Monetite (Dibasic calcium phosphate anhydrate, DCPA, CaHPO 4 ) belongs to the sub-category of dibasic calcium phosphates in the diverse calcium phosphate system with its tremendous applications in orthopedics and other biomedical fields.... more
Monetite (Dibasic calcium phosphate anhydrate, DCPA, CaHPO 4 ) belongs to the sub-category of dibasic calcium phosphates in the diverse calcium phosphate system with its tremendous applications in orthopedics and other biomedical fields. Over the past fifteen years, the research on monetite has increasingly revealed its useful properties. Yet, in comparison to its vastly popular counterparts, hydroxyapatite (HA) and tricalcium phosphates (TCPs), monetite has not gained the attention it deserves. The motivation behind this paper is to provide a comprehensive review of the state-of-the-art of research and development on monetite. After a brief introduction, the paper follows the typical materials science correlations on “Structure-Property-Processing” and relating those aspects to research translation. Indeed, the last few years witnessed increasing numbers of studies on applications of monetite in the form of granules, 3-D printed scaffolds, cements, composites, and coatings with promising outcomes in both in vitro and in vivo studies. The paper concludes with a summary and potential future research directions and its translation. It is hoped that this timely review will present a comprehensive landscape of research on monetite and will enable and entice researchers and engineers across the globe into this important calcium phosphate.
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Abstract This chapter is devoted to reviewing the translatory aspects of calcium phosphates (CaPs) from laboratory to commercialized medical devices. Today, the regulatory clearance is still a significant challenge to market entry for... more
Abstract This chapter is devoted to reviewing the translatory aspects of calcium phosphates (CaPs) from laboratory to commercialized medical devices. Today, the regulatory clearance is still a significant challenge to market entry for CaPs, and that has kept many CaP prototypes at the developmental stage far away from successful commercialization. Implant coatings and synthetic bone grafts are the main products with decades’ applications in orthopedics. The specification and validation of the products are covered by FDA guidelines, ISO, and ASTM standards. Detailed information of regulatory documents are provided as well. In addition, typical materials physical and chemical properties correlated to clinical performances are addressed. Followed by the illustrations to current CaP products, newer concepts for these devices including carrier for active agents and 3D printing in future are also briefly introduced.
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This review recognizes a unique calcium phosphate (CaP) phase known as monetite or dicalcium phosphate anhydrous (DCPA, CaHPO4), and presents an overview of its properties, processing, and applications in orthopedics. The motivation for... more
This review recognizes a unique calcium phosphate (CaP) phase known as monetite or dicalcium phosphate anhydrous (DCPA, CaHPO4), and presents an overview of its properties, processing, and applications in orthopedics. The motivation for the present effort is to highlight the state-of-the-art research and development of monetite and propel the research community to explore more of its potentials in orthopedics. After a brief introduction of monetite, we provide a summary of its various synthesis routes like dehydration, solvent-based, energy-assisted processes and also discuss the formation of different crystal structures with respect to the synthesis conditions. Subsequently, we discuss the material's noteworthy physico-chemical properties including the crystal structure, vibrational spectra, solubility, thermal decomposition, and conversion to other phases. Of note, we focus on the biological (in vitro and in vivo) properties of monetite, given its ever-increasing popularity as a biomaterial for medical implants. Appropriately, we discuss various orthopedic applications of monetite as bone cement, implant coatings, granules for defect fillers, and scaffolds. Many in vitro and in vivo studies confirmed the favorable osteointegration and osteoconduction properties of monetite products, along with a better balance between implant resorption and new bone formation as compared to other CaP phases. The review ends with translational aspects of monetite and presents thoughts about its possible future research directions. Further research may explore but not limited to improvements in mechanical strength of monetite-based scaffolds, using monetite particles as a therapeutic agent delivery, and tissue engineering strategies where monetite serves as the biomaterial. STATEMENT OF SIGNIFICANCE: This is the first review that focusses on the favorable potential of monetite for hard tissue repair and regeneration. The article accurately covers the "Structure-Property-Processing" correlations elaborating on monetite's diverse material properties. Special focus is put on the in vitro and in vivo properties of the material highlighting monetite as an orthopedic material-of-choice. The synthesis techniques are discussed which provide important information about the different fabrication routes for monetite. Most importantly, the review provides comprehensive knowledge about the diverse biomedical applications of monetite as granules, effect-specific scaffolds, bone cements and implant coatings. This review will help to highlight monetite's potential as an effective regenerative medicine and catalyze the continuing translation of this bioceramic from the laboratory to clinics.
