Despite the fact that metal-ceramic crowns have many advantages over other types of prosthetics, many patients refuse them. The reason for this is the presence of various myths about their disadvantages, which can be found on the Internet and heard from friends. Below are common patient fears and the reality of things.
Metal ceramics are harmful to health
A high-quality prosthesis that is installed correctly cannot cause any harm to the patient. In most cases, metal-ceramic coating does not cause any discomfort. It is important to understand that the base of the crown is made of metal, and it can cause allergies. If after dentures there is a burning sensation in the mouth, a metallic taste or swelling, you should consult a dentist. Such patients, as a rule, have an all-ceramic prosthesis installed instead of metal ceramics. To avoid crown replacement, if you have any allergic reactions, you must immediately notify your doctor so that he can select the optimal material.
Metal-ceramic crowns are too fragile
It all depends on the quality of the prosthesis and the material used to make its base. Ceramic crowns without a metal base really do not have sufficient strength. Metal-ceramic structures do not have this drawback, therefore they are suitable for prosthetics of any teeth. Various metals are used as base materials. IN Lately The most common are crowns with a frame made of aluminum dioxide and zirconium, as they are highly durable and can withstand chewing loads well. In addition, it is important that the prosthetics are performed with high quality.
The crown will need to be replaced within a few years
There are two diametrically opposed myths regarding the durability of such crowns. According to the first, the prosthesis lasts 3-5 years, and then it has to be changed. There is another extreme. Some patients believe that the crown will last a lifetime. The truth, as usual, is in the middle. The service life of crowns is 10-15 years or more. The most durable designs are those with a frame made of an alloy of gold and platinum.
If you are planning to install a metal-ceramic crown, contact our TakiMed clinic. Our experienced specialists will perform prosthetics efficiently and absolutely painlessly.
P According to dentists, owners of crowns installed ten or more years ago need to seriously think about
what impact they have on health. The metals that were used in those days to make crowns oxidize in the oral cavity and provoke associated diseases - from stomach ulcers to oncology. It is not surprising that many diseases supposedly arise without a reason and cannot be completely cured. Few doctors pay attention to the composition of the crowns in the patient’s mouth. Therefore, dentists urge you to take this issue more seriously. Orthopedic dentist Rafael Aleksandrovich Shakhnazarov tells more about the composition of crowns and the reasons for their replacement.
Why can old crowns be harmful to health?
Very often in my clinical practice there are cases when patients come with a complaint about the inadequacy or unaesthetics of bridge-like prosthetic crowns on teeth made earlier: either many years ago, or recently made. Crowns that were manufactured more than 10-15 years ago in our country did not always meet the requirements of orthopedic dentistry.
What metals are old crowns made of?
The composition of the crowns, in particular the metal of these crowns, often did not even meet the technical standards for the manufacture of crowns. These are nickel-chrome, nickel-palladium. Accordingly, nickel is a cheap metal, but it has many disadvantages. Its main disadvantage is very strong oxidation. In the oral cavity, oxidation occurs excessively. The oral cavity is the beginning of the digestive tract, and all ions and metal oxides will move further along the digestive tract, ending up in the stomach and intestines. Several years ago, the Ministry of Health adopted a resolution to extract this metal from dentistry. Nickel has a very strong destructive effect on the gastrointestinal tract, which leads to the formation of ulcers in the stomach. Accordingly, stomach ulcers may occur. And what is important, nickel has a very strong influence on the development of cancer.
What materials are used in modern crowns?
In modern dentistry, slightly different materials are used. The most common metal in modern dentistry is cobalt, which is used together with chromium, cobalt-chromium alloys, from which modern metal-ceramic crowns are made. Very often patients come, as I said, with the desire to replace old crowns. It happens that there is a fairly large number of old crowns in the oral cavity. And we always tell patients: if you want to change the crowns in the oral cavity, if you have crowns made of nickel-chromium alloy in the oral cavity, then it is necessary to remove all the crowns with a one-time replacement with permanent modern crowns or with periodic replacement, respectively, with the production of a temporary one designs.
Why do you need to change all the crowns at once?
