Hard Tissue Implants Research Articles

Corrosion Behavior of P-Coated Biomedical Pure Magnesium

Magnesium and its alloys are potential materials in biodegradable hard tissue implants. However, the fast degradation rates in a physiological environment constitute the main limitation for biomedical application. In this work, the NH4H2PO4- KMnO4chemical conversion treatment on the surface was used. The morphology and structure of the coating was observed and analyzed by SEM. The electrochemical behavior in Hanks' simulated body fluid of the coated magnesium was systematically investigated. Our results disclose that the corrosion resistance of the P-coated magnesium is significantly improved.

Nitrogen Ion Beam Modification of Alumina for Hard Tissue Implants

SummaryAlumina has wide applications in industry, automobiles, electrical appliances etc. However its application as biomaterial has started recently. We propose to improve the bio‐physical, bio‐chemical and bio‐medical properties of alumina for its application as biomaterial by nitrogen ion implantation. Alumina is implanted with nitrogen ions at different energies (30 keV to 90 keV) and various ion doses (1 × 1015 ions/cm2 to 5 × 1017 ions/cm2). The microstructural changes and surface roughness of the specimens are characterized using Optical Microscope, Scanning Electron Microscope (SEM) and Atomic Force Microscope (AFM). Nano‐layered compound formation of nitrides & oxynitrides were observed using Glancing angle X‐ray Diffraction (GXRD). Mechanical changes like hardness are studied using nanoindentation method. It is observed that corrosion resistance studied using Electrochemical analyzer (ECA) increases at lower energy and at intermediate ion dose. At higher energy and higher ion doses corrosion resistance deteriorates which is in co‐ordinance with the micrstructural analysis. Bio‐medical characterization of the specimens has been carried out by Wettability and Thrombogenicity tests. Wettability decreases in comparison with unimplanted samples. The thrombogenicity of unimplanted and implanted samples were evaluated using a whole blood kinetic clotting time method. From thrombogenicity test, it is concluded that at lower energy, thrombogenicity increases whereas for higher energy thrombogenicity decreases in comparison with the unimplanted samples. On the basis of all the above studies, best suitable energy and ion‐dose is decided for the hard tissue replacement by alumina.

Fatigue behavior of Ti–6Al–4V foams processed by magnesium space holder technique

Abstract Porous Ti–6Al–4V alloys are widely used in the biomedical applications for hard tissue implantation due to their elastic moduli being close to that of bone. In this study, porous Ti–6Al–4V alloys were produced with a powder metallurgical process, space holder technique, where magnesium powders were utilized to generate porosity in the range of 51–65 vol%. The production of porous Ti–6Al–4V alloys was composed of three steps. Firstly, spherical Ti–6Al–4V powders with an average size of 55 μm were mixed with spherical magnesium powders, which have been sieved to an average size of 375 μm. Secondly, the mixtures were compacted with a hydraulic press under 500 MPa pressure by using a double-ended steel die. Finally, the green compacts were heated to 1200 °C, during which magnesium powder evaporates, and sintered for 2 h under high purity argon gas atmosphere. Processed foams were investigated under scanning electron microscope and yielded that the foams were composed of spherical, interconnected macropores and irregular shaped micropores. Monotonic compression tests were conducted under quasi-static test conditions to the processed foams. Yield strengths of the foams were found to vary between 69 and 167 MPa and elastic moduli were between 4 and 12 GPa. Processed foams were also dynamically tested under compression–compression fatigue with a stress ratio of 0.1. The foams exhibited similar fatigue response when maximum applied stress was normalized with the average yield strength of the corresponding porosity content. It was found that foams were fatigue immune with a practical limit of 1 million cycles under a maximum applied stress of 0.75σ (normalized).

