Aim: The study was to fabricate FA nanopowder/Co-Cr-Mo dental alloy nanocomposite using pulsed laser deposition (PLD), and to evaluate bioactivity properties on simulated body fluid. Methods: In this work, the FA nanopowder was prepared by mixing calcium hydroxide (Ca(OH) 2), phosphorouspent oxide (P 2O 5) and calcium fluoride (CaF 2) in a planetary high energy ball mill using zirconium vial. Fluorapatite (FA) nanopowder was processed in the form of pellet for pulsed laser deposition process. The Co-Cr-Mo alloy was coated with FA nanopowder which was approximately 35 - 65 nm at various laser energy, pressure and time. The X-ray diffraction (XRD) was used to analyze phase, crystallinity and size distribution of Co-Cr-Mo/FA nanocomposite. The surface analysis was by scanning electron microscopy (SEM), Atomic Force microscopy (AFM) and Energy dispersive spectroscopy (EDS). Results: From the results obtained, It was shown that FA nanopowder deposited on Co-Cr-Mo alloy was stable during 14 days of incubation on simulated body fluid. It was also observed that the FA nanopowder coated on the surface of the alloy was still intact after the deposition process, which indicated the bioactivity and biocompatibility of the material. Conclusions: The fabrication of FA nanocomposite based dental alloys (Co-Cr-Mo) using PLD was done successfully. This was confirmed by various characterization techniques, which included XRD, AFM, SEM and EDS.
Dental alloys and metals play an important role in dentistry. Although the latest trend is towards the “metal free” dentistry, the metals remain the only clinically proven material for long term dental applications. Dental alloy is a mixture of metallic elements or compounds with other metalloic elements in varying proportions for use in restorative or prosthetic dentistry. The alloys are widely used in dentistry for many years. However, it is of paramount importance to understand the biocompatibility of alloys for their long term success in rendering successful dental treatment [
Metallic materials play an essential role in assisting with the repair or replacement of diseased or damage bone tissue. Metals are more suitable for load bearing applications compared with ceramics or polymeric materials because they combine high mechanical strength and fracture toughness [
Metals had been used in dentistry for many years [
The Co-Cr-Mo dental alloys were purchased from American Elements (USA), and were provided as a small disk (ASTM F75). The Co-Cr-Mo alloy chemical composition is shown in
Element | wt% |
---|---|
Co | 64 |
Cr | 28 |
Mo | 5 |
C | Max 0.35 |
Mn | Max 0.35 |
Si | Max 0.35 |
The dental alloys (Co-Cr-Mo) shown in
The preparation of fluorapatite nanopowder was performed as described in the literature [
The pellets of diameter 20 mm and a 3 mm height were prepared using the lab pellet presses, (Beckman, Scotland) (
The dental alloys were cut into four quarts section and were cleaned by acetone and distilled water prior to PLD analysis. The target-to-substrate distance was maintained at 3.8 cm. Various samples were prepared at different deposition time laser energy and pressure. All of the depositions were performed at room temperature following procedure indicated in
The simulated body fluid was prepared in the laboratory with the ionic concentration nearly similar to human blood plasma. The fluid was prepared according to a procedure developed by Kokubo, as reported in the literature [
Sample | Laser energy (mJ) | Presser | Deposition time |
---|---|---|---|
a | 130 mJ | 7 × 10−9 MPa | 5 min |
b | 130 mJ | 7 × 10−9 MPa | 10 min |
c | 130 mJ | 7 × 10−9 MPa | 20 min |
d | 170 mJ | 7 × 10−9 MPa | 10 min |
e | 170 mJ | 7× 10−9 MPa | 15 min |
of various inorganic ions similar to those of the human blood plasma. The reagents were added, one after another, ensuring complete dissolution. HCl was added to maintain the pH of the solution at 7.4. The temperature of the solution was maintained at 37˚C.
