Technical Field of the Invention

The present invention relates to a new generation of biomaterials that are developed for use in both orthopedic and dental implants among biomedical applications, that have a low elastic modulus and hardness value to ensure maximum compatibility with the human body. These biomaterials, which eliminate the need for repeated replacement, can also be used continuously by means of their high corrosion resistance and ductility properties, and they do not cause complaints in the related patients after implantation.

State of the Art

Biomaterials are naturally or synthetically prepared materials that can heal or replace an organ, tissue or functional part of the human body. These materials, which are produced to support the functioning of the body, are in contact with living tissue. Again, these materials must maintain their physical properties over time. These materials, which do not show toxic, carcinogenic and allergic properties, should have a long physical life. In addition, they should be sterilizable and biocompatible.

The most fundamental factors in the phase transformation of a material are the chemical composition of the material and the external physical effects applied to this material (individual or combined application of external effects such as Thermal Effect, Mechanical Deformation, Hydrostatic Pressure, Magnetic Field). Said external physical effects can cause phase transformations in the relevant material. The temperatures associated with these transformations are characterized by As, Af, Ms, and Mf for the Austenite-Martensite phase transformations and are very sensitive parameters dependent on the chemical composition (stoichiometric distribution). Because the chemical composition not only determines the kinetics of transformation in a material but also clearly reveals the time dependence of the transformation kinetics. The morphology of the product phase, which consists of a transforming main phase after phase transformations, also largely depends on the chemical composition of the material studied, which is the most fundamental factor determining the mechanical properties of the material (morphology of the resulting product phase). Therefore, the stoichiometric composition of the studied material is the main factor both before and after the phase transformation of the material.

Metal alloys in biomaterials used in biomedical implant applications in humans must have high corrosion resistance, ductility, and desirable elastic properties [1 -5], on the other hand, intensive scientific studies are carried out to introduce new materials that meet these standards for the production of biomedical materials with an elastic module close to that of human cortical bone (10 GPa - 30 GPa), especially for bone implants [6-11 ].

Biomaterials with higher elastic moduli than human bones cause incompatibility between bone and implant. As a result, it causes the resorption of bones after implantation. This can also cause contact loosening of the implant, implant failure, or infections from debris in the human body [2, 12-15], and to meet these challenges, research has focused extensively on current challenges. Also, new biomaterials are researched for practical applications. At this point, the use of titanium (Ti) alloys as biomaterials is important due to their excellent biocompatibility in addition to their superior mechanical and corrosion properties [16-20], for example, one of the most desirable mechanical properties for orthopedic implants is the elastic (Young) modulus, and it is denoted by E.

Ti-based alloys exhibit relatively high elastic modulus (E) values (110-120 GPa) compared to human cortical bone (10-30 GPa). Therefore, scientific studies currently continue to improve new binary, ternary, and multicomponent titanium alloys with low elastic modulus [21-23], Among them, Ti-Nb binary, ternary and multicomponent alloys and their derivatives stand out due to their low elastic modulus [24],

As is often indicated in the published literature [1 -33], titanium (Ti) has a hexagonal close-packed structure (a-phase) at room temperature, and it can transform into a body-centered cubic structure ([3-phase) at temperatures above 882°C. In addition, binary Ti-Nb alloys obtained through adding niobium (Nb) to a-Ti are one of the focuses of interest in biomaterial technology. Using less Nb during alloying with titanium is beneficial for low-cost production and other production perspectives. In addition, elements such as tin (Sn), tantalum (Ta), palladium (Pd), zirconium (Zr), molybdenum (Mo), and copper (Cu) are alloying elements with effects that change the mechanical properties of Ti-Nb alloys [25], In the literature, there are many theoretical and experimental studies carried out for ternary Ti-Nb-X [26-31 ] and multicomponent Ti-Nb-X-Y-Z alloys [32,33] to obtain low Young modulus.

In the state of the art, US patent document numbered “US9828655B2” discloses alloys of titanium with 20-22 at. % niobium (Nb) and 12-13 at. % zirconium (Zr). These alloys are prepared by mechanical alloying of elemental powders and spark plasma sintering technique. The alloys have a nanoscale, coaxial granular structure, microhardness of at least 650 HV, and Young's modulus of 90-140 GPa. Said alloy is corrosion-resistant, biocompatible and has higher wear resistance and mechanical durability compared to the Ti-6AI-4V alloy. The bioactive surface of this nano-structured alloy supports higher protein adsorption that stimulates new bone formation compared to other titanium- based alloys. These alloys are suitable for a variety of biomedical and dental applications. Here, in addition to zirconium and niobium, titanium is used in an amount of less than 68%. However, in the aforementioned patent, it is observed that titanium alloys containing niobium and zirconium have Young's modulus of 90-140 GPa. The use of alloys with this value, especially for bone implants, leads to a flexible mismatch between bone and implant in biomedical applications, since they do not have Young's modulus (10-30 GPa) close to human cortical bone, and this can cause resorption of bones after implantation.