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OBJECTIVE The aim of this study was to develop bioactive and osseointegrable polyetheretherketone (PEEK)-based composite filaments melt-blended with novel amorphous magnesium phosphate (AMP) particles for 3D printing of dental and... more
OBJECTIVE The aim of this study was to develop bioactive and osseointegrable polyetheretherketone (PEEK)-based composite filaments melt-blended with novel amorphous magnesium phosphate (AMP) particles for 3D printing of dental and orthopedic implants. MATERIALS AND METHODS A series of materials and biological analyses of AMP-PEEK were performed. Thermal stability, thermogravimetric and differential scanning calorimetry curves of as-synthesized AMP were measured. Complex viscosity, elastic modulus and viscous modulus were determined using a rotational rheometer. In vitro bioactivity was analyzed using SBF immersion method. SEM, EDS and XRD were used to study the apatite-forming ability of the AMP-PEEK filaments. Mouse pre-osteoblasts (MC3T3-E1) were cultured and analyzed for cell viability, proliferation and gene expression. For in vivo analyses, bare PEEK was used as the control and 15AMP-PEEK was chosen based on its in vitro cell-related results. After 4 or 12 weeks, animals were euthanized, and the femurs were collected for micro-computed tomography (μ-CT) and histology. RESULTS The collected findings confirmed the homogeneous dispersion of AMP particles within the PEEK matrix with no phase degradation. Rheological studies demonstrated that AMP-PEEK composites are good candidates for 3D printing by exhibiting high zero-shear and low infinite-shear viscosities. In vitro results revealed enhanced bioactivity and superior pre-osteoblast cell function in the case of AMP-PEEK composites as compared to bare PEEK. In vivo analyses further corroborated the enhanced osseointegration capacity for AMP-PEEK implants. SIGNIFICANCE Collectively, the present investigation demonstrated that AMP-PEEK composite filaments can serve as feedstock for 3D printing of orthopedic and dental implants due to enhanced bioactivity and osseointegration capacity.
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Bioprinting, a promising field in regenerative medicine, holds great potential to create three-dimensional, defect-specific vascularized bones with tremendous opportunities to address unmet craniomaxillofacial reconstructive challenges. A... more
Bioprinting, a promising field in regenerative medicine, holds great potential to create three-dimensional, defect-specific vascularized bones with tremendous opportunities to address unmet craniomaxillofacial reconstructive challenges. A cytocompatible bioink is a critical prerequisite to successfully regenerate functional bone tissue. Synthetic self-assembling peptides have a nanofibrous structure resembling the native extracellular matrix (ECM), making them an excellent bioink component. Amorphous magnesium phosphates (AMPs) have shown greater levels of resorption while maintaining high biocompatibility, osteoinductivity, and low inflammatory response, as compared to their calcium phosphate counterparts. Here, we have established a novel bioink formulation (ECM/AMP) that combines an ECM-based hydrogel containing 2% octapeptide FEFEFKFK and 98% water with AMP particles to realize high cell function with desirable bioprintability. We analyzed the osteogenic differentiation of dental pulp stem cells (DPSCs) encapsulated in the bioink, as well as in vivo bone regeneration, to define the potential of the formulated bioink as a growth factor-free bone-forming strategy. Cell-laden AMP-modified bioprinted constructs showed an improved cell morphology but similar cell viability (~90%) compared to their AMP-free counterpart. In functional assays, the cell-laden bioprinted constructs modified with AMP exhibited a high level of mineralization and osteogenic gene expression without the use of growth factors, thus suggesting that the presence of AMP-triggered DPSCs’ osteogenic differentiation. Cell-free ECM-based bioprinted constructs were implanted in vivo. In comparison with the ECM group, bone volume per total volume for ECM/1.0AMP was approximately 1.7- and 1.4-fold higher at 4 and 8 weeks, respectively. Further, a significant increase in the bone density was observed in ECM/1.0AMP from 4 to 8 weeks. These results demonstrate that the presence of AMP in the bioink significantly increased bone formation, thus showing promise for in situ bioprinting strategies. We foresee significant potential in translating this innovative bioink toward the regeneration of patient-specific bone tissue for regenerative dentistry.
