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Development of Technologies for Manufacturing Medical Implants Using CNC Machines and Microplasma Spraying of Biocompatible Coatings

Authors:
  • E.O. Paton Electric Welding Institute of the National Academy of Sciences of Ukraine

Abstract and Figures

The paper describes the main technological approaches for manufacturing medical implants from titanium alloy using Computer Numerical Control (CNC) machines and microplasma spraying of hydroxyapatite (HA) coatings. New approaches to the formation of coatings with the desired structure and properties and the challenges of developing the technologies for producing modified implants are discussed. Streszczenie. W artykule opisano główne podejścia technologiczne do wytwarzania implantów medycznych ze stopu tytanu przy użyciu maszyn CNC do sterowania numerycznego i mikroplazmowego natryskiwania powłok hydroksyapatytowych (HA). Omówiono nowe podejścia do tworzenia powłok o pożądanej strukturze i właściwościach oraz wyzwania związane z opracowaniem technologii wytwarzania zmodyfikowanych implantów. (Rozwój technologii wytwarzania implantów medycznych z wykorzystaniem maszyn CNC i rozpylania mikroplazmowego powłok biokompatybilnych)
Prototypes of hip joint endoprosthesis modified by the Research Institute of Traumatology and Orthopedics of the Republic of Kazakhstan Microplasma spraying of the powders and wires has been carried out by microplasmatron MP-004 (produced by E.O. Paton Institute of Electric Welding, Kiev, Ukraine) [14]. The microplasmatron has been mounted on an industrial robot arm (Kawasaki RS-010LA, Kawasaki Robotics, Japan). It is able to move horizontally along a computed trajectory at designed speed. The thickness of the coatings has been varied from 100 μm to 300 μm by changing the modes of microplasma spraying. The speed of linear movement of plasmatron along the substrate was chosen to be 50 mm/min. Argon served as a plasma-forming and transporting gas; additional heating of the substrate was not carried out. Implants made of medical titanium alloy of Grade 5 ELI (ISO 5832-3) were used as substrates for microplasma spraying. HA powder with the particle size in the range of 40 to 90 μm and with the ratio Ca/P of 1.67 was used as a sprayed coating material. The process of synthesis of hydroxyapatite powder was described in our paper [10]. For the deposition of titanium coatings, wires of VT1-00 (GOST 19807-91) unalloyed (commercially pure) titanium with a diameter of 0.3 mm were used. Experimental methods of analysis of materials structure and chemical compositions included Scanning Election Microscopy (SEM) by JSM-6390LV ("JEOL", Japan) with Energy Dispersive X-ray (EDX) microanalysis system INCA ENERGY (Oxford Instruments, UK), X-ray diffraction (XRD) by X'Pert PRO ("PANalytical", the Netherlands), infra-red (IR) spectroscopy by FT801 FT-IR spectrometer (SIMEX, Russia). To evaluate the porosity of biocompatible coatings, the images being obtained by the scanning electron microscope JSM-6390LV (JEOL, Japan) were processed using ZAF/PB, Micro Capture, and Atlas computer-aided programs. The measurements were carried out on the polished cross section of the coatings as per ASTM E2109-01 standard [15]. The crystallinity and the structure-phase compositions of HA powders and plasma sprayed HA coatings were measured by X'Pert PRO diffractometer (PANalytical, the Netherlands). The interpretation of the X-ray diffraction patterns was carried out using Rietveld method and licensed data of the PCF DFWIN (140,000 connections), the ASTM card file and Diffracts Plus software. The percentage of crystallinity of the HA powder was calculated using the area of crystalline peaks in the region 20 to 40° 2θ and the area of the amorphous diffuse background in this region.