Sometimes in my practice there were cases when doctors changed only part of the crowns, and left part of the old ones. Very often, the patient experienced cases of the effect of galvanization of different ionic metals, when the patient feels constant or periodic tingling in the oral cavity, which does not go away by any means: neither ointments, nor mouth rinsing. These complaints went away only after either the old crowns were removed, or all the crowns in the oral cavity were completely changed and all the crowns were made from the same material.
Our oral cavity is a biosystem in which all components must be compatible. This means that any orthopedic intervention, any other dental treatment must be biocompatible and not cause harm to the body. Crowns must be made of the same metal.
As science knows, about 80 of the 92 elements that can be found naturally on our planet are metallic in nature. The exception is precious metals, which, as a rule, do not change their natural state, and, therefore, are virtually not subject to further chemical reactions, that is, they are chemically inert.
It is not surprising that since ancient times it has been customary to use instruments and materials made of noble metals in medicine. Prosthetics was no exception. It was prostheses made of noble metals that were best perceived by the human body.
However, questions arose regarding the strength of such materials, as well as their availability. The fact is that most noble metals are highly ductile, and, therefore, products made from them cannot be durable. In addition, noble metals are usually quite heavy. And if we talk about cost, then such prostheses were available only to a very narrow circle of patients.
The history of the development of dentistry also remembers attempts at prosthetics using cheap metal alloys, but such “teeth” very quickly failed. The metal quickly oxidized and corroded. In addition, the by-products of the reaction that occurred with the alloy in the human oral cavity, under the influence of oxidation, as well as acid-base effects, were extremely harmful to human health.
The attempt to obtain an alloy for prosthetics that combines strength, biocompatibility with the human body, high aesthetic qualities and functionality has been ongoing for several centuries.
And only in 1986 it was possible to obtain a more or less stable alloy that could be considered relatively safe for human health. If we talk about strength, then the VMK 68 metal-ceramic with Degudent U alloy from the German company VITA was virtually flawless. For almost 30 years, this alloy has been used everywhere as best material for prosthetics and today is still considered quite competitive, given its low cost.
However, is this method as safe for health as was thought? After all, it is known that it, although not to a significant extent, is still susceptible to corrosive changes. Modern clinical studies allow a more meticulous analysis of the impact of minor changes occurring with the VMK 68 sample with Degudent U alloy and determine its impact on the patient’s health.
To increase biocompatibility with the human body ceramic materials, their composition is mainly, and sometimes completely, made up of metal oxides such as Al2O3. In this case, pure metals are extracted from oxides and metal compounds found in nature, using very complex technological processes. They do this in order to further use their special properties in dentistry (and not only).
Of course, these metals tend to dissolve again in aqueous solutions, for example, in the oral cavity, or in the atmosphere. In doing so, they leave the state of pure metal - a process called corrosion - to enter a new, more stable compound.
And if the described reactions occur in the human body, through chemical bonds with proteins, such processes are usually called resorption.
Sometimes the resulting elements can be beneficial, but more often they have a harmful effect on the human body.
Concentration plays a big role here. Any metals are harmful to human body if their concentration exceeds the permissible limits.
In low concentrations, metals can be roughly divided into essential trace elements and non-essential trace elements. In this case, a low concentration is referred to in the ppb range, taking its parts per billion, or ppm, that is, parts per million. The exact location of the transition to higher concentrations, that is, the concentrations at which such trace metal elements may be considered toxic or harmful, is difficult to determine for many metals.
Possible assumptions and assumptions can be considered as alarmism. In fact, in order to evaluate their impact objectively, it is necessary to take into account many associated factors, such as the usual normal concentrations of various trace metal elements in the human body. To do this, let's look at the data in Table 1.