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The ultimate goal of this paper is to develop novel ceramic-polymer-based biocomposite orthopedic scaffolds with the help of additive manufacturing. Specifically, we incorporate a bioceramic known as amorphous magnesium phosphate (AMP)... more
The ultimate goal of this paper is to develop novel ceramic-polymer-based biocomposite orthopedic scaffolds with the help of additive manufacturing. Specifically, we incorporate a bioceramic known as amorphous magnesium phosphate (AMP) into polylactic acid (PLA) with the help of the melt-blending technique. Magnesium phosphate (MgP) was chosen as the bioactive component as previous studies have confirmed its favorable biomaterial properties, especially in orthopedics. Special care was taken to develop constant diameter AMP-PLA composite filaments, which would serve as feedstock for a fused filament fabrication (FFF)-based three-dimensional (3D) printer. Before the filaments were used for FFF, a thorough set of characterization protocols comprising of phase analysis, microstructure evaluations, thermal analysis, rheological analysis, and in vitro degradation determinations was performed on the biocomposites. Scanning electron microscopy (SEM) results confirmed a homogenous dispersion of AMP particles in the PLA matrix. Rheological studies demonstrated good printability behavior of the AMP-PLA filaments. In vitro degradation studies indicated a faster degradation rate in the case of AMP-PLA filaments as compared to the single phase PLA filaments. Subsequently, the filaments were fed into an FFF setup, and tensile bars and design-specific macroporous AMP-PLA scaffolds were printed. The biocomposite exhibited favorable mechanical properties. Furthermore, in vitro cytocompatibility results revealed higher pre-osteoblast cell attachment and proliferation on AMP-PLA scaffolds as compared to single-phase PLA scaffolds. Altogether, this study provides a proof of concept that design-specific bioactive AMP-PLA biocomposite scaffolds fabricated by FFF can be potential candidates as medical implants in orthopedics.
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This paper reports for the first time the development of a biodegradable, non-exothermic, self-setting orthopedic cement composition based on amorphous magnesium phosphate (AMP). The occurrence of undesirable exothermic reactions was... more
This paper reports for the first time the development of a biodegradable, non-exothermic, self-setting orthopedic cement composition based on amorphous magnesium phosphate (AMP). The occurrence of undesirable exothermic reactions was avoided through using AMP as the solid precursor. The phenomenon of self-setting with optimum rheology is achieved by incorporating a water soluble biocompatible/biodegradable polymer, polyvinyl alcohol (PVA). Additionally, PVA enables a controlled growth of the final phase via a biomimetic process. The AMP powder was synthesized using a precipitation method. The powder, when in contact with the aqueous PVA solution, forms a putty resulting in a nanocrystalline magnesium phosphate phase of cattiite. The as-prepared cement compositions were evaluated for setting times, exothermicity, compressive strength, biodegradation, and microstructural features before and after soaking in SBF, and in vitro cytocompatibility. Since cattiite is relatively unexplored in the literature, a first time evaluation reveals that it is cytocompatible, just like the other phases in the MgO-P2O5 (Mg-P) system. The cement composition prepared with 15% PVA in an aqueous medium achieved clinically relevant setting times, mechanical properties, and biodegradation. Simulated body fluid (SBF) soaking resulted in coating of bobierrite onto the cement particle surfaces.