Fabrication and properties of porous NiTi alloys by microwave sintering for biomedical applications

Biomedical porous NiTi alloys, being composed of mainly NiTi phase with a little Ti2Ni phase and no Ni3Ti phase, were fabricated by a microwave sintering technique. They presented an isotropic and three-dimensionally interconnected pore microstructure with the pore size of 20–100μm. The compressive strength and elastic modulus of the porous NiTi alloy were about 360MPa and 5.5GPa, respectively. At the same time, the porous NiTi alloys possessed excellent corrosion resistance in Hank׳s solution. Therefore, the porous NiTi alloys fabricated by the microwave sintering technique would be good candidates for ideal biomaterials, used potentially as the heavy load-bearing hard tissue implants.

Saccharose Particles as a Space Holder for Ti-Void Composite Preparation

In this work a new method of Ti-void composites (foam, scaffold) preparation is shown. In this process as a space holder particles we have applied a saccharose crystals (table sugar) with size up to 1.3 mm. After Ti and saccharose particles mixing and pressing, a green compacts composed of sugar and Ti grains were produced. Then, the sugar crystals were removed by its dissolution in water, which lead to open spaces (pores) formation in the green compacts. Then the compacts were sintered at 1250 °C. Alternatively, a sugar was evaporated during sintering without water dissolution. The foams were investigated by SEM, XRD and computed tomography. Such prepared void metal composites have porosity of about 72% and average pore size of about 0.7 mm. The pores have cubical shape corresponding to sugar crystals shape. The method is very promising in foams preparation and the made Ti-void composites can be applied for hard tissue implants, for example.

Phase composition, microstructure, and mechanical properties of porous Ti–Nb–Zr alloys prepared by a two-step foaming powder metallurgy method

Porous Ti–Nb–Zr alloys with different porosities from 6.06 to 62.8% are prepared by a two-step foaming powder metallurgy method using TiH2, Nb, and Zr powders together with 0 to 50wt% of NH4HCO3. The effects of the amounts of Nb and Zr as well as the sintering temperature (1473 to 1673K) on their phase composition, porosity, morphology, and mechanical characteristics are investigated. By controlling the porosity, Nb and Zr concentrations as well as the sintering temperature, porous Ti–Nb–Zr alloys with different mechanical properties can be obtained, for example, the hardness between 290 and 63HV, the compressive strength between 1530.5 and 73.4MPa, and the elastic modulus between 10.8 and 1.2GPa. The mechanical properties of the sintered porous Ti–Nb–Zr alloys can be tailored to match different requirements for the human bones and are thus potentially useful in the hard tissue implants.

A Modified Surface on Titanium Alloy by Micro-Blasting Process

Hydroxyapatite (HA) coating of hard tissue implants is widely employed for its biocompatible and osteoconductive properties as well as its improved mechanical properties. In this study, a novel micro-blasting process has been used to successfully modify a titanium alloy substrate with a HA treatment using a dopant/abrasive regime. The impact of a series of apatite abrasives, was investigated to determine the effect of abrasive particle size on the surface properties of both micro-blasting (abrasive only) and continuous (HA/abrasive) treatments. The resultant HA treated substrates were compared to substrates treated with abrasive only (micro-blasted) and an untreated Ti. The HA powder, apatite abrasives and the treated substrates were characterized for chemical composition, coating coverage, crystalline and topography. The results show that the surface roughness of the HA blasted modification was affected by the particle size of the apatite abrasives used. This study demonstrates the ability of the continuous process to deposit HA coatings with a range of surface properties onto Ti alloy substrates. The ability of the continuous technology to offer diversity in modifying surface topography offers exciting new prospects in tailoring the properties of medical devices for applications ranging from dental to orthopedic settings.