Table 1. Normal concentrations of various elements in human blood (S – blood serum, P – blood plasma, B – blood)
| Element | Mol/l | ppm |
| Aluminum (S) | 0.04 | 0.001 |
| Beryllium | 0.5 | 0.004 |
| Cadmium (S) | 0.03 | 0.003 |
| Chrome (S) | 0.01 | 0.0006 |
| Cobalt (S) | <0.002 | <0.0002 |
| Gallium | 0.0014 | 0.0001 |
| Gold | 0.0003 | 0.00006 |
| Indium | Not detected | Not detected |
| Iron (P) | 18 | 1 |
| Copper | 18 | 1.1 |
| Lead | 1 | 0.02 |
| Lithium | 4.5 | 0.031 |
| Magnesium (P) | 780 | 19 |
| Manganese (S) | 0.1 | 0.006 |
| Mercury (B) | 0.006 | 0.001 |
| Molybdenum (S) | 0.006 | 0.0006 |
| Nickel | 0.05 | 0.003 |
| Palladium | Not detected | Not detected |
| Platinum | Not detected | Not detected |
| Potassium (P/S) | 4000 | 170 |
| Silver | Not detected | Not detected |
| Sodium (P) | 140000 | 3200 |
| Tin | 0.31 | 0.94 |
| Titanium (in urine) | <0.004 | <0.0002 |
| Vanadium (P) | 0.2 | 0.01 |
| Zinc (P/S) | 14/16 | 0.9/1 |
Table 2. Normal concentrations of various elements contained in human tissues
| ppm | |
| Aluminum | 1 |
| Beryllium | 0.001 |
| Cadmium | 0.1 |
| Chrome(e) | 0.2 |
| Cobalt (e) | 0.05 |
| Gallium | 0.001 |
| Gold | 0.001 |
| Indium | <0.01 |
| Iron(e) | 70 |
| Copper(e) | 2 |
| Lead | 0.5 |
| Magnesium | 270-420 |
| Manganese | 0.02 |
| Mercury | 0.02 |
| Molybdenum (e) | 0.2 |
| Nickel(e) | 0.1 |
| Palladium | Not detected |
| Platinum | Not detected |
| Silver | 0.01 |
| Tin(e) | 1 |
| Titanium | 0.2 |
| Vanadium (e) | 0.1 |
| Zinc(e) | 40-100 |
Table 3. Daily human intake of trace elements (per 70 kg of body weight).
| Element (e – valuable, necessary) | In mg |
| Chrome(e) | 0.9-0.13 |
| Cobalt (e) | 0.015-0.95 |
| Copper(e) | 2-6 |
| Gallium | Not known |
| Gold | Not known |
| Indium | Not known |
| Iron(e) | 8-18 |
| Magnesium (e) | 240-280 |
| Manganese (e) | 2-3 |
| Mercury | Up to 0.02 |
| Molybdenum (e) | 0.1-0.3 |
| Nickel(e) | 0.14-0.6 |
| Palladium | Not known |
| Platinum | Not detected |
| Tin(e) | 0.2-1 |
| Titanium | 0.3-1 |
| Zinc(e) | 10-15 |
Table 1 presents a list of normal concentrations of various elements in human blood, taken from various literary sources. Table 2 shows the normal concentrations of essential and non-essential elements in human tissue.
Based on the data presented, we can conclude that normal concentrations for zinc and copper in the bloodstream are considered to be 1 ppm, while for tin, for example, the normal value is 0.04 ppm.
For a number of elements, such as gallium, palladium or indium, normal concentrations of which are less than 1 ppb are not determined at all. Zinc has an average concentration in human tissues, different for various organs, from 40 ppm to a maximum of 100 ppm. While copper is 2 ppm, tin is 1 ppm, gallium and indium have a concentration of several ppb, and palladium is not detected at all.
It is no coincidence that we mentioned two elements, copper and zinc. After all, they are vital trace elements. Thus, the daily requirement of an adult for copper is 2-6 mg, and the required daily intake of zinc is 10-15 mg (Table 3). Moreover, if the need for these elements is not met, the body experiences a deficiency.
Clinical studies have shown that in biopsies of gums that are in direct contact with dental alloys, consumption rates of such elements are significantly higher than normal concentrations, for example, values from 30 to 200 ppm were recorded for copper.
The most harmless consequences of such contact are clinically detectable unwanted color changes, irritation of the gums near the metal edges of the crown, and others. But much greater concern should be caused by the fact that at the point of contact between the crown and human tissue, trace metal elements accumulate over time in fairly high concentrations, which with a certain probability can cause local toxic reactions in the future.
