Research on bone regeneration has always been an intense and challenging field of tissue engineering. Biodegradable metals represent a novel class of biomaterials combining superior mechanical qualities with a capacity to promote bone growth. Among them, magnesium (Mg) and its alloys have been proposed as innovative biomaterials for bone grafting therapy due to their non-toxic nature and comparable mechanical properties to bones. In addition, they are lightweight, biocompatible and biodegradable. They offer several advantages over other implant metals, including reduced stress-shielding effects and unnecessity for a second surgery to remove them. Unfortunately, their clinical application is limited due to the rapid degradation rates in rather aggressive physiological conditions. Therefore, the development of Mg-based implants possessing a controlled degradation in accordance with the kinetics of bone healing is necessary. On the other hand, protective yet biocompatible and biodegradable surface coatings have emerged as a useful strategy to fulfill the diverse clinical requirements, including effective corrosion resistance. Calcium orthophosphates (abbreviated as CaPO4) are excellent candidates for producing such coatings as they are well tolerated by living organisms. However, due to its high chemical reactivity and a low melting point, Mg-based grafts require specific parameters for successful CaPO4 deposition. This paper reviews currently available preparation methods of CaPO4 deposits on Mg and its alloys, aiming to build up a comprehensive knowledge framework of deposition techniques, processing parameters, performance measures in terms of corrosion resistance, adhesion strength and biocompatibility. The literature analysis shows that CaPO4 protective coatings increase the ability of magnesium-based metallic biomaterials to withstand corrosion and improve the biocompatibility of their surfaces in all cases.

The goal of this review is to present a wide range of hybrid formulations and composites containing calcium orthophosphates (abbreviated as CaPO4) that are suitable for use in biomedical applications and currently on the market. The bioactive, biocompatible, and osteoconductive properties of various CaPO4-based formulations make them valuable in the rapidly developing field of biomedical research, both in vitro and in vivo. Due to the brittleness of CaPO4, it is essential to combine the desired osteologic properties of ceramic CaPO4 with those of other compounds to create novel, multifunctional bone graft biomaterials. Consequently, this analysis offers a thorough overview of the hybrid formulations and CaPO4-based composites that are currently known. To do this, a comprehensive search of the literature on the subject was carried out in all significant databases to extract pertinent papers. There have been many formulations found with different material compositions, production methods, structural and bioactive features, and in vitro and in vivo properties. When these formulations contain additional biofunctional ingredients, such as drugs, proteins, enzymes, or antibacterial agents, they offer improved biomedical applications. Moreover, a lot of these formulations allow cell loading and promote the development of smart formulations based on CaPO4. This evaluation also discusses basic problems and scientific difficulties that call for more investigation and advancements. It also indicates perspectives for the future.

A The present overview describes various production techniques for biocompatible calcium orthophosphate (abbreviated as CaPO4) deposits (coatings, films and layers) on the surfaces of various types of substrates to impart the biocompatible properties for artificial bone grafts. Since, after being implanted, the grafts always interact with the surrounding biological tissues at the interfaces, their surface properties are considered critical to clinical success. Due to the limited number of materials that can be tolerated in vivo, a new specialty of surface engineering has been developed to desirably modify any unacceptable material surface characteristics while maintaining the useful bulk performance. In 1975, the development of this approach led to the emergence of a special class of artificial bone grafts, in which various mechanically stable (and thus suitable for load-bearing applications) implantable biomaterials and artificial devices were coated with CaPO4. Since then, more than 7500 papers have been published on this subject and more than 500 new publications are added annually. In this review, a comprehensive analysis of the available literature has been performed with the main goal of finding as many deposition techniques as possible and more than 60 methods (double that if all known modifications are counted) for producing CaPO4 deposits on various substrates have been systematically described. Thus, besides the introduction, general knowledge and terminology, this review consists of two unequal parts. The first (bigger) part is a comprehensive summary of the known CaPO4 deposition techniques both currently used and discontinued/underdeveloped ones with brief descriptions of their major physical and chemical principles coupled with the key process parameters (when possible) to inform readers of their existence and remind them of the unused ones. The second (smaller) part includes fleeting essays on the most important properties and current biomedical applications of the CaPO4 deposits with an indication of possible future developments.