BIO-CORROSION RESISTANCE AND BIOCOMPATIBILITY OF A ZrTi-BASED BMGMC AS POTENTIAL HARD TISSUE IMPLANTS

In this study, we compared the bio-corrosion resistance and biocompatibility of a ZrTi -based BMGMC ( Zr 58.5 Ti 14.3 Ni 4.9 Cu 6.1 Nb 5.2 Be 11.0). The Ti - 6Al - 4V alloy was used as a reference material. By utilizing the electrochemical measurements and M3T3 cell culture, the corrosion resistance and biocompatibility of this BMGMC were evaluated. The BMGMC displayed high positive corrosion potentials and low corrosion current densities, which indicated that this material exhibited a highly improved corrosion resistance than the Ti alloy. The cells could adhere on the surface of this BMGMC and exhibited improved cellular behaviors, such as cellular viability and cytoskeketal structure. In summary, the ZrTi -based BMGMC showed great potential for applications in the hard tissue implants.

Tailoring properties of microsphere‐based poly(lactic‐co‐glycolic acid) scaffolds

Biodegradable polymer scaffolds are being extensively investigated for uses in tissue engineering because of their versatility in fabrication methods and range of achievable chemical and mechanical properties. In this study, poly(lactic-co-glycolic acid) (PLGA) was used to make various types of microspheres that were processed into porous scaffolds that possessed a wide range of properties. A heat sintering step was used to fuse microspheres together around porogen particles that were subsequently leached out, allowing for a 10-fold increase in mechanical properties over other PLGA scaffolds. The sintering temperature was based on the glass transition temperature that ranged from 43 to 49°C, which was low enough to enable drug loading. Degradation times were observed to be between 30 and 120 days, with an initial compressive modulus ranging from 10 to 100 MPa, and after 5 days of degradation up to 10 MPa was retained. These scaffolds were designed to allow for cell ingrowth, enable drug loading, and have an adjustable compressive modulus to be applicable for soft or hard tissue implants. This study combined well-established methods, such as double emulsion microspheres, polymer sintering, and salt leaching, to fabricate polymer scaffolds useful for different tissue engineering applications.

Bio-Properties of Zr-Based BMGMC as Potential Hard Tissue Implants

In this study, an in situ formed bulk metallic glass matrix composite (BMGMC) (Zr58.5Ti14.3Ni4.9Cu6.1Nb5.2Be11.0) was synthesized. Bulk metallic glass (BMG) (Zr52.5Cu17.9Ni14.6Al10.0Ti5.0) was also included in this work and a Ti-6Al-4V alloy was used as a reference material. Due to the glassy matrix that postpones the growth of corrosion pits, the BMGMC displays high positive corrosion potentials and low corrosion current densities. The BMGMC exhibited a higher improved corrosion resistance than the Ti alloys. Furthermore, the biocompatibility of this BMGMC was assessed by studying the cellular behavior of bone-forming mouse M3T3-E1 pre-osteoblast cells. The matrix did not significantly affect cell adhesion, proliferation and ALP activity. The general biosafety of Zr-based BMGMC for M3T3-E1 cells was revealed as normal cell responses. Zr-based BMGMC shows great potential for applications in the hard tissue implants.

Formation of bioactive coatings on Ti–13Nb–13Zr alloy for hard tissue implants

In an attempt to increase the bioactivity of a vanadium-free titanium alloy, Ti–13Nb–13Zr, the plasma electrolytic oxidation (PEO) process for surface modification was utilised. Select samples were subjected to further treatment, either thermal or alkali. The morphology, chemical composition, and phase composition of the treated Ti–13Nb–13Zr alloy were investigated using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). It was observed that during the anodic process under sparking discharge conditions, the simultaneous incorporation of calcium and phosphorus in the forming oxide layer occurs. The resulting layers were porous and exhibited the typical morphology for layers formed during the PEO process. After the alkali treatment of samples oxidised at 150 V, a gel-like titanate layer was formed. The bioactivity investigations in simulated body fluid (SBF) solution indicated that after anodising at 150 V and following alkali treatment the Ti–13Nb–13Zr alloy exhibits osteoinductive properties. The approach presented here may be applied for fabricating Ti–13Nb–13Zr-based implants for hard tissue regeneration.