Therefore, to minimize the risk, it was necessary to modernize the process of performing metal dental restorations so that they are sufficiently resistant to corrosion, and therefore eliminate the likelihood of such reactions occurring.
A problem area regarding biocompatibility is the unveneered parts of crowns and bridges, for example, unveneered elements of bridges and distal molars or metal edges of crowns. The result is an increased risk of corrosion, and therefore a threat to the patient’s health.
Thus, from a materials technology, biological and also aesthetic perspective, despite all its advantages, the traditional standard system of the VMK 68/Degudent U sample required serious revision, optimization and modernization. The first step towards improvement was Golden Gate metal ceramics from the German company Degussa. However, it did not show the desired results in terms of biocompatibility.
With the advent of innovative metal ceramics Omega 900 from Vita, it can be stated that work to improve the biocompatibility of crowns with human tissue, and to reduce the harmful effects of alloys on the human body, has had positive results.
The use of the revolutionary Omega 900/Bio Herador SG metal-ceramic system takes into account functionality, aesthetics, durability and is significantly better than previous ones in terms of biocompatibility. According to preclinical observations and studies, this metal-ceramic system has extremely effective biological and aesthetic capabilities compared to a conventional system such as VMK 68/Degudent U.
Of course, it is impossible to completely exclude corrosion of the alloy. But in the case of the Bio Herador SG alloy, when it corrodes, only zinc is released, classified as biologically safe.
Metallic elements are not the main components of this alloy, but are secondary to indium and gallium.
The basic principle taken by specialists in developing the Omega concept was that the degree of corrosion for precious metal alloys not containing copper should be significantly lower than for alloys containing copper.
For example, for alloys with a high gold content, the degree of corrosion is much lower than for the same alloys with a reduced gold content.
Numerous corrosion tests have shown that only under truly extreme conditions, which cannot be found in the oral cavity, only a few micrograms (mg), and in very long-term studies, several nanograms (ng) of trace metal elements can be dissolved daily by corrosion.
These indicators are so insignificant that we can safely summarize that the concentration of trace elements, which is distributed daily with 2 liters of saliva throughout the human body (this is about 70 kg and 6 liters of blood) not only does not exceed, but is much lower than the permissible norm.
However, it must be admitted that the possibility of local toxic reactions that result from accumulation in the gingival margin cannot be ruled out. Research in this direction is still ongoing.
In conclusion, it can be noted that the use of a new prosthetic technique through the use of innovative metal ceramics Omega 900/Bio Herador SG has made it possible to achieve a significant reduction in the negative impact on the human body of the products of corrosive changes that occur over time with the alloy. In addition, this metal-ceramic has higher strength and good aesthetic characteristics. Omega 900/Bio Herador SG also showed positive results when working with the formation of a prosthesis and in the process of placing it on the patient. However, it is not fully known how likely local toxic reactions are to occur as a result of accumulation in the gingival margin.
However, today Omega 900/Bio Herador SG is probably the best metal alloy for prosthetics
P According to dentists, owners of crowns installed ten or more years ago need to seriously think about
what impact they have on health. The metals that were used in those days to make crowns oxidize in the oral cavity and provoke associated diseases - from stomach ulcers to oncology. It is not surprising that many diseases supposedly arise without a reason and cannot be completely cured. Few doctors pay attention to the composition of the crowns in the patient’s mouth. Therefore, dentists urge you to take this issue more seriously. Orthopedic dentist Rafael Aleksandrovich Shakhnazarov tells more about the composition of crowns and the reasons for their replacement.
Why can old crowns be harmful to health?
Very often in my clinical practice there are cases when patients come with a complaint about the inadequacy or unaesthetics of bridge-like prosthetic crowns on teeth made earlier: either many years ago, or recently made. Crowns that were manufactured more than 10-15 years ago in our country did not always meet the requirements of orthopedic dentistry.
What metals are old crowns made of?
