Preferred grades of titanium in dentistry. biological indifference and anti-corrosion resistance to acids and alkalis in small concentrations

Titanium alloys have high technological and physical-mechanical properties, as well as toxicological inertness. Titanium sheet grade VT-100 is used for stamped crowns (thickness 0.14-0.28 mm), stamped bases (0.35-0.4 mm) of removable dentures, frames of titanium-ceramic dentures, implants of various designs. Titanium VT-6 is also used for implantation.

It is used to create cast crowns, bridges, arched (clasp) frames, splinting prostheses, and cast metal bases. cast titanium VT-5L. The melting point of titanium alloy is 1640° C.

In foreign specialized literature there is a point of view according to which titanium and its alloys act as an alternative to gold. When exposed to air, titanium forms a thin inert oxide layer. Its other advantages include low thermal conductivity and the ability to bond with composite cements and porcelain. The disadvantage is the difficulty of obtaining a casting (pure titanium melts at 1668 ° C and easily reacts with traditional molding compounds and oxygen). Consequently, it must be cast and soldered in special devices in an oxygen-free environment. Alloys of titanium and nickel are being developed that can be cast using the traditional method (such an alloy releases very few nickel ions and bonds well to porcelain). New methods of creating fixed prostheses (primarily crowns and bridges) using CAD/CAM technology (computer-aided modeling/computer-aided milling) immediately eliminates all casting problems. Some successes have also been achieved by domestic scientists.

Removable dentures with thin-sheet titanium bases 0.3-0.7 mm thick have the following main advantages over dentures with bases made of other materials:

Absolute inertness to oral tissues, which completely eliminates the possibility of an allergic reaction to nickel and chromium, which are part of metal bases made of other alloys; - complete absence of toxic, thermal insulating and allergic effects typical of plastic bases; - small thickness and weight with sufficient base rigidity due to the high specific strength of titanium; - high accuracy reproduction of the smallest details of the relief of the prosthetic bed, unattainable for plastic and cast bases made of other metals; - significant relief in the patient’s adaptation to the prosthesis; - maintaining good diction and perception of the taste of food.

Porous titanium and titanium nickelide, which has shape memory, are used in dentistry as materials for implants. There was a period when coating of metal prostheses with titanium nitride became widespread in dentistry, giving a golden hue to steel and CHS and isolating, according to the authors of the method, the soldering line. However, this technique is not widely used for the following reasons:

1) titanium nitride coating of fixed prostheses is based on old technology, i.e. stamping and soldering;

2) when using prostheses with titanium nitride coating, old prosthetic technology is used, thus, the qualifications of orthopedic dentists do not increase, but remain at the level of the 50s;

3) prostheses with titanium nitride coating are unaesthetic and designed for the bad taste of a certain part of the population. Our task is not to emphasize the defect in the dentition, but to hide it. And from this point of view, these prostheses are unacceptable. Gold alloys also have aesthetic disadvantages. But the commitment of orthopedic dentists to gold alloys is explained not by their color, but by their manufacturability and high resistance to oral fluid;

4) clinical observations showed that the titanium nitride coating peels off, in other words, this coating has the same fate as other bimetals;

5) it should be borne in mind that the intellectual level of our patients has increased significantly, and at the same time the requirements for the appearance of the prosthesis have increased. This flies in the face of efforts by some orthopedists to find a gold alloy surrogate;

6) the reasons for the appearance of the proposal - coating fixed dentures with titanium nitride - are, on the one hand, the backwardness of the material and technical base of orthopedic dentistry, and on the other, the insufficient level of professional culture of some dentists.

To this can be added a large amount of toxic allergic reactions patients' bodies on the titanium nitride coating of fixed prostheses.

Numerous basic and applied studies state that the best material titanium is used for the manufacture of dental implants.

In Russia, commercially pure titanium grades BT 1-0 and BT 1-00 (GOST 19807−91) are used for the production of various structures, and so-called “commercially pure” titanium is used abroad, which is divided into 4 grades (Grade 1−4 ASTM , ISO). Titanium alloy Ti-6Al−4V (ASTM, ISO) is also used, which is an analogue of the domestic alloy BT-6. All these substances differ in chemical composition and mechanical properties.

Titanium Grade 1,2,3 – not used in dentistry, because too soft.

Advantages of pure titanium Grade 4 (CP4)

• Better biological compatibility
• Absence of toxic vanadium (V)
• Better corrosion resistance
• 100% absence of allergic reactions

According to a study of scientific articles, methodological and presentation publications of foreign companies, ASTM, ISO, GOST standards are available comparison tables properties and composition of titanium of different grades.

Table 1. Chemical composition of titanium according to ISO 5832/II and ASTM F 67−89.

** ISO and ASTM data agree on many points; if they differ, ASTM values ​​are given in parentheses.

Table 2. Mechanical properties of titanium according to ISO 5832/II and ASTM F 67−89.

Table 3. Chemical composition of titanium alloys according to GOST 19807−91.

* In titanium grade VT 1−00, the mass fraction of aluminum is allowed to be no more than 0.3%, in titanium grade VT 1−0 no more than 0.7%.

Table 4. Mechanical properties of titanium alloys according to GOST 19807−91.

** Data are given according to OST 1 90 173−75.
*** No data found in available literature.

The strongest of the materials considered is the Ti-6Al−4V alloy (domestic analogue of VT-6). An increase in strength is achieved by introducing aluminum and vanadium into its composition. However, this alloy belongs to the first generation biomaterials and, despite the absence of any clinical contraindications, it is used less and less. This provision is given in the aspect of problems of endoprosthetics of large joints.

From the point of view of better biological compatibility, substances belonging to the group of “pure” titanium seem more promising. It should be noted that when they talk about “pure” titanium, they mean one of the four grades of titanium approved for introduction into body tissues in accordance with international standards. As can be seen from the above data, they differ in chemical composition, which, in fact, determines biological compatibility and mechanical properties.

The question of the strength of these materials is also important. The best characteristics titanium is class 4 in this regard.
When considering its chemical composition, it can be noted that this grade of titanium has an increased content of oxygen and iron. The fundamental question is: does this impair biological compatibility?

The increase in oxygen will probably not be negative. An increase in iron content by 0.3% in Grade 4 titanium (compared to Grade 1) may cause some concern, since, according to experimental data, iron (as well as aluminum) when implanted into body tissue leads to the formation of connective tissue around the implant -fabric layer, which is a sign of insufficient bioinertness of the metal. In addition, according to the same data, iron suppresses the growth of organic crops. However, as mentioned, the above data relate to the implantation of “pure” metals.

In this case, the important question is: is it possible for iron ions to escape through a layer of titanium oxide into the surrounding tissues, and if so, at what speed and what is the subsequent metabolism? We have not found information on this matter in the available literature.

When comparing foreign and domestic standards, it can be noted that the titanium alloys VT 1−0 and VT 1−00 approved for clinical use in our country practically correspond to grades of “pure” titanium Grade 1 and 2. Reduced content oxygen and iron in these grades leads to a decrease in their strength properties, which cannot be considered favorable. Although titanium grade VT 1−00 has an upper limit of tensile strength that corresponds to a similar indicator of Grade 4, the yield strength of the domestic alloy is almost two times lower. In addition, it may contain aluminum, which, as mentioned above, is undesirable.

When comparing foreign standards, it can be noted that the American standard is more stringent, and ISO standards refer to American ones in a number of points. In addition, the US delegation expressed opposition to the approval of the ISO standard for titanium used in surgery.

Thus, it can be stated that:
The best material for the manufacture of dental implants today is “pure” titanium class 4 according to the ASTM standard, since it:

• does not contain toxic vanadium, such as the Ti-6Al−4V alloy;
• the presence of Fe in its composition (measured in tenths of a percent) cannot be considered negative, since even in the case of possible release of iron ions into the surrounding tissues, their effect on the tissues is not toxic, like vanadium;
• titanium class 4 has better strength properties compared to other materials of the “pure” titanium group;

Cobalt-chrome alloys

Cobalt-chrome alloys grade KHS

cobalt 66-67%, which gives the alloy hardness, thus improving the mechanical qualities of the alloy.

chromium 26-30%, introduced to impart hardness to the alloy and increase anti-corrosion resistance, forming a passivating film on the surface of the alloy.

nickel 3-5%, increasing the ductility, toughness, and malleability of the alloy, thereby improving the technological properties of the alloy.

molybdenum 4-5.5%, which is of great importance for increasing the strength of the alloy by making it fine-grained.

manganese 0.5%, which increases strength and casting quality, lowers the melting point, and helps remove toxic granular compounds from the alloy.

carbon 0.2%, which reduces the melting point and improves the fluidity of the alloy.

silicon 0.5%, which improves the quality of castings and increases the fluidity of the alloy.

iron 0.5%, increasing fluidity, increasing the quality of casting.

nitrogen 0.1%, which reduces the melting point and improves the fluidity of the alloy. At the same time, an increase in nitrogen of more than 1% worsens the ductility of the alloy.

beryllium 0-1.2%

aluminum 0.2%

PROPERTIES: KHS has high physical and mechanical properties, relatively low density and excellent fluidity, allowing the casting of openwork dental products of high strength. The melting point is 1458C, the mechanical viscosity is 2 times higher than that of gold, the minimum tensile strength is 6300 kgf/cm2. A high modulus of elasticity and lower density (8 g/cm3) allow the production of lighter and more durable prostheses. They are also more resistant to abrasion and retain the mirror-like shine of the surface given by polishing for a longer time. Due to its good casting and anti-corrosion properties, the alloy is used in orthopedic dentistry for the manufacture of cast crowns, bridges, various designs of solid-cast clasp dentures, frames of metal-ceramic dentures, removable dentures with cast bases, splinting devices, cast clasps.