Formation and Bioactivity of Porous and Nanostructured TiO2/β-TCP Coating on Titanium

Titanium and its alloys have been widely used as hard tissue implants due to their excellent mechanical properties and biocompatibility. However, their near bio-inertness and metallic ion release are still the problems with clinical uses. In this paper, porous and nanostructured TiO2/beta-tricalcium phosphate (beta-TCP) composite coatings were prepared on titanium substrates by plasma electrolytic oxidation (PEO) in a Ca and P-containing electrolyte. The influence of PEO electric current density on phase composition and bioactivity of the coatings were studied. X-ray diffraction, scanning electron microscopy and Fourier transfer infrared spectroscopy were utilized to characterize the phase composition and microstructure of the coatings. Simulated body fluid immersion tests were employed on the coatings to evaluate their bioactivity. The results reveal that TiO2/beta-TCP composite coating with pores size less than 10 microm and grains of 50-100 nm in size was prepared. The electric current density of PEO is an important factor in the formation of the composite coating. The TiO2/beta-TCP composite coating shows good bioactivity, which are attributed to the incorporation of beta-TCP.

A Modified Surface on Titanium Deposited by a Blasting Process

Hydroxyapatite (HA) coating of hard tissue implants is widely employed for its biocompatible and osteoconductive properties as well as its improved mechanical properties. Plasma technology is the principal deposition process for coating HA on bioactive metals for this application. However, thermal decomposition of HA can occur during the plasma deposition process, resulting in coating variability in terms of purity, uniformity and crystallinity, which can lead to implant failure caused by aseptic loosening. In this study, CoBlastTM, a novel blasting process has been used to successfully modify a titanium (V) substrate with a HA treatment using a dopant/abrasive regime. The impact of a series of apatitic abrasives under the trade name MCD, was investigated to determine the effect of abrasive particle size on the surface properties of both microblast (abrasive only) and CoBlast (HA/abrasive) treatments. The resultant HA treated substrates were compared to substrates treated with abrasive only (microblasted) and an untreated Ti. The HA powder, apatitic abrasives and the treated substrates were characterized for chemical composition, coating coverage, crystallinity and topography including surface roughness. The results show that the surface roughness of the HA blasted modification was affected by the particle size of the apatitic abrasives used. The CoBlast process did not alter the chemistry of the crystalline HA during deposition. Cell proliferation on the HA surface was also assessed, which demonstrated enhanced osteo-viability compared to the microblast and blank Ti. This study demonstrates the ability of the CoBlast process to deposit HA coatings with a range of surface properties onto Ti substrates. The ability of the CoBlast technology to offer diversity in modifying surface topography offers exciting new prospects in tailoring the properties of medical devices for applications ranging from dental to orthopedic settings.

Biomedical nanocomposites of poly(lactic acid) and calcium phosphate hybridized with modified carbon nanotubes for hard tissue implants

Degradable polymer-based materials are attractive in orthopedics and dentistry as an alternative to metallic implants for use as bone fixatives. Herein, a degradable polymer poly(lactic acid) (PLA) was combined with novel hybrid nanopowder of carbon nanotubes (CNTs)-calcium phosphate (CP) for this application. In particular, CNTs-CP hybrid nanopowders (0.1 and 0.25% CNTs) were prepared from the solution of ionically modified CNTs (mCNTs), which was specifically synthesized to be well-dispersed and thus to effectively adsorb onto the CP nanoparticles. The mCNTs-CP hybrid nanopowders were then mixed with PLA (up to 50%) to produce mCNTs-CP-PLA nanocomposites. The mechanical tensile strength of the nanocomposites was significantly improved by the addition of mCNTs-CP hybrid nanopowders. Moreover, nanocomposites containing low concentration of mCNTs (0.1%) showed significantly stimulated biological responses including cell proliferation and osteoblastic differentiation in terms of gene and protein expressions. Based on this study, the addition of novel mCNT-CP hybrid nanopowders to PLA biopolymer may be considered a new material choice for developing hard tissue implants.

