Features of dental prosthetics with metal-ceramics

Today, dentists have a lot of options for prosthetics - restoring a damaged or missing tooth. One of the most effective solutions is metal ceramics - it is reliable and aesthetic. With its help, you can restore one or more teeth, and the structure is supported by implants or the patient’s own teeth.

Metal-ceramics are orthopedic structures - crowns and bridges, which are made by spraying or casting ceramics onto a metal base or frame. This method of prosthetics is in great demand, since the material used to restore the shape and function of the tooth does not cause allergic reactions. Metal-ceramic prosthetics are more often performed for the masticatory region, since in this case the strength of the structure is a priority, but this does not at all deprive artificial teeth of their aesthetics. Such designs closely replicate the structure and color of natural teeth.

Structure and types

Metal-ceramic dental prosthetics got its name due to the structure of the structures: inside it has a cast metal frame with a thickness of 0.3-0.5 mm. The material of manufacture is cobalt or nickel-chromium alloys. In some cases, alloys of precious metals - platinum or gold, palladium and others in different proportions - can be used. Crowns are divided into corresponding types according to this parameter.

The use of gold has an undeniable advantage - due to the natural yellowness of the precious metal, it is possible to achieve a natural shade of the structure, which is especially in demand when it is necessary to replace the front teeth.

The metal frame is covered with ceramics. The base is veneered using manual layer-by-layer application of ceramic mass. The structure is fired in a kiln after each layer is applied - this allows for the best connection between metal and ceramics.

As for the structure of the structure, the following types of metal-ceramics in dental prosthetics are distinguished:

Actually single crowns. They are widely used to restore teeth in the lateral zone when they are more than ⅔ destroyed.
Bridges. They are designed to restore several missing teeth in a row. The most reliable design is considered to be two crowns for supporting teeth and 2 artificial teeth between them.

Cutting from a plaster die model

To obtain a metal stamp, a plaster stamp is cut from a plaster model of the jaw. A low-melting stamp will be exactly the same. Before cutting, the model is immersed in water for several minutes.

The plaster stamp is cut using a flat saw. An important point is that the width of the base of the stamp should be equal to the equator of the tooth. (Wider - and the stamped cap will rest against the base; narrower - there will be folds on the crown).

In the finished plaster stamp (on its base), another line is drawn 1 mm below the previously outlined clinical neck. Use a sharp spatula to make a groove along this line. Then the plaster is cut between the first and second lines.

Important: the area between the first and second lines determines the parameters of the subgingival part of the crown. Its diameter should be equal to the diameter of the neck. If it is wider, the crown will be large. If it’s already, the crown simply won’t fit. Ideally, this area should appear as a vertical line below the clinical neck.

As a result of the above steps, we will eventually lengthen the crown by 1 mm. What is it for? To create a reserve for future circumcision and crown grinding. Otherwise, the crown may end up short. And also, so that it is located 0.2 mm under the gum.

I - highlighting the simulated tooth on the model; II - contours for processing a gypsum column. III - guidelines for determining the length and width of an artificial crown: a - correct, b - incorrect.

Advantages and disadvantages of metal ceramics

Compliance with manufacturing standards and installation technology almost completely eliminates possible harm from installing the structure. The use of modern materials eliminates the release of toxic substances, but it is important to remember that an individual reaction may occur.

The ceramics itself, used in the manufacture of artificial teeth, does not cause allergies - a possible reaction is provoked by the metals in the frame of the structure. For example, chromium-nickel alloys can provoke an allergic reaction to nickel, and the use of base metals under the influence of saliva can be susceptible to oxidation reactions. Symptoms of an allergic reaction may include:

burning in the mouth;
metallic taste;
swelling of the gums in the area of contact of soft tissues with the crown.

If such symptoms occur, it is important to consult a dentist - you will probably need to replace the structure with an all-ceramic crown or use another prosthetic method.

Other disadvantages include the possibility of exposing the metal frame in the event of receding gums. It is worth noting that structures made of zirconium dioxide are not subject to this phenomenon. In addition, the technology of metal-ceramic dental prosthetics involves grinding the tooth under a crown and removing the pulp in many cases, which is also a disadvantage.

The advantages of metal ceramics include high strength and long service life. Today, metal-ceramics are used for both single crowns and bridges - it is in demand when it is necessary to replace teeth with a significant chewing load. The frame made of aluminum dioxide or zirconium is strong enough, so the dentures can withstand heavy loads.

