Ceramics and its derivatives are a group of materials frequently used in dentistry. These materials, which are called dental ceramics, are generally known as “porcelain” among the people. In this group, which includes a wide range of products, the main ones are silicate ceramics, namely porcelain, zirconium oxide and aluminum oxide ceramics. These materials are used in many dentistry applications, from veneer crown production, which is known as “coating” among the people, to the production of dental implants. The purpose of this article is to enlighten patients by giving information about dental porcelain.
Ceramic It is an inorganic compound formed as a result of processing and sintering one or more metals at high temperature by combining with non-metallic elements. Today, this definition includes pottery, brick and porcelain It includes a wider material group than the classical ceramic definition, which includes The word originates from the ancient Greek word meaning “burnt/burnt matter”. keramikos It comes from. The ceramic group includes oxides, nitrites, borides, carbides, silicates and sulfides. Pottery is the dough obtained from clay soil by baking at a temperature of several hundred °C. Chronologically, the next stage is porcelain, which started to be developed in China after the 7th century. Traditionally, porcelain is made by firing two types of clay, Chinese clay (kaolin) and Chinese stone, at a temperature above 1300°C. Unlike pottery, it is vitrified (glassy) and transparent. Examples of the most well-known types of porcelain are decorative Chinese work, dental crowns, and electrical insulators. The main raw materials of porcelain are clay, feldspar or flint and silicate, all used in small particle size. Etymologically medieval Italian porcellaIt comes from. porcella expressed the white-shiny folds of mother-of-pearl on the inner surface of the oyster shell. These folds are reminiscent of the back lines of small pigs and porcella It originally means “little pig” in Latin. Porcelains are physically fluorescent, translucent and opalescent ceramics. In other words, within the group of ceramics, which emit visible light under ultraviolet; transparent; Materials that give blue color under reflected light and orange-yellow color under transmitted light are called porcelain.
Quartz, kaolin and feldspar are the three main components of porcelain. There is no feldspar in pottery, there is less feldspar in the mixture in glazed porcelain, and the rate of feldspar is higher in hygiene products.
In dentistry, ceramics and porcelains are used as prefabricated teeth in inlay, onlay type restorations, crown and bridge works (fixed restorations) and full dentures.
In terms of content, the majority of dental porcelain systems are called feldspathic porcelain because they contain feldspar (German feld: earth, spar: rock). In terms of composition, dental porcelains contain more feldspar and very little kaolin and quartz. In addition, there are also “leucite porcelains” enriched with leucite – K[AlSi2O6] – which is a kind of feldspar. On the contrary, there are leucite-free porcelain systems in order to keep the firing degrees low. There are also porcelains that contain flourapatite (Pearlceram) instead of feldspar. Recently, self-healing hydrothermal porcelains have been introduced to the market. Hydrothermal porcelains use the function of self-repairing of micro-fractures formed in the porcelain by using the molecular displacement feature of glasses, which are liquids with very slow flow.
Both porcelain and ceramics are used in dentistry. Dental porcelains belong to the group of “silicate ceramics”. They are distinguished from other ceramics by their optical properties. These optical properties transform this light into different wavelengths under the reflected light, reflecting the incoming beam back and giving a bluish image, that is, functioning as a kind of light source (fluorescence); They reflect some of it under direct light and absorb some of it (translucency), giving an image in yellow-orange tones (opalessens).
Dental porcelains are classified as low temperature porcelain between 900-1200˚C, medium temperature porcelain between 1200-1300˚C and high temperature porcelain over 1300˚C by ADA (American Dental Association) according to their firing temperature. Low-temperature porcelain is used in metal-ceramic or alumina, zirconia-ceramic works, and high-temperature porcelain is used in prefabricated teeth used in full dentures.
There are different carrier systems on which dental porcelains are supported. These are mica (Dicor), platinum foil, gold foil (Sunrize), electrophoretic gold (Galvano), non-precious metal alloys (CrCoNi), precious alloys (Au-Pl), infiltrated glass ceramics (InCeram), glass ceramics (Empress), polycrystalline ceramics (Spinell, Alumina, Zirconia). When metal ones are used among these carrier systems, metal-ceramic studies are carried out. Others are referred to as metal-free studies or all-ceramic studies.
In all ceramic works, porcelain is studied on the ceramic carrier infrastructure. In other words, the ceramic is covered with porcelain (silicate ceramic). The cores used in the infrastructure can be from mica, glass ceramic, infiltrated glass ceramic or polycrystalline group. Mica is not widely used (only Dicor produces). Glass ceramics and infiltrated glass ceramics are also marketed by certain manufacturers (Inceram, VITA; IPS e.max, IPS Empress, IVOCLAR). Magnesium oxide (spinell) is also a less consumed aesthetic material. Aluminum oxide (alumina) is used more than spinel (Procera, etc.). The infrastructure material that has been very popular lately is zirconium oxide (zirconia). Due to its hardness, zirconia blocks are shaped by computerized milling machines with CAD/CAM (Computer Aided Design/Computer Aided Manufacturing) technology. Available in systems that work without using CAD/CAM. However, they can be worked without sintering (solidifying) the blocks, and when sintered after milling, 30% shrinkage occurs, which greatly reduces the sensitivity of the bridge or crown to settling. In systems using polycrystalline ceramics, the substructures are covered with porcelain systems whose surface energies and firing degrees are compatible. These coating processes are performed by hand modeling and firing the porcelain or by wax modeling and porcelain injection.
The use of zirconium has come to the fore due to its durability and corrosion resistance. Implant and its components are used as post material, orthodontic brackets, composite material, crown and bridge material. It is seen that there are some conceptual confusions about the favorite material of recent times, and the ceramic obtained from the zirconium mineral and its metal form and metal oxide, although they have very different properties, are perceived as the same material.
When performing crown and bridge studies in dentistry, porcelain is usually applied on metal or polycrystalline infrastructures. Polycrystalline substructures are ceramics, porcelain is also a type of ceramic, silicate ceramic; in other words, ceramic is processed on the ceramic core.
As a result, whether it is all-ceramic or metal-ceramic studies, they give successful results within the correct indications.