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154 PRZEGLĄD ELEKTROTECHNICZNY, ISSN 0033-2097, R. 96 NR 4/2020
Darya ALONTSEVA1, Bagdat AZAMATOV1, Sergii VOINAROVYCH2, Oleksandr KYSLYTSIA2,
Tomasz N. KOLTUNOWICZ3, Aigerim TOXANBAYEVA4
D. Serikbayev East Kazakhstan State Technical University (1), E. O. Paton Electric Welding Institute, Ukraine (2),
Lublin University of Technology (3), K. Satpayev Kazakh National Research Technical University, Kazakhstan (4)
doi:10.15199/48.2020.04.32
Development of Technologies for Manufacturing Medical
Implants Using CNC Machines and Microplasma Spraying
of Biocompatible Coatings
Abstract. The paper describes the main technological approaches for manufacturing medical implants from titanium alloy using Computer Numerical
Control (CNC) machines and microplasma spraying of hydroxyapatite (HA) coatings. New approaches to the formation of coatings with the desired
structure and properties and the challenges of developing the technologies for producing modified implants are discussed.
Streszczenie. W artykule opisano główne podejścia technologiczne do wytwarzania implantów medycznych ze stopu tytanu przy użyciu maszyn
CNC do sterowania numerycznego i mikroplazmowego natryskiwania powłok hydroksyapatytowych (HA). Omówiono nowe podejścia do tworzenia
powłok o pożądanej strukturze i właściwościach oraz wyzwania związane z opracowaniem technologii wytwarzania zmodyfikowanych implantów.
(Rozwój technologii wytwarzania implantów medycznych z wykorzystaniem maszyn CNC i rozpylania mikroplazmowego powłok
biokompatybilnych)
Keywords: CNC machines, microplasma spraying, hydroxyapatite coatings, medical implants.
Słowa kluczowe: maszyny CNC, natryskiwanie mikroplazmowe, powłoki hydroksyapatytowe, implanty medyczne.
Introduction
Nowadays, the production technologies of medical
implants are constantly being improved in order to
accelerate a patient's recovery and increase the service life
of the implant, with special attention being paid to applying
biocompatible coatings on the implant surface [1]. The most
advanced technologies for manufacturing patient-oriented
medical implants include the integration of additive
manufacturing (AM) technology or rapid prototyping (RP)
with Computer Numerical Control (CNC) machining [2, 3],
as well as with 3D scanning and computed tomography
technologies [4]. At present, there are numbers of materials
and manufacturing technologies available to produce
orthopedics implants [2-5]. These technologies such as AM
or RP, CNC, hybrid CNC and high precision machining
technology can make significant impact in the field of
biomedical engineering and surgery [3].
However, despite the variety of existing approaches to
the production of orthopedic implants with coatings from
biocompatible materials, it is rather difficult to select a
satisfactory combination of equipment and techniques for
the development of flexible production of inexpensive
medical implants. Since the market for medical implants is
very competitive, the successful development of implants
manufacturing technologies may be provided with the
novelty of technological approaches, coupled with patient-
oriented production. In order to create a technology for the
production of patient-oriented implants from local materials
in the Republic of Kazakhstan, the authors of this paper are
developing a technology for manufacturing cheaper and
patient specific medical implants.
The manufacturing process involves two main
approaches:
1) implant lathing by numerically controlled machines,
followed by surface purification and quality control;
2) Microplasma Spraying (MPS) of biocompatible Ti wires
and hydroxyapatite (HA) powders onto implants using
an industrial robot to obtain the two-layer Ti/HA coating
with a dense Ti sublayer that provides good adhesion to
the substrate and a porous HA top layer, which can
accelerate implant growth with bone.
Hydroxyapatite (HA) is the calcium phosphate mineral
Ca10(PO4)6(OH)2 of the apatite group, which is chemically
similar to the apatite of the host bone, and is a source of
calcium and phosphate for the bone-HA interface [6-8].
HA coatings improve osseointegration and can significantly
reduce the duration of implantation of the endoprosthesis,
provide a reliable connection with the bone and increase
the reliability of implants [1, 7-10]. In case of thermal
spraying of HA powder, the chemical composition of the
final HA coating is dependent on the thermal decomposition
occurring during spraying. The high temperatures
experienced by HA powder particles in the plasma spraying
process lead to the dehydroxylation and decomposition of
the particles. At temperatures of above 1050°C HA
decomposes to tricalcium phosphate β-TCP -Ca3(PO4)2
and tetracalcium phosphate TTCP-Ca4(PO4)2O, and above
1120°C β-TCP is converted to α-tricalcium phosphate -
Ca3(PO4)2. [9]. Thus the resulted coating phase composition
depends on the thermal history of the powder particles. The
higher the plasma jet temperature and the longer the
exposure of the particles to plasma, the greater the degree
of phase transformation is. According to the ISO standard
specification ISO 13779-2:2000 [11], the maximum
allowable content of non-HA phases in a HA coating is 5%,
and the percentage of crystallinity is no less than 50% [11].
