The pros and cons of cobalt chromium dentures

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The use of cobalt-chromium alloy is widely used in the practice of orthopedic dentists. The resulting metal products are reliable, durable and relatively safe for the patient’s health.

Structures made of hard alloys are used for the manufacture of both single crowns and bridges.

General overview

The alloy of cobalt and chromium has a wide range of applications. It is used for the manufacture of crowns, bridges and clasp systems. In implantology it is used in the production of abutments.

Recently, this type of alloy has been used less frequently, as the latest developments have made it possible to produce more durable materials.

Cobalt-chrome crowns are installed in the following cases:

if there is a need to restore the crown part of a tooth with significant destruction;
when pathological abrasion of the surface enamel occurs;
in case of severe manifestation of fluorosis;
if chips or cracks appear as a result of injury;
with an abnormal tooth shape.

Prosthetics with the installation of a bridge connection (from high-alloy steel) occurs according to the following indicators:

if partial adentia leads to the loss of several teeth standing in a row in a row;
in case of expiration of the service life of the bridge (planned replacement);
lack of alternative to another type of prosthetics.

Installation of orthopedic structures using cobalt and chromium is not carried out in the following situations:

when the patient has an allergic reaction to the alloy components;
if periodontal disease has led to the loosening of dental units that are supposed to be used as supporting ones;
low coronal part;
advanced forms of abnormal bite, and impaired functionality of the mandibular joint;
dental diseases in the acute phase (gingivitis, stomatitis).

Reasons for the development of a cyst under the tooth crown and treatment of pathology in modern dentistry.

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At this address https://www.vash-dentist.ru/protezirovanie/nesemnyie-p/koronki-np/kombinirovannuyu-luchshe-vyibrat.html we will consider the positive properties of a cast combined crown.

Stages of creating dentures and crowns

The procedure for prosthetics depends on the type of prosthesis and the chosen manufacturing technology, which may differ for the same source material (casting, stamping, milling).

Let's consider the simplest option - manufacturing a metal-ceramic crown with a cobalt-chrome base using casting and sintering of ceramic mass.

The process consists of the following clinical and laboratory steps:

Making a diagnosis, drawing up a treatment plan (examination and interview of the patient, radiographic studies, selection of prosthesis design).
Grinding a tooth for a crown.
Taking an impression of the prepared tooth and its antagonists.
Making a plaster model based on a cast.
Wax modeling of a metal frame.
Crown casting.
Fitting it to the tooth, finalizing it.
Selecting the color of ceramic cladding.
Installation of a metal frame on a tooth model, application of ceramic mass in layers, sintering in an oven.
Trying on a finished crown on a tooth, modification if necessary.
Glazing, finishing.
Fixing the crown on the tooth with cement.

In some cases, at the request of the patient, a provisional (temporary) plastic crown is made and installed while the permanent crown is being manufactured. But this is not always done.

The video shows the process of welding a denture made of cobalt chromium.

Overview of materials

Orthopedic structures made of high-alloy steel have been used since 1933. They contain the following components:

Cobalt. The percentage of this component ranges from 66 to 67%. Its presence provides the main mechanical properties of the product.
Chromium. Its percentage should not be less than 30%. The presence of this component ensures the hardness and strength of the structure, and also increases the material’s resistance to corrosion and oxidation.
Nickel. Its content in the alloy does not exceed 5%. It ensures the malleability and ductility of the material.
Molybdenum. A small concentration (up to 5%) gives the material a fine grain structure, which makes dental products durable.
Manganese. Simultaneously performs several tasks - improves the characteristics of the finished product and increases its strength; the quality of casting improves; The melting point decreases, which ensures comfortable production and subsequent processing.
Carbon. An additional element that gives the alloy fluidity properties and reduces the melting point.

In addition to the above materials, nitrogen and silicon can sometimes be added to the high-alloy steel composition. In this case, the content of the first element should not exceed 0.1%, and the second 1%. Otherwise, the products will lose their plasticity and their fragility increases.

It is important to note! Abroad (USA), beryllium and gallium are added to the cobalt-chromium alloy. In Russia, such components are not used due to their toxicity and ability to accumulate in the body.

Common parameters

Each alloy option for dental prostheses has its own composition; manufacturers often use their own developments and combinations.