A long service life - 10-12 years for alloys of base metals and about 15 in the case of using a gold-platinum alloy - is a key advantage of the designs. This is only relevant for those prostheses that are made using individual casts. It is also important to follow the doctor’s recommendations for care - in this case, the prosthesis will last as long as it should. This is necessary because one of the common reasons for premature crown removal is the development of secondary caries at the junction of natural and artificial tissues, so it is very important to visit a doctor in a timely manner.

To summarize, we can say that the advantages of metal ceramics are as follows:

comfort of wearing structures;
functionality - function is restored due to the flawless modeling of masticatory hillocks;
strength;
long service life;
acceptable aesthetics;
biological compatibility - in the absence of allergic reactions to metals;
the possibility of prosthetics for both anterior and chewing teeth;
shade fastness - ceramics are not susceptible to the action of dyes;
comparative cheapness;
the possibility of restoring the structure without removing it in the event of minor chips.

What to do if there is pain after turning

It happens that after the anesthetic wears off, the patient experiences unpleasant sensations. They can be either a type of norm or a pathology. Teeth hurt after grinding for the following reasons:

overheating occurred: the bur rotates at a very high speed, so if the doctor performed the procedure quickly, without stopping, tissue overheating could occur. In this case, the pain will be monotonous, but will go away on its own after a few days or weeks, less often - after a couple of months,
During preparation, too much was removed: the dentin layer has become thin, the nerve is close, so it is completely normal that the tooth will react with pain. But this is no longer the norm - to prevent such situations from occurring, most doctors still suggest depulping before installing a prosthesis,
the gums are injured: quite often doctors use special threads and metal plates to push back the mucous membrane. Therefore, slight inflammation and swelling of the gums after the procedure is normal, which disappears on its own within a few days.
errors when grinding: what to do after the procedure for processing units if the painful symptoms do not disappear even after several days? This is a reason to visit the dentist. It is possible that the nerve was injured or the root split, which led to the development of an inflammatory process. In such a situation, the pain will be acute, tissue swelling is possible (and not only the gums, but even the face). This situation requires a prompt solution.

On a note! The important point is that after turning, a temporary prosthesis is almost always installed - be it a veneer or a plastic crown. After all, after preparing the support, impressions are taken, based on which the dental technician in the laboratory will work on the design of the prosthesis. To save the tooth and restore its aesthetics, the doctor will suggest a temporary replacement.

Color of metal-ceramic structures

Separately, I would like to note the advantage of metal-ceramics, due to which many patients prefer it - ceramics, which is used for the manufacture of structures, allows you to imitate the shade and structure of your own tooth enamel. Therefore, the prosthetic tooth is similar to the patient’s natural teeth. The shade is selected according to the Vita scale - the selected color will remain that way throughout its entire service life, since ceramics are not subject to darkening and do not tend to absorb dyes from drinks and food.

The only thing that can change the shade of an artificial tooth is pigmented plaque, which is easily removed with professional oral cleaning.

Will it hurt when turning?

The word “grinding” used to sound scary coming from a dentist. Today, the preparation process does not last long and takes place without any discomfort or pain. Before starting the procedure, the doctor will “freeze” the mucous membrane with a special gel, and the patient will not feel the injection with a good local anesthetic at all. Anesthesia is used both in the case of working with living units (in order to “turn off” for a while the nerve that is sensitive to any manipulation) and with “dead” units in which the nerve is absent. After all, turning involves a very painful retraction of the gums.

Indications for metal-ceramic prosthetics

A doctor may recommend this method of tooth restoration for the following indications:

severe tooth decay as a result of caries or injury - the impossibility of restoring it with fillings;
anomalies of dental development that disrupt the function and aesthetics of the dentition;
the absence of 2 or more teeth in a row and the presence of supporting teeth on the sides of the dentition defect (cermet bridges can be used here);
inability or unwillingness to use other prosthetic methods.

What anesthesia is used?

Anesthesia is mandatory when grinding down “living”, non-pulp teeth. But it is also given to patients with “dead” units, if they have increased sensitivity or if the gingival margin is being retracted.

Whether to leave the pulp or not depends on the clinical picture, the technique of the orthopedic dentist and the wishes of the patient. “Living” units are stronger and less susceptible to caries. However, with “dead” teeth there is no risk of burns, swelling or trauma to the neurovascular bundle and subsequent development of pulpitis.

In domestic dentistry they prefer to remove the nerve to avoid risks. But installing crowns is not an indication for depulpation.

When preparing for a crown or bridge made of metal ceramics, the following types of anesthesia are used:

application: a solution with an anesthetic is sprayed or lubricated on the gums - this drug is needed so that the administration of basic anesthesia is painless;
infiltration - the injection is administered into the projection of the root apex;
conductive - an injection is placed in the trunk of the nerve, after which the entire jaw, tongue, cheeks, lips go numb.