The degree of crystallinity of the HA coating largely affects
the process of osseointegration [9]. The amorphous phase
of HA has a higher rate of dissolution, which reduces the
recovery time of the patient, but at the same time some
reduction of the reliability of fixation of the endoprosthesis in
the bone is also possible. Thus, increased crystallinity
appears to slow resorption of HA, which leads to a slight
decrease of bone ingrowth [9], yet provides reliable fixation
of the implant in the bone [6, 10]. The sublayer from
unalloyed titanium is used to improve the adhesion of the
upper HA layer and because of its highly corrosion
resistance, bio inertness and biocompatibility.
The technology of Microplasma Spraying has been
chosen based on the analysis of existing technologies for
the production of biocompatible coatings, of which the most
widely applicable are the technologies of plasma spraying
[1, 6, 10]. Among the different existing plasma spraying
processes, the Microplasma Spraying (MPS) is particularly
characterized by low plasma power (up to 4 kW), small
spray spot (up to 15 mm), and a possibility of forming a
PRZEGLĄD ELEKTROTECHNICZNY, ISSN 0033-2097, R. 96 NR 4/2020 155
laminar jet with the length of up to 150 mm, which heats the
refractory material in a stream of Ar plasma and provides
low heat input into the substrate [10]. The process provides
Ti wire or HA powder deposition on small-sized parts and
components, including those with fine sections, this being
unachievable with any other methods. The MPS generally
provides a micro-rough surface and a higher degree of
porosity (~20%) that in case of biocompatible coatings
facilitates bony tissues in-growth; in most cases the bond
strength of MPS coatings with substrates is good enough
[10, 12]. However, there are still a number of challenges,
and the most important among them is the problem of the
formation of coatings with specified structure and
properties.
The aim of this work was to develop the technologies for
manufacturing medical implants using CNC machines and
microplasma spraying of biocompatible coatings, including
the selection of modes for microplasma spraying of HA
powder to obtain a porous HA coating with the desired
structural phase composition.
Experimental procedure
To manufacture the medical implants the Computer
Numerical Control (CNC) machines have been used: CTX
510 ecoline CNC turning and milling machine (DMG MORI,
Germany) and DMU 50 CNC milling machine (DMG MORI,
Germany). The universal mobile 3D scanner “scan3D
Universe” (SMARTTECH3D, Poland) has been used to
obtain a 3D model of a physical object for further digital and
real processing.
The following sequence of technological processes has
been developed:
1) Receiving prototypes of implants modified by the
Research Institute of Traumatology and Orthopedics of
the Republic of Kazakhstan. 3-D scanning of implants’
prototypes and 3-D designing using the SolidWorks
software. Preparation of design documentation
according to USDD (Unstructured Supplementary
Service Data).
2) MasterCam for SolidWorks programming. Transfer of
the controlling program in G codes to the machine
column and Siemens programming on CNC machines.
Implant lathing by CNC machines. Implant quality visual
and dimensional inspection.
3) Implants' surface preparation for coating. Microplasma
spraying of biocompatible coatings followed by testing
the laboratory prototypes of medical implants for
compliance with the requirements of International
Standards Organization [11, 13].
Prototypes of some medical implants made of titanium
alloy, such as the hip joint endoprosthesis (Fig.1), have
been obtained and tested. At this stage of the research, no
clinical tests on humans or animals have been carried out.
Before microplasma spraying, the surfaces of the samples
were degreased with acetone and subjected to ultrasonic
cleaning. To ensure proper adhesion of the coatings, it is
important to pre-treat the surfaces of the substrates to
increase their roughness. For surface activation, gas
abrasive treatment is used. Since the activity of the base
rapidly reduces due to the adsorption of chemical gases
from the atmosphere and oxidation, the time between the
gas abrasive preparation and the coating of the surface
should not exceed 2 hours. Samples before coating are
stored in a tightly closed container. Gas abrasive surface
treatment was carried out on the CONTRACOR machine
(Russia) using normal grade A14 electrocorundum.
