What kind of crowns are there?.. What materials are modern crowns made of?.. Which crowns to choose?.. Here is a far from complete list of questions that torment patients. I will try to give answers to them in the second part of the article on dental crowns.
So, let's go from simple...
1. Metal dental crowns
Here it must be said that metal dental crowns can be made by two completely different methods.
A) Stamped dental crowns
They are made from standard blanks (stainless steel, in more rare cases gold). In our country, they are still used, unfortunately, and are also very fashionable to this day in the countries of Asia closest to us.
If you do not plan to settle in an African-American ghetto or in the Asian countries of the former USSR, then such a smile is unlikely to cause admiring glances from others...
In the whole civilized world, our person can easily be calculated by such "fixes". In fact, the place of this technology has long been in the museums of medical universities and students should not pass it in the cycle of orthopedic dentistry (as it still happens), but exclusively within the framework of such a useful subject as the "history of medicine". Therefore, I will not to dwell on these dental crowns in detail.The technology is the simplest (the technician cuts a metal blank-cylinder to the desired length and, tapping with a hammer, brings it closer in shape to the likeness of a tooth), the cost is cheap.
The complete absence of any aesthetics (although some residents of the aforementioned countries could argue with me in this place);
The edge of the crown hangs between the tooth and the gum, being an excellent help for the accumulation of food reserves for a rainy day, causing chronic inflammation of the gums, circular caries, giving the breath an appropriate aroma;
The inability to make a normal anatomical shape, most often such crowns have an absolutely flat chewing surface, worsening the chewing process and causing problems in the temporomandibular joints;
The thin walls of such crowns often wear out and rub through, leading to the destruction of the tooth under them by caries ...
I think this is quite enough.
In this photo, stamped dental crowns with gold-plated titanium nitride. The coating itself is a carcinogen and is prohibited for use in civilized countries. Here you can clearly see the state of the crowns themselves and the tissues surrounding them after several years of wearing. Oddly enough, a crown that has not fallen out for many years does not yet speak of high-quality treatment. Here you can see what is happening around the crown...
An example of a single stamped dental crown without spraying...
And the whole bridge. Such flat chewing surfaces without pronounced anatomical relief lead to numerous problems that are not always easy to treat later. This is especially true for diseases of the temporomandibular joint.
It would be unfair not to mention at least some positives. If you show miracles of tolerance, then I can hardly squeeze out two - low cost, minimal processing of tooth tissues. Everyone, forget about them.
B) Cast metal dental crowns
This is a more modern version, which is widely used in modern dentistry and has the right to life. The technology for manufacturing a cast dental crown implies the entire standard sequence (this is discussed in the first part of how dental crowns are installed): processing a tooth with a ledge, taking an impression, casting a model, modeling a crown from wax and melting the wax blank into metal. When all steps are properly performed by the dentist and technician, a crown that fits exactly to the tooth and reproduces its anatomical shape well is obtained. It can be made from a conventional alloy (most often CCS - cobalt-chromium alloy) or from a precious alloy, which is certainly better.
Cast metal crowns function at the proper level, durable and reliable. Therefore, if you are not embarrassed by the prospect of putting sunbeams into the eyes of your interlocutor with a smile in clear weather, then it is quite possible to opt for them ...
Extremely low aesthetics, although the side teeth, which are not so noticeable when smiling and communicating (especially the upper ones), can be restored with just such crowns
Possible allergic reactions to metal (especially common alloy)
High wear resistance
Relatively low price
2. Plastic dental crowns
Sometimes in our country, where there are no treatment standards, they are used as permanent crowns. Although all over the world, according to all standards, they can only be used as temporary (wearing period, depending on the manufacturing technology, from several days to several months). Why? Plastic is a fairly soft material that wears out quickly. The surface is unstable to mechanical and chemical influences - it quickly loses its appearance, stains with dyes from food, becomes uneven, contributing to increased accumulation of soft plaque, provoking bad breath. Both bridges and single crowns can easily break due to the brittleness of the plastic. The marginal fit of such crowns to the tooth is quickly broken - accordingly, caries already under the crown easily develops. In general, where do not spit - solid cons. Of the advantages - simplicity and low cost of manufacture, an acceptable appearance (although mostly only at the very beginning of wearing them). These advantages determine their widespread use as temporary restorations.
Plastic dental crowns - white, fast, cheap ... but not for long
3. Metal-plastic dental crowns
Another type of unclaimed modern dentistry technology. It combines, as you might guess, a metal frame and a plastic lining (full or only from the outside). The metal frame can also be stamped or cast. This technology combines all the advantages and disadvantages already mentioned. A special disadvantage is only that the metal has no chemical bond with the plastic, and therefore the adhesion strength is very low. From here, often the plastic lining flies off, leaving bare metal underneath. It can be used in a good way except for the manufacture of temporary crowns for long-term wear (several months).
Metal-plastic stamped dental crowns...
Metal-plastic cast crowns... The absence of a chemical bond between plastic and metal leads to frequent chipping of the veneer
4. Metal-ceramic dental crowns
In fact, if we talk about modern options for prosthetics, then it was possible not to mention all the previous points at all (well, maybe, except for metal cast crowns), but to start with metal ceramics (MK). Because it metal-ceramic dental crowns are currently at the “bottom step” of the evolution of materials for the manufacture of dental crowns.