The turning procedure is carried out under anesthesia.
In 80% of cases, infiltration anesthesia is used - as a rule, this is enough so that the patient does not feel pain. If not, install a conductor one. And the application is just auxiliary, preliminary.

The most commonly used anesthetic drugs are Ultracain and Ubistezin. Less commonly - lidocaine, Artican, Xylocytin.

Also, when grinding a non-pulp tooth, electroodontodiagnosis (EDD) is performed: before grinding, 3 days after and shortly before installation of the prosthesis. Diagnostics will reveal possible damage to the pulp during preparation. And after the procedure, pads made of disinfectants and anti-inflammatory agents are placed under the temporary crowns.

Contraindications

This prosthetic method cannot be used for:

periodontal disease;
bruxism (in this case, it is important to first correct the condition or cure the disease, otherwise the structure may damage the teeth that come into contact with the crown when the jaws close);
malocclusion;
allergic reactions to metals and alloys;
shortened crown parts of teeth;
periodontitis is a temporary contraindication that requires preliminary treatment of the disease.

Taking impressions

Since a stamped crown is a budget prosthesis, and the technology for its manufacture does not imply high accuracy, the impression does not have to be accurate.

In the USSR, the most popular impression material was gypsum. Now, out of humanity towards patients, impressions are often taken with alginate.

As usual, 2 impressions are taken: a working one - of the jaw where the crown will be. And auxiliary - jaws with antagonist teeth.

Stages of metal-ceramic prosthetics

The process of dental prosthetics with metal-ceramics can be divided into two large stages: preparation and prosthetics itself. An initial consultation with an orthopedic dentist allows you to determine the scope of work to be done, assess the condition of the oral cavity, and discuss options for restoring the shape and function of the tooth. According to the drawn up treatment plan, the patient is sent for diagnostics.

Preparing teeth for metal-ceramic prosthetics consists of the following:

Performing X-ray diagnostics. It allows you to determine the absence of inflammatory changes in the periodontal tissues and evaluate the quality of filling if endodontic treatment was previously carried out (the pulp was removed and the root canals were sealed). If the canals are sealed poorly - not completely or, conversely, with the filling material extending beyond the apex of the root, the doctor will unseal them and carry out repeated treatment.

Professional teeth cleaning and caries treatment, replacing old fillings, if necessary.
Depulpation - removal of a nerve. If the damaged tooth has not been depulped previously, the doctor performs this procedure in the following cases:
the need for prosthetic replacement of a single-rooted tooth - the pulp must be removed.

If prosthetics of a multi-rooted chewing tooth is required, the pulp can be left intact - but the final decision on this is made by the dentist, taking into account the individual characteristics of the condition of the oral cavity and the structure of the dental system.

In order to determine how dental prosthetics are done with metal-ceramics, it is necessary to take into account the degree of tooth destruction. Thus, a stump inlay for a metal-ceramic crown is made in cases where the tooth’s own crown is destroyed by more than half - at the root, or if only thin walls remain.

And if a larger volume of tissue is preserved, a pin can be used - it is screwed into the root canal, and an artificial crown is installed on it.

The actual stages of dental prosthetics with metal-ceramics are as follows:

Tooth preparation - grinding. The question of whether teeth are anesthetized during metal-ceramic prosthetics, as a rule, is not raised - of course, the specialist performs preliminary anesthesia to eliminate the patient’s discomfort during the procedure.

The doctor grinds the teeth and then takes impressions - this is necessary for the further production of artificial structures according to individual parameters. Turning is carried out in one of two ways:

with a ledge - the orthopedic dentist forms a circular ledge along the lower edge, which protects the gums from contact with the metal frame and reduces the likelihood of possible complications - swelling, irritation from contact of tissues with metal. This method also allows the use of metal ceramics with shoulder mass - it is applied in the area of the ledge to increase the aesthetics of the structure, and makes it possible to hide a strip of metal that can be visible through the ceramics at the base of the structure. Turning with a shoulder also makes it possible to extend the life of the structure;
without a ledge - this method is outdated, so it is rarely used today. It has significant disadvantages - it does not provide enough space for a crown and can disrupt the contours of the gums. A space is formed between the structure and the gum tissue, in which dental plaque accumulates, and the edge of the denture looks quite unaesthetic. The design may cause irritation to soft tissues.

When contacting the clinic, find out how dental prosthetics are done with metal-ceramics - using the first or second method. This will avoid possible troubles with further wearing of the structure.