The composition of the crowns, in particular the metal of these crowns, often did not even meet the technical standards for the manufacture of crowns. These are nickel-chrome, nickel-palladium. Accordingly, nickel is a cheap metal, but it has many disadvantages. Its main disadvantage is very strong oxidation. In the oral cavity, oxidation occurs excessively. The oral cavity is the beginning of the digestive tract, and all ions and metal oxides will move further along the digestive tract, ending up in the stomach and intestines. Several years ago, the Ministry of Health adopted a resolution to extract this metal from dentistry. Nickel has a very strong destructive effect on the gastrointestinal tract, which leads to the formation of ulcers in the stomach. Accordingly, stomach ulcers may occur. And what is important, nickel has a very strong influence on the development of cancer.
What materials are used in modern crowns?
In modern dentistry, slightly different materials are used. The most common metal in modern dentistry is cobalt, which is used together with chromium, cobalt-chromium alloys, from which modern metal-ceramic crowns are made. Very often patients come, as I said, with the desire to replace old crowns. It happens that there is a fairly large number of old crowns in the oral cavity. And we always tell patients: if you want to change the crowns in the oral cavity, if you have crowns made of nickel-chromium alloy in the oral cavity, then it is necessary to remove all the crowns with a one-time replacement with permanent modern crowns or with periodic replacement, respectively, with the production of a temporary one designs.
Why do you need to change all the crowns at once?
Sometimes in my practice there were cases when doctors changed only part of the crowns, and left part of the old ones. Very often, the patient experienced cases of the effect of galvanization of different ionic metals, when the patient feels constant or periodic tingling in the oral cavity, which does not go away by any means: neither ointments, nor mouth rinsing. These complaints went away only after either the old crowns were removed, or all the crowns in the oral cavity were completely changed and all the crowns were made from the same material.
Our oral cavity is a biosystem in which all components must be compatible. This means that any orthopedic intervention, any other dental treatment must be biocompatible and not cause harm to the body. Crowns must be made of the same metal.
Prosthetics are a quick and easy way to restore the functionality of your teeth and the aesthetics of your smile. This method has fewer side effects and contraindications than implantation, but one complication exists in each type - an allergic reaction. Allergy - the body’s reaction to the introduction of a foreign structure, followed by its rejection and the appearance of vivid symptoms, irritation, and pain.
We will look at why allergies to dentures occur, its symptoms and treatment methods, allergenic materials, etc.
If a test has not been carried out to identify allergies to the components of the product, the patient will notice symptoms after installation.
First of all, there is redness of the soft tissues and mucous membranes, palate, and tongue. Immediately after this, swelling quickly increases, pain, itching, severe discomfort when chewing, swallowing, yawning, coughing, etc. appear.
Inflammation of the gums under the denture
Also, microcracks, ulcers and rashes may appear on the mucous membrane, which gradually spread to the tongue, cheeks and lips. There may be a strong metallic or bitter taste in the mouth.
One of the primary (hidden) symptoms of allergies may be dry mouth or, conversely, increased salivation. The throat may feel sore, and an unusual coating may appear on the tongue.
Patients with bronchial asthma often experience an exacerbation of the disease due to allergies.
Mumps may occur (the salivary gland in the parotid area becomes swollen and inflamed).
The spread of allergies is indicated by rashes on other areas - the face, hands, and skin in general. The limbs and cheeks may swell.
In advanced cases, the patient experiences hyperthermia, which lasts for several days.
A dangerous symptom is swelling of the laryngeal region (Quincke's edema). If the reaction is not removed and prompt medical assistance is not provided, a sudden disruption of the functions of the respiratory system and suffocation are possible. Often these symptoms are caused by an allergy to metal-ceramic crowns.
Allergenic components in dentures
Metal (chrome, steel, copper, cobalt, zinc, etc.) crowns have always been considered the most common allergens. The use of non-precious alloys greatly reduces the cost of production of structures. They are actively used for the manufacture of not only crowns (metal and metal-ceramic), but also bridges, and also as a basis for clasp products.
Allergy to metal crowns (symptoms discussed above) is caused by the use in production of cheap alloys and impurities that are not biointeractive components.
Allergy to metal crowns A completely different picture can be observed if we consider products made from noble metals (gold, silver, platinum). They are not so popular, because the price of precious metals in the modern world is very high and is accessible only to the wealthy. And yet, models and implants made from them rarely cause an allergic reaction and are well accepted by the body with minimal risk of rejection.