The band structures of Zn-based hydroxyapatites co-doped with Mg at varying amounts from 0 to 2.0 at. % have been investigated theoretically in more detail. The calculations were done to obtain the band structure, density of states, and band gap for all the modeled structures to study their electronic properties. It was seen that the co-doping has an effect on the structural and electronic properties of all the as-investigated structures. The bandgap energy for all samples in each group was found to be reduced gradually with varying doping rates of Mg into Zn-doped HAp. The band gap decreased from 4.54 to 3.84 eV for samples of 0.4Zn–0.4 Mg-HAp and 2.0Zn–0.4 Mg-HAp with the same amount of Mg, respectively, as a result of increasing the doping levels of Zn from 0.4 to 2.0 at.%. The lattice parameters, unit cell volume, and density decrease with increase in doping of Zn-containing HAp and in addition of second dopant Mg at varying amounts 0.4 , 0 . 8 , 1.2 , 1.6, and 2.0 at . % in all of the modeled sample group. Furthermore, it is observed that the declining values of the aforementioned parameters are significantly impacted by the increasing Zn doping rates.

Following the increased demand for water in addition to water resources' strain, treatments of polluted water allow its reutilization after getting rid of all the impurities.In this work, the defluoridation of industrial wastewater by adsorption on natural clay by applying the Doehlert design was investigated.The optimized factors were the mass of clay chosen in the range 2-6 g, the concentration of fluoride ions which varies from 2,000 to 4,000 mg L -1 , the pH of the medium opted in the range 2-9 and the contact time is taken varying between 20 and 40 min.The experimental response was fluoride levels in used water were considerably reduced.The elsewhere cited factors influenced the performance of the wastewater defluoridation and the quality of the rejected water after application of the Doehlert design.Herein, it is possible to determine the optimum conditions for the treatment of industrial water discharge by natural clay.The application of these conditions on a sample of industrial wastewater discharge treated with this clay gave rise to a remarkable defluoridation rate of around 99.6% which corresponded to a fluoride concentration value reduced from 4,320 mg L -1 contained in the wastewater to the standard value of 11.2 mg L -1 contained in the treated one.

This chapter is intended to point the readers' attention to the subject of calcium phosphates (CaPs). Sections 7.1 and 7.2 discuss these materials and their special significance for biology, because they represent the major inorganic part of calcified tissues, both normal (bones, teeth, and antlers) and pathological. For example, atherosclerosis is caused by a solid composite of cholesterol with calcium phosphates, while dental caries (tooth decay) and osteoporosis represent partial decalcification of teeth and bones, respectively, that result from replacement of biological apatite by more soluble and softer calcium hydrogen phosphates. Although the biological mechanisms appear to be quite different, chemically, the processes of both normal and pathological conditions might be considered as an in vivo crystallization or dissolution of calcium phosphates (CaPs). Section 7.3 discusses industrial uses of calcium phosphates, primarily their controlled precipitation in water treatment applications. CaPs are important corrosion inhibitors in water treatment, but must be carefully controlled to avoid scale deposition. This section describes the nature of CaPs compared to other precipitates, and especially the important distinction between crystalline and amorphous materials. This leads to the difference between threshold inhibitors (for crystalline) and dispersants (for amorphous). For dispersant polymers, polymer solubility as a function of temperature and calcium concentration is recommended as the best predictor of activity. This makes it easier to determine which polymers can work under given conditions. At the highest hardness and temperatures, only the most soluble polymers can act as effective dispersants. This is explained in terms of known physical chemical properties of polyelectrolyte solutions.

In the present study, the effects of variable amounts of Yb addition on the structural, thermal, and in vitro biocompatibility properties of Ce-doped hydroxyapatite (HAp) samples synthesized via the wet chemical method were investigated. Besides, the prepared formulations were also modeled for making the theoretical investigations. The single-phase compositions were detected for all samples, and no formation of additional phases was observed. Doping with Yb was observed to produce some variations in the lattice parameters, unit cell volume, lattice strain, and lattice stress. While a decreasing trend in the crystallite size and crystallization percent with increasing Yb content was found, a gradual increase in the anisotropic energy density was observed. All samples were found to be thermally stable from room temperature to 1000 degrees C with negligible mass losses during heating. No significant morphological changes were caused by the addition of Yb. For all samples, the numerical values of (Ca + Ce + Yb)/P molar ratio were found to be close to that for stoichiometric HAp (1.67). It was observed that the increased Yb additive caused a decrease in cell viability values. A continuous decrease in the bandgap energy with the increasing amounts of Yb added to the Ce-based HAp structure was observed from the theoretical investigations. A sharp decrease in the cell viability of the Ce-based HAp was observed with the addition of Yb.