RELEASE FORM: produced in the form of round blanks weighing 10 and 30 g, packaged in 5 and 15 pcs.

All produced metal alloys for orthopedic dentistry are divided into 4 main groups:

Bygodents are alloys for cast removable dentures.

KH-Dents - alloys for metal-ceramic dentures.

NX-Dents - nickel-chrome alloys for metal-ceramic dentures.

Dentans are iron-nickel-chrome alloys for dentures.

1. Byugodents. They are a multicomponent alloy.

COMPOSITION: cobalt, chromium, molybdenum, nickel, carbon, silicon, manganese.

PROPERTIES: density - 8.35 g/cm 3, Brinell hardness - 360-400 HB, melting point of the alloy - 1250-1400C.

APPLICATION: used for the manufacture of cast clasp dentures, clasps, splinting devices.

Bygodent CCS vac (soft)- contains 63% cobalt, 28% chromium, 5% molybdenum.

Bygodent CCN vac (normal) - contains 65% cobalt, 28% chromium, 5% molybdenum, and increased content carbon and does not contain nickel.

Bygodent CCH vac (solid)- the basis is cobalt - 63%, chromium - 30% and molybdenum - 5%. The alloy has a maximum carbon content of 0.5%, is additionally alloyed with niobium - 2% and does not contain nickel. It has exceptionally high elastic and strength parameters.

Byugodent CCC vac (copper)- the base is cobalt - 63%, chromium - 30%, molybdenum - 5%. The chemical composition of the alloys includes copper and a high carbon content - 0.4%. As a result, the alloy has high elastic and strength properties. The presence of shallows in the alloy facilitates polishing, as well as other mechanical processing of prostheses made from it.

Bygodent CCL vac (liquid)- in addition to cobalt - 65%, chromium - 28% and molybdenum - 5%, the alloy contains boron and silicon. This alloy has excellent fluidity and balanced properties.

2. KH-Dents

APPLICATION: Used to make cast metal frames with porcelain linings. Oxide film, formed on the surface of alloys, allows the application of ceramic or glass-ceramic coatings. There are several types of this alloy: CS, CN, CB, CC, CL, DS, DM.

KH-Dent CN vac (normal) contains 67% cobalt, 27% chromium and 4.5% molybdenum, but does not contain carbon and nickel. This significantly improves its plastic characteristics and reduces hardness.

KH-Dent CB vac (Bondy) has the following composition: 66.5% cobalt, 27% chromium, 5% molybdenum. The alloy has a good combination of casting and mechanical properties.

3. NH-Dents

COMPOSITION: nickel - 60-65%; chromium - 23-26%; molybdenum - 6-11%; silicon - 1.5-2%; do not contain carbon.

NH-Dent alloys on a nickel-chrome base

APPLICATION: for quality metal-ceramic crowns and small bridges have high hardness and strength. Denture frames can be easily ground and polished.

PROPERTIES: the alloys have good casting properties and contain refining additives, which allows not only to obtain a high-quality product when casting in high-frequency induction melting machines, but also to reuse up to 30% of the gates in new melts. There are several types of this alloy: NL, NS, NH.

NH-Dent NS vac (soft) - contains nickel - 62%, chromium - 25% and molybdenum - 10%. It has high dimensional stability and minimal shrinkage, which makes it possible to cast long bridges in one step.

NH-Dent NL vac (liquid) - contains 61% nickel, 25% chromium and 9.5% molybdenum. This alloy has good casting properties, making it possible to obtain castings with thin, openwork walls.

4.Dentans

PROPERTIES: Dentan type alloys are developed to replace cast stainless steels. They have significantly higher ductility and corrosion resistance due to the fact that they contain almost 3 times more nickel and 5% more chromium. The alloys have good casting properties - low shrinkage and good fluidity. Very malleable in machining.

APPLICATION: used for the production of cast single crowns, cast crowns with plastic lining. There are several types of this alloy: DL, D, DS, DM.

Dentan D contains 52% iron, 21% nickel, 23% chromium. It has high ductility and corrosion resistance, has low shrinkage and good fluidity.

Dentan DM contains 44% iron, 27% nickel, 23% chromium and 2% molybdenum. Molybdenum was additionally introduced into the alloy, which increased its strength in comparison with previous alloys, when comparing the same level of workability, fluidity and other technological properties.

For some nickel-chrome alloys, the presence of an oxide film can have a negative effect, since at high firing temperatures, nickel and chromium oxides dissolve in the porcelain, coloring it. An increase in the amount of chromium oxide in porcelain leads to a decrease in its coefficient of thermal expansion, which can cause the ceramic to break off from the metal.

Titanium alloys

PROPERTIES: titanium alloys have high technological and physical-mechanical properties, as well as biological inertness. The melting point of titanium alloy is 1640C. Products made of titanium are absolutely inert to oral tissues, complete absence toxic, thermal insulating and allergic effects, small thickness and weight with sufficient rigidity of the base due to the high specific strength of titanium, high precision in reproducing the smallest details of the relief of the prosthetic bed.

VT-100 sheet- used for the manufacture of stamped crowns (thickness 0.14-0.28mm), stamped bases (0.35-0.4mm) of removable dentures.

VT-5L - injection molding - used for the manufacture of cast crowns, bridges, frames of clasp splinting prostheses, cast metal bases.

Introduction

Dentistry today does not stand still. Almost every month we hear about new techniques, equipment, materials, etc. Of course, not all innovations resonate with professionals. But, there is one material that has seriously and for a long time occupied its niche in dentistry, which, thanks to its qualities, has proven itself brilliantly. And the name of this material is titanium.

The range of uses of titanium is constantly expanding. Today it is used in both removable and non-removable prosthetics, implantology, orthodontics, etc.

Currently, the production of teeth from titanium has already been mastered, and studies have shown that titanium is not inferior to precious metals in terms of corrosion resistance in the oral cavity. And this is not the limit. It would not be an exaggeration to say that there is no longer any direction left in dentistry where there is a place for titanium.

As for the application, the introduction of titanium alloys was not limited to dentistry. Titanium is widely used in all areas of medicine without exception, not to mention industry. If we talk about titanium, then a whole series of advantages immediately come to mind, which in their entirety are unique to it. Biological indifference, lack of magnetization properties, low specific gravity, high strength, corrosion resistance in many aggressive environments and availability have made titanium an almost universal and necessary material. And this is only a small part of the advantages that titanium alloys can provide.

This graduation project will reveal all the facets of this revolutionary material. Through the lens of the profession of a dental technician, the properties of titanium and its alloys, methods for their production, nuances of processing titanium alloys, errors that arise when working with it, and much more will be carefully examined. Attention will be paid to the latest advances in science and technology. Both long-existing titanium alloys, which are widely used throughout the world, and the latest developments in this area will be examined in detail. And of course, we cannot ignore processing methods such as milling, grinding titanium alloys, etc.

The relevance of research

The choice of material for a prosthesis is one of the important stages of prosthesis planning, since the future properties of the prosthesis will depend on the material. Currently, it seeks to combine two key and important properties and dental materials – bioinertness and aesthetics. One of the materials with the first quality is titanium. The use of titanium in combination with cladding with ceramic masses allows us to solve the second problem. In this way, both problems are solved - bioinertness and aesthetics. But in modern literature, and even when teaching in educational institutions, the nuances of working with titanium are poorly covered. Therefore, it is necessary to study the literature on titanium in detail, summarize it, systematize it and summarize it in this thesis project to facilitate the study of this topic by dental technicians in the future.

Subject of study

Titanium for the manufacture of dental prostheses

Object of study

Titanium processing technology

Purpose of the study

Study technologies for manufacturing titanium prostheses in dentistry

Research objectives

1. Studying literature on this topic;
2. Study of the properties of titanium used in dentistry;
3. Studying technologies for its processing;
4. Comparison of titanium processing technologies.

Hypothesis

Studying this material will allow you to identify positive and negative sides various titanium processing technologies and identify the best of them, which can further improve the quality of prosthetics.

Research methods

Study of domestic and foreign literature, comparative analysis, systematization.

Chapter 1. Features of titanium and difficulties when working with it

1.1. Advantages of titanium

In the periodic table D.I. Mendeleev titanium has the number 22 (Ti). Externally, titanium is similar to steel (Fig. 1).

Fig.1. Titanium implants and abutments.

Titanium alloys have high technological and physical-mechanical properties, as well as bioinertness.

Structural and high-strength titanium alloys are solid solutions, which allows them to provide an optimal balance between strength and ductility characteristics.

Porous titanium and titanium nickelide, which has shape memory, have been used as materials for implants.

In foreign literature, there is a point of view according to which titanium and its alloys are an alternative to gold. Upon contact with air, passivization occurs, i.e. A thin inert layer of oxide forms on the titanium surface. Its other advantages include low thermal conductivity and the ability to combine with composite cements and porcelain. The disadvantage is the difficulty of obtaining a casting (pure titanium melts at 1668°C and reacts with traditional molding compounds and oxygen). Consequently, it must be cast and soldered in special devices in an oxygen-free environment. Alloys of titanium and nickel are being developed that can be cast using the traditional method (such an alloy releases very few nickel ions and bonds well to porcelain). New methods for creating fixed prostheses (primarily crowns and bridges) using CAD/CAM technology immediately eliminate all casting problems.

Prosthetics of the crown part of the tooth occupies a leading place in the clinic of orthopedic dentistry and is used during all periods of formation and development of the masticatory apparatus, starting from infancy and up to old age. A special place in orthopedics is occupied by titanium crowns, which are distinguished by the following characteristics:

• Biological inertness;
• Ease of crown removal;
• Low thermal conductivity compared to other metals and alloys;
• Low specific gravity, which makes the prostheses light;
• Have high elasticity;
• Less abrasion resistance than stainless steel for prosthetics of primary teeth.