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Abstract 3D printing is a process to produce objects by adding selected materials together where necessary following digital 3D model guidance. The significances of this technology, such as the ability to construct complex geometric... more
Abstract 3D printing is a process to produce objects by adding selected materials together where necessary following digital 3D model guidance. The significances of this technology, such as the ability to construct complex geometric structures matched to patient’s anatomy or surgeon’s requirement, enable its wide applications in medicine, ranging from surgical planning tools to custom surgical devices. The translation of 3D printing in health care has been enhanced recently under the guidance of the regulatory agency. The focus of the present work is to demonstrate the translation aspects of 3D printing in medical devices. An overview of current 3D printing technologies, regulatory guidance, and 3D printed medical devices in the market is carried out in this chapter, along with a brief introduction of laboratory concepts such as bioprinting and 4D printing.
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Due to the combination of many unique properties, magnesium alloys have been widely recognized as suitable metallic materials for fabricating degradable biomedical implants. However, the extremely high degradation kinetics of magnesium... more
Due to the combination of many unique properties, magnesium alloys have been widely recognized as suitable metallic materials for fabricating degradable biomedical implants. However, the extremely high degradation kinetics of magnesium alloys in the physiological environment have hindered their clinical applications. This paper reports for the first time the use of a novel microwave-assisted coating process to deposit magnesium phosphate (MgP) coatings on the Mg alloy AZ31 and improve its in vitro corrosion resistance. Newberyite and trimagnesium phosphate hydrate (TMP) layers with distinct features were fabricated at various processing times and temperatures. Subsequently, the corrosion resistance, degradation behavior, bioactivity and cytocompatibility of the MgP coated AZ31 samples were investigated. The potentiodynamic polarization tests reveal that the corrosion current density of the AZ31 magnesium alloy in simulated body fluid (SBF) is significantly suppressed by the deposited MgP coatings. Additionally, it is seen that MgP coatings remarkably reduced the mass loss of the AZ31 alloy after immersion in SBF for two weeks and promoted precipitation of apatite particles. The high viability of preosteoblast cells cultured with extracts of coated samples indicates that the MgP coatings can improve the cytocompatibility of the AZ31 alloy. These attractive results suggest that MgP coatings, serving as the protective and bioactive layer, can enhance the corrosion resistance and biological response of magnesium alloys.
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The Center of Disease Control and Prevention states that about one in every thirty‐one patients gets infected with ‘hospital‐acquired infections'. Bacterial colonization on surgical instruments remains one of the most significant... more
The Center of Disease Control and Prevention states that about one in every thirty‐one patients gets infected with ‘hospital‐acquired infections'. Bacterial colonization on surgical instruments remains one of the most significant factors for causing them. Such infections not only hinder a patient's recovery but can evolve into life‐threatening scenarios. Further, the moderate surface hardness of instruments might degrade their performance. Considering these issues, the central goal of this paper is to develop antibacterial coatings with favourable hardness. The main objective was to take advantage of the hardness property of titanium oxynitride (TiOxNy) while combining silver's (Ag) antibacterial properties. As surgical instruments are mainly fabricated using Ti6Al4V, we chose this material as our substrate. Radiofrequency magnetron sputtering was employed to develop several multi‐phasic coatings. Phase compositions, morphology and hardness values were analysed by X‐ray diffraction, scanning electron microscopy and nanoindentation, respectively. The antibacterial efficacy was evaluated against Escherichia coli using zone of inhibition, plate counting assay and Live/Dead assay. The effect of repetitive sterilization of coated samples was also examined. Results indicated the successful formation of antibacterial coatings with favourable hardness. Ag‐containing coatings exhibited pronounced antibacterial effect by ‘contact killing' method with no functionality change even after five sterilizing cycles.