Fig.1. Prototypes of hip joint endoprosthesis modified by the
Research Institute of Traumatology and Orthopedics of the
Republic of Kazakhstan
Microplasma spraying of the powders and wires has
been carried out by microplasmatron MP-004 (produced by
E.O. Paton Institute of Electric Welding, Kiev, Ukraine) [14].
The microplasmatron has been mounted on an industrial
robot arm (Kawasaki RS-010LA, Kawasaki Robotics,
Japan). It is able to move horizontally along a computed
trajectory at designed speed.
The thickness of the coatings has been varied from
100 μm to 300 μm by changing the modes of microplasma
spraying. The speed of linear movement of plasmatron
along the substrate was chosen to be 50 mm/min. Argon
served as a plasma-forming and transporting gas; additional
heating of the substrate was not carried out.
Implants made of medical titanium alloy of Grade 5 ELI
(ISO 5832-3) were used as substrates for microplasma
spraying. HA powder with the particle size in the range of
40 to 90 μm and with the ratio Ca/P of 1.67 was used as a
sprayed coating material. The process of synthesis of
hydroxyapatite powder was described in our paper [10]. For
the deposition of titanium coatings, wires of VT1-00 (GOST
19807-91) unalloyed (commercially pure) titanium with a
diameter of 0.3 mm were used.
Experimental methods of analysis of materials structure
and chemical compositions included Scanning Election
Microscopy (SEM) by JSM-6390LV (“JEOL”, Japan) with
Energy Dispersive X-ray (EDX) microanalysis system INCA
ENERGY (Oxford Instruments, UK), X-ray diffraction (XRD)
by X’Pert PRO (“PANalytical”, the Netherlands), infra-red
(IR) spectroscopy by FT801 FT-IR spectrometer (SIMEX,
Russia).
To evaluate the porosity of biocompatible coatings, the
images being obtained by the scanning electron microscope
JSM-6390LV (JEOL, Japan) were processed using ZAF/PB,
Micro Capture, and Atlas computer-aided programs.
The measurements were carried out on the polished cross
section of the coatings as per ASTM E2109-01 standard
[15].
The crystallinity and the structure-phase compositions of
HA powders and plasma sprayed HA coatings were
measured by X’Pert PRO diffractometer (PANalytical, the
Netherlands). The interpretation of the X-ray diffraction
patterns was carried out using Rietveld method and
licensed data of the PCF DFWIN (140,000 connections),
the ASTM card file and Diffracts Plus software. The
percentage of crystallinity of the HA powder was calculated
using the area of crystalline peaks in the region 20 to 40° 2θ
and the area of the amorphous diffuse background in this
region.
Discussion
The experimental studies of the influence of such
parameters of microplasma spraying as amperage (I, А),
plasma gas flow rate (Vpg, slpm), spraying distance (H, mm)
156 PRZEGLĄD ELEKTROTECHNICZNY, ISSN 0033-2097, R. 96 NR 4/2020
and powder consumption (Ppowder, g/min) on the surface
morphology, porosity and structural-phase transformations
in the HA coatings in the process of micro-plasma spraying
have been performed. The coating experiments for MPS
were accomplished in a two level fractional factorial design
(24-1).
XRD and IR-spectrometry analysis confirmed that the
phase composition of the initial HA powder was fully
crystalline Ca10(PO4)6(OH)2 with the ratio Ca/P of 1.67.
