Types of crowns for teeth: what are crowns on teeth
Modern fixed dentures based on the reconstruction of hard tissues of teeth by crowns and retail – tabs or veneers. Types of crowns for teeth are currently very diverse, which is associated with the development of new methods of their creation, development of new aesthetic and biologically inert materials. The need for prosthesis defective from the point of view of the functions of enamel and dentin is determined by the doctor the stomatologist-orthopedist. Prosthetics for cosmetic reasons is made at the patient’s request, with explanation, all the positive and negative aspects of this intervention. With the development of the possibilities of implantology, the value and relevance of artificial fixed constructions has increased significantly. In this article, learn what are crowns on teeth and what they are.
What they need
A crown for the tooth is a cap cover that protects its own tissues from external influences, preventing their premature destruction. In some cases, they also improve imperfect appearance own enamel. The indication for the manufacturer is determined by the dental index destruction occlusal (chewing) surface of the tooth. If you saved more than 50% of the surface is sufficient to apply the indirect tab or seal. If the area of destruction is in the range of 60-80%, the patient is shown a crown. In more severe situation you need to make a pin tab. If the method of recovery selected pin stump inlay will be, it is necessary to fix an artificial crown.
Small amount of your own tissue indicates that the seal or located very close to the nerves of the tooth (the pulp), or occupies the entire cavity of the tooth. In the first case, there is a risk of pulpitis, because the filling material is much worse withstands the masticatory load. In the second case the nerve has been removed, and therefore, the tooth loses its main source of power is fragile, weak and brittle.
Preparation for prosthetics
Even pulpless, devoid of nerves and blood vessels the tooth is much better and fizjologiczne any alternatives. The main condition for this is resistance, immobility, lack of inflammatory lesions, full gum and bone holding the root. If at least one of the parameters has pathological changes, the feasibility of manufacturing the fixed products are questionable. Since the production of prostheses is a complex clinical-laboratory interaction, a prosthesis always paid, usually expensive and may have certain warranty period and service. No doctor or technician is not interested in redoing unreliable and therefore of questionable teeth often have to be removed and sometimes replaced by implants. It often happens that only a non-removable prostheses can not do, then are assigned to dental crowns and the types of dentures to choose from.
In preparation for the installation of any prosthetic devices required to carry out a complete reorganization of the mouth. This includes the removal of devitalized teeth, treatment of carious lesions and complicated forms of caries, fillings of wedge-shaped defects, the removal of dental plaque and eliminate inflammation of the gums. In some cases, the podiatrist will not be able to hold a rational prosthesis, to completely restore the broken teeth without the involvement of the orthodontist, however, such interventions are lengthy, time-consuming, and patients often consider them to be unreasonably expensive.
Usually at the first consultation, the podiatrist explains to the patient what are the different types of crowns on teeth, demonstrates the examples. Then determines what types of crowns for teeth are shown in a specific clinical case.
What are the design
- Cast metal;
- Plastic (including the so-called provisory);
This type of crowns many doctors considered obsolete, but remains widespread. For the manufacture of such crowns use a socket, billet stainless steel or gold 900 samples. These crowns differ in that the thickness of the metal minimal and then preparation of the teeth is very gentle, zashlifovyvayutsya of less than a millimeter’s own tissues. Ready stamp of a certain size with a small hammer, literally, to fit the stump of the tooth so that the chewing surface was not created over-bite, and the cervical part were tightly wrapped around the equator of the tooth.
The popularity of steel crowns due to their low cost, ease of manufacture. If you need to replace a missing tooth, made of stamped-soldered bridge. Crowns and artificial teeth are connected by solder, which is almost impossible to control, and so many different impurities in it can lead to the phenomenon of galvanism – the pathological reaction of the mucous of the difference of electric potentials in the saliva. To avoid these complications, it is possible to order the design with a coating of zircon or titanium nitride. This method gives the crown a Golden color and protects from irritation. Unfortunately, this coating is extremely short-lived.
Gold design do not enter into any interaction with the tissues of the human body, however, have several disadvantages. As steel, gold crowns maloestetichny as different from the natural teeth of man. In addition, they are expensive, and the license for operations with precious metals has not every laboratory. Since the metal is soft, such crowns are fairly quickly eaten away and require replacement. In the absence of alternatives, these crowns were very popular, but now much more rational to choose the metal.
Predominantly made such designs from kobylino-chromium alloy (KHS). They represent one or multiple crowns and bridges made simultaneously. The technician models the next tooth or bridge with the help of wax model, and then simulated design cast in metal. This method allows you to more accurately convey the topography of the tooth, however, the thickness of a crown above, and hence the tooth preparation occurs at a greater thickness. The advantage in this case is the strength of the metal in comparison with stamped product. For these crowns is also possible to use spraying.