The SBF was then prepared according to
Human Plasma | Ringer | EBSS | HBSS | Kokubo-SBF | Tas-SBF | |
---|---|---|---|---|---|---|
Na+ | 142 | 130 | 143.6 | 138 | 142 | 142 |
K+ | 5 | 4 | 5.37 | 6.14 | 5 | 5 |
Ca2+ | 2.5 | 1.4 | 1.8 | 1.26 | 2.5 | 2.5 |
Mg2+ | 1.5 | - | 0.81 | 0.81 | 1.5 | 1.5 |
Cl− | 103 | 109 | 125.3 | 144.8 | 147.8 | 125 |
HCO3− | 27 | - | 26.2 | 4.2 | 4.2 | 27 |
1 | - | 1 | 0.78 | 1 | 1 | |
0.5 | - | 0.81 | 0.81 | 0.5 | 0.5 | |
Ca/P | 2.5 | - | 1.8 | 1.62 | 2.5 | 2.5 |
Buffer | - | - | - | - | Tris | Tris |
pH | 7.4 | 6.5 | 7.2 - 7.6 | 6.7 - 6.9 | 7.4 | 7.4 |
Order | Reagent | Amount (g/l) |
---|---|---|
1 | NaCl | 7.996 g |
2 | NaHCO3 | 0.350 g |
3 | KCl | 0.224 g |
4 | K2HPO4∙3H2O | 0.228 g |
5 | MgCl2∙6H2O | 0.305 g |
6 | 1 M-HCl | 40 ml |
7 | CaCl2 | 0.278 g |
8 | Na2SO4 | 0.071 g |
9 | (CH2OH)3CNH2 | 6.057 g |
Pulsed laser deposition (PLD) is a growth technique in which the photon, laser energy is characterized by pulse duration and laser frequency, interacting with a bulk material [
Scanning electron microscopy (SEM) is a type of electron microscope, which is used for various purposes: Topographic studies, Microstructure analysis, Phase morphology, Chemical composition, Elemental mapping and Elemental analysis if equipped with appropriate detector (energy/wavelength dispersive X-rays).
The EDAX system is mostly connected to the electron microscopes such as SEM, FE-SEM and HR-TEM. EDAX spectra of the corresponding elements of the sample are obtained by measuring the energy of X-rays emitted from the sample during e-beam bombardment. X-rays are produced as a result of ionization of an atom when the incident electrons have removed an inner shell electron.
The SEM micrographs showing surface morphology of fluorapatite nanopowder/Co-Cr-Mo alloy nanocomposites before exposed to the simulated body fluid are presented in Figures 2-7. The particles of different sizes and their dispersity were observed.
The laser energy was 130 mJ and the pressure was maintained at 7 × 10−9 MPa. The exposure time was five minutes. The micrograph was obtained by irradiating the specimen with a beam of electrons of energy 5 keV. The irradiation live-time was 120 seconds and the working distance was kept maintained at 4.2 ± 0.2 mm.
The laser energy was 130 mJ and the pressure was maintained at 7 × 10−9 MPa. The exposure time was 10 minutes. The micrograph was obtained by irradiating the specimen with a beam of electrons of energy 5 keV. The irradiation live-time was 120 seconds and the working distance was kept maintained at 4.2 ± 0.2 mm.
The laser energy was 130 mJ and the pressure was maintained at 7 × 10−9 MPa. The exposure time was 20 minutes. The micrograph was obtained by irradiating
the specimen with a beam of electrons of energy 5 keV. The irradiation live-time was 120 seconds and the working distance was kept maintained at 4.2 ± 0.2 mm.
The laser energy was 170 mJ and the pressure was maintained at 7 × 10−9 MPa. The exposure time was 10 minutes. The micrograph was obtained by irradiating the specimen with a beam of electrons of energy 5 keV. The irradiation live-time was 120 seconds and the working distance was kept maintained at 4.2 ± 0.2 mm.
The laser energy was 170 mJ and the pressure was maintained at 7 × 10−9 MPa. The exposure time was 15 minutes. The micrograph was obtained by irradiating the specimen with a beam of electrons of energy 5 keV. The irradiation live-time was 120 seconds and the working distance was kept maintained at 4.2 ± 0.2 mm.
Figures 8-12 indicate the EDAX analysis of the deposited fluorapatite on the Co-Cr-Mo alloy at energy 130 mJ. It is noticeable that the density of the deposition increased significantly and therefore correlated to the exposure time of FA deposited on the Co-Cr-Mo alloy. In the instance where the energy was 170 mJ, a significant in the density was also observed.
The laser energy was 130 mJ and 170 mJ and the pressure was maintained at 7 × 10−9 MPa. The exposure times were varying from five to 20 minutes. The micrographs were obtained by irradiating the specimens with a beam of electrons of energy 5 keV. The irradiation live-time was 120 seconds. The surface area
scanned was approximately 10 μm × 10 μm and where necessary, a larger area was selected.