Lidocaine Loaded Ca/P Scaffolds for Bone Regeneration and Local Drug Delivery

Local drug delivery devices especially based on osteoconductive porous calcium phosphate ceramics are of clinical importance. However, the brittleness, pore structure, porosity and pore size should be controlled for their wider applications in hard tissue implants and load bearing compartments. An approach to the fabrication of the bone graft exhibiting bone regeneration function as well as the local drug delivery was made. Hydroxyapatite (HAp)/β-tricalcium phosphate (β-TCP) porous scaffolds were prepared and mechanical properties (compression strength 20MPa), porosity (>50%), pore size (60-350µm) and structure as well as interconnectivity of pores were investigated. Porous scaffolds were impregnated with 4-5 mg of lidocaine hydrochloride (LidHCl) and drug release rate was evaluated and compared for scaffolds with and without poly lactic acid (PLA), poly(-caprolactone) (PCL) and polyvinyl alcohol (PVA) coatings. From in vitro dissolution tests it was seen that biopolymer coatings sustained the drug release up to 12h.

Reviews of Current Literature

Lozada JL, Goodacre C, Al-ardah AJ, Garbadea A. Lateral and crestal bone planing antrostomy: a simplified surgical procedure to reduce the incidence of membrane perforation during maxillary sinus augmentation procedures. J Prosthet Dent. 2011;105:147–153.This clinical report of 2 patients presents a variation to conventional surgical techniques for opening the maxillary sinus antrum via lateral and crestal approaches. This procedure, described as a lateral/crestal bone planing antrostomy (LBPA, CBPA) involves the use of specially designed rotary instruments that plane away the bone in thin layers. This technique has the potential to reduce the perforation rate of the maxillary sinus membrane during the access process. The authors provide a good review of conventional lateral wall and crestal access techniques and discussion concerning the most common surgical complication of sinus membrane perforation. Two clinical case reports (one LBPA and one CBPA) with detailed stepwise procedural details are presented using bone planing. Excellent color photographs enhance the reader's ability to understand the surgical process.These case reports provide an interesting alternative to existing techniques, however controlled clinical studies with randomized designs are needed before a definitive conclusion can be drawn concerning wide spread acceptance of the technique.James L. RutkowskiEditor-in-Chief, Journal of Oral ImplantologyChairman, Clarion Research GroupFellow AAIDDiplomat ABOI/IDSilverstein LH, Kurtzman D, Shatz PC. Principles of Hard Tissue Regeneration and Implant Therapy: A Complete Step-by-Step Guide. Newton, Pa: Aegis Communications.This textbook is a comprehensive step-by-step manual available to teach surgical hard tissue regeneration for implant dentistry including: socket grafting, ridge augmentation, and maxillary subantral augmentation using either a Caldwel-Luc or crestal approach. The authors describe each procedure in detail with 7 layered animation type visual technology illustrations. One such procedure illustrated describes how to split a posterior ridge for facial expansion and an anterior ridge labially. Instructions are provided on “how-to-do” mono cortical ridge grafting with either the ramus or symphysis as the donor site. Multiple grafting techniques are covered.Readers are shown all steps for each procedure, from administering local anesthetic, to the specific surgical blades, blade angles, sites, and parameters of where the incisions should be made. All surgical procedural steps are explained in detail with corresponding illustrations. Each procedure details the description of suturing; which needles, threads, surgical knots, and specific techniques to use. Specific postoperative instruction sheets are provided that can be copied and given to the patient.The text was refereed and has received CERP accreditation. After successful completion of the test located at the back of the book and proper submission of the CE form, the clinician will receive three hours of Continuing Education credit.This textbook provides a thorough step-by-step outline for multiple hard tissue regeneration procedures as they apply to implant dentistry and should be a well-used reference by all clinicians. This is a must-have text for the Implant Dentist's library.James L. RutkowskiEditor-in-Chief, Journal of Oral ImplantologyChairman, Clarion Research GroupFellow AAIDDiplomat ABOI/ID