The main thing is to bring the composition and characteristics of the substance to a certain standard and obtain a combination of certain qualities:

- safety. The metal must be absolutely safe, maintain its parameters and not emit harmful compounds during operation;

— corrosion resistance. Raw materials must resist corrosive processes, which eliminates oxidation and related problems throughout the entire guaranteed service life;

- strength. Components made from an alloy must withstand significant variable and static loads, such as compression, bending, and methodical movements in a certain direction;

- aesthetics. The use of parts should not come at the expense of appearance; first of all, it is necessary to recreate the appearance of natural units and obtain acceptable operational parameters;

- availability. This version of prostheses, although inferior to others in a number of aspects, surpasses them in the combination of price and quality. For example, the products are aesthetically comparable to zirconium dioxide, but the price tag is several times lower.

The alloy is non-toxic, but during service, especially if the processing features, recommended composition or care are not followed, they can release components that provoke reactions in the body. Because of this, the designs are considered more allergic and will require a comprehensive examination in the dentist's chair before choosing this type of denture.

The metal resists corrosion for a long time, but can cause another negative effect - a galvanic reaction. It can only be provoked by the presence of artificial components made of another metal, in particular stainless steel, in the oral cavity. Therefore, before carrying out operations, you need to make sure that no conflict will arise. Often in this case, existing elements are replaced with ones similar to those being installed.

The strength of the alloy is maintained only under strict compliance with the processing conditions, composition and recommended parameters of the implanted elements. You can get a low-quality product due to the negligence of the technician or the company producing the blanks. In the second situation, problems most often arise when purchasing blanks from untested and little-known companies. You can navigate by price; high-quality ones cannot be too cheap, but there is no point in purchasing prohibitively expensive ones.

Metal ceramics are one of the examples of the best products in terms of compliance with natural units. Components (crowns) are obtained by layer-by-layer application of a ceramic composition to the alloy surface. Due to the possibility of color adjustment, it is possible to bring products into full compliance with natural teeth, either preserved ones, or to fulfill non-standard wishes of the client.

Material forms

Ingots weighing 7-10 g. Produced by casting in an atmosphere. Disadvantages include casting defects due to the increased gas content.

Rods. The molten metal is sucked into metal or quartz tubes, acquiring their shape as they solidify. Subsequently it is cut into cylindrical blanks. This is the most common manufacturing method
Discs of various diameters and thicknesses. Manufactured in induction vacuum installations. Used for the manufacture of prosthetic structures using CAD/CAM technology.
Granules. It is obtained by pouring the alloy into a liquid.

Physical and chemical properties

The set of alloy parameters completely depends on the constituent elements.

In the case of dental cobalt chromium, these are the following components:

- base in the form of cobalt. The element must be at least 66-67 percent; it is responsible for the increased mechanical properties of the resulting metal;

- chromium is in second place, it should be at least 26-30 percent. The component is responsible for increased hardness and improved resistance to oxidative processes and corrosion;

- Nickel is the third most important, it is responsible for increasing technological parameters. At a percentage within 3-5 percent, the material becomes more malleable, ductile and viscous. Aspects make it possible to obtain a simpler substance in terms of release;

— molybdenum gives the structure a fine grain, which has a positive effect on the strength characteristics. The element can be added no more than 4-5.5 percent;

— manganese serves to solve a whole range of problems. Firstly, it increases the strength parameters of finished products. Secondly, the quality of casting increases due to the modernization of the alloy structure. Thirdly, the melting point of the substance drops noticeably, which is beneficial under production conditions and subsequent processing. Fourth, sulfur compounds, which are considered toxic to humans, are removed.

Two more components that can be found in blanks are beryllium and gallium. The problem is that the components are toxic and during operation can release a large amount of harmful substances, some of which can be accumulated by the body. The production of such products is carried out only by the USA, adding within 2% to the composition for the purpose of alloying it. You won't find such products in Europe.

These first three elements are the main ones, thanks to them the alloy matrix is formed, therefore cobalt-chromium-nickel should be at least 85%. The data is fixed by an international standard, therefore, when purchasing a workpiece of any brand, you can expect consistently high quality and similar characteristics. If components break during molding, the chromium content threshold of 30 percent is most likely exceeded, which causes the alloy to become brittle and the mechanical and casting parameters to drop.

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Another important element is carbon, however, it is not found in all products. Its positive quality is an increase in fluidity in the molten state and a decrease in the melting point.

Nitrogen and silicon have a similar effect, but they need to be added in a very small percentage:

- no more than 0.1 percent for the first;

- up to 1% for the second.

If this threshold is exceeded, plasticity will suffer.