The present study describes the influence of potassium and hydroxyl substitutions on the structural, thermal and mechanical properties of fluorapatite bioceramics. A set of non-stoichiometric ion-substituted compounds, with a chemical formula of Ca10−xKx(PO4)6F(2−2x)(OH)x with 0 ≤ x ≤ 1 synthesized by the wet precipitation method, were found to be single-phase apatites crystallizing in the hexagonal P63/m space group. The structural parameters, as well as the crystallite sizes, increased accordingly to the amount of added dopant-ions. The thermal behavior of these compounds, studied within the temperature range 500–1200 °C, indicated a partial decomposition of the apatitic phase and its transformation to tricalcium phosphate β-Ca3(PO4)2 at temperatures exceeding 750 °C. A relative density of the sintered samples achieved the highest value with x = 0.25 and reached about 95% after sintering at 1050 °C for 1 h. The microstructures of the sintered samples were of a trans-granular aspect and experienced an increase in the radius of their pores as x increased. The prepared bioceramic materials were mechanically characterized by means of Young’s modulus, flexural strength and fracture toughness measurements. The overall trend of these parameters evolved comparably to the relative density, and the maximum values obtained for x = 0.25 were measured to be 96 MPa, 47 MPa and 1.14 MPa·m1/2, respectively.

Amorphous calcium phosphates (ACPs) represent a metastable amorphous state of other calcium orthophosphates (abbreviated as CaPO4) possessing variable compositional but rather identical glass-like physical properties, in which there are neither translational nor orientational long-range orders of the atomic positions. In nature, ACPs of a biological origin are found in the calcified tissues of mammals, some parts of primitive organisms, as well as in the mammalian milk. Manmade ACPs can be synthesized in a laboratory by various methods including wet-chemical precipitation, in which they are the first solid phases, precipitated after a rapid mixing of aqueous solutions containing dissolved ions of Ca2+ and PO43- in sufficient amounts. Due to the amorphous nature, all types of synthetic ACPs appear to be thermodynamically unstable and, unless stored in dry conditions or doped by stabilizers, they tend to transform spontaneously to crystalline CaPO4, mainly to ones with an apatitic structure. This intrinsic metastability of the ACPs is of a great biological relevance. In particular, the initiating role that metastable ACPs play in matrix vesicle biomineralization raises their importance from a mere laboratory curiosity to that of a reasonable key intermediate in skeletal calcifications. In addition, synthetic ACPs appear to be very promising biomaterials both for manufacturing artificial bone grafts and for dental applications. In this review, the current knowledge on the occurrence, structural design, chemical composition, preparation, properties, and biomedical applications of the synthetic ACPs have been summarized.

This study presents a more extensive report on the experimental and theoretical characterization of the Ce-doped hydroxyapatite (HAp) samples additionally doped with Pr at varying amounts. To achieve this goal, four Ce-containing (a constant amount of 0.35 at.%) HAps additionally doped with Pr at various amounts (0.35, 0.70, 1.05, and 1.40 at.%) were synthesized via a combustion method. Besides, all these samples were modeled theoretically by using a density functional theory (DFT). Theoretical results showed that the bandgap energy decreased continuously from 4.5156 to 4.3097 eV. For all samples, the linear attenuation (or absorption) coefficient increased with the increasing amount of Pr and this parameter had a decreasing trend with the increase in the photon energy. An increase in the theoretical density and the lattice parameter c and a decrease of both the lattice parameter a and the unit cell volume were found. After analyzing the experimental data, the following results were observed: X-ray diffraction (XRD) and Fourier transform infrared (FTIR) data verified the formation of HAp phase (above 94% for all the samples) as the major phase and beta-tricalcium phosphate (beta-TCP) as the minor one. The amount of beta-TCP phase was found to increase from 3.4 to 5.9% with the addition of Pr. Similar to the theoretical findings, an increasing trend for the density and decreasing one for the unit cell volume were detected. Both a decrease in the crystallinity and an increase in the anisotropic energy density were found. The results of the thermal analysis supported the thermal stability of all the samples. The cell viability was found to be affected by Pr-content. (C) 2021 Elsevier B.V. All rights reserved.