When mentioning the importance of using titanium crowns, we should focus on this dental disease hard dental tissues, such as aplasia and hypoplasia of enamel. These defects are malformations of the hard tissues of the tooth and arise as a result of disturbances in mineral and protein metabolism in the body of the fetus or child. Underdevelopment of enamel is an irreversible process and remains for the entire period of life. Therefore, the presence of these diseases is an absolute indication for the use of thin-walled titanium crowns.

As for removable prosthetics, dentures with thin-sheet titanium bases 0.3-0.7 mm thick have the following main advantages over dentures with bases made of other materials:

• absolute inertness to oral tissues, which completely eliminates the possibility of an allergic reaction to nickel and chromium, which are part of metal bases made of other alloys;
• complete absence of toxic, thermal insulating and allergic effects typical of plastic bases;
• small thickness and weight with sufficient base rigidity due to the high specific strength of titanium;
• high accuracy of reproduction of the smallest details of the relief of the prosthetic bed, unattainable for plastic and cast bases made of other metals;
• significant relief in the patient’s adaptation to the prosthesis;
• maintaining good diction and perception of the taste of food.

1.2. Features of titanium and difficulties of working with it

Titanium (Titanium) Ti - element of group IV of the 4th period of the periodic system of D.I. Mendeleev, serial number 22, atomic mass 47.90. Obtained in its pure form only in 1925. The main raw materials are the minerals rutile TiO2, ilmenite FeTiO3, etc. Titanium is a refractory metal.

Titanium is obtained by reducing titanium dioxide with calcium metal, calcium hydride, reducing titanium tetrachloride with molten sodium, magnesium metal. Titanium is a promising material for the aviation, chemical and shipbuilding industries and medicine. In most cases, titanium is used in the form of alloys with aluminum, molybdenum, vanadium, manganese and other metals.

Table 1.

Comparative properties of various alloys.

Properties				Silver-palladium alloy	Stainless steel
Density (g/cm³)
Hardness (HB) MPa
Strength MPa (N/mm 2), Rm
Modulus of elasticity, GPa
Melting point (°C)
Thermal conductivity W/(m K)
KTR (α 10 –6 °C –1)

It is known that some chemical elements can exist in the form of two or more simple substances that differ in structure and properties. Typically, a substance passes from one allotropic modification to another at a constant temperature. Titan has two such modifications. The α-modification of titanium exists at temperatures up to 882.5 °C. The high-temperature β-modification can be stable from 882.5 °C to the melting point.

Alloying elements give titanium alloy different properties. Aluminum, molybdenum, manganese, chromium, copper, iron, tin, zirconium, silicon, nickel, and others are used for this.

Alloying additives behave differently in different allotropic modifications of titanium. They also change the temperature at which the α/β transition occurs. Thus, an increase in the concentration of aluminum, oxygen and nitrogen in a titanium alloy increases this temperature value. The range of existence of the α-modification is expanding. And these elements are called α-stabilizers.

Tin and zirconium do not change the temperature of α/β transformations. Therefore, they are considered neutral titanium hardeners.

All other alloying additives to titanium alloys are considered β-stabilizers. Their solubility in titanium modifications depends on temperature. And this makes it possible to increase the strength of titanium alloys with these additives through hardening and aging. Using different types alloying additives, titanium alloys with a wide variety of properties are obtained.

To create cast crowns, bridges, arched (clasp) frames, splinting prostheses, cast metal bases, cast titanium VT-5L is used. The melting point of titanium alloy is 1640°C.

Alloy VT5 (VT5L) is alloyed only with aluminum. Aluminum is one of the most common alloying elements in titanium alloys. This is due to the following advantages of aluminum over other alloying components:

1. aluminum is widespread in nature, available and relatively cheap;
2. the density of aluminum is significantly lower than the density of titanium, and therefore the introduction of aluminum increases their specific strength;
3. with increasing aluminum content, the heat resistance and creep resistance of titanium alloys increase;
4. aluminum increases elastic moduli;
5. As the aluminum content in alloys increases, their tendency to hydrogen embrittlement decreases. VT5 alloy differs from technical titanium in greater strength and heat resistance. At the same time, aluminum significantly reduces the technological ductility of titanium. The VT5 alloy is deformed in a hot state: forged, rolled, stamped. However, they prefer to use it not in a deformed state, but in the form of shaped casting (in this case it is given the VT5L brand).

Titanium VT-6 is used for implantation. Alloys of the VT6 type (Ti-6A1-4V) (α + β) class are among the most common titanium alloys in other fields.

This wide use of this alloy is explained by its successful alloying. Aluminum in alloys of the Ti-Al-V system increases strength and heat-resistant properties, and vanadium is one of those few alloying elements in titanium that increases not only strength properties, but also ductility.

Along with high specific strength, alloys of this type have lower sensitivity to hydrogen compared to OT4 and OT4-1 alloys, low susceptibility to salt corrosion and good manufacturability.

VT6 type alloys are used in annealed and thermally strengthened states. Double annealing also improves fracture toughness and corrosion resistance.

Titanium sheet grade VT1-00 is used for stamped crowns (thickness 0.14-0.28 mm), stamped bases (0.35-0.4 mm) of removable dentures, frames of titanium-ceramic dentures, implants of various designs.

The metallurgical industry supplies semi-finished products of technical titanium of two grades VT1-00 and VT1-0, differing in the content of impurities (oxygen, nitrogen, carbon, iron, silicon, etc.). These are materials of low strength, and titanium VT1-00, which contains fewer impurities, is characterized by lower strength and greater ductility. The main advantage of titanium alloys VT1-00 and VT1-0 is their high technological ductility, which even makes it possible to produce foil from them.

The strength properties of titanium can be increased by cold hardening, but at the same time the plastic properties are greatly reduced. The decrease in ductility characteristics is more pronounced than the increase in strength characteristics, so cold hardening is not the best way to improve the complex properties of titanium. The disadvantages of titanium include a high tendency to hydrogen embrittlement, and therefore the hydrogen content should not exceed 0.008% in VT1-00 titanium and 0.01% in VT1-0.

1.3. Features of titanium processing (grinding and polishing)

Physical properties, oxidation phases and lattice changes must be taken into account when processing titanium. Proper processing can be successfully produced only with special cutters for titanium, with a special cross-shaped notch (Fig. 2). A reduced angle of the working surface, which makes it possible to optimally remove fairly soft metal, while at the same time ensuring good cooling of the tool. Titanium processing should be done without applying strong pressure to the tool.

Fig.2.

Titanium cutters should be stored separately from other tools. They must be regularly cleaned with a steam jet and fiberglass brushes to remove any remaining titanium shavings, which are deposited quite firmly.

If you use the wrong tool or apply strong pressure, local overheating of the metal is possible, accompanied by strong oxide formation and a change in the crystal lattice. Visually, a color change occurs on the processed object and the surface becomes slightly rougher. In these places there will not be the necessary adhesion to the ceramics (the possibility of cracks and chips); if these are not areas to be veneered, then further processing and polishing will also not meet the requirements.

When processing titanium, the use of various carborundum discs and stones, or diamond heads, greatly contaminates the surface of titanium, which subsequently also leads to cracks and chips in ceramics. Therefore, the use of the above tools is only suitable for processing, for example, frames of clasp dentures, and the use of diamond heads should be completely avoided. Grinding and further polishing of exposed areas of titanium is only possible with titanium-specific abrasive rubber heads and polishing pastes. Many companies involved in the production of rotary tools currently produce a large range of cutters and rubber grinding heads for titanium.

Suitable processing parameters for titanium:

• Low tip rotation speed – max. 15,000 rpm;
• Low pressure on the tool;
• Batch processing;
• Frame processing in one direction only;
• Avoid sharp corners and metal overlaps;
• When grinding and polishing, use only suitable abrasive rubber heads and polishing pastes;
• Periodically clean cutters with a steam jet and a fiberglass brush.

Sandblasting, before applying the bonding layer for ceramic coatings, as well as for cladding with composite materials, must meet the following requirements:

• Pure, disposable aluminum oxide only;
• The maximum sand grain size is 150 µm, optimally 110–125 µm;
• The maximum pressure from the pencil is 2 bar;
• The direction of sand flow is at right angles to the surface.

After treatment, it is necessary to leave the treated object to passivate for 5–10 minutes, and then clean the surface with steam.

Oxide firing or similar procedures are completely excluded when working with titanium. The use of acids or etching is also completely excluded.

1.4.Conclusions on the first chapter

Based on the material presented above, we can conclude that titanium alloys have a significant number of very important properties that are indispensable in dental prosthetics. The main ones are bioinertness, corrosion resistance, strength and hardness with low specific gravity. However, obtaining titanium is considered an expensive process, but since the amount used in the manufacture of the prosthesis is small, this does not greatly affect the cost. But due to the fact that the technology for producing titanium prostheses is more expensive, titanium prostheses are more expensive than CHS or stainless steel.

Also, until recently, titanium processing caused problems, but the advent and spread of special tools has made possible applications titanium alloys in dentistry. The positive properties of titanium were known before, but it was the lengthy and expensive processing that was the very obstacle to its introduction into dental practice.

Despite the specific requirements that are absent when processing other metals, and the features of the tools, a whole list positive qualities titanium nevertheless led to the improvement of processes for working with it. The chemical properties of titanium, on the one hand, open up new opportunities for dental technicians, but on the other hand, they require more careful adherence to processing technology and consideration of all features.