The downside of carbon is that it can damage the ceramic layer during the release process of the prosthesis. During high-temperature firing, it can be released in the form of gas, entering the lining. Because of this, bubbles appear at the junction of metal and ceramics and the connection between the components weakens, reducing the service life and reliability of the finished oral element.

Due to these weaknesses, a number of companies, including many domestic ones, are engaged in the production of carbon-free billets.

If the composition is observed, the finished material has a mechanical viscosity twice that of gold. Metal melts at more than 1450 degrees.

The process of creating structures

The process of manufacturing crowns and bridges from cobalt-chromium compounds occurs in stages in the following sequence:

At the first appointment with the dentist, the oral cavity is examined , after which tactics for the treatment process are developed.
The material is selected and the cost of the product is announced. If necessary, additional research methods are prescribed (an X-ray or computed tomography is performed).
During the preparatory stage, the destroyed part of the crown of the tooth is restored. For this purpose, pins or stump inlays can be used.
To prevent the development of possible complications, pulp devitalization is performed. This is due to the fact that when grinding there is a risk of burns. Removal of the nerve also occurs when the visible part of the tooth is severely destroyed.
Preparation takes place for reliable fastening of the future orthopedic structure. For this purpose, burs with a diamond attachment are used.
If the manipulation occurs on “living” teeth (when the pulp is not removed), then it involves the use of local anesthesia. The thickness of the surface to be turned does not exceed 2 mm. A minimum degree of grinding is allowed if cast products are to be installed.
Impressions are made using a special silicone mass. It is applied to a special spoon and placed in the oral cavity, repeating the shape of the jaw row.
The impression is sent to the laboratory to make a model on the basis on which the orthopedic structure (bridge or crown) will be made.
After successful fitting, the finished products are fixed in the oral cavity using a cement composition.

Metal structures can be manufactured using the following techniques:

Casting. This technology provides the best final result, due to which the structure adheres well to the tooth surface without putting increased pressure on the gum tissue.
This minimizes the chance of pathogenic microflora penetrating under the prosthesis. In addition, the technique allows you to take into account the individual characteristics of the dentition.
Punching. It is used in rare cases, since the technique is considered outdated. Products obtained in this way do not take into account the anatomical features of the patient’s oral cavity, which is why the edges of the structure do not fit tightly to the gums.

The video shows the process of welding a denture made of cobalt chromium.

The processing process and its subtleties

One of the methods of material processing is casting. The technology has been tested on dozens of alloys with different properties, allowing us to obtain high-quality products with a homogeneous structure.

To create the frames of removable, fixed and partially removable dentures, which are produced on the basis of an alloy, crowns, the casting method is used; using a similar technology, blanks for milling are obtained, for example, pre-milled abutments.

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When casting, crucibles made of refractory material are used, which, in a prepared state, are loaded into an induction installation for the corresponding tasks. Melting is carried out to fill the prepared forms, the material turns into a liquid state and burns out the components of the models.

To do this, it is necessary to heat the metal elements to 1315 degrees, at which point its transition to a liquid state begins. At this stage, it is important to avoid overheating; in this case, the alloy alloy may burn out, so at the first sign of a change in shape, the technician starts the foundry unit.

It is important to fully maintain the set temperature level during the process. If overheating occurs, the structure becomes contaminated with oxidizing impurities. An experienced technician will immediately identify such discrepancies, since the processing crucible will be contaminated by the specified oxides after melting the workpieces. The absence of these elements and the cleanliness of the crucible is evidence of the high quality of the resulting product. In this case, the physical and chemical characteristics are not distorted, which has a positive effect on service life and reliability.

The prepared parts need to be processed; if all stages of the technical process are followed, then the stage takes a minimum of time. There will be no need to remove sagging, deformations and adjust the product to the required shape. Sandblasting occurs (aluminum oxide is used as a harder and finer-grained composition, giving maximum surface quality) and polishing.

Initially, sprues, flash marks and similar foreign components are removed. It is important to pay attention to the presence of visual defects on the internal surfaces of the metal structure, such as burrs or pearls.

Advantages and disadvantages

This type of material when used has the following advantages:

There are no changes in its structure during the manufacturing process. Raw materials are not subject to contamination during the melting process.
There is no loss of physico-chemical properties due to the absence of significant thermal effects. During the manufacturing process, overheating of the workpiece and tools is avoided.
The products practically do not shrink , which eliminates the appearance of microcracks. The material is resistant to corrosion and oxidation processes.
The alloy composition does not tarnish for a long time, and is lightweight in comparison with structures made of platinum or gold. The products are well stamped and soldered together.
The low cost makes it possible for people with varying incomes to get prosthetics.