The influence of various metals is important when considering such a complication as “galvanic syndrome”. It occurs due to the incompatibility of certain metals in the alloy, which causes a galvanic current that is harmful to the patient. The consequences are sleep disturbance, increased salivation, and intoxication of the body as a whole.
In order for a metal to be used in orthopedics, it must meet the requirements - hardness, aesthetics, lightness and chemical resistance to external factors (saliva, food fibers, pathogenic microflora). The listed factors can provoke oxidation of the metal in the oral cavity, its gradual destruction and corrosion.
Allergy to metal prostheses in dentistry is caused by electrochemical processes that arise due to a conflict between the types of metals, their structure, characteristics of the alloy, temperature conditions of manufacture, the chemical composition of saliva, etc.
Nickel, which is part of the so-called “stainless steel”, is actively used in orthopedics, but saliva causes its corrosion and, as a result, allergies. The alloy with its composition is prohibited from being offered to patients who have had dermatitis in the past or an individual reaction to nickel bracelets, zippers, fasteners and steel jewelry.
Chromium, manganese, and cobalt can also cause various reactions, including allergic stomatitis.
Aluminum silicate or kaolin is often used as a filling composite. This should be taken into account when installing a prosthesis next to a filled tooth, since dissimilar metals may react chemically.
Zirconium crowns are based on zirconium oxide and dioxide, which rarely causes adverse reactions, including allergies.
Zirconium crowns Ordinary iron, unlike budget alloys, has excellent corrosion resistance, so allergic complications practically do not arise.
But copper in smaller grade gold, solders and fastening materials can react with saliva. The release of metal into saliva, and then gastric juice, blood, and lymph causes general poisoning of the body.
Oxidized zinc is also used in solders, amalgams, and dental cement. In conditions of high humidity, this metal quickly breaks down and dissolves, causing mild toxic reactions.
But the destruction of lead in the process of wearing metal prostheses leads to severe intoxication, an increase in the amount of the substance in the body above permissible limits.
Tin is used in the manufacture of budget crowns from low-melting metals. The component is very toxic, so it is practically not used for medical purposes.
Titanium, molybdenum, and indium in stainless steel practically do not cause allergic reactions.
Silver has a disinfectant and anti-inflammatory effect, so dentures made from this component have a positive effect on the mucous membrane, reducing the risk of infectious processes and diseases.
Silver and gold are resistant to corrosion and rarely cause allergies, which cannot be said about platinum and palladium (strong allergens). Noble metals are non-toxic and do not cause general poisoning of the body.
Let's move on to plastic. Acrylic dentures are considered organic, bioinert and high-polymer models, which, unfortunately, can cause allergic stomatitis and intoxication. The main factor in the development of complications is the residual monomer, which is part of the acrylic composite. Soft plastics and polyurethane rarely cause allergies.
Allergy to plastic prosthesis Modern silicone and nylon prostheses are considered biologically compatible, protecting the patient as much as possible from side effects.
Ceramics also does not cause allergies.
Sometimes an individual reaction manifests itself to various pigments used in the manufacture of prostheses. Dyes are used to improve the aesthetic characteristics of crowns and acquire the shade chosen by the patient.
What factors contribute to allergies?
There are nonspecific factors that favor the absorption of the allergen from the oral cavity into the blood. Hapten accumulates in the serum to a certain level, after which an allergic reaction occurs in the body. Let's consider these factors.
Actions to determine allergies
All patients should know what to do if they are allergic to removable dentures, implants, fixed structures, etc.
Acute allergies appear within a few hours. If you notice the symptoms listed above, immediately remove the irritant (prosthesis) from the oral cavity or contact the clinic to remove a fixed structure (implant).
In just a few minutes, an allergy can develop to swelling of the larynx and blocking of the airways, so you can’t hesitate.
Allergy to acrylic implants If symptoms gradually develop (increased salivation, dry mouth, reddened gums), take antiallergic medications and also see a doctor.
Remember, in order not to treat the consequences of intoxication and individual reactions, before choosing a design, the orthopedist must conduct a test for an allergic reaction. This could be a screening technique, a skin “patch test” to determine a contact allergen, or a lymphocyte stimulation test.