Progress in Research on the Surface/Interface of Materials for Hard Tissue Implant

The investigation of the surface/interface of hard tissue implant materials is very important for improving their properties and application. This paper reviews the research progress and tendency of studies on the surface/interface for hard tissue implant, especially on titanium and titanium alloys, based on the law of hard tissue implant. The improvement of the bone regeneration and antibacterial properties of titanium-based alloys by surface modification has become the hot topics in recent years. Generally, loading growth factors and coating bioactive ceramics onto the surfaces of titanium and its alloys are valid ways to improve their ability of bone regeneration. And loading antibiotics and antibacterial agents have been proven to be an effective method to improve the antibacterial property of titanium implant. With the development of nanotechnology and biotechnology as well as the innovation of surface modification technologies, it is expected that to obtain titanium implants with combining bone regeneration and antibacterial properties by the hybrid surface modification.

Divalent Mn in calcium hydroxyapatite by pulse laser deposition

Pulse laser deposition (PLD) was used to deposit Mn containing calcium hydroxyapatite (HAMn). The PLD process ensures that the composition of the target and the deposited layer is the same. In some cases additional effort should be made to preserve some volatile components, namely OH. This was ensured by water steam supply. Calcium hydroxyapatite deposited by this method has the same properties as the target in respect to lattice parameters and valence state of Mn, which ensures the fixation between hard tissue and metal implants. This fact makes PLD grown HAMn layer covering implants to be improved for practical use.

Wear behaviour of ceramic biocomposites based on hydroxiapatite nanopowders

The biomaterials most widely used for hard tissue implants (in orthopaedics, dental implants, and skull bones) are Ti-based biomaterials and Ti coated with hydroxiapatite (HAP). Because metallic biomaterials have some disadvantages as reported previously (mainly due to the difference between the mechanical characteristics of the human bone and the metallic implant), biocomposites have become an interesting solution to improve the hard tissue implants for the human body. This article presents the experimental results concerning the processing of HAP/Ti biocomposites by powder metallurgy technology. The initial powder mixture consists of HAP powder particles (<200 nm) reinforced with 100μm titanium particles in the ratio 3:1 (wt%). Two different sintering routes are used: spark plasma sintering (SPS) at (1000—1100)°C for 10 or 20 min and two-step sintering (TSS) with the first step at 900 °C/1 min, followed by the second step at 800 °C for 300, 600, 900 or 1200 min. The ball-on-disc dry wear tests are developed using, as a moving counterpiece, DIN 100Cr6 tool steel balls (6 mm diameter; Ra<3.2μm; HRc 60—64; density>7.6 g/cm3). The tribological behaviour of the processed biocomposites is appreciated on the basis of the coefficient of friction and wear rate, corroborated with the wear track depth. The final remarks of this article underline the potential use of SPS technology to obtain HAP/Ti biocomposites with comparable wear properties as similar materials processed by more complex technologies. Also, TSS allows processing HAP/Ti materials comparable with the SPS-ed ones from the point of view of the wear behaviour, except for the dwell time of the second step, which is critical for the wear behaviour.

Design and fabrication strategy in the world of functional gradation

The concept of Functionally Graded Materials, FGM, was introduced in 1980s for the development of reliable thermal shock resistant components for high temperature applications. Later on biomimetic approaches were included, to arrive at multifunctional, multiscale FGM's for numerous applications, including abrasion resistant materials and materials for implants. The paper briefly reviews the past achievements and highlights future trends in multi-scale graded materials science and technology, with the aim at utilisation of bio-inspired methods in design and fabrication strategy. Examples are given for systems with hierarchically graded porosity for application in hard tissue implants and in diesel engine filters, respectively.