In the state of the art, another US patent document numbered “US6238491 B1” discloses an example of a medical implant manufactured in any form from niobium (Nb)-titanium (Ti)-zirconium (Zr)-Molybdenum (Mo) alloy (NbTiZrMo alloy). In the example, it has components made of a metal alloy with a) about 29 to 70 weight percent of Nb; b) about 10 to 46 weight percent Zr; and c) between about 3 and 15 weight percent of Mo, and in the titanium balance. Said alloy has a uniform beta phase that is corrosion-resistant. This easily processable alloy has high oxidation resistance. However, this niobium-titanium-zirconium alloy doped with molybdenum also does not have the desired Young's modulus, which should be compatible with human bone. This mismatch can cause contact loosening of the implants, potential implant problems, or infections in the human body from debris. These disadvantages also cause biomaterials not to be able to maintain their physical properties over time, such as to be non-toxic, to have a long physical life, and not to lose their functionality throughout their life.

Since existing solutions do not have Young's modulus values required for compatibility with human bone, it leads to incompatibility between bone and implant. In this incompatibility, during the period following implantation, it causes bone resorption and contacts loosening after a certain period of use in the body. Additionally, this disadvantage establishes a ground for other implant application failures and infections resulting from these failures. Due to these deficiencies and the inadequacies of available solutions, it has become inevitable to improve in the relevant technical field.

Objects of the Invention and Advantages Thereof

In the present invention, it is aimed to develop a biomaterial, the properties such as Young's modulus, hardness values, corrosion resistance, and ductility of which are highly compatible with the human body. These biomaterials, which eliminate many of the disadvantages described above, do not need constant replacement/renewal, and are developed in a way that will not cause complaints in the patients after the implantation procedure, are materials that can be easily used in both orthopedics and dental implants and surgeries.

An object of the present invention is to obtain a new generation biomaterial with Young's modulus (10-30 GPa) and hardness value (0.25-0.80 GPa) that is close to human cortical bone. Ti-15%Nb-X%Ge systematic alloys of the present invention contain 15% Nb by weight, and the weight ratios of Ge indicated as X can be 0.8%, 1 %, 1.2%, 1.4%, 1.6% or 1.8%, respectively. The Young's modulus (E) values of biomaterials made of this alloy containing 0.8%, 1 %, 1 .2%, 1 .4%, 1 .6% or 1 .8% GE by weight, respectively, are 43, 36.5, 30.5, 25, 19.9, 14.8 (GPa), respectively, and hardness (H) values thereof are 0.794, 0.556, 0.446, 0.322, 0.132 (GPa). Thus, a new generation of biomaterials with Young's modulus (10-30 GPa) and hardness value (0.25-0.80) close to human cortical bone are obtained. Another object of the present invention is to obtain a biomaterial with properties that can be used in both orthopedic and dental implantation. With the invention, elastic constants, Bulk (volume), shear and Young's modulus, Pugh's ratio, Poisson ratio, anisotropy coefficient and hardness of all alloys were determined under varying %Ge concentrations. All studied compositions of alloys show structural stability. Young's modulus values were obtained as 43 GPa for Ti-15%Nb-0.8% Ge alloy, 14.8 GPa for Ti-15%Nb-1 ,8%Ge alloy, and Young's modulus range as compared to 10 GPa-30 GPa, which is the human cortical bone Young's modulus. Except for the Poisson's and Pugh's ratios, it was observed that all other calculated parameters of the alloys are decreased under increasing Ge concentrations. Thus, a wide range of biomaterials can be used with the present invention, from orthopedic implantation to dental implantation. At the same time, the invention brings effective and efficient economic advantages due to its suitability for material production.

Another object of the present invention is to provide a biomaterial with improved corrosion resistance and ductility properties. B/G ratios of Ti-15%Nb-X%Ge alloys are illustrated in Figure 2. According to this graph, it is observed that Ti-15%Nb-X%Ge alloys have significant ductility under different Ge concentrations. One of the most necessary properties of a biomaterial is its ductility.

At the same time, biomaterials of the present invention can also be used continuously by means of their good corrosion resistance and ductility properties, eliminate the need for repeated replacement, and is of the quality not to cause complaints in the related patients after implantation.

Description of the Figures

Figure 1 is the graphic that illustrates elastic constants for a-Ti.

Figure 2 is the graphic that illustrates the elastic constants of Ti-15%Nb-X%Ge alloys varying with Ge percentage.

Figure 3 is the graphic that illustrates the Bulk (B) and Shear (G) Modulus of Ti- 15%Nb-X%Ge alloys varying with Ge percentage.

Figure 4 is the graphic that illustrates the change of Young's Modulus (E) of Ti-15%Nb- X%Ge alloys with Ge percentage. Figure 5: is the graphic that illustrates the ductility properties of Ti-15%Nb-X%Ge alloys with Ge percentages.

Figure 6 is the graphic that illustrates the changes of Poisson's ratios depending on Ge percentage in Ti-15%Nb-X%Ge alloys.