Making an impression. Using impression material, the doctor takes impressions of the ground teeth. In order to accurately reproduce the parameters of the teeth, the gums are shifted using rings or retraction threads.
Installation of a temporary crown. Due to the fact that the production of a permanent structure takes a certain time - about 1-2 weeks, the doctor installs a temporary crown made of plastic. This is necessary to protect the tooth core from food and saliva, as well as to ensure aesthetics. While the patient wears a temporary crown, a metal frame is made in the dental laboratory, onto which ceramic mass is subsequently applied layer by layer.
After the permanent crown is made, it is installed using temporary cement after preliminary fitting of the structure. If it does not cause discomfort, the doctor will fix the crown using other, permanent materials.

Why is tooth preparation necessary?

Wearing down of enamel and dentin before metal-ceramic prosthetics is inevitable, here is an article about metal-ceramic dental bridges. Without the procedure, it is impossible to restore a tooth because:

there will be no room for the crown - you need to free up a few millimeters, otherwise the structure will be out of line;
it is unrealistic to make a prosthesis according to the natural shape of the teeth - by nature they are uneven, with many tubercles, dimples and gaps that cannot be repeated;
It is impossible to securely fasten the structure to an unprepared unit - it will not be fixed tightly and will quickly fall out.

Preparation for metal-ceramic crowns is the main disadvantage of prosthetics. But this is a necessary “evil”. But orthopedic structures extend the life of teeth by at least 7-10 years.

How is a crown made?

Many patients wonder how long it takes to have metal-ceramic dental prosthetics. It is important to understand here that the procedures for preparing the teeth and the installation itself are carried out quite quickly, but the manufacture of the structure takes longer. As a rule, 1-2 weeks are enough to make a metal-ceramic crown. Based on the casts created, specialists make a plaster model - it is cast according to the impression after a preliminary assessment of its quality.

Then a dental laboratory specialist models a framework for metal-ceramics using wax. The finished frame is fixed on a plaster model and sent to an orthopedic doctor so that he can try it on in the patient’s mouth.

Then ceramic mass is applied to the frame. Before this is done, it is fired in a kiln and sandblasted - this allows for better adhesion of the metal and the ceramic mass.

The opaque is applied first - this is an opaque composition, then the structure is covered with a dentin layer (more transparent), and then with an enamel layer. This technology makes it possible to recreate the natural appearance of a tooth, taking into account the individual characteristics of the color of the enamel of your own teeth.

After the patient has tried on the design, glazing and final firing are carried out - then the crown is installed.

How much will the turning cost?

The cost of dental preparation differs depending on the economic policy of the clinic.
But in most situations, no one highlights it as a separate service - it is simply included in the overall price of prosthetics. That is, for example, if installing a ceramic crown costs 20 thousand rubles, this implies that the price also includes preparation. But sometimes you will have to pay an additional 500 to 2000 rubles for a temporary crown, which is placed on a ground tooth to protect it. Not all clinics operate on an all-inclusive basis, so you definitely need to clarify what exactly is included in the price of prosthetics. Belenchikov A. A., Biragova A. K., Epkhiev A. A. Assessment of changes in the microstructure of hard dental tissues after preparation with various types of burs. Journal of health and education in the 21st century, 2021. [ii] Vedernikova L. V., Zholudev S. E. Planning the aesthetics of ceramic veneers without preliminary tooth preparation, 2013.

Features of caring for metal ceramics

Everyday hygiene measures do not differ from normal procedures - it is important to brush your teeth twice a day, and also rinse your mouth, if possible, after eating.

Cleaning the teeth should be carried out as follows: using sweeping movements, you need to go over all the teeth in the direction from the gums to the cutting edge. You should not ignore the use of dental floss, or better yet, an irrigator.

You can clean metal ceramics in the same way as regular teeth - a toothbrush should be purchased in accordance with the doctor’s recommendations (the degree of stiffness of the bristles is determined by individual characteristics), the toothpaste can also be selected based on your needs.

Remember that it is better to protect metal-ceramic structures from mechanical damage. It is not recommended to bite into hard foods - this can result in cracks and chips, and subsequent breakage of the prosthesis.

Making a die from low-melting metal

To make a metal stamp from a plaster stamp, use a special metal frame. The blanks are immersed in water for 5-10 minutes to prevent them from sticking to the plaster mold. Then the plaster is mixed, poured into the mold and smoothed with a spatula. The plaster stamp is half immersed in plaster and waits for it to harden. After this, the mold is removed from the frame, 2 recesses are made (to accommodate the protrusions of the other half of the mold) and lowered into cold water (to prevent sticking). This structure is then filled with plaster again to form the second part of the mold.

