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Luting Agent
A luting agent is an application of a dental cement connecting the underlying tooth structure to a fixed Dental prosthesis, prosthesis. To Lute (material), lute means to glue two different structures together. There are two major purposes of luting agents in dentistry – to secure a cast restoration in fixed prosthodontics (e.g. for use of retaining of an Inlays and onlays, inlay, Crown (dentistry), crowns, or Bridge (dentistry), bridges), and to keep orthodontic bands and appliances ''in situ''. In a complex restoration procedure, the selection of an appropriate luting agent is crucial to its long-term success. In addition to preventing the fixed prosthesis from dislodging, it is also a seal, preventing bacteria from penetrating the tooth-restoration interface. Zinc phosphate is the oldest material available and has been used in dentistry for more than a century. The introduction of adhesive resin systems made a wide range of dental materials available as luting agents. The choic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fluoride
Fluoride (). According to this source, is a possible pronunciation in British English. is an inorganic, monatomic anion of fluorine, with the chemical formula (also written ), whose salts are typically white or colorless. Fluoride salts typically have distinctive bitter tastes, and are odorless. Its salts and minerals are important chemical reagents and industrial chemicals, mainly used in the production of hydrogen fluoride for fluorocarbons. Fluoride is classified as a weak base since it only partially associates in solution, but concentrated fluoride is corrosive and can attack the skin. Fluoride is the simplest fluorine anion. In terms of charge and size, the fluoride ion resembles the hydroxide ion. Fluoride ions occur on Earth in several minerals, particularly fluorite, but are present only in trace quantities in bodies of water in nature. Nomenclature Fluorides include compounds that contain ionic fluoride and those in which fluoride does not dissociate. The nom ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Catalysis
Catalysis () is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recycles quickly, very small amounts of catalyst often suffice; mixing, surface area, and temperature are important factors in reaction rate. Catalysts generally react with one or more reactants to form intermediates that subsequently give the final reaction product, in the process of regenerating the catalyst. Catalysis may be classified as either homogeneous, whose components are dispersed in the same phase (usually gaseous or liquid) as the reactant, or heterogeneous, whose components are not in the same phase. Enzymes and other biocatalysts are often considered as a third category. Catalysis is ubiquitous in chemical industry of all kinds. Estimates are that 90% of all commercially produced chemical products involve catalysts at some s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Attenuation
In physics, attenuation (in some contexts, extinction) is the gradual loss of flux intensity through a medium. For instance, dark glasses attenuate sunlight, lead attenuates X-rays, and water and air attenuate both light and sound at variable attenuation rates. Hearing protectors help reduce acoustic flux from flowing into the ears. This phenomenon is called acoustic attenuation and is measured in decibels (dBs). In electrical engineering and telecommunications, attenuation affects the propagation of waves and signals in electrical circuits, in optical fibers, and in air. Electrical attenuators and optical attenuators are commonly manufactured components in this field. Background In many cases, attenuation is an exponential function of the path length through the medium. In optics and in chemical spectroscopy, this is known as the Beer–Lambert law. In engineering, attenuation is usually measured in units of decibels per unit length of medium (dB/cm, dB/km, etc.) and is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Photoinitiator
A photoinitiator is a molecule that creates reactive species (free radicals, cations or anions) when exposed to radiation (UV or visible). Synthetic photoinitiators are key components in photopolymers (for example, photo-curable coatings, adhesives and dental restoratives). Some small molecules in the atmosphere can also act as photoinitiators by decomposing to give free radicals (in photochemical smog). For instance, nitrogen dioxide (NO2) is produced in large quantities by gasoline-burning internal combustion engines. NO2 in the troposphere gives smog its brown coloration and catalyzes production of toxic ground-level ozone (O3). Molecular oxygen (O2) also serves as a photoinitiator in the stratosphere, breaking down into atomic oxygen and combining with O2 in order to form the ozone in the ozone layer. Reactions Photoinitators can create reactive species by different pathways including photodissociation and electron transfer. As an example of dissociation, hydrogen peroxide c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
US Navy 110603-N-AW868-178 Lt
The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territories, nine Minor Outlying Islands, and 326 Indian reservations. The United States is also in free association with three Pacific Island sovereign states: the Federated States of Micronesia, the Marshall Islands, and the Republic of Palau. It is the world's third-largest country by both land and total area. It shares land borders with Canada to its north and with Mexico to its south and has maritime borders with the Bahamas, Cuba, Russia, and other nations. With a population of over 333 million, it is the most populous country in the Americas and the third most populous in the world. The national capital of the United States is Washington, D.C. and its most populous city and principal financial center is New York City. Paleo-Americans ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radiodensity
