Dental crown is a fixed prosthesis which is used in more than 50% of teeth destruction cases to return the tooth functional load and aesthetic view. In other words it is the prosthesis which imitates real tooth.
Dental crowns: types and characteristics
Dental crowns could be divided by different types and characteristics:
- temporary and permanent
- by production type: stamping, casting, pressing
- by material: metal, plastic, composite, porcelain, zirconia crowns, combined
- by fixation: dental cement, dental pin screwing, crown post
- by abutment elements: single, bridge-like protethis or part of telescopic crown
- by production method: direct/clinical (is made directly in the patient’s mouth) and indirect (is made by technologist in laboratory).
Dental crown production stages
Dental crown production process is almost similar everywhere and consists of two main stages: clinical and laboratory.
Clinical stage: depending on the dental crown type dentist removes from 1 to 3 mm of tooth tissue by filing. If the tooth is already dead or its canals must be treated (depulpation is needed) than dental pin screwing must be applied to insure strength and security for the future construction. Dental pins can be standard: made of titanium, fiberglass, steel, carbon or cast: made of steel, titanium, silver, gold and combined. As well as milling pins: zirconic or iron.
Historically gypsum impression taking was thе most secure method due to the fact that it has not been shrinked. But it was not very comfortable. The real breakthrough in dentistry was an invention of silicons and polyvinylsiloxanes in the 19-20 centuries. But they had a shrinkage that had a very bad impact on the final result.
Laboratory stage: after receiving a dental impression the dental laboratory technician starts to make a master cast and auxiliary cast. Once the gypsum has hardened, the next step is to model the future tooth from wax under a solid crown or under a cap for applying ceramic, plastic or composite.
Then the work is transferred to the foundry laboratory, where the founder solders sprue to the wax and casts the prosthesis from metal.
Afterwards the dental technician cuts the sprue, adapts the prosthesis to a plaster model and passes it to the clinic for fitting. If the patient and the doctor are satisfied with the fitting, the prosthesis is returned to the laboratory for grinding and polishing, if it is a metal prosthesis and for applying ceramic / plastic / composite, if it is a combined prosthesis and then again to the doctor.
The medical stage is the fixation of the finished crown on the tooth.
So let's try to look at the types of the dental crowns and choose the best variant.
Single-piece dental crown
Single-piece implant is modeled from wax, casted from metal and polished. It can also be coated with damask steel or made of gold.
Advantages: affordable price (20-40 EUR), durability.
Disadvantages: low level of aesthetics.
Conclusion: economy crown, which may perform its function well.
Notes: most often are used on the last upper masticatory teeth because these teeth are not so visible as others. Do not use these crowns if the antagonistic crowns are ceramic or metal-ceramic this leads to chipping of the ceramic.
Temporary dental crown
Most often are made of plastic for a short time while the dental technician makes a permanent crown.
Advantages: optimal level of aesthetics and costs (20-30 EUR)
Disadvantages: fragility, porosity and the presence of residual monomer, which destroys the gums and, in some cases, causes allergies.So technically the powder (polymer) and liquid (monomer) are mixed and polymerized to the final result. However, the residual monomer (solvent) still remains.The need to fit the structure in the patient's mouth (due to the peculiarities of the crown). Often it is problematic to reach a perfect result using this type of crown. Prolonged use of such dental crowns can cause inflammation of the gums (gingivitis or periodontitis) due to residual monomer.
But there are alternative variants. At our clinic temporary crowns are milled and / or printed from special composite of PMMA (Poly(methyl methacrylate)) thermoplastic, synthetic material or PEEK (Polyether ether ketone) a biocompatible and wear-resistant material, strong as A human bone.
Advantages: accuracy and time control in manufacturing due to the digital technologies, strength due to the composition of the material. The absence of residual monomer and the absence of allergic reactions. The inert material is resistant to oxidation and has low weight. And what is most important these materials are chemically and biologically inert, which allows them to be disposed of without danger to the environment.
Disadvantages: are used as a temporary construction.
Notes: temporary dental crown is recommended to be used as a tooth substitute for a short period. Please pay attention to the ways of its manufacturing to avoid any problems with gums and allergy reactions. The price for such dental service is about 30 EUR.