The disadvantages of products made of chromium and cobalt include:

Possibility of developing galvanic syndrome. In this case, the patient has a sour taste in the mouth and discomfort when eating. These symptoms can only be eliminated by removing the prosthesis.
Low aesthetic value. The products are not used for prosthetics of frontal incisors.
Prolonged wear may cause a change in the color of the gingival surface (it becomes blue), which comes into contact with the installed crown or bridge.

Does the price of a metal-free crown per tooth correspond to its quality characteristics?

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Here https://www.vash-dentist.ru/protezirovanie/nesemnyie-p/koronki-np/metallicheskuyu-s-napyileniem.html you will find detailed information about metal crowns with white coating.

Titanium alloy crowns

Advantages of titanium crowns

Titanium has been successfully used in dental and orthopedic practice over the past decades. Alloys based on this metal have:

highest biocompatibility,
ease,
strength and reliability.

Dental prosthetics using titanium crowns are suitable for people suffering from allergies: the material never causes hypersensitivity reactions.

In addition, such prosthetic structures are low in cost compared to their analogues, although they are somewhat inferior to the latter from an aesthetic point of view.

Titanium-based carbide crowns last up to 15 years.

Disadvantages of titanium crowns

At the same time, crowns made of titanium alloys also have a number of negative features. Thus, due to the high complexity of the material processing process, prosthetic structures very often turn out to be inaccurate and require additional adjustment. In addition, ceramic coating on titanium frames does not adhere very well, so special ceramic masses that have an unnatural and unaesthetic grayish tint are used as a decorative and protective coating.

Since all materials used for the manufacture of carbide crowns have a number of disadvantages, modern scientists continue their work to improve their quality and consumer properties. To give prosthetic devices a more natural look, dental clinics use titanium-zirconium and titanium nitride protective and decorative coatings, plastic or ceramics.

Lifetime

Crowns and bridges made from an alloy of cobalt and chromium have high strength, which is why products of this class can last from 15 to 20 years.

Most experts recommend replacing the structure after 10 years. This is due to the fact that during prolonged wear, atrophic changes occur in the gum, causing it to sag, exposing the edges of the crown. This contributes to the leaching of cement and the occurrence of pain.

The following factors may affect the service life:

private inflammatory processes of the gums and root canals reduce the life of the crown or bridge;
if the stamping technique was used in the manufacture of the product, then such a structure is subject to rapid wear due to the small thickness of its walls;
eating solid foods causes deformation or breakage of the structure;
Failure to comply with hygienic care is accompanied by the penetration of bacterial pathogens under the prosthesis, which causes its premature removal.

Rules of care

After installing crowns or bridges made of high-alloy steel, daily care is carried out as for natural teeth (twice a day). The situation is different if an alloy of cobalt and chromium was used as a frame for plastic or ceramic products.

In this case, the following rules and recommendations must be observed:

Oral care with a toothbrush and hygienic paste should be carried out twice a day. After each meal (if this is not possible), you need to use elixirs or antiseptic rinses.
To prevent discoloration of the crown part of the tooth, you should limit your consumption of foods with coloring properties (beets, sauces, tomatoes).
Completely exclude rough foods (nuts, crackers) from the diet.
Visit the dentist's office once every six months for a preventive examination. If necessary, undergo a professional cleaning procedure.

Important! During the period of cleansing the oral cavity, special attention should be paid to the place where the structure comes into contact with the gums. The accumulation of food debris leads to the development of bacterial microflora, which causes inflammatory processes.

Price

Despite the fact that the alloy of cobalt and chromium has practically ceased to be used in prosthetics of frontal incisors, it is often used as a base when making prostheses made of plastic or ceramics. In this case, aesthetics in the smile area are not lost, and the products become publicly available due to their low cost.

Products made from cobalt-chromium alloy have a low cost. Pricing is influenced by the status of the clinic, the region of Russia and the qualifications of the specialist.

Products using casting technology will cost from 4,000 to 4,500 rubles. Accordingly, a bridge of 3 units can be installed for 12,000 rubles.

Stamped designs have a starting price of 1000 rubles. At the same time, the final cost may be slightly higher due to the need for procedures to prepare for prosthetics.

Reviews, opinions, comments

Most dental practitioners note that products made from high-alloy steel are gradually losing their relevance.

This is due to the use of higher quality materials, which make orthopedic structures not only durable, but also provide a high degree of aesthetic value.

You can share your opinions in the “Comments” section of this article.

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