Chapter 2. Technologies for manufacturing titanium prostheses

2.1.Stamping of titanium

Stamping (stamping) is the process of plastic deformation of a material with a change in the shape and size of the body. In dentistry, metals are stamped.

It is worth noting that stamped titanium crowns are quite rare phenomenon to date. The technology for making crowns by stamping from titanium has not found widespread use, since titanium is difficult to stamp in a cold state. However, within general study The technology for manufacturing titanium crowns using the stamping method will be considered.

Titanium stamped crowns have the same disadvantages as conventional stamped crowns, namely:

• Lack of wear resistance;
• The presence of a flat chewing surface of the tooth;
• Insufficiently tight fit to the neck of the tooth;
• Lack of aesthetics.

The properties of titanium crowns are similar to the alloys of more expensive gold crowns.

The process of stamping from titanium alloys does not differ significantly from the process of manufacturing conventional stamped stainless steel crowns.

When making stamped crowns, impressions are usually taken with standard alginate trays.

Manufacturing technology of titanium stamped crown:

The laboratory stage of making a crown begins with obtaining a model. Next, the tooth is modeled with modeling wax. By layering molten wax on the surface of a plaster tooth, we achieve an increase in volume necessary to restore the anatomical shape. After modeling, it is necessary to cut out a plaster die from the model. Then you need to make a copy of it from low-melting metal. To do this, you need to make a plaster mold. The gypsum block is made in two stages. The plaster die is removed, and the split parts of the block are put together and the low-melting metal is melted. When melting, it is important not to overheat the metal; when overheated, some components of the alloy evaporate, and it becomes more brittle. And then they fill out the form. The mold must be well dried, since moisture, evaporating, will make the metal porous.

In total, you need to make two metal dies. The first is the most accurate for final stamping. The second is for pre-stamping. After making a metal die, you need to select a titanium sleeve.

The sleeve should reach the equator of the tooth and push it somewhat forcefully. The annealed sleeve on the punches of a special dental anvil is given the approximate shape of the future crown by hammer blows. And then annealing follows again. During hammer blows, changes occur in the structure of the metal, it becomes more elastic and unyielding to further processing, that is, hardening is formed, through annealing the crystal lattice of the metal is restored and the metal becomes more ductile. After this, they take the die that was cast second, put a sleeve on it and, with several strong and precise blows of a hammer, hammer it into the lead “cushion”. Lead pad is an ingot of soft lead of various sizes.

It is necessary to drive in the die with the sleeve to the level of the equator of the crown. The lead presses the metal sleeve tightly against the die. The die with the sleeve is removed from the lead and the quality of the preliminary stamping is assessed. There should be no folds or cracks on the sleeve. The final stamping is carried out in a press, either manual or mechanized hydraulic. There is only one meaning - at the base of the press there is a ditch filled with unvulcanized rubber. The stamp is inserted into the cuvette into the rubber and the press rod, under the influence of the force of a spun flywheel or hydraulics, presses on the rubber, the latter transmits pressure to the sleeve, which in turn, under pressure, is tightly pressed against the metal stamp.

It is worth noting that cold titanium is extremely difficult to stamp. During hot deformation and, especially, at temperatures of 900°C and above, when softening processes develop, titanium and titanium alloys have fairly high ductility. Titanium alloys are used for forging and hot stamping to produce products with complex geometric shapes, which include teeth.

The ductility of titanium and titanium alloys sharply decreases in the presence of an alpha layer on the surface. The alfinized layer is a solid solution of oxygen in titanium. A metal having an alpha layer is extremely sensitive during forging and hot stamping to changes in the stress-strain state with increasing stresses and tensile strains. Since practically all forging and stamping methods involve tensile stresses and deformations, the formation of an alpha layer should be avoided when heating titanium and titanium alloys for hot machining. This is achieved by heating for forging and stamping in heating furnaces with a neutral or non-oxidizing atmosphere. The most suitable medium for heating titanium and titanium alloys is argon.

2.2.Injection method

The high reactivity of titanium and its high melting point require a special casting installation and investment material. There are currently several systems on the market that allow titanium casting.

An example is the Autocast foundry installations, which are based on the principle of melting titanium in a protective atmosphere of argon on a copper crucible using a voltaic arc, just as titanium sponge is melted in industry to produce pure titanium. The metal is poured into the cuvette using a vacuum in the casting chamber and high argon pressure in the melting room - while the crucible is tipping.

The appearance and principle of how the installation functions is shown in Figure 3.

Fig.3.

At the beginning of the process, both chambers, the melting chamber (top) and the foundry chamber (bottom), are purged with argon, then a mixture of air and argon is evacuated from both chambers, after which the melting chamber is filled with argon, and a vacuum is formed in the casting chamber. The voltaic arc is turned on and the titanium melting process begins. After a certain time has passed, the melting crucible sharply overturns and the metal is sucked into the mold located in a vacuum; its own weight, as well as the increasing pressure of argon at this moment, also contribute to its filling of the injection mold. This principle makes it possible to obtain good, dense castings from pure titanium.

The next component of the casting system is the investment material. Since the reactivity of titanium in the molten state is very high, it requires special investment compounds, which are made on the basis of aluminum and magnesia oxides, which in turn make it possible to reduce the reaction layer of titanium to a minimum.

The correct creation of the gating system, as well as the correct location in the ditch, plays a huge role and is carried out strictly according to the rules proposed by the manufacturer of the foundry equipment. For crowns and bridges, it is permissible to use only a special casting cone, which allows the metal to be optimally directed towards the object being cast. The height of the input sprue channel from the cone to the supply beam is 10 mm with a diameter of 4–5 mm. The diameter of the supply beam is 4 mm.

The underwater gating channels to the object being cast have a diameter of 3 mm and a height of no more than 3 mm. Very important: underwater channels should not be located opposite the inlet gate channel (Fig. 4), otherwise the possibility of gas pores is very high.

Fig.4.

All connections must be very smooth, without sharp corners, etc. in order to minimize the turbulence that occurs during metal pouring, which leads to the formation of gas pores. The gating system for clasp dentures, and especially for solid bases of complete removable dentures, is also different from the gating systems that we use for casting clasp dentures from chrome-cobalt alloys.

For dental applications, the transition of titanium at a temperature of 882.5 °C from one crystalline state to another is very important. Titanium transforms at this temperature from α-titanium with a hexagonal crystal lattice to β-titanium with a cubic lattice. What this entails is not only a change in its physical parameters, but also an increase in its volume by 17%.

For this reason, it is also necessary to use special ceramics, the firing temperature of which must be below 880 °C.

Titanium has a very strong tendency at room temperature with atmospheric oxygen to instantly form a thin protective oxide layer, which protects it in the future from corrosion and makes titanium well tolerated by the body. This is the so-called passive layer.

The passive layer has the ability to regenerate itself. This layer, at various stages of working with titanium, must be guaranteed. After sandblasting, before cleaning the frame with steam, it is necessary to leave the frame to passivate for at least 5 minutes. A freshly polished prosthesis must be passivated for at least 10-15 minutes, otherwise there is no guarantee of a good shine of the finished work.

2.3.Superplastic molding

For 15 years, titanium denture casting has been promoted in Japan, the USA and Germany, and more recently in Russia. Developed different kinds equipment for centrifugal or vacuum casting, x-ray quality control of castings, special refractory materials.

The methods listed above are very technologically complex and expensive. A way out of this situation may be superplastic molding. The essence of superplasticity is that at a certain temperature, a metal having an ultra-fine grain behaves like a heated resin, that is, it can elongate by hundreds and thousands of percent under the influence of very small loads, which makes it possible to produce thin-walled parts of complex shapes from a sheet of titanium alloy. This phenomenon and the process consists in the fact that a superplastic sheet blank is pressed against a matrix and under the influence of a small gas pressure (maximum 7–8 atm) it is superplastically deformed, taking on a very precise shape of the matrix cavity in one operation.

Let us consider the use of the sphere-plastic molding method using the example of manufacturing a removable lamellar prosthesis. Dentures made by superplastic molding have significant advantages. The main ones are lightness (light weight) compared to prostheses made of cobalt-chrome or nickel-chrome alloys, as well as high corrosion resistance and strength. The sufficient simplicity of manufacturing the prosthesis makes it indispensable for mass production in orthopedic dentistry.

The initial clinical stages of manufacturing a complete removable denture with a titanium base do not differ from traditional ones in the manufacture of plastic dentures. This includes a clinical examination of patients, obtaining anatomical casts, making an individual tray, obtaining a functional cast, and making a working high-strength model from superplaster.

A model made of supergypsum with an alveolar ridge pre-insulated with clasp wax is duplicated into a fire-resistant mass. Fireproof models are placed in a metal cage made of heat-resistant alloy, which has special cutouts, the size and shape of which allows you to place a model of the upper jaw of any patient in it.

A titanium alloy sheet 1 mm thick is placed on top of ceramic models. The sheet blank is clamped between the two halves of the mold. The half-molds form a sealed chamber, divided by a sheet into two parts, each of which has a communication channel with the gas system and can be independently either evacuated or filled with an inert gas under some pressure (Fig. 5).

Fig.5.

The sealed mold halves are heated and create a pressure difference. A vacuum of 0.7-7.0 Pa is created under the sheet. A sheet of titanium alloy bends towards the evacuated half-mold and is “blown” into the ceramic model located in it, fitting its relief. During this period, the pressure is maintained according to a certain program. At the end of this program the mold halves are cooled.

After this, the pressure in both halves is equalized to normal and the workpiece is removed from the mold. Bases of the required profile are cut along the contour, for example, with a laser beam, the edge is ground on an abrasive wheel, scale is removed, retention strips are cut with an abrasive disk in the saddle-shaped part of the base to the middle of the alveolar process and electropolished according to the developed method.