This type of crowns doctors recommend in exceptional cases, when restoring anterior teeth, the patient is not able to choose a more expensive and high-quality treatment. Plastic cladding can be used both for extruded and cast crowns, however, its adhesion to the metal has a low life span, often can not withstand even minimal exertion, and to a liner to apply, it creates the need soshlifovat a much thicker layer of enamel from the front surface of the tooth.
This option crowns today is a leader in prosthetic dentistry. Metal successfully combines excellent aesthetic quality, high durability, reliability of structures. Bridges made of porcelain fused to metal are made on the basis of cast metal frames, which are later applied opaque ceramic layer, paint that imitates a natural color transitions from the neck to the cutting edge and glaze, transparent mass, recreating the enamel.
With the help of ceramic veneers can recreate the natural color of their own teeth or to change the color of all teeth in the smile line to the desired. The ceramic mass is hypoallergenic, does not react with tissues and fluids in the oral cavity, that is, not have a negative impact on the patient and do not corrode or stain. At the moment metal is the ideal method of prosthetic posterior teeth.
Despite many positive qualities, sintered products have a number of disadvantages. Among them:
- High cost (relative to simple metal). Alas, even the metal itself today can afford not all patients;
- The considerable thickness of the crowns, the need to dissect more of the tooth structure;
- Deepening the edges of the crowns under the gums to cover up the metal shoulder of the crown;
- The need to remove the pulp of live teeth. In fact, to remove the pulp need not always, but for certain indications, given the state of the actual tooth, gums;
- Giving the gums a gray color due to the transmission through the mucosa subgingival part of the metal frame.
In most cases, used as a temporary measure to manufacture more reliable and durable design. Plastic crown made in the lab, can last for several months, for example, in the case that the patient saves money on expensive prosthetics, or are not yet sure which will choose the method of treatment in the future. They are mounted solely on the front group of teeth with a warning that they will not withstand the minimum the load of chewing. Laboratory-made plastic crown can quite realistically simulate the color of the living tissues of the tooth, although the range is not as extensive as those of ceramic crowns.
Provisional crowns are made directly to the doctor, literally in the mouth of a patient. Method is the following:
- The doctor takes impression of the teeth of natural form, to preparation;
- Conducts preparation (grinding) of the tooth under the crown;
- Makes impression for making a model in the laboratory;
- In preliminary impression making a fast-curing plastic and placed on the milled teeth. Thus, the plastic mass fills the space caslifornia tissues of the teeth, taking their original shape;
- The resulting crowns are processed, eliminates sharp edges and unnecessary elements;
- The finished dentures are fixed in the patient’s mouth to the manufacture of permanent construction.
These crowns are in most cases applied to the frontal group of teeth in order to maintain the appearance of the patient. However, such a plastic has a poor palette, is opaque (or matte, without Shine), so from natural teeth to distinguish easily. Another important function – protection of the pulp from the irritating effects if the tooth is vital.
Most aesthetic today are porcelain dentures, absolutely metal free, made from pressed ceramics, the technology is similar to veneers. Unfortunately, in comparison with the ceramics they have only one advantage – the absence of negative influence of the metal frame on the aesthetic. However, this feature allows you to deepen the dissection deep under the gum to «hide» the metal, and means less pressure on the mucosa of the gums, more favorable long-term results.
Crowns made of zirconium dioxide
The latest innovation in prosthetics, which very successfully caught on the dental market – zirconium prosthesis manufactured by CAD/CAM technology, the most accurate and automated. Plaster model of the jaw of the patient is scanned three-dimensional computer image is processed and a project is actually crowns. Zirconia billet machined selected shade of the ready design, which it only remains to try and fix.
Common misconception that zirconium crown – metal free. This is not so. Zirconium – metal, but not typical for metal optical properties. These dentures are made of zirconium dioxide – inorganic compounds, which includes metal and two molecules of oxygen.
For a patient this option is ideal for the number of visits (there are only 2). However, the cost of such work can not afford all patients. Another disadvantage in comparison with ceramics are less realistic optical properties of the material.
Perfect absolutely all the parameters of the work to date is a zirconium frame with ceramic lining. This design is perfect for any group of teeth and the support will last long and effectively. Thus, the types of metal-ceramic crowns can be distinguished on the basis of the material from which made the frame.
The combination of different crowns
If the comprehensive oral prosthetics, it is important to note that all products in the oral cavity, made of metal (except Zirconia), can create electric potential difference, causing irritation of mucous membranes. This pathology is called galvanos. To avoid it, you either have to use solely bioinert materials, or to produce prostheses, all strictly of one kind, remembering also that amalgam fillings (which are now rare) must be replaced also.
The choice of design
It is important to remember that dental crowns, which are many – it is the responsibility of the doctor, so that he can properly determine what types of crowns are shown to the patient, and what treatment plan is most suitable. At the end of the prosthesis, the orthopedic surgeon makes a number of recommendations for the care of mouth and dentures, doing that you can count on long life and quality results.