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Several statistical reports confirm that surgical site infections (SSI) remain one of the predominant reasons for the failure of orthopedic implant working. Indeed, foreign implant materials are preferential sites for bacterial... more
Several statistical reports confirm that surgical site infections (SSI) remain one of the predominant reasons for the failure of orthopedic implant working. Indeed, foreign implant materials are preferential sites for bacterial infestation and formation of biofilms causing deadly infections. It results in delayed recovery with significant prolongation in hospital stays, expensive bills, patient stress, and revision surgeries, which may not solve the problem but drastically increase the chances of infection reoccurrence. Perioperative antibiotic prophylaxes have been used for decades to prevent and treat SSI, simultaneously also contributing to the mutation of antibiotic-resistant bacterial strains. Thus, the need for developing alternative therapeutics to treat wide-spectrum SSI is essential. In this attempt, transition metals, especially silver (Ag), copper (Cu), zinc (Zn), and their complexes have garnered significant attention as effective antibacterial agents in the orthopedic industry. Given the fact that hydroxyapatite (HA) is a traditional and benchmark material for developing orthopedic scaffolds and coatings, a diverse range of studies has been focused on developing antibacterial HA. This chapter presents an overview of those advancements that have been made in developing antibacterial HA with the help of transition metals over the years. The first part focuses on the fabrication of material-specific antibacterial HA, and in the second part, various kinds of conventional and state-of-the-art antibacterial HA coatings are discussed.
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Subcritical crack growth phenomenon in zirconia is modelled in this paper. The model simulates subcritical crack growth by deflection mechanism. Due to phase transformation in zirconia, KI, the applied stress intensity factors in the... more
Subcritical crack growth phenomenon in zirconia is modelled in this paper. The model simulates subcritical crack growth by deflection mechanism. Due to phase transformation in zirconia, KI, the applied stress intensity factors in the subcritical crack growth range get affected. This is the main reason for the following observations: (i) scattering in KI—Vdata, (ii) biassing of N values to higher magnitude and (iii) calculating erroneous life times. All the above mentioned experimental observations are explained by the present model.
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This paper reports the preliminary results of fabricating Al2O3-ZrO2composites by Hot Isostatic Pressing (HIPing). The idea was to produce toughened (by addition of ZrO2) and completely dense Al2O3—ZrO2 composites. 15 mol % of ultrafine... more
This paper reports the preliminary results of fabricating Al2O3-ZrO2composites by Hot Isostatic Pressing (HIPing). The idea was to produce toughened (by addition of ZrO2) and completely dense Al2O3—ZrO2 composites. 15 mol % of ultrafine unstabilized ZrO2 was milled with Al2O3. The as-mixed powder was cold isostatically pressed (CIPed), sintered at 1400°C for 1 hr and HIPed at 1450°C for 0.5 hr. The samples reached their theoretical density values. The results were compared to HIP diagrams described in the literature. It could be seen that in spite of some simplifying assumptions, theoretical predictions matched with the experimental results. Boundary diffusion was interpreted to be the dominant mechanism.
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Fabrication of toughened Ce‐TZPs by conventional low‐cost processing (ball‐milling and cold‐pressing followed by sintering) affords materials with properties which are quite comparable to other toughened zirconia related systems processed... more
Fabrication of toughened Ce‐TZPs by conventional low‐cost processing (ball‐milling and cold‐pressing followed by sintering) affords materials with properties which are quite comparable to other toughened zirconia related systems processed by special techniques.