The plastic limiter is formed at different levels of the titanium base from the palatal and oral surfaces below the top of the alveolar ridge by 3-4 mm, using chemical milling. Chemical milling is also carried out along line “A” to create a retention area when fixing the base plastic. The presence of plastic along line “A” is necessary for further correction of the valve zone.

In the clinic, the doctor determines the central relationship of the jaws using traditional methods. Setting up teeth and fitting in the oral cavity do not differ from similar operations in the manufacture of simple removable dentures. Next, in the laboratory, the wax is replaced with plastic and polished. At this point, the production of a removable denture with a titanium base is completed (Fig. 6).

Fig.6.

For superplastic molding in Russia, domestic technology, domestic installation (original Russian patented installation and technique) and domestic sheet blanks of domestic VT 14 alloy are often used.

It is safe to say that superplastic molding of titanium alloys has excellent prospects for further development, because combines high durability, bioinertness and aesthetics.

2.4.Computer milling (CAD/CAM)

CAD/CAM is an acronym that stands for computer-aided design/drafting and computer-aided manufacturing, which literally translates as “computer-assisted design and manufacturing.” The meaning is production automation and computer-aided design and development systems.

With the development of technology, prosthetic dentistry has also evolved from the times of the Bronze Man, when artificial teeth were tied with gold wire to neighboring teeth, to modern man, which uses CAD/CAM technology. At the time of the advent of CAD/CAM technology, the technology is free of all the disadvantages inherent in casting technologies, for example, shrinkage, deformation, including when removing cast crowns, bridges or their frames. There is no danger of technology violations, for example, overheating of the metal during casting or reuse of gates, which leads to a change in the composition of the alloy. There is no shrinkage of the frame after applying ceramic cladding, no possible deformation when removing wax caps from the plaster model, pores and cavities during casting, non-shed areas, etc. The main disadvantage of CAD/CAM technology is its high cost, which does not allow this technology to be widely introduced into orthopedic dentistry. Although, in fairness, it is worth noting that almost every year cheaper and cheaper installations appear. The original CAD/CAM technology was a computer with the necessary software, which produced three-dimensional modeling of a fixed prosthesis, followed by computer milling with an accuracy of 0.8 microns from a solid metal or ceramic block. Figure 7 shows a modern CAD/CAM setup.

Fig.7.

Using CAD/CAM you can produce:

• single crowns and bridges of small and large extent;
• telescopic crowns;
• custom abutments for implants;
• recreate the full anatomical shape for models of press ceramics applied to the frame (overpress);
• create temporary crowns in full profile and various casting models.

Currently, if we consider CAD/CAM as an installation for processing titanium alloys, then the production of individual abutments has become very widespread (given the relatively low cost). The appearance of such abutments is shown in Figure 8.

Fig.8.

Below is an example of the algorithm of a dental technician using a CAD/CAM installation. It is quite versatile. And if we are talking directly about titanium, then this algorithm will be approximately the same.

Description of work using modern CAD/CAM technologies:

Step 1: Cast. Plaster model. Taking an impression of the oral cavity is performed in exactly the same way as for traditional methods Dental prosthetics. From the resulting cast, a plaster model patient's jaws.

Step 2: Scan. The main goal of this step is to obtain digital data on the basis of which electronic three-dimensional models of the required products (crowns, dentures, bridges, etc.) will be built. Digitized data is saved in STL format. The result of the scanning and the basis of the work is a three-dimensional computer geometric model (in the form of an STL file) of the area of ​​the oral cavity on which the denture is planned to be installed. The Nobel scanner is shown in Figure 9.

Fig.9.

Step 3: Three-dimensional modeling (3D). The STL file obtained in step 2 is imported into the CAD system. It is intended for creating computer models of crowns, dentures, bridges, etc. with their subsequent transfer to the CAM system for programming processing on a CNC machine. The system was designed specifically for technicians, using appropriate terminology and a user-friendly, intuitive interface. The program is aimed at users who are inexperienced in using CAD systems.

At this step, the dental technician must select the most suitable tooth shape from the database and modify it with tools to the desired shape. The supplied database contains a model of crowns for each tooth. Use intuitive sculpting features to edit geometry. During the modeling process, you can scale the computer model in order to compensate for shrinkage during the sintering process and obtain the maximum possible crown exact dimensions. As an example, Figure 10 shows the program interface on which an individual abutment was modeled.

Fig. 10.

Step 4: Processing programming. After working out the geometry of products in the system, the received data is transferred to the CAM system. It is intended for programming the processing of products on CNC machines. In the CAM system, processing trajectories are generated, which, using a postprocessor, are translated into a “language” understandable to the machine - into the control program. This program is aimed at inexperienced users who do not have experience working with CAM systems and programming CNC machines.

Step 5: Processing of dentures on a CNC machine. The resulting control programs are sent to a CNC machine. Below, Figure 11 shows an example of the process of milling three abutments for application and two beams for dentures.

Fig. 11.

2.5.3D printing (CAD/CAM)

Thanks to the further evolution of CAD/CAM technology, computer milling was replaced by 3D printing technology, which reduced costs and made it possible to produce objects of any shape and complexity that could not be produced before by any of the existing technologies. For example, thanks to 3D printing, it is possible to produce a solid hollow object with any shape of the internal surface. In relation to orthopedic dentistry, it is possible to produce a hollow body of the prosthesis, which will allow, without reducing the strength of the structure, to reduce its weight.

In addition, 3D printers in dentistry guarantee accelerated production volumes and the accuracy of finished products. 3D printers, like computer-controlled milling machines (CNC), relieve dental technicians from a very time-consuming process in their work - manual modeling of dentures, crowns and other products. Figure 12 shows the X350pro 3D printer from the German company RepRap.

Fig. 12.

CAD technology in 3D printing is no different from CAD technology in computer milling, and it is described in detail in the previous chapter.

The principle of the process is that a layer of metal powder having a microscopic thickness is applied to the substrate. Then sintering, or more precisely microwelding, occurs with a laser in a vacuum of microscopic grains of metal in the required areas of the layer. Welding is the process of converting powder into a solid material using high heat without melting the material itself. After this, another layer of metal powder is applied on top, and micro-grains of metal are micro-welded with a laser not only to each other, but also to the bottom layer.

The unique shape of each tooth is difficult to accurately reproduce using handcrafting. However, dental 3D printers make complex and outdated manufacturing methods unnecessary. Thanks to the latest technologies and most modern materials finished products are produced several times faster than before.

Advantages of 3D printing in the dental field:

• the ability to manufacture products with hollow internal sections, which cannot be done by milling;
• significant acceleration of the production of necessary products;
• increasing production volumes without additional personnel;
• the ability to reuse the material after cleaning, which reduces production waste to almost zero.

2.6. Conclusions on the second chapter.

From all of the above, certain conclusions can be drawn. Titanium has been known since ancient times, but has not found application in dentistry due to the fact that for a long time there were no technologies for its processing. Over time, the situation began to change and today titanium is processed in several ways without compromising the aesthetics of the final restorations.

Since the advent of titanium in dentistry to the present day, many methods of processing it have appeared. They all have both their disadvantages and their advantages. Such diversity is naturally an undeniable advantage of titanium, since each laboratory, and each dental technician in particular, can choose exactly the method of working with titanium that is more suitable depending on the tasks at hand.

After analyzing the literature, we found that of all the existing or known methods of processing titanium in dentistry, the most promising and best method is the 3D printing method with titanium, since it has the greatest number of advantages and practically no disadvantages.

Conclusion

From all the material discussed above, only one conclusion can be drawn: titanium gave new ideas and significantly speeded up many operations. Despite its more than modest history, titanium has become a leading material in dentistry. Titanium alloys have almost all the qualities necessary in orthopedic dentistry, namely: bioenergy, strength, hardness, rigidity, durability, corrosion resistance, low specific gravity. Despite the many qualities that are indispensable for dentistry, titanium can nevertheless be processed in many ways without losing the quality of the finished products. Today, we already have all the necessary tools and equipment for high-quality processing of titanium alloys.

After analyzing all the methods for manufacturing titanium products, we can conclude that the most progressive method is 3D printing. Compared to other methods, it has a number of advantages, such as the simplicity of the process itself. Unlike stamping titanium, 3D printing has almost perfect accuracy. Computer milling technology also provides high precision, but unlike 3D printing, it cannot reproduce the hollow internal parts of a product. And besides, 3D printing is very economical, since there is practically no production waste, and the remaining material used in printing can be reused after cleaning. The injection molding method and the plastic deformation method require complex technological equipment. But the precision of product manufacturing still cannot be compared with 3D printing.

In conclusion, we can conclude that the 3D printing method is currently the most promising, progressive and cost-effective method of working with products made of titanium alloys in dentistry.

Bibliography

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Titanium and tantalum – “compromise” metals for medicine
The use of various metal products in medicine has been practiced since ancient times. A combination of these beneficial properties metals and their alloys, such as strength, durability, flexibility, ductility, elasticity, have no alternatives, in particular, in the manufacture of orthopedic structures, medical instruments, devices for rapid healing of fractures. And in recent decades, thanks to the discovery of the “shape memory” effect and the introduction of other innovations, metals have also become widely used in vascular and neurosurgery for the manufacture of suture material, mesh stents for dilating veins and arteries, large endoprostheses, and in ophthalmological and dental implantology.

However, not all metals are suitable for use in the medical field, and the main destructive reasons here are susceptibility to corrosion and reaction with living tissues - factors that have destructive consequences for both the metal and the body itself.

Of course, gold and platinum group metals (platinum, iridium, osmium, palladium, rhodium, etc.) stand out of competition. However, the possibility of using precious metals for mass use is practically absent due to their prohibitively high cost, and the combination of useful properties that are in demand in certain specific clinical situations is not always inherent in noble metals.