Figure 7 is the graphic that illustrates the change of anisotropy coefficients of Ti- 15%Nb-X%Ge alloys depending on Ge percentage.

Figure 8 is the graphic that illustrates the hardness values varying with Ge percentage in Ti-15%Nb-X%Ge alloys.

Detailed Description of the Invention

The present invention relates to a new generation of biocompatible materials that are developed for use in both orthopedic and dental implantation from biomedical applications, that have low Young's modulus and hardness value to ensure maximum compatibility with the human body. Said biomaterials can also be used continuously by means of their good corrosion resistance and ductility properties, eliminate the need for repeated replacement, and is of the quality not to cause complaints in the related patients after implantation.

The present invention is a biomaterial made of an alloy of titanium, niobium, and germanium (Ti-Nb-Ge). Alloys that enable biomaterials to have the above-mentioned properties are especially Ti-15%Nb-X%Ge systematic alloys and contain 15% Nb by weight, and Ge denoted as X can have a ratio of 0.8-1 .8% by weight.

In Table 1 below, various titanium alloys and various mechanical properties of these titanium alloys are given together with the available studies in the literature [34-35], According to this table, The Young's modulus (E) of biomaterials made of this alloy containing 0.8%, 1 %, 1.2%, 1.4%, 1.6%, or 1.8% Ge by weight are 43, 36.5, 30.5, 25, 19.9, or 14.8 (GPa), respectively; and hardness (H) values thereof are 0.794, 0.556, 0.446, 0.322, or 0.132 (GPa). Thus, a new generation of biocompatible materials with Young's modulus (43, 36.5, 30.5, 25, 19.9, 14.8) close to the human cortical bone in the range of 10-30 GPa and hardness value (0.794, 0.556, 0.446, 0.322, 0.132) in the range of 0.25-0.80 Gpa are obtained. In the process of revealing this alloy, the niobium (Nb) composition was kept at 15% by weight (in the a phase) and studies were carried out for Ti-15%Nb by means of the virtual-crystal approach (VCA). Thus, the results were compared with previous experimental and theoretical data on the elastic and mechanical properties of a -Ti and Ti-15%Nb. Since Nb is a rare metal with a high melting point, it has been found that using fewerNb elements during alloying with Ti is indeed beneficial for low-cost production and other production perspectives. Young's modulus of Ti-15%Nb alloy is 91.5 GPa (Table 1 ). To reduce Young's modulus value of the available Ti-15%Nb alloy, germanium (Ge) doping was carried out to Ti-15%Nb alloys in the range of 0.8% - 1.8% by weight. Theoretical calculations were made with the generalized gradient approximation (GGA) within the density functional theory (DFT),

The Perdew-Burke-Ernzerhof (PBE) functional and virtual crystal approximation (VCA) were used.

Table 1 : Values indicating various mechanical properties of a -Ti, Ti-15%Nb and Ti- 15%Nb-X%Ge alloys are data of the invention and all % compositions indicate % by weight (wt.). As can be seen in Table 1 , the required and compatible Young's modulus (10-30 GPa) values for the human body are met with the specified content and doping rates. At the same time, the hardness values of these alloys meet the hardness value of human tooth enamel in the range of 0.25-0.80 GPa, quite successfully.

In the first stage of the study, elastic constants for a-Ti were obtained (Figure 1 ) and results that are very close to the literature were found. With the invention, elastic constants, Bulk (volume), shear and Young's modulus, Pugh's ratio, Poisson ratio, anisotropy coefficient and hardness of all alloys were determined under varying %Ge concentrations. According to these results, all the examined compositions of the alloys demonstrate structural stability. Young's modulus values were obtained as 43 GPa for Ti-15Nb-0.8% Ge alloy, 14.8 GPa for Ti-15%Nb-1.8%Ge alloy. The calculated Young's modulus range was compared with human cortical bone (10-30 GPa). Except for the Poisson's and Pugh's ratios indicated in Figure 6, it was observed that all other calculated parameters of the alloys are decreased under increasing Ge concentrations. Moreover, all the studied alloys reveal that the biomaterials exhibit the desired ductile mechanical behavior. The calculated hardness values of these alloys are satisfactory when compared with the hardness of human tooth enamel, as seen in Figure 8 and Table 1 . Therefore, it is very suitable for dental implantation with the invention.

In Table 2, the calculated elastic constants values of a -Ti, Ti-15%Nb and Ti-15%Nb- X%Ge alloys and found in the literature [34-35] are given comparatively. The information obtained from the correct calculation of the elastic constants is closely related to the hardness of the material, its mechanical stability and the bond strengths formed between the atoms forming the structure and the closest neighboring atoms. The structure is mechanically stable if the elastic constants of material are positive. The results given in Table 2 show that these alloys have a stable structure.

Table 2 indicates elastic constants of a -Ti, Ti-15%Nb and Ti-15%Nb-X%Ge alloys

Values

are the data of the invention.

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