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Abstract As a potential orthopedic biomaterial, calcium sodium phosphate (CNP) represents a viable alternative to the quintessentially important β-tricalcium phosphate (β-TCP). The conventional solid-state synthesis of CNP requires... more
Abstract As a potential orthopedic biomaterial, calcium sodium phosphate (CNP) represents a viable alternative to the quintessentially important β-tricalcium phosphate (β-TCP). The conventional solid-state synthesis of CNP requires extensive time and energy with ease of introduction of impurities and formation of coarse particles needing further comminution. The present work demonstrates a simple but versatile microwave assisted method to prepare CNP with negative zeta potential using sodium polyphosphate and calcium chloride as precursors. There are several important characteristics of the product. The as-synthesized CNP crystals showed two different morphologies- polygonal and whisker-like. The as-formed CNP was thermally stable without new phase nucleation after calcination at 1000 °C. This material promoted the proliferation of osteoblast cells as compared to HA in vitro. Additionally, the particles can be easily dispersed because of their negative zeta potential. Finally, the particles revealed their anti-Escherichia coli attachment potential. With all of these attributes, it is expected CNP can be a potential biomaterial in orthopedics and a good candidate for fabrication of composites with relevant biopolymer matrices.
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Magnesium phosphate compounds such as newberyite (MgHPO4·3H2O) and struvite (MgNH4PO4·6H2O) are becoming important alternatives to calcium phosphates in hard tissue replacements. So far, newberyite has received lesser attention with... more
Magnesium phosphate compounds such as newberyite (MgHPO4·3H2O) and struvite (MgNH4PO4·6H2O) are becoming important alternatives to calcium phosphates in hard tissue replacements. So far, newberyite has received lesser attention with respect to struvite. Therefore, the broad aim of this paper is to report an easy synthesis technique and characterization of single‐phase newberyite, which may have diverse uses as a bioceramic material. Specifically, we describe a simple and robust microwave‐assisted process for the synthesis of single‐phase newberyite in tabular hexagonal form. Second, we soak the newberyite powders in simulated body fluid, a solution which mimics the pH and ion concentration of human blood plasma, for 7 days and analyze the apatite formation on the crystals. Third, we report that single‐phase newberyite, by itself, does not possess antibacterial property.
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Abstract This article reports on the fabrication and evaluation of 3-D printed polyetheretherketone (PEEK) scaffolds with controlled macroporosity. Specifically, uniform macropore sizes ranging from 800 to 1800 µm by design were generated... more
Abstract This article reports on the fabrication and evaluation of 3-D printed polyetheretherketone (PEEK) scaffolds with controlled macroporosity. Specifically, uniform macropore sizes ranging from 800 to 1800 µm by design were generated by varying processing parameters. It is expected that the 3-D printing ability to obtain customized macropores can help arriving at the optimum pore size in scaffolds to encourage bone regeneration. This study conclusively showed optimal cell adhesion and proliferation in scaffolds containing uniform pores of an average size of 800 μm. A construct containing a wide distribution of pores cannot come to this conclusion. In this context, the precision and reproducibility of additive manufacturing in scaffold fabrication play an important role.
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Following a brief introduction to monolithic structural ceramics and their mechanical properties and micromechanisms of toughening, the materials development and salient features of various high- and ultrahigh-temperature (UHT) ceramics... more
Following a brief introduction to monolithic structural ceramics and their mechanical properties and micromechanisms of toughening, the materials development and salient features of various high- and ultrahigh-temperature (UHT) ceramics are discussed. The discussion includes alumina, zirconia, silicon nitride, silicon carbide, molybdenum disilicide and carbon-based ceramics. Subsequently, emerging ceramics such as the titanium- and zirconium-boride ceramics are introduced and discussed. Finally, the Indian scenario on the development and production of these materials is described.
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Abstract The objective of this work is to develop silica sol reinforced monetite cement matrix and study the related reinforcement kinetics. Preparation of monetite cement powder was done using a microwave processing method with active... more
Abstract The objective of this work is to develop silica sol reinforced monetite cement matrix and study the related reinforcement kinetics. Preparation of monetite cement powder was done using a microwave processing method with active Ca2+ present on particles surface as effective silica bonding sites. The incorporated silica sol significantly improved the compressive strength of the final matrix. It was noted surface areas of silica particles in solution together with the solution concentration were the main factors influencing reinforcement level. In vitro bioactivity and biodegradation indicated silica sol can be a beneficial additive to bone cement.