A significant place in this area to this day is occupied by stainless steels, alloyed with certain additives to obtain the required characteristics. But such metal materials, which are hundreds of times cheaper than precious metals, do not effectively resist corrosion and other aggressive influences, which significantly limits the possibility of their use for a number of medical needs. In addition, an obstacle to the engraftment of stainless steel products implanted inside the body is their conflict with living tissues, causing high risk rejection and other complications.

A kind of compromise between these two poles are metals such as titanium and tantalum: strong, malleable, almost not subject to corrosion, having high temperature melting, and most importantly - completely neutral in biological terms, due to which they are perceived by the body as its own tissue and practically do not cause rejection. As for the cost, it is not high for titanium, although it significantly exceeds that of stainless steels. Tantalum, being a fairly rare metal, is more than ten times more expensive than titanium, but it is still much cheaper compared to precious metals. Although most of the basic operational properties are similar, in some of them it is still inferior to titanium, although in some it is superior to it, which, in fact, determines the relevance of the application.

It is for these reasons that titanium and tantalum, often referred to as “medical metals,” as well as a number of their alloys, have become widespread in many medical fields. Differing in a number of characteristics and thereby complementing each other, they reveal modern medicine truly immense prospects.

Below we will talk in more detail about the unique characteristics of titanium and tantalum, the main areas of their use in medicine, and the use of various forms of production of these metals for the manufacture of instruments, orthopedic and surgical equipment.

Titanium and tantalum – definition, current properties

Titanium for medicine

Titanium (Ti), a light metal with a silvery hue that looks like steel, is one of the chemical elements Periodic table placed in the fourth group fourth period, atomic number 22 (Fig. 1).

Figure 1. Titanium nugget.

It has an atomic mass of 47.88 with a specific density of 4.52 g/cm 3 . Melting point – 1669°C, boiling point –3263°C. In industrial grades with high stability it is tetravalent. Characterized by good ductility and malleability.

Being both lightweight and having high mechanical strength, twice that of Fe and six times that of Al, titanium also has a low coefficient of thermal expansion, which allows it to be used over a wide temperature range.

Titanium is characterized by a low thermal conductivity, four times less than iron and more than an order of magnitude less than aluminum. The coefficient of thermal expansion at 20°C is relatively small, but increases with further heating.

This material is also distinguished by a very high electrical resistivity, which, depending on the presence of foreign elements, can vary in the range of 42·11 -8 ...80·11 -6 Ohm cm.

Titanium is a paramagnetic metal, having a low electrical conductivity. And although in paramagnetic metals the magnetic susceptibility, as a rule, decreases as it warms up, titanium in this regard can be classified as an exception, since its magnetic susceptibility, on the contrary, increases with increasing temperature.

Due to the sum of the above properties, titanium is absolutely indispensable as a raw material for various fields of practical medicine and medical instrument making. And yet, the most valuable quality of titanium for use for this purpose is its highest resistance to corrosion, and, as a result, hypoallergenicity.

Titanium owes its corrosion resistance to the fact that at temperatures up to 530-560 °C the metal surface is covered with the strongest natural protective film of TiO 2 oxide, completely neutral with respect to aggressive chemical and biological environments. In terms of corrosion resistance, titanium is comparable to platinum and platinum metals, and even surpasses these noble metals. In particular, it is extremely resistant to acid-base environments, not dissolving even in such an aggressive “cocktail” as aqua regia. It is enough to note that the intensity of the corrosive destruction of titanium in sea water, which has a chemical composition in many ways similar to human lymph, does not exceed 0.00003 mm/year or 0.03 mm over a millennium!

Due to the biological inertness of titanium structures to the human body, when implanted they are not rejected and do not provoke allergic reactions, quickly becoming covered with musculoskeletal tissues, the structure of which remains constant throughout subsequent life.

A significant advantage of titanium is its affordability, which makes it possible for mass use.

Titanium grades and titanium alloys
The most popular medical grades of titanium are technically pure VT1-0, VT1-00, VT1-00sv. They contain almost no impurities, the amount of which is so insignificant that it fluctuates within zero error. Thus, the VT1-0 grade contains about 99.35-99.75% of pure metal, and the VT1-00 and VT1-00sv grades, respectively, contain 99.62-99.92% and 99.41-99.93 %.

Today, a wide range of titanium alloys are used in medicine, varying in their chemical composition and mechanotechnological parameters. Ta, Al, V, Mo, Mg, Cr, Si, Sn are most often used as alloying additives. The most effective stabilizers include Zr, Au and platinum group metals. When up to 12% Zr is introduced into titanium, its corrosion resistance increases by orders of magnitude. The greatest effect can be achieved by adding a small amount of Pt and platinoids Pd, Rh, Ru to titanium. The introduction of only 0.25% of these elements into Ti makes it possible to reduce the activity of its interaction with boiling concentrated H 2 SO 4 and HCl by tens of orders of magnitude.

The Ti-6Al-4V alloy has become widespread in implantology, orthopedics and surgery, significantly superior in performance parameters to “competitors” based on cobalt and stainless steels. In particular, the elastic modulus of titanium alloys is two times lower. For medical applications (implants for osteosynthesis, joint endoprostheses, etc.) this is a great advantage, since it ensures higher mechanical compatibility of the implant with dense bone structures of the body, in which the elastic modulus is 5¸20 GPa. Titanium-niobium alloys, the development and implementation of which are especially relevant, are characterized by even lower indicators in this regard (up to 40 GPa and below). However, progress does not stand still, and today the traditional Ti-6Al-4V is being replaced by new medical alloys Ti-6Al-7Nb, Ti-13Nb-13Zr and Ti-12Mo-6Zr, which do not contain aluminum and vanadium - elements that, although minor, but still toxic effect on living tissue.

Recently, biomechanically compatible implants, the material for which is titanium nickelide TiNi, are becoming increasingly in demand for medical needs. The reason for the growing popularity of this alloy is its inherent so-called. Shape memory effect (SME). Its essence lies in the fact that the control sample, being deformed at low temperatures, is able to constantly retain its newly acquired shape, and upon subsequent heating, restore its original configuration, while demonstrating superelasticity. Nickelide-titanium structures are indispensable, in particular, in the treatment of spinal injuries and dystrophy of the musculoskeletal system.

Tantalum for medicine

Definition and useful characteristics
Tantalum (Ta, lat. Tantalum) is a heavy, refractory metal of a silver-bluish “lead” hue, which is due to the Ta 2 O 5 pentoxide film covering it. It is one of the chemical elements of the Periodic Table, located in a secondary subgroup of the fifth group of the sixth period, atomic number 73 (Fig. 2).

Figure 2. Tantalum crystals.

Tantalum has an atomic mass of 180.94 with a high specific density of 16.65 g/cm 3 at 20 °C (for comparison: the specific density of Fe is 7.87 g/cm 3, Pv is 11.34 g/cm 3). Melting point – 3017 °C (only W and Re are more refractory). 1669°C, boiling point – 5458°C. Tantalum is characterized by the property of paramagneticity: its specific magnetic susceptibility at room temperature is 0.849·10 -6.

This structural material, combining high levels of hardness and plasticity, in its pure form lends itself well to mechanical processing by any means (stamping, rolling, forging, drawing, twisting, cutting, etc.). At low temperatures it is processed without strong hardening, subjected to deformation effects (compression level 98.8%) and without the need for pre-firing. Tantalum does not lose its ductility even if it is frozen to –198 °C.

The modulus of elasticity of tantalum is 190 H/m2 or 190·102 kgf/mm2 at 25 °C, due to which it is easily processed into wire. We also produce the thinnest tantalum sheet (thickness approximately 0.039 mm) and other structural semi-finished products.

A kind of “twin” of Ta is Nb, characterized by many similar properties.

Tantalum is distinguished by exceptional resistance to aggressive environments. This is one of its most valuable properties for use in many industries, including medicine. It is resistant to such inorganic aggressive acids as HNO 3, H 2 SO 4, HCl, H 3 PO 4, as well as organic acids of any concentration. In this parameter, it is surpassed only by noble metals, and even then not in all cases. Thus, Ta, unlike Au, Pt and many other precious metals, “ignores” even aqua regia HNO 3 +3HCl. Tantalum is slightly less resistant to alkalis.

The high corrosion resistance of Ta also manifests itself in relation to atmospheric oxygen. The oxidation process begins only at 285 °C: a surface protective film of tantalum pentoxide Ta 2 O 5 is formed on the metal. It is the presence of a film of this, the only stable of all Ta oxides, that makes the metal immune to aggressive reagents. Hence, such a particularly valuable characteristic of tantalum for medicine as high biocompatibility with the human body, which perceives tantalum structures implanted into it as its own tissue, without rejection. Based on this most valuable quality medical use That in such areas as reconstructive surgery, orthopedics, implantology.

Tantalum is one of the rare metals: its reserves in the earth's crust are approximately 0.0002%. This causes the high cost of this structural material. That is why the use of tantalum in the form of thin films of protective anti-corrosion coatings applied to the base metal, which, by the way, have a hardness three to four times greater than pure annealed tantalum, is so widespread.

Even more often, tantalum is used in the form of alloys as an alloying additive in less expensive metals to impart the resulting compounds with a complex of necessary physical, mechanical and chemical properties. Steel, titanium and other metal alloys with the addition of tantalum are widely in demand in chemical and medical instrument making. Of these, in particular, they practice the manufacture of coils, distillers, aerators, X-ray equipment, control devices, etc. In medicine, tantalum and its compounds are also used to manufacture equipment for operating rooms.