The exposure time in the specimen preparation was five minutes. The EDAX analysis was obtained by irradiating the specimen with a beam of electrons of energy 20 keV. The irradiation live-time was 120 seconds. The data were measured with a silicon ultra-thin window (SUTW).
In the specimen preparation the laser energy was 130 mJ and the pressure was maintained at 7 × 10−9 MPa. The exposure time in the specimen preparation was 10 minutes. The EDAX analysis was obtained by irradiating the specimen with a beam of electrons of energy 20 keV. The irradiation live-time was 120 seconds.
The data were measured with a silicon ultra-thin window (SUTW).
The exposure time in the specimen preparation was 20 minutes. The EDAX analysis was obtained by irradiating the specimen with a beam of electrons of energy 20 keV. The irradiation live-time was 120 seconds. The data were measured with a silicon ultra-thin window (SUTW).
The exposure time in the specimen preparation was 10 minutes. The EDAX analysis was obtained by irradiating the specimen with a beam of electrons of energy 20 keV. The irradiation live-time was 120 seconds. The data were measured with a silicon ultra-thin window (SUTW).
In the specimen preparation the laser energy was 170 mJ and the pressure was
maintained at 7 × 10−9 MPa. The exposure time in the specimen preparation was 15 minutes. The EDAX analysis was obtained by irradiating the specimen with a beam of electrons of energy 20 keV. The irradiation live-time was 120 seconds. The data were measured with a silicon ultra-thin window (SUTW).
The electron micrographs of the microstructural topologies of the fluorapatite nanopowder Co-Cr-Mo alloy nanocomposite after exposed to simulated body fluid are shown in Figures 13-17. The laser energies were 130 mJ and 170 mJ and the pressure was maintained at 7 × 10−9 MPa. The exposure times varied from five to 20 minutes. The micrographs were obtained after irradiating the specimens with a beam of electrons of energy 5 keV. The irradiation live-time was 120 seconds. The surface area scanned was approximately 10 μm × 10 μm, and a larger area was selected where necessary. The magnification was 9000× and the working distance was kept at 4.2 ± 0.2 mm.
A significant degree of agglomeration occurred in the specimen prepared at 130 mJ energy and an exposure time period of five minutes. Void (only the Co-Cr-Mo alloy surface visible) areas were observed. This is indicative of the depletion of the deposited layer. A similar phenomenon occurred in the instance of the specimen prepared at the same energy but for an exposure time of 10 minutes. The extent of depletion of the deposited layer is however not as extensive as in the case of the five minute exposure specimen. As the layer thickness increased, the extent of depletion of the deposited layer decreased.
The laser energy was 130 mJ and the pressure was maintained at 7 × 10−9 MPa. The exposure time was five minutes. The micrograph was obtained by irradiating the specimen with a beam of electrons of energy 5 keV. The irradiation
live-time was 120 seconds and the working distance was kept maintained at 4.2 ± 0.2 mm. The surface area scanned was 10 μm × 10 μm and where necessary, a larger area was selected.
The laser energy was 130 mJ and the pressure was maintained at 7 × 10−9 MPa. The exposure time was 10 minutes. The micrograph was obtained by irradiating the specimen with a beam of electrons of energy 5 keV. The irradiation live-time was 120 seconds and the working distance was kept maintained at 4.2 ± 0.2 mm. The surface area scanned was 10 μm × 10 μm and where necessary, a larger area was selected.
The laser energy was 130 mJ and the pressure was maintained at 7 × 10−9 MPa.
The exposure time was 20 minutes. The micrograph was obtained by irradiating the specimen with a beam of electrons of energy 5 keV. The irradiation live-time was 120 seconds and the working distance was kept maintained at 4.2 ± 0.2 mm. The surface area scanned was 10 μm × 10 μm and where necessary, a larger area was selected.
The laser energy was 170 mJ and the pressure was maintained at 7 × 10−9 MPa. The exposure time was 10 minutes. The micrograph was obtained by irradiating the specimen with a beam of electrons of energy 5 keV. The irradiation live-time was 120 seconds and the working distance was kept maintained at 4.2 ± 0.2 mm. The surface area scanned was 10 μm × 10 μm and where necessary, a larger area was selected.
The laser energy was 170 mJ and the pressure was maintained at 7 × 10−9 MPa. The exposure time was 15 minutes. The micrograph was obtained by irradiating the specimen with a beam of electrons of energy 5 keV. The irradiation live-time was 120 seconds and the working distance was kept maintained at 4.2 ± 0.2 mm. The surface area scanned was 10 μm × 10 μm and where necessary, a larger area was selected.
