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Dental Impression
A dental impression is a negative imprint of hard and soft tissues in the mouth from which a positive reproduction, such as a cast or model, can be formed. It is made by placing an appropriate material in a dental impression tray which is designed to roughly fit over the dental arches. The impression material is liquid or semi-solid when first mixed and placed in the mouth. It then sets to become an elastic solid, which usually takes a few minutes depending upon the material. This leaves an imprint of a person's dentition and surrounding structures of the oral cavity. Digital impressions using CAD/CAM dentistry, computerized scanning are now available. Uses Impressions, and the study models, are used in several areas of dentistry including: * diagnosis and treatment planning * prosthodontics (such as making dentures) * orthodontics * restorative dentistry (e.g. to make impressions of teeth which have been prepared to receive indirect extracoronal restorations such as crowns, b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alginate Impression Body
Alginic acid, also called algin, is a naturally occurring, edible polysaccharide found in brown algae. It is hydrophilic and forms a viscous natural gum, gum when hydrated. When the alginic acid binds with sodium and calcium ions, the resulting salts are known as alginates. Its colour ranges from white to yellowish-brown. It is sold in wikt:filamentous, filamentous, granular, or powdered forms. It is a significant component of the biofilms produced by the bacterium ''Pseudomonas aeruginosa'', a major pathogen found in the lungs of some people who have cystic fibrosis. The biofilm and ''P. aeruginosa'' have a high resistance to antibiotics, but are susceptible to inhibition by macrophages. Alginate was discovered by British chemical scientist E. C. C. Stanford in 1881, and he patented an extraction process for it in the same year. The alginate was extracted, in the original patent, by first soaking the algae in water or diluted acid, then extracting the alginate by soaking it in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Curing (chemistry)
Curing is a chemical process employed in polymer chemistry and process engineering that produces the toughening or hardening of a polymer material by cross-linking of polymer chains. Even if it is strongly associated with the production of thermosetting polymers, the term "curing" can be used for all the processes where a solid product is obtained from a liquid solution, such as with PVC plastisols. Curing process During the curing process, single monomers and oligomers, mixed with or without a curing agent, react to form a tridimensional polymeric network. In the very first part of the reaction Branching (polymer chemistry), branches of molecules with various architectures are formed, and their molecular weight increases in time with the extent of the reaction until the network size is equal to the size of the system. The system has lost its solubility and its viscosity tends to infinite. The remaining molecules start to coexist with the macroscopic network until they react wit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polyethers
In organic chemistry, ethers are a class of compounds that contain an ether group, a single oxygen atom bonded to two separate carbon atoms, each part of an organyl group (e.g., alkyl or aryl). They have the general formula , where R and R′ represent the organyl groups. Ethers can again be classified into two varieties: if the organyl groups are the same on both sides of the oxygen atom, then it is a simple or symmetrical ether, whereas if they are different, the ethers are called mixed or unsymmetrical ethers. A typical example of the first group is the solvent and anaesthetic diethyl ether, commonly referred to simply as "ether" (). Ethers are common in organic chemistry and even more prevalent in biochemistry, as they are common linkages in carbohydrates and lignin. Structure and bonding Ethers feature bent linkages. In dimethyl ether, the bond angle is 111° and C–O distances are 141 pm. The barrier to rotation about the C–O bonds is low. The bonding of oxygen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polysulphide
Polysulfides are a class of chemical compounds derived from anionic chains of sulfur atoms. There are two main classes of polysulfides: inorganic and organic. The inorganic polysulfides have the general formula . These anions are the conjugate bases of polysulfanes . Organic polysulfides generally have the formulae , where R is an alkyl or aryl group. Polysulfide salts and complexes The alkali metal polysulfides arise by treatment of a solution of the sulfide with elemental sulfur, e.g. sodium sulfide to sodium polysulfide: In some cases, these anions have been obtained as organic salts, which are soluble in organic solvents. The energy released in the reaction of sodium and elemental sulfur is the basis of battery technology. The sodium–sulfur battery and the lithium–sulfur battery require high temperatures to maintain liquid polysulfide and -conductive membranes that are unreactive toward sodium, sulfur, and sodium sulfide. Polysulfides are ligands in coordination chemi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Prosthesis