It is noteworthy that in a number of areas tantalum, being less expensive but having many adequate performance characteristics, can successfully replace precious metals of the platinum-iridium group.

Grades of tantalum and its alloys
The main grades of unalloyed titanium with impurity content within the statistical error are:

• HDTV: Ta - 99.9%, (Nb) - 0.2%. Other impurities, such as (Ti), (Al), (Co), (Ni), are contained in thousandths and ten thousandths of a percent.
• HDTV 1: The chemical composition of the specified grade consists of 99.9% Ta. Niobium (Nb), which is always present in industrial tantalum, corresponds to only 0.03%.
• TC: Yes – 99.8%. Impurities (no more than %): Nb - 0.1%, Fe - 0.005%, Ti, H - 0.001% each, Si - 0.003%, W+Mo, O - 0.015% each, Co - 0.0001%, Ca - 0.002%, Na, Mg, Mn - 0.0003% each, Ni, Zr, Sn - 0.0005% each, Al - 0.0008%, Cu, Cr - 0.0006% each, C, N - each 0.01%.
• T: Ta - 99.37%, Nb - 0.5%, W - 0.05%, Mo - 0.03%, (Fe) - 0.03%; (Ti) - 0.01%, (Si) - 0.005%.

The high hardness values ​​of Ta make it possible to produce structural hard alloys based on it, for example, Ta with W (TV). Replacing the TiC alloy with the tantalum analogue TaC significantly optimizes the mechanical characteristics of the structural material and expands the possibilities of its application.

Relevance of Ta use for medical purposes
Approximately 5% of the tantalum produced in the world is spent on medical needs. Despite this, the significance of its use in this industry cannot be overestimated.

As already noted, tantalum is one of the best metallic bioinert materials due to the thin, but very strong and chemically resistant film of Ta 2 O 5 pentoxide that self-forms on its surface. Due to the high rates of adhesion, which facilitates and accelerates the process of fusion of the implant with living tissue, there is a low percentage of rejection of tantalum implants and the absence of inflammatory reactions.

Tantalum semi-finished products such as sheets, rods, wires and other forms are used to make structures that are in demand in plastic, cardiac, neuro- and osteosurgery for suturing, fusing bone fragments, stenting and clipping of vessels (Fig. 3).

Figure 3. Tantalum fastening structure in the shoulder joint.

The use of thin tantalum plate and mesh structures is practiced in maxillofacial surgery and for the treatment of traumatic brain injuries. Tantalum yarn fibers replace muscle and tendon tissue. Using tantalum Surgeons use tantalum fiber during abdominal operations, in particular, to strengthen the walls of the abdominal cavity. Tantalum meshes are indispensable in the field of ophthalmic prosthetics. The finest tantalum threads are even used to regenerate nerve trunks.

And, of course, Ta and its compounds, along with Ti, are widely used in orthopedics and implantology for the manufacture of joint endoprostheses and dental prosthetics.

Since the beginning of the new millennium, the innovative field of medicine has become increasingly popular, based on the principle of using static electric fields to activate human body desired bioprocesses. The presence of high electret properties of tantalum pentoxide coating Ta 2 O 5 has been scientifically proven. Titanium oxide electret films have already become widespread in vascular surgery, endoprosthetics, and the creation of medical instruments and devices.

Practical application of titanium and tantalum in specific branches of medicine

Traumatology: structures for healing fractures

Currently, to speed up the healing of fractures, such methods are increasingly used. innovative technology, like metal osteosynthesis. In order to ensure a stable position of bone fragments, various fixing structures are used, both external and internal, implanted into the body. However, previously used steel products show low efficiency due to their susceptibility to corrosion under the influence of the aggressive environment of the body and the phenomenon of galvanization. The result is both rapid destruction of the fixatives themselves and a rejection reaction, causing inflammatory processes against the background of severe pain due to the active interaction of Fe ions with the physiological environment of the musculoskeletal tissues in the body's electric field.

To avoid undesirable consequences allows the production of titanium and tantalum fixative implants that are biocompatible with living tissues (Fig. 4).

Figure 4. Titanium and tantalum structures for osteosynthesis.

Such designs of simple and complex configurations can be used for long-term or even permanent implementation in the human body. This is especially important for older patients because it eliminates the need for surgery to remove the anchor.

Endoprosthetics

Artificial mechanisms implanted surgically into bone tissue are called endoprostheses. The most widespread are endoprosthetics of joints - hip, shoulder, elbow, knee, ankle, etc. The process of endoprosthesis replacement is always a complex operation, when part of a joint that is not subject to natural restoration is removed and then replaced with an endoprosthetic implant.

A number of serious requirements are imposed on the metal components of endoprostheses. They must simultaneously possess the properties of rigidity, strength, elasticity, the ability to create the necessary surface structure, resistance to corrosive effects from the body, eliminating the risk of rejection, and other useful qualities.

Various bioinert metals can be used for the manufacture of endoprostheses. The leading place among them is occupied by titanium, tantalum and their alloys. These durable, strong and easy-to-process materials provide effective osseointegration (they are perceived by the bone tissue as natural tissues of the body and do not cause negative reactions) and rapid fusion of bones, guaranteeing the stability of the prosthesis for long periods, estimated in decades. In Fig. Figure 5 shows the use of titanium in hip arthroplasty.

Figure 5. Titanium hip replacement.

In endoprosthetics, as an alternative to the use of all-metal structures, the method of plasma spraying of protective biocompatible coatings based on Ti and Ta oxides onto the surface of non-metallic components of the prosthesis is widely used.

Pure titanium and its alloys. In the field of endoprosthetics they find wide application both pure Ti (eg CP-Ti with a Ti content of 98.2-99.7%) and its alloys. The most common of them is Ti-6AI-4V at high rates strength, characterized by corrosion resistance and biological inertness. The Ti-6A1-4V alloy is characterized by particularly high mechanical strength, having torsional-axial characteristics extremely close to those of bone.

To date, a number of modern titanium alloys have been developed. Thus, the chemical composition of the Ti-5AI-2.5Fe and Ti-6AI-17 Niobium alloys does not contain toxic V, in addition, they are characterized by a low elastic modulus. And the Ti-Ta30 alloy is characterized by the presence of a thermal expansion modulus comparable to that of metal-ceramics, which determines its stability during long-term interaction with metal-ceramic components of the implant.

Tantalum-zirconium alloys. Ta+Zr alloys combine such important properties for endoprosthetics as biocompatibility with body tissues based on corrosion and galvanic resistance, surface rigidity and trabecular (porous) structure metal surface. It is thanks to the trabecular property that a significant acceleration of the process of osseointegration is possible - the growth of living bone tissue on the metal surface of the implant.

Elastic endoprostheses made of titanium wire mesh. Due to their high plasticity and lightness, modern reconstructive surgery and other medical industries actively use innovative elastic endoprostheses in the form of the finest titanium wire mesh - “spider web”. Elastic, strong, elastic, durable and maintaining bioinert properties, mesh is an ideal material for soft tissue endoprostheses (Fig. 6).

Figure 6. Titanium alloy mesh endoprosthesis for soft tissue plastics.

The “web” has already been successfully tested in such areas as gynecology, maxillofacial surgery and traumatology. According to experts, titanium mesh endoprostheses have no equal in terms of stability with almost zero risk of side effects.

Titanium-nickel medical alloys with shape memory effect

Today, in various fields of medicine, alloys made of titanium nickelide are widely used, having the so-called. with shape memory effect (SME). This material is used for endoprosthetics of ligamentous-cartilaginous tissue of the human musculoskeletal system.

Titanium nickelide (international term nitinol) is an intermetallic compound TiNi, which is obtained by alloying Ti and Ni in equal proportions. The most important characteristic of nickelide-titanium alloys is the property of superelasticity, on which EFM is based.

The essence of the effect is that the sample, when cooled in a certain temperature range, is easily deformed, and the deformation self-corrects when the temperature rises to the initial value with the appearance of superelastic properties. In other words, if a plate of nitinol alloy is bent at a low temperature, then at the same temperature conditions it will retain its new shape indefinitely. However, as soon as the temperature is increased to the original one, the plate will straighten again like a spring and take on its original shape.

Product examples medical purposes made of nitinol alloy are shown in the figures below. 7, 8, 9, 10.

Figure 7. A set of implants made of titanium nickelide for traumatology (in the form of staples, clamps, clamps, etc.).

Figure 8. A set of titanium nickelide implants for surgery (in the form of clamps, dilators, surgical instruments).

Figure 9. Samples of porous materials and implants made of titanium nickelide for vertebrology (in the form of endoprostheses, plate-shaped and cylindrical products).

Figure 10. Materials and endoprostheses made of titanium nickelide for maxillofacial surgery and dentistry.

In addition, nickelide-titanium alloys, like most titanium-based products, are bioinert due to their high corrosion and galvanic resistance. Thus, it is an ideal material in relation to the human body for the manufacture of biomechanically compatible implants (BCI).

Application of Ti and Ta for the manufacture of vascular stents

Stents (from the English stent) - in medicine they call special, elastic mesh cylindrical frames, metal structures placed inside large vessels (veins and arteries), as well as other hollow organs (esophagus, intestines, bile-urinary ducts, etc.) on pathologically narrowed areas in order to expand them to the required parameters and restore patency.

The most popular application of the stenting method is in such areas as vascular surgery, and, in particular, coronary angioplasty (Fig. 11).

Figure 11. Samples of titanium and tantalum vascular stents.

To date, more than five thousand vascular stents have been scientifically developed and introduced into real practice. various types and designs. They differ in the composition of the original alloy, length, hole configuration, type of surface coating, and other operating parameters.

The requirements for vascular stents are designed to ensure their impeccable functionality, and therefore are varied and very high.