The plasma spraying of HA powders was carried out
using nine different modes (Table 1), the key criteria were
the phase composition and the degree of crystallinity (Aph
the proportion of the amorphous phase, HAcryst. – the
proportion of the crystalline phase), and the powder
consumption ratio (PCR). Using the method of
mathematical planning, an experiment was conducted to
determine the degree of influence on the PCR of such
factors of the MPS process as amperage, plasma gas flow
rate and spraying distance. The regression equation (1) for
the PCR is as follows:
PCR%=2.575I–0.246Vpg–0.203H+4.06Ppowder–0.825 (1)
The analysis of the equation (1) shows that in the case
of increasing the amperage, the PCR grows due to the rise
of the plasma jet temperature and more intense heating of
the powder particles. With these values of the micro-plasma
spraying parameters the amperage magnitude has the
strongest impact on the value of the PCR. The increase in
gas flow rate leads to a decrease in the PCR. This is
because the increase in gas flow rate leads not only to a
decrease in the temperature of the jet and, therefore, the
temperature of the particles reduces, but also to the
increase in the speed of the jet. The growth in the speed of
the jet increases the speed of powder particles, which in
turn, reduces their time in high temperature zone of the
plasma jet and also leads to insufficient heating. As the
distance of spraying rises, the fall of the PCR is due to
partial cooling of the sprayed particles during the approach
to the substrate. The consumption of powder under
conditions of MPS also has some influence on the degree
of the particles heating, and, therefore, on the PCR. Thus,
the increase in the powder consumption leads to the
decrease in the speed of the jet, thereby increasing the time
of heating the particles in a plasma jet, and thus the degree
of fusion penetration. With the increase of the amount of
powder introduced into the jet, the PCR will grow till the
stored energy of the plasma jet can heat the incoming
powder to the melting temperature of the powder material.
Then plasma supercooling takes place, and there will come
a point when the quantity of molten powder particles will
start to decrease. The comparison of calculated
and experimental results shows their good convergence
(Table 1).
The analysis of the received results of X-ray diffraction
analysis presented in Table 1 shows that the phase
compositions of all coatings comply with ISO 13779-2: 2000
[11]. The areas of existence of amorphous HA have been
found on the X-ray diffraction patterns between 28.9
and 34.2 2θ (°). The peaks in the X-ray diffraction
patterns match the standard diffraction pattern for
HA (JCPDS 9-432), which provides evidence that the
analyzed coatings are in the HA zone. All the diffraction
patterns in the range of 37.3 2θ (°) were thoroughly
investigated, but even weak peaks of Calcium oxide (CaO)
were not found. This confirms that the purity meets the
requirements of ISO 13779-2:2000 [11]; no harmful СаО
compound is formed through the MPS coating of HA
powder. However, the mode No.3 provides the highest
powder consumption ratio (Table 1) and the smallest
diameter of the spraying spot – 8 mm (with a maximum of
12 mm corresponding to Mode No.1). Thus, we consider
the mode No.3 to be optimal, the most cost-effective. This
mode allows obtaining a desired HA coating thickness
(about 100 µm) in one pass of a plasma jet.
The images of microstructure of microplasma sprayed
under specified above mode HА coating are presented in
Fig.2 and Fig.3. Pore sizes in the coating are in the range of
20-60 μm, and the porosity is about 30% (Fig.2). Regarding
the results of measuring the level of porosity in the НА
coating it should be noted that for biocompatible coatings
open porosity is essential – the egress of the pore on the
surface of the coating, where the bone grows. Therefore, in
this case, it would be more correct to talk about the relief or
morphology of the surface, perhaps by measuring the
diameters of the pore craters on the surface of the coating.
In our experiment, the maximum pore diameter on the
surface of the HA coating was about 100 μm (Fig. 3).
Fig.2. The SEM image of cross-section of HA coating sprayed by
Mode No.3 (Table 1) onto titanium sublayer
Fig.3. The SEM image of HA coating sprayed by Mode No.3
(Table 1) onto titanium sublayer
It is assumed that to increase the biocompatibility of the
implants rapid accretion with the bone, the implant surface
should be covered with a biocompatible coating with an
extensive surface morphology, with pore sizes in the
coating from 20 to 100 µm, and closed porosity of at least
30% [5-10]. Thus, the HA coating is designed to meet these
requirements. The use of robotic movement of plasmatron
allowed to deposit coatings onto implants with complex
surface geometry with high accuracy. Thus, the chosen
equipment and techniques allow machining such a
challenging material as titanium, efficiently manufacture
small-batch or custom one-off complex parts and handle the
complex geometries, which is in good agreement with the
data presented in the papers [2, 3].
