioceramic Coating on Titanium Surface

This research is aimed at the development and characterization of a novel bioceramic coating on the surface of pure titanium. Nano-TiO2/HA composite bioceramic coating was designed and developed on the surfaces of pure titanium discs by sol-gel route. The TiO2 anatase bioceramic coating was employed as the inner layer, which could adhere tightly to the titanium substrate. The porous HA bioceramic coating was employed as the outer layer, which has higher solubility and better short term bioactivity. Conventional HA coatings and commercially pure titanium (cpTi) were taken as control. XRD and SEM were employed to characterize the crystallization, surface morphology and thickness of the coatings. The bioactivities of the coatings were evaluated by the in vitro osteoblasts culture. Results show the nano-TiO2/HA composite bioceramic coating has good crystallization and homogeneous, nano-scale surface morphology. And it adheres tightly to the substrate. The in vitro osteoblasts culture exhibits satisfactory bioactivity.