These products must be:

• biocompatible with body tissues;
• flexible;
• elastic;
• durable;
• radiopaque, etc.

The main materials used today in the manufacture of metal stents are compositions noble metals, as well as Ta, Ti and its alloys (VT6S, VT8, VT 14, VT23, nitinol), which are completely biointegrated with body tissues and combine a complex of all other necessary physical and mechanical properties.

Stitching of bones, blood vessels and nerve fibers

Peripheral nerve trunks damaged as a result of various mechanical injuries or complications of certain diseases require serious surgical intervention for restoration. The situation is aggravated by the fact that usually similar pathologies observed against the background of injury related organs, such as bones, blood vessels, muscles, tendons, etc. In this case, a comprehensive treatment program is developed with the application of specific sutures. As a starting material for the manufacture of suture material - threads, fasteners, fasteners, etc. – titanium, tantalum and their alloys are used as metals that have chemical biocompatibility and the whole range of necessary physical and mechanical properties.

The figures below show examples of such operations.

Figure 12. Bone suturing with titanium clamps.

Figure 13. Stitching a bundle of nerve fibers using the finest tantalum threads.

Figure 14. Sealing of vessels using tantalum staples.

Currently, more and more advanced technologies for neuro-osteo- and vasoplasty are being developed, but the titanium-tantalum materials used for this continue to hold the palm over all others.

Plastic surgery

Plastic surgery refers to the surgical removal of organ defects in order to recreate their ideal anatomical proportions. Often, such reconstructions are performed using various metal products implanted into the tissue in the form of plates, meshes, springs, etc.

Particularly indicative in this regard is cranioplasty - an operation to correct cranial deformities. Depending on the indications in each specific clinical situation, cranioplasty can be performed by applying rigid titanium plates or elastic tantalum meshes to the operated area. In both cases, the use of both pure metals without alloying additives and their bioinert alloys is allowed. Examples of cranioplasty using titanium plate and tantalum mesh are shown in the figures below.

Figure 15. Cranioplasty using a titanium plate.

Figure 16. Cranioplasty using tantalum mesh.

Titanium-tantalum structures can also be used for cosmetic restoration of the face, chest, buttocks and many other organs.

Neurosurgery (application of microclips)

Clipping (English clip clamp) is a neurosurgical operation on the vessels of the brain, aimed at stopping bleeding (in particular, when an aneurysm ruptures) or switching off injured patients from the blood circulation. small vessels. The essence of the clipping method is that miniature metal clamps - clips - are applied to the damaged areas.

The demand for the clipping method, primarily in the neurosurgical field, is explained by the impossibility of ligating small cerebral vessels using traditional methods.

Due to the diversity and specificity of emerging clinical situations, a wide range of vascular clips is used in neurosurgical practice, differing in specific purpose, method of fixation, size and other functional parameters (Fig. 17).

Figure 17. Clips for disconnecting cerebral aneurysms.

In photographs, the clips appear large, but in reality they are no larger than a child’s fingernail and are installed under a microscope (Fig. 18).

Figure 18. Surgery to clip a cerebral aneurysm.

To make clips, as a rule, flat wire made of pure titanium or tantalum, and in some cases silver, is used. Such products are absolutely inert in relation to the brain matter, without causing counter reactions.

Dental orthopedics

Titanium, tantalum and their alloys have found wide medical use in dentistry, namely in the field of dental prosthetics.

The oral cavity is a particularly aggressive environment that negatively affects metal materials. Even precious metals traditionally used in dental prosthetics, such as gold and platinum, oral cavity cannot completely resist corrosion and subsequent rejection, not to mention the high cost and large mass, causing discomfort in patients. On the other hand, lightweight orthopedic structures made of acrylic plastic also do not withstand serious criticism due to their fragility. A true revolution in dentistry was the production of individual crowns, as well as bridges and removable dentures based on titanium and tantalum. These metals, due to their inherent valuable qualities, how biological inertness and high strength with relative cheapness successfully compete with gold and platinum, and in a number of parameters even surpass them.

In particular, stamped and solid titanium crowns are very popular (Fig. 19). And plasma-coated crowns made of titanium nitride TiN are practically indistinguishable from gold ones in appearance and functional properties (Fig. 19)

Figure 19. Solid titanium crown and titanium nitride coated crown.

As for prostheses, they can be permanent (bridge-like) to restore several nearby standing teeth or removable, used in case of loss of the entire dentition (completely edentulous jaw). The most common dentures are clasp dentures (from the German der Bogen “arch”).

The clasp prosthesis is distinguished by the presence of a metal frame on which the base part is attached (Fig. 20).

Figure 20. Clasp prosthesis of the lower jaw.

Today, the clasp part of the prosthesis and clasps are made, as a rule, from pure medical titanium of high purity of the HDTV grade.

A true revolution in dentistry has been the increasingly popular technology of implant dental prosthetics. Prosthetics on implants is the most reliable way to attach orthopedic structures, which in this case last for decades or even a lifetime.

A dental (dental) implant is a two-part structure that serves as a support for crowns, as well as bridges and removable dentures, the base part of which (the implant itself) is a conical threaded pin that is screwed directly into the jaw bone. An abutment is installed on the upper platform of the implant, which serves to fix the crown or prosthesis (Fig. 21).

Figure 21. Nobel Biocare dental implant made of pure medical grade 4 titanium (G4Ti).

Most often, for the manufacture of the screw part of the implant, pure medical titanium with a surface tantalum-niobium coating is used, which helps to activate the process of osseointegration - the fusion of metal with living bone and gingival tissues.

However, some manufacturers prefer to produce not two-piece, but one-piece implants, in which the screw part and the abutment have a monolithic rather than separate structure. At the same time, for example, the German company Zimmer produces solid implants from porous tantalum, which, in comparison with titanium, has greater flexibility and is embedded into bone tissue with almost zero risk of complications (Fig. 22).

Figure 22. Zimmer solid porous tantalum dental implants.

Tantalum, unlike titanium, is a heavier metal, so the porous structure significantly lightens the product, without causing the need for additional external coating of an osseointegrating coating.

Examples of implant prosthetics for individual teeth (crowns) and by installing removable dentures on implants are shown in Fig. 23.

Figure 23. Examples of the use of titanium-tantalum implants in dental prosthetics.

Nowadays, in addition to existing ones, new methods of prosthetics on implants are being developed, showing high efficiency in various clinical situations.

Manufacturing of medical instruments

Today in the world clinical practice hundreds of varieties of various surgical and endoscopic instruments and medical equipment are used, manufactured using titanium and tantalum (GOST 19126-79 “Medical metal instruments. General technical conditions”. They compare favorably with other analogues in terms of strength, ductility and corrosion resistance, causing biological inertness .

Titanium medical instruments are almost twice as light as their steel counterparts, while being more convenient and durable.

Figure 24. Surgical instruments made on a titanium-tantalum base.

The main medical industries in which titanium-tantalum instruments are most in demand are ophthalmological, dental, otolaryngological and surgical. The extensive range of instruments includes hundreds of types of spatulas, clips, retractors, mirrors, clamps, scissors, forceps, scalpels, sterilizers, tubes, chisels, tweezers, and all kinds of plates.

The biochemical and physical-mechanical characteristics of lightweight titanium instruments are of particular value for military field surgery and various expeditions. Here they are absolutely irreplaceable, since in extreme conditions literally every 5-10 grams of excess weight is a significant burden, and corrosion resistance and maximum reliability are mandatory requirements.

Titanium, tantalum and their alloys in the form of monolithic products or thin protective coatings are actively used in medical instrument making. They are used in the manufacture of distillers, pumps for pumping aggressive media, sterilizers, components of anesthesia-respiratory equipment, complex devices for duplicating the work of vital organs such as “artificial heart”, “artificial lung”, “artificial kidney”, etc.

Titanium heads of ultrasound machines have the longest service life, while analogues made of other materials, even with irregular exposure to ultrasonic vibrations, quickly become unusable.

In addition to the above, it can be noted that titanium, like tantalum, unlike many other metals, have the ability to desorb (“repel”) radiation from radioactive isotopes, and therefore are actively used in the production of various protective devices and radiological equipment.

Conclusion

The development and production of medical products is one of the most rapidly developing areas of scientific and technological progress. With the beginning of the third millennium, medical science and technology became one of the main driving forces of modern world civilization.

The importance of metals in human life is steadily increasing. Revolutionary changes are taking place against the backdrop of intensive development of scientific materials science and practical metallurgy. And in recent decades, industrial metals such as titanium and tantalum have been raised “on the shield of history,” which with all good reason can be called the structural materials of the new millennium.

The importance of titanium in modern healing simply cannot be overestimated. Despite its relatively short history of use in practical purposes, it has become one of the leading materials in a variety of medical industries. Titanium and its alloys have the sum of all the necessary characteristics for this: corrosion resistance (and, as a consequence, bioinertness), as well as lightness, strength, hardness, rigidity, durability, galvanic neutrality, etc.

Tantalum is not inferior to titanium in terms of practical significance. Despite the general similarity of most beneficial properties, in some qualities they are inferior, and in others they are superior to each other. That is why it is difficult, and hardly reasonable, to objectively judge the priority of any one of these metals for medicine: they rather organically complement each other rather than conflict with each other. Suffice it to note that medical structures based on titanium-tantalum alloys, which combine all the advantages of Ti and Ta, are now being actively developed and are being put into real use. And it is no coincidence that in recent years, increasingly successful attempts have been made to create full-fledged artificial organs made of titanium, tantalum and their compounds implanted directly into the human body. The time is approaching when, say, the concepts of “titanium heart” or “tantalum nerves” will confidently move from the category of figures of speech to a purely practical plane.