PRZEGLĄD ELEKTROTECHNICZNY, ISSN 0033-2097, R. 96 NR 4/2020 157
Table 1. The dependence of the powder consumption ratio (PCR), phase composition and crystallinity of HA coating on the spraying
parameters
Conclusions
The technologies for manufacturing medical implants
using CNC machines and microplasma spraying of
biocompatible coatings have been developed and
prototypes of orthopedic implants have been obtained.
The modes for microplasma spraying of HA powder
have been selected; they allow to obtain the porous HA
coating with the thickness up to 100 µm with a 95% level of
HA phases and 93% level of crystallinity controlled by
changing the spraying modes. The small size of the
spraying spot (up to 8 mm) provides a significant reduction
in powder consumption when depositing on implants of
small size compared to conventional plasma spraying.
The results of the research are of significance for a wide
range of researchers developing the technologies of
manufacturing of orthopedic implants with biocompatible
coatings.
The authors gratefully acknowledge funding from the Ministry of
Education and Science of the Republic of Kazakhstan under the
target financing program for the 2017-2019 years by the program
0006/PTF “Production of titanium products for further use in
medicine” and support from the Polish Ministry of Science and
Higher Education from science fund of the Lublin University of
Technology, at the Faculty of Electrical Engineering and Computer
Science FN-28/E/EE/2019, entitled ‘Researches of electrical,
magnetic, thermal and mechanical properties of modern
electrotechnical and electronic materials, including nanomaterials
and diagnostic of electrical devices and their components’
Authors: Prof. Darya Alontseva Ph.D., D.Sc., Bagdat Azamatov
Ph.D. (Eng.), D. Serikbayev East Kazakhstan State Technical
University, 69, Protozanov Street, 070004 Ust-Kamenogorsk,
Kazakhstan, E-mail: dalontseva@mail.ru, azamatovy@mail.ru;
Sergii Voinarovych Ph.D. (Eng.), Oleksandr Kyslytsia Ph.D. (Eng.),
E.O. Paton Electric Welding Institute, 11 Bozhenko Street, 03680,
Kiev, Ukraine, E-mail: serge.voy@gmail.com, kisl@i.ua;
Associate Professor Tomasz N. Koltunowicz Ph.D., D.Sc. (Eng.),
Lublin University of Technology, 38D Nadbystrzycka Street,
20-618, Lublin, Poland, E-mail: t.koltunowicz@pollub.pl;
Ph.D. student Aigerim Toxanbayeva, Department of Engineering
Physics, K. Satpayev Kazakh National Research Technical
University, 22 Satpayev Street, Almaty, 050013, Kazakhstan,
Email: aigerim.toxanbayeva@mail.ru.
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Mode No.
Set spraying parameters Powder Consumption Ratio Phase composition and crystallinity of HA coating
I,
A
Vpg,
slpm
H,
mm
Ppowder,
g/min PCR,% PCR, %
estimated
HA
Ca10(PO4)6(OH)2
β- TCP
Ca3(PO4)2 Aph HAcryst.
1 45 2.0 160 1.2 54 58 97 3 5 92
2 45 2.0 80 0.4 64 71 98 2 0 98
3 45 1.0 160 0.4 89 89 95 5 2 93
4 45 1.0 80 1.2 69 69 96 4 0 96
5 35 2.0 160 0.4 29 29 97 3 4 93
6 35 2.0 80 1.2 48 48 97 3 3 94
7 35 1.0 160 1.2 40 47 95 5 7 88
8 35 1.0 80 0.4 56 60 98 2 0 98
9 40 1.5 120 0.8 60 59 94 6 4 90
... The use of robotic MPS allows for precision coating deposition on complex-shaped implant parts, such as parts of elbow and hip replacements. In our previous papers [18][19][20][21][22], it was shown that robotic microplasma spraying can produce coatings on medical implants made of biocompatible titanium and hydroxyapatite materials with the desired porosity and roughness, meeting the requirements of international standards for implants for surgery in terms of coating adhesive strength [23], crystallinity and purity [24]. ...