The energy dispersive analysis of X-rays (EDAX) analysis (shown in Figures 18-22) of the samples were fluorapatite nanopowder was coated onto the Co-Cr-Mo alloy are shown in Figures 3-7. The laser energy was set at 130 mJ and 170 mJ and the pressure was maintained at 7 × 10−9 MPa. The exposure times varied from five to 20 minutes. The micrographs were obtained by irradiating the specimens with a beam of electrons of energy 5 keV. The irradiation live-time was 120 seconds. The surface area scanned was approximately 10 μm × 10 μm.
In the specimen preparation the laser energy was 130 mJ and the pressure was maintained at 7 × 10−9 MPa. The exposure time in the specimen preparation was five minutes. The EDAX analysis was obtained by irradiating the specimen with a beam of electrons of energy 20 keV. The irradiation live-time was 120 seconds. The data were measured with a silicon ultra-thin window (SUTW).
In the specimen preparation the laser energy was 130 mJ and the pressure was maintained at 7 × 10−9 MPa. The exposure time in the specimen preparation was 10 minutes. The EDAX analysis was obtained by irradiating the specimen with a beam of electrons of energy 20 keV. The irradiation live-time was 120 seconds. The data were measured with a silicon ultra-thin window (SUTW).
In the specimen preparation the laser energy was 130 mJ and the pressure was maintained at 7 × 10−9 MPa. The exposure time in the specimen preparation was 20 minutes. The EDAX analysis was obtained by irradiating the specimen with a
beam of electrons of energy 20 keV. The irradiation live-time was 120 seconds. The data were measured with a silicon ultra-thin window (SUTW).
In the specimen preparation the laser energy was 170 mJ and the pressure was maintained at 7 × 10−9 MPa. The exposure time in the specimen preparation was 10 minutes. The EDAX analysis was obtained by irradiating the specimen with a beam of electrons of energy 20 keV. The irradiation live-time was 120 seconds. The data were measured with a silicon ultra-thin window (SUTW).
In the specimen preparation the laser energy was 170 mJ and the pressure was maintained at 7 × 10−9 MPa. The exposure time in the specimen preparation was
15 minutes. The EDAX analysis was obtained by irradiating the specimen with a beam of electrons of energy 20 keV. The irradiation live-time was 120 seconds. The data were measured with a silicon ultra-thin window (SUTW).
In this study, the FA/Co-Cr-Mo nanocomposite was successfully synthesized using pulsed laser deposition technique. The bioactivity assay of the nanocomposite after 14 days test on SBF, showed no corrosion but intact stability and biocompatibility. These were confirmed using various characterizing techniques
such as XRD, SEM and EDAX. The EDAX results indicated that the decrease in the degree of depletion was also connected with the increase in the comparative concentration ratio of the concentration of Ca to that of Cr. Considering the results obtained from this study, for the samples prepared at 130 mJ and exposed for five minutes, the concentration ratio of Ca to Cr was found to be 0.91 before immersed in the test solution (SBF), of which after the test solution (SBF) the concentration increased to greater than 200. As the time of exposure increased to 10 minutes the concentration ratio of Ca to Cr also increased to 5.0 before test solution, of which increased to 0.5 and 3 respectively after test solution (SBF). From these results, it can be deduced that the increase in exposure time as well as the energy of the laser beam, which should be greater or equivalent to 170 mJ must be taken into consideration during laser deposition.
The research programme was generously supported by grants from Libyan Government and Libyan Embassy funding agency, the National Research Foundation of South Africa (NRF, MM 2015-TANZ), the French Center National pour la Recherche Scientifique (MM2015 CNRS), iThemba LABS, The UNESCO- UNISA African Chair in Nanoscience and Nanotechnology (MM2015U2ACN2), the Organization of Women in Science for the Developing World (OWSDW, MM2015OWSDW) and the Abdus Salam ICTP via the Nanoscience African network (NANOAFNET, MM2015ICTP) as well as the African Laser Center (ALC, MM2015ALC) to whom we are grateful.
Khfagi, O., Thovhogi, N., Gihwala, D., Maaza, M. and Mars, J.A. (2017) Synthesis of Co-Cr-Mo Fluorapatite Nano-Composite Coatings by Pulsed Laser Deposition for Dental Applications. Materials Sciences and Applications, 8, 135- 152. https://doi.org/10.4236/msa.2017.82009