Five different samples of Sr-based Er-doped hydroxyapatites (HAps) in the dissimilar quantities like 0, 0.35, 0.70, 1.05 and 1.40 at% were produced via a wet chemical process. The prepared samples were investigated experimentally by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), Fourier transform infrared (FTIR) spectroscopy, differential thermal analysis (DTA), and in vitro biocompatibility tests. In addition, the density of states (DOS) and band structures were investigated theoretically. It was found that the presence of Er as a dopant affected the lattice parameters, while the EDX measurements confirmed that the presence of Er at various concentrations caused a Ca-deficiency because the addition of Er decreased the Calcium/Phosphorus molar ratio from 1.67 to 1.61. For all samples, the single-phase distribution of HAp was observed. The crystallinity percentage of the samples was found to be 89% or more according to two different methods. The calculations with respect to Scherrer and Williamson-Hall methods showed that the crystallite sizes of the samples were found to be in the ranges of 29-34 nm and 25-42 nm, respectively. DTA investigations revealed that all samples exhibited thermal stability in the temperature range of 25 degrees C - 1000 degrees C. No remarkable morphological alterations were observed. Furthermore, the theoretical studies confirmed that the band structures narrowed with an increase in Er concentration.

Five samples of hydroxyapatite (HAp) doped with praseodymium (Pr) at various amounts (2, 4, 6, 8, and 10 at.%) were synthesized by using the wet chemical route. The effects of Pr doping on the structural and thermal properties, as well as on the in vitro performance of HAp, were investigated experimentally. The band structure and density of states (DOS) of HAp were studied theoretically. Incorporation of Pr into the crystal lattice of HAp was observed. A gradual increase in the crystallite size, lattice parameter a , and unit cell volume was found, and a gradual decrease in the crystallinity degree was seen. Pr content from 2 to 10 at.% did not affect the thermal stability of HAp. The theoretical results showed that the bandgap energy of HAp decreased steadily from 3.82 to 1.32 eV with the adding of Pr, and the DOS was also affected by the Pr content. The cell viability tests showed that among all the as-synthesized samples, the best biocompatible properties were found for the sample which was doped with 10 at.% Pr, and the amount of Pr affected significantly the cell viability property of HAp. Except for the sample having 6 at.% Pr, all the remaining samples appeared to be potentially good candidates for biomedical applications.

One of the most exciting and rewarding areas of the engineering discipline involves the development of various devises for health care. Some of them are implantable. Examples comprise sutures, catheters, heart valves, pacemakers, breast implants, fracture fixation plates, nails and screws in orthopedics, various filling formulations, orthodontic wires, and total joint replacement prostheses. However, in order to be accepted by the living body without any unwanted side effects, all implantable items must be prepared from a special class of biotolerable materials, called biomedical materials or biomaterials, in short. The physical character of the majority of the available biomaterials is solids.

Dental caries, also known as tooth decay or a cavity, remains a major public health problem in the most communities even though the prevalence of disease has decreased since the introduction of fluorides for dental care. In addition, there is dental erosion, which is a chemical wear of the dental hard tissues without the involvement of bacteria. Besides, there are other dental losses, which may be of a medical (decay or periodontal disease), age (population aging), traumatic (accident) or genetic (disorders) nature. All these cases clearly indicate that biomaterials to fill dental defects appear to be necessary to fulfill customers’ needs regarding the properties and the processing of the products. Bioceramics and glass-ceramics are widely used for these purposes, as dental inlays, onlays, veneers, crowns or bridges. Among them, calcium orthophosphates (abbreviated as CaPO4) have some specific advantages over other types of biomaterials due to a chemical similarity to the inorganic part of both human and mammalian teeth's and bones. Therefore, CaPO4 (both alone and as constituents of various complex formulations) are used in dentistry as both fillers and implantable scaffolds. This review provides a brief knowledge on CaPO4 and describes in details current state-of-the-art on their applications in dentistry and dentistry-related fields. Among the recognized dental specialties, CaPO4 are most frequently used in periodontics; however, the majority of the publications on CaPO4 in dentistry are devoted to unspecified “dental” fields.