... The production and research site, where experimental medical implants from titanium alloys are manufactured by CNC machines, operates at D. Serikbayev East Kazakhstan Technical University [18,20,21]. Titanium alloys are the preferred material for the production of orthopedic and dental prostheses. ...
... These specimen dimensions are also optimal for further studies, both for placement in the SEM chamber and for the preparation of cross-sections. To manufacture the medical implants (parts of the elbow and hip joint components) the CTX 510 ecoline CNC turning and milling machine and DMU 50 CNC milling machine (DMG MORI AG, Germany) have been used [18,20]. Before MPS, for the substrate surface activation [28], the substrate surface was subjected to gas abrasive blasting treatment followed by cleaning. ...
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This paper presents new results of studying the influence of parameters of microplasma spraying (MPS) of Zr wire on the structure of Zr coatings. The coating experiments were accomplished in a two level fractional factorial design. Individual particles of sprayed Zr wire and their splats on the substrate were collected under various spraying parameters (amperage, spraying distance, plasma gas flow rate and wire flow rate) and evaluated by Scanning Electron Microscopy (SEM) to establish the effect of particle size and shape on the coating microstructure. The particles were characterized by measurement of their sizes and the obtained results were evaluated in terms of their degree of melting. This was compared with the experimentally observed coating microstructure type and finally correlated to the investigated coating porosity to select the specific MPS parameters of Zr coatings depositing onto medical implants from Ti alloy. It was found that the main parameters influencing the size of the sprayed Zr particles and the porosity of the Zr coatings are the plasma gas flow rate and amperage. It was demonstrated that it is possible to control the porosity of Zr microplasma coatings in the range from 2.8% to 20.3% by changing the parameters of the MPS. The parameters of microplasma spraying of Zr wire were established to obtain medical implant coatings with porosity up to 20.3% and pore size up to 300 μm.
Conference Paper
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The paper presents new results of studying the influence of the parameters of microplasma spraying of Zr wire on the structure of Zr coatings. This study focuses on new robot-assisted technologies for plasma coating of medical implants. This includes robotic microplasma spraying of Zr coatings on biomedical Ti implants. The design of the movement of the robot arm provides a coordinated and individual operation of the plasma coating. Scanning electron microscopy was used to analyse the structure of the coatings. The possibility of controlling the porosity of Zr microplasma coatings in the range from 2.8% to 20.3% by changing the parameters of microplasma deposition was established. The new robotic microplasma spraying technology developed from this research represents a promising solution for medical implant manufacturing.
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Orthopedic and dental implants have been used successfully for decades to replace or repair missing or damaged bones, joints, and teeth, thereby restoring patient function subsequent to disease or injury. However, although device success rates are generally high, patient outcomes are sometimes compromised due to device-related problems such as insufficient integration, local tissue inflammation, and infection. Many different types of surface coatings have been developed to address these shortcomings, including those that incorporate therapeutic agents to provide localized delivery to the surgical site. While these coatings hold enormous potential for improving device function, the list of requirements that an ideal combination coating must fulfill is extensive, and no single coating system today simultaneously addresses all of the criteria. Some of the primary challenges related to current coatings are non-optimal release kinetics, which most often are too rapid, the potential for inducing antibiotic resistance in target organisms, high susceptibility to mechanical abrasion and delamination, toxicity, difficult and expensive regulatory approval pathways, and high manufacturing costs. This review provides a survey of the most recent developments in the field, i.e., those published in the last 2-3 years, with a particular focus on technologies that have potential for overcoming the most significant challenges facing therapeutically-loaded coatings. It is concluded that the ideal coating remains an unrealized target, but that advances in the field and emerging technologies are bringing it closer to reality. The significant amount of research currently being conducted in the field provides a level of optimism that many functional combination coatings will ultimately transition into clinical practice, significantly improving patient outcomes.
Manufacturing Methods for Medical Prostheses -A Review
  • A M A B D U L R A N I
  • R F U A -N I Z A N
  • M Ya Z I D D I N
A b d u l R a n i A. M., F u a -N i z a n R., Ya z i d D i n M., A b d u A l i y u A. A., Manufacturing Methods for Medical Prostheses -A Review. International Medical Device and Technology Conference (2017), 138-142