Radiodensity (or radiopacity) is opacity to the radio wave and X-ray portion of the electromagnetic spectrum: that is, the relative inability of those kinds of electromagnetic radiation to pass through a particular material. Radiolucency or hypodensity indicates greater passage (greater transradiancy) to X-ray photonsNovelline, Robert. ''Squire's Fundamentals of Radiology''. Harvard University Press. 5th edition. 1997. . and is the analogue of transparency and translucency with visible light. Materials that inhibit the passage of electromagnetic radiation are called radiodense or radiopaque, while those that allow radiation to pass more freely are referred to as radiolucent. Radiopaque volumes of material have white appearance on radiographs, compared with the relatively darker appearance of radiolucent volumes. For example, on typical radiographs, bones look white or light gray (radiopaque), whereas muscle and skin look black or dark gray, being mostly invisible (radiolucent). Th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dental Floss
Dental floss is a cord of thin filaments used in interdental cleaning to remove food and dental plaque from between teeth or places a toothbrush has difficulty reaching or is unable to reach. Its regular use as part of oral cleaning is designed to maintain oral health. Use of floss is recommended to prevent gingivitis and the build-up of plaque. The American Dental Association claims that up to 80% of plaque can be removed by flossing, and it may confer a particular benefit in individuals with orthodontic devices. However, empirical scientific evidence demonstrating the clinical benefit of flossing as an adjunct to routine tooth brushing alone remains limited. A Japanese macaque and long-tailed macaques have been observed in the wild and in captivity flossing with human hair and feathers. History Levi Spear Parmly (1790-1859), a dentist from New Orleans, is credited with inventing the first form of dental floss. In 1819, he recommended running a waxen silk thread "through the i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Borosilicate Glass
Borosilicate glass is a type of glass with silica and boron trioxide as the main glass-forming constituents. Borosilicate glasses are known for having very low coefficients of thermal expansion (≈3 × 10−6 K−1 at 20 °C), making them more resistant to thermal shock than any other common glass. Such glass is subjected to less thermal stress and can withstand temperature differentials without fracturing of about . It is commonly used for the construction of reagent bottles and flasks as well as lighting, electronics, and cookware. Borosilicate glass is sold under various trade names, including Borosil, Duran, Pyrex, Glassco, Supertek, Suprax, Simax, Bellco, Marinex (Brazil), BSA 60, BSC 51 (by NIPRO), Heatex, Endural, Schott, Refmex, Kimax, Gemstone Well, and MG (India). Single ended self-starting lamps are insulated with a mica disc and contained in a borosilicate glass gas discharge tube (arc tube) and a metal cap. They include the sodium-vapor lamp tha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aluminosilicate
Aluminosilicate minerals ( IMA symbol: Als) are minerals composed of aluminium, silicon, and oxygen, plus countercations. They are a major component of kaolin and other clay minerals. Andalusite, kyanite, and sillimanite are naturally occurring aluminosilicate minerals that have the composition Al2 Si O5. The triple point of the three polymorphs is located at a temperature of and a pressure of . These three minerals are commonly used as index minerals in metamorphic rocks. Naturally occurring microporous, hydrous aluminosilicate minerals are referred to as zeolites. Feldspar is a common tectosilicate aluminosilicate mineral made of potassium, sodium, and calcium cations surrounded by a negatively charged network of silicon, aluminium and oxygen atoms. The catalyst silica-alumina is an amorphous substance which is not an aluminosilicate compound. Aluminosilicate glasses There exist a wide variety of glass types. The characteristics of these different types depend on t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Silicon Dioxide
Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , most commonly found in nature as quartz and in various living organisms. In many parts of the world, silica is the major constituent of sand. Silica is one of the most complex and most abundant families of materials, existing as a compound of several minerals and as a synthetic product. Notable examples include fused quartz, fumed silica, silica gel, opal and aerogels. It is used in structural materials, microelectronics (as an electrical insulator), and as components in the food and pharmaceutical industries. Structure In the majority of silicates, the silicon atom shows tetrahedral coordination, with four oxygen atoms surrounding a central Si atomsee 3-D Unit Cell. Thus, SiO2 forms 3-dimensional network solids in which each silicon atom is covalently bonded in a tetrahedral manner to 4 oxygen atoms. In contrast, CO2 is a linear molecule. The starkly different structures of the dioxid ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Quartz
Quartz is a hard, crystalline mineral composed of silica (silicon dioxide). The atoms are linked in a continuous framework of SiO4 silicon-oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical formula of SiO2. Quartz is the second most abundant mineral in Earth's continental crust, behind feldspar. Quartz exists in two forms, the normal α-quartz and the high-temperature β-quartz, both of which are chiral. The transformation from α-quartz to β-quartz takes place abruptly at . Since the transformation is accompanied by a significant change in volume, it can easily induce microfracturing of ceramics or rocks passing through this temperature threshold. There are many different varieties of quartz, several of which are classified as gemstones. Since antiquity, varieties of quartz have been the most commonly used minerals in the making of jewelry and hardstone carvings, especially in Eurasia. Quartz is the mineral defining the val ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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