Dental caries, also known as tooth decay or a cavity, remains a major public health problem in most communities even though the prevalence of disease has decreased since the introduction of fluoride for dental care. In addition, there is dental erosion, which is a chemical wear of the dental hard tissues without the involvement of bacteria. Besides, there are other dental losses, which may be of a medical (decay or periodontal disease), age (population aging), traumatic (accident), or genetic (disorders) nature. All these cases clearly indicate that biomaterials to fill dental defects appear to be necessary to fulfill customers' needs regarding the properties and the processing of the products. Bioceramics and glass-ceramics are widely used for these purposes, as dental inlays, onlays, veneers, crowns, or bridges. Among these, calcium orthophosphates (CaPO4) has some specific advantages over other types of biomaterials due to a chemical similarity to the inorganic part of both human and mammalian teeth and bones. Therefore CaPO4 (both alone and as constituents of various complex formulations) is used in dentistry as both fillers and implantable scaffolds. This review provides a brief knowledge on CaPO4 and describes in details current state-of-the-art on their applications in dentistry and dentistry-related fields. Among the recognized dental specialties, CaPO4 is most frequently used in periodontics; however, the majority of the publications on CaPO4 in dentistry are devoted to unspecified "dental" fields.

The present study describes the effects of dopants of Mn and/or Ni on the structural, magnetic and in vivo/in vitro performances of beta-tricalcium phosphate (beta-TCP) bioceramics synthesized by a sol-gel method. Both types of dopants caused significant effects on the structure-related parameters of beta-TCP, including the crystallite dimensions and lattice parameters. The magnetic properties of as-prepared samples were found to be affected by the type and amount of the dopant(s). The in vitro antimicrobial activities of doped beta-TCPs against American Type Culture Collection (ATCC) reference bacterial and fungal strains were evaluated. Among them, only 1.35Ni-TCP displayed an effective antimicrobial activity against Gram-positive bacteria (50 mu g/mL Minimum Inhibitory Concentration (MIC) range), while other types of doped beta-TCPs did not possess with such effect. The in vivo tests showed that each formulation could be a good nominate for bone healing and bone treatment.

Due to the chemical similarity to natural calcified tissues (bones and teeth) of mammals, calcium orthophosphates (abbreviated as CaPO4) appear to be good biomaterials for creation of artificial bone grafts. However, CaPO4 alone have some restrictions, which limit their biomedical applications. Various ways have been developed to improve the properties of CaPO4 and their functionalization is one of them. Namely, since surfaces always form the interfaces between implanted grafts and surrounding tissues, the state of CaPO4 surfaces plays a crucial role in the survival of bone grafts. Although the biomedically relevant CaPO4 possess the required biocompatible properties, some of their properties could be better. For example, functionalization of CaPO4 to enhance cell attachment and cell material interactions has been developed. In addition, to prepare stable formulations from nanodimensional CaPO4 particles and prevent them from agglomerating, the surfaces of CaPO4 particles are often functionalized by sorption of special chemicals. Furthermore, there are functionalizations in which CaPO4 are exposed to various types of physical treatments. This review summarizes the available knowledge on CaPO4 functionalizations and their biomedical applications.

Due to the chemical similarity to natural calcified tissues (bones and teeth) of mammals, calcium orthophosphates (abbreviated as CaPO4) appear to be good biomaterials for creation of artificial bone grafts. However, CaPO4 alone have some restrictions, which limit their biomedical applications. Various ways have been developed to improve the properties of CaPO4 and their functionalization is one of them. Namely, since surfaces always form the interfaces between implanted grafts and surrounding tissues, the state of CaPO4 surfaces plays a crucial role in the survival of bone grafts. Although the biomedically relevant CaPO4 possess the required biocompatible properties, some of their properties could be better. For example, functionalization of CaPO4 to enhance cell attachment and cell material interactions has been developed. In addition, to prepare stable formulations from nanodimensional CaPO4 particles and prevent them from agglomerating, the surfaces of CaPO4 particles are often functionalized by sorption of special chemicals. Furthermore, there are functionalizations in which CaPO4 are exposed to various types of physical treatments. This review summarizes the available knowledge on CaPO4 functionalizations and their biomedical applications.