Acceptable aesthetics (especially when it comes to posterior teeth). Ceramics, with which the technician covers the metal frame of the dental crown, can recreate many shades and nuances. Its color is stable over time. However, the opaque metal frame inside the crown does not allow, most often, to bring the view of the metal-ceramic crown closer to the view of a natural tooth by 100%.
Here, all the front upper teeth were restored with MK crowns. In contrast with the lower ones, everything looks good, but still the lack of "color depth", opacity (especially noticeable in bright light), unnatural fluorescence (in the ultraviolet of a nightclub, the crown will differ from its natural neighbor, and on the front teeth it will be very noticeable) are not allow us to consider them the optimal solution for the restoration of the anterior group of teeth...
High strength - it is very difficult to chip off a ceramic veneer, if the dental crown is made in accordance with all the rules, unlike plastic
Relatively low cost. Now it is the most demanded technology, which has become the standard in cases that do not require high aesthetic solutions.
Insufficient aesthetic possibilities in the prosthetics of the anterior teeth. Especially problematic is the cervical zone, which will almost always look more "dead", opaque compared to a natural tooth. In addition, the metal edge of the dental crown may produce a dark rim around the tooth. To disguise it, the doctor often makes a ledge on the outer (front) side of the tooth just below the gum level. But over time, the gum can change its position in relation to the edge of the crown and it can become noticeable.
After several years of wearing, the metal frame of the crown may appear in the cervical region as a dark stripe. For the front teeth - not the most pleasant prospect ...
Another option to combat this undesirable property of metal-ceramic dental crowns is the use of the so-called. shoulder mass. To do this, the technician removes the metal edge on the front side of the crown by 0.5-1mm and “builds up” it with special ceramics. That. the edge of the crown on the front side is purely ceramic, which improves its aesthetics.
On the left photo, the arrow indicates the so-called. "ceramic shoulder". Masking the metal edge helps improve the aesthetics of metal-ceramic dental crowns. Thus, the hands of a good dental technician have a tool to make the appearance of metal-ceramic crowns as close as possible to that of a natural tooth. And over time, such a crown will not give itself away as a dark strip near the gums.
Allergy to the metal from which the framework of the dental crown is made (most often CCS). The way out is the use of titanium or gold-platinum alloy (ZPS) for casting the frame
Metal-ceramic dental crowns on a gold-platinum alloy frame. In addition to the greater bioinertness of the framework, such crowns, due to the base of golden yellow, and not gray as in the CCS, are more advantageous in aesthetic terms...
5. Metal-free ceramic dental crowns
For simplicity, I have combined several different materials and technologies at the top of the hierarchy into this group at once. Since all of them have the main advantage over others - the absence of metal and high aesthetic properties. There are 2 large groups here.
A) Dental crowns that do not have a framework (i.e. crowns made only of pure ceramic).
The advantage of such crowns is their impeccable aesthetic possibilities. The downside is a rather high fragility. Therefore, their use is very limited - basically this technology can be used only on the front teeth and only in the form of single crowns.
A darkened pulpless incisor (top 2) with a crack in the enamel is the best indication for an all-ceramic frameless crown. The load on the tooth is small, the aesthetics are required high...The result of the work of a high-class dental technician will not allow even a professional to identify a crown among natural teeth at first glance...
B) Crowns based on non-metallic translucent zirconia dental crown framework, lithium disilicate (E.max technology) or alumina.
These types of dental crowns have both significant mechanical strength (i.e., not only single crowns for the front teeth, but also for lateral and even small bridges can be made on these frames) and high aesthetics. In fact, they are devoid of shortcomings, which include only a high price. In addition to everything else frameworks of dental crowns based on zirconium dioxide and aluminum oxide are manufactured on modern precision milling machines controlled by computers.
First, the frame of the future structure made of zirconium dioxide is modeled on a computer using a special program...... then a computer-controlled milling machine grinds the framework of future crowns from the workpiece. Since the computer does not get tired, does not come to work with shaky hands after a stormy weekend, the result of its work is predictably more accurate ... the importance of the human factor in such an important part as the manufacture of a precision crown framework is significantly reduced.
At the output, this technology gives a predictably more accurate fit of the edge of the crown to the ledge on the tooth, compared to a metal-ceramic dental crown, where the framework is made by casting. And this means, on average, a longer service life of such crowns. Another indisputable advantage of metal-free crowns is their absolute biocompatibility. I have never heard of an allergic reaction to zirconia. While allergies to metals, incl. and on precious alloys it is not so rare in practice.
Zirconia frame ready for ceramic veneering...... ready-made crowns on a zirconia framework have all the necessary advantages - reliability, strength, biocompatibility, excellent aesthetics ... a fly in the ointment in this barrel of honey is a high price. The average cost of 1 unit of ceramics on a zirconium frame in St. Petersburg is approximately equal to 1 average salary in our city (20-30 thousand rubles)...
...but if it's done well, the result is worth it...
Now you have a very complete information about dental crowns, which will help you make the right choice together with your doctor. This topic is too extensive to fit the answers to all the most frequently asked questions in 2 parts, so I will definitely return to it in the future and try to highlight specific types of materials and technologies in more detail and clearly. Metal-ceramic and non-metal ceramic dental crowns, which are the most common in modern practice, deserve a separate discussion.
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