After hardening, the mold is opened (with a hammer), the plaster stamps are removed, the 2 parts of the mold are connected and secured in a special retainer. Low-melting metal is melted (there is a spoon with a spout) over an alcohol lamp and poured into a plaster mold, into specially pre-made holes. In total, you need to cast 2 dies for each tooth. One is for preliminary stamping, the second is for final stamping.

Making a metal stamp

Warranty for metal ceramics

A good dental clinic provides a guarantee for metal-ceramic dentures - its period, as a rule, is less than the service life of the structure. If the prosthesis breaks before the warranty period expires, the clinic provides restoration or replacement services free of charge.

Restoration is carried out in case of mechanical damage to the crown - for example, chips. In this case, the prosthodontist assesses the extent of the problem and determines whether the framework of the structure is exposed. Restoration of a small chip that does not expose metal is carried out using composite materials. However, restoration when the frame is exposed may be impossible; the optimal solution here would be to remove the structure and re-prosthetics. In order to prevent unpleasant situations (chipping, crown loss), it is important to promptly replace metal-ceramics after their service life has expired.

It is important to make a choice regarding the type of metal-ceramic structure, taking into account how long you plan to wear the structure. Of course, the best can be considered to be made from a gold-platinum alloy; its service life reaches 15 years, and zirconium dioxide crowns can last even longer with proper care. However, the cost of such solutions will vary.

What preparation is needed before turning?

In order to secure the future prosthesis well, the prepared crown must be strong, free of plaque and stone, and free of carious lesions (if any, the doctor will, of course, remove them first). Also, before treating the enamel under any prosthesis, it is important to remove soft and hard plaque.

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Comparison with classic pins

Standard pins - pros:

gentle tissue preparation;
the ability to conduct therapy in one session;
low price.

Minuses:

the coronal and intraradicular segments of the restoration may become separated because there is no chemical bond between them;
in the case of active rods, there is a risk of a wedging effect during the screwing process;
the absence of a base in the structure leads to a sharp increase in the propping load on the root during operation;

Pros:

the stump and the pin are cast from identical material and connected, which 100% eliminates the possibility of their separation;
slight wedging effect during cementation of the stump inlay;
minimizing disjoining pressure, since the chewing load is transferred to the walls of the root, along its axis, to the rod.

Stump pin inlays can be used when the destruction index of the occlusal surface of a unit is more than 60-100% (standard pins - 50-60%). They are durable and guarantee the reliability of the structure.

Our dentistry offers installation of several types of core microprostheses

serve within 5-25 years;
reliability of fixation;
excellent strength;
simplification of subsequent fastening of bridges;
the ability to work with any degree of destruction, restoration of bite;
lack of access for pathogens. No inflammatory processes;
simple replacement of the prosthesis if necessary.

Selection of a blank sleeve

Standard steel sleeves are used for stamping. They are produced by the manufacturer in various diameters. All that remains is to choose the appropriate technique. If suddenly a suitable sleeve is not found, you can reduce the sleeve to a larger diameter.

To reduce shell casings, two types of devices are used: the Sharp apparatus and the Samson apparatus. The mechanism of operation of these devices is as follows: There is a matrix with holes of a given diameter and metal pins (Punches). The gap between them is 0.3 mm, just the thickness of the metal. When the handle is twisted, the pin lowers and enters the hole, and the sleeve is pulled out along the diameter of the specified hole. A correctly selected sleeve is difficult to fit onto the die.

During machining, the liner loses its plasticity. Therefore, it needs to be periodically calcined (annealed); without this, the sleeve is difficult to process.

Before stamping, the sleeve is subjected to free forging. In this case, the sleeve is given the orienting shape of the future tooth using a hammer on the anvil. The sleeve is annealed.

Preliminary stamping (Carried out on a special lead plate. Before stamping, a small recess is made on it, using the first stamp, for the occlusal surface of the tooth. The stamp is hammered into the lead plate with a hammer): the sleeve is put on the first stamp and hammered into this stamp in the indicated recess, so that the contours of the chewing surface are imprinted on the sleeve. Forging continues, striking from the chewing surface to the equator. Once the chewing surface is completely finished, the sleeve is removed from the die and annealed again.

Advantages of stump inlays

Compared to other post systems, the stump post is much stronger. It distributes the load more evenly and fits tightly to dental remains, which prevents the formation of cracks and the development of caries.

Other advantages include the possibility

regenerate destroyed/lost units;
support natural teeth with bulk fillings;
remove increased enamel abrasion;
restore anatomical form/functionality;
align curvature, maintain aesthetics;
make prosthetics on implants.