Combined dental crowns
These crown are made of metal plastic, metal composite, metal ceramics. The principle and purpose of these crowns are almost the same. The purpose is to satisfy the aesthetic need of the patient. It is, in a manner of speaking, a compromise between aesthetics and strength.The manufacturing principle is as follows: the tooth is prepared, the mold is removed from it and transferred to the laboratory equipment. The technician casts a collapsible model and models a cap from wax, which is later replaced by metal. Then the metal is processed and covered by plastic (please read below about the disadvantages) or composite material (it is short-lived) or ceramics, which is sintered afterwards.
Advantages: aesthetics, relative strength (refers to cermets, approximately 50-70 MPa). It has a relatively low cost of 50 to 250 euros, depending on the qualifications of the technician and the ceramic mass.
Disadvantages: it is dissected too much tissue. As a result, the tooth needs to be depulped (the nerve will be removed) and pinned for this type of crown.
Subsequently, it could be detected the presence of cyanotic gums caused by the entering of the gum crown into the gum. This leads to the recession of the gums (lowering of the gums). So when using such a type of the crown, there should be a normal clinical height of your tooth and there should be no deep bite. Due to the multi-stage performance of the work there is no accuracy and there are probable errors at each stage.
Conclusion: this crown is durable and can last 5-8 years, but in terms of aesthetics it loses to metal-free crowns. And in 2-4 years there may appear cyanosis of the gums around the crown.
Notes: it is important to pay attention to the material from which your other crowns were made of (if you already have them) to avoid oxidation and galvanization.
Metal-free ceramic crowns
These are crowns Е.мах (lithium disilicate). They are made of zirconium oxide, zirconium oxide covered with ceramics, feldspar ceramics.
Feldspar crown (ceramics)
This material is well known on the dental market. It is usually milled on special equipment for about 30 minutes, then cemented to the tooth. This is exactly the type of crown that is used on the front group of teeth to achieve the aesthetic needs of the patient.
Disadvantages: costs 150-250 EUR, it is impossible to implement it in bridge construction.
Advantages: has a high aesthetic result, serves more than 8 years. There is no need to bake it in a special oven. It has a wide range of colors,high biocompatibility and excellent translucency (chameleon effect), the refraction of light corresponds to your teeth. You do not need to depulp the tooth.
Conclusion: perfect as a replacement for a cermet crown on the front teeth.
Notes: is made only on the special equipment (Milling cutter).
Teeth crowns Е.мах (lithium disilicate).
It is a very durable material and is used to make dental crowns, inlays, overlays, veneers and luminaires. Their strength is approximately 400 MPa.
Disadvantages: high price (250-500 EUR).
Advantages: high aesthetics and durability, almost completely repeats the color and structure of the natural tooth. Minimal tooth preparation, and in some cases can be done without preparation. High biocompatibility and no allergies in patients.
Conclusion: this is exactly the version of crowns that even a dentist will not be able to distinguish from real teeth. The service life is from 10 years.
Notes: the patient can be present during the whole process of selecting the shape and color of the tooth. These crowns are also milled on special equipment and therefore have high accuracy.
Crowns made of zirconium oxide
This is a great alternative to cermets. It is possible to make both all-anatomical crowns, and a cap under drawing ceramics.
Disadvantages: costs 150-400 EUR.
Advantages: strength 600-1400 MPa. Aesthetics (due to a wide range of shades). The possibility of making bridges, no allergic reactions, biocompatibility, no need to depulp the tooth. The service life is from 10 years.
Basic requirements for the dental crowns
After reading the brief characteristics of crowns, we can conclude that the basic requirements for dental crowns are as follows:
- high strength
- biocompatibility with periodontal tissues (gums, tooth tissues)
- service life and warranty (as well as production time)
Which dental crown to choose?
Returning to the choice of crown (cermets or ceramics?), The manufacture of cermet crowns is:
- the cost of depulping the tooth
- the cost of making the pin
- the cost of the crown itself
for the same money you can install a ceramic (metal-free) crown, which will:
- maintain tooth viability
- get an aesthetically correct solution (no cyanotic gums)
- get a higher structural strength (approx. 10-20 times)
- avoid allergic reactions in the future.
Our digital laboratory uses CEREC equipment, which allows us to create a ceramic crown as quickly and accurately as possible. Usually it could be made in one visit.
We give a 3 years guarantee for all ceramic crowns (zirconium dioxide, E.MAX, feldspar). This proposal is valid only by following all the doctor recommendations. If you have any questions please contact us.