In medicine, a prosthesis (: prostheses; from ), or a prosthetic implant, is an artificial device that replaces a missing body part, which may be lost through physical trauma, disease, or a condition present at birth (Congenital, congenital disorder). Prostheses may restore the normal functions of the missing body part, or may perform a cosmetic function. A person who has undergone an amputation is sometimes referred to as an Amputation, amputee, however, this term may be offensive. Rehabilitation for someone with an amputation is primarily coordinated by a Physical medicine and rehabilitation, physiatrist as part of an inter-disciplinary team consisting of physiatrists, prosthetists, nurses, physical therapists, and occupational therapists. Prostheses can be created by hand or with computer-aided design (CAD), a software interface that helps creators design and analyze the creation with computer-generated Technical drawing, 2-D and 3D computer graphics, 3-D graphics as well as an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Imbibition
Imbibition is a special type of diffusion that takes place when liquid is absorbed by solids-Colloid, colloids causing an increase in volume. Water surface potential movement takes place along a concentration gradient; some dry materials absorb water. A gradient between the absorbent and the liquid is essential for imbibition. For a substance to imbibe a liquid, there must first be some attraction between them. Imbibition occurs when a wetting fluid displaces a non-wetting fluid, the opposite of drainage in which a non-wetting phase displaces the wetting fluid. The two processes are governed by different mechanisms. Imbibition is also a type of diffusion since water movement is along the concentration gradient. Seeds and other such materials have almost no water hence they absorb water easily. Water potential gradient between the absorbent and liquid imbibed is essential for imbibition. Examples One example of Imbibition in nature is the absorption (chemistry), absorption of w ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Syneresis (chemistry)
Syneresis (also spelled 'synæresis' or 'synaeresis'), in chemistry, is the solvent extraction, extraction or expulsion of a liquid from a gel, such as when Serum (blood), serum drains from a contracting clot of blood. Another example of syneresis is the collection of whey on the surface of yogurt. Syneresis can also be observed when the amount of diluent in a swollen polymer exceeds the solubility limit as the temperature changes. A household example of this is the counterintuitive expulsion of water from dry gelatin when the temperature increases. Syneresis has also been proposed as the mechanism of formation for the Silicon dioxide, amorphous silica composing the frustule of diatoms. Examples In the processing of dairy milk, for example during cheese making, syneresis is the formation of the curd due to the sudden removal of the hydrophilic peptides, macropeptides, which causes an imbalance in intermolecular forces. Bonds between hydrophobic sites start to develop and are enfor ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alginic Acid
Alginic acid, also called algin, is a naturally occurring, edible polysaccharide found in brown algae. It is hydrophilic and forms a viscous gum when hydrated. When the alginic acid binds with sodium and calcium ions, the resulting salts are known as alginates. Its colour ranges from white to yellowish-brown. It is sold in filamentous, granular, or powdered forms. It is a significant component of the biofilms produced by the bacterium ''Pseudomonas aeruginosa'', a major pathogen found in the lungs of some people who have cystic fibrosis. The biofilm and ''P. aeruginosa'' have a high resistance to antibiotics, but are susceptible to inhibition by macrophages. Alginate was discovered by British chemical scientist E. C. C. Stanford in 1881, and he patented an extraction process for it in the same year. The alginate was extracted, in the original patent, by first soaking the algae in water or diluted acid, then extracting the alginate by soaking it in sodium carbonate, and finall ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dental Impression Upper Teeth
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Dental may refer to: * Dental consonant, in phonetics * Dental Records, an independent UK record label * Dentistry, oral medicine * Teeth See also * * Dental care (other) * Dentist (other) * Tooth (other) A tooth (: teeth) is a small, calcified, whitish structure found in the jaws (or mouths) of many vertebrates. Tooth or Teeth may also refer to: Music *Teeth (Filipino band), a Filipino rock band *Teeth (electronic band), UK electronic pop punk b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fixed Prosthodontics
Fixed prosthodontics is the branch of prosthodontics that focuses on dental prosthesis, dental prostheses that are permanently affixed (fixed). Crown (dental restoration), Crowns, bridge (dentistry), bridges (fixed dentures), inlays, onlays, and Veneer (dentistry), veneers are some examples of indirect dental restorations. Prosthodontists are dentists who have completed training in this specialty that has been recognized by academic institutes. Fixed prosthodontics can be used to reconstruct single or many teeth, spanning tooth loss areas. The main advantages of fixed prosthodontics over direct restorations are improved strength in big restorations and the possibility to build an aesthetic-looking tooth. The concepts utilised to select the suitable repair, as with any dental restoration, include consideration of the materials to be used, the level of tooth destruction, the orientation and placement of the tooth, and the condition of neighboring teeth. Preparation techniques A la ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Agar
Agar ( or ), or agar-agar, is a jelly-like substance consisting of polysaccharides obtained from the cell walls of some species of red algae, primarily from " ogonori" and " tengusa". As found in nature, agar is a mixture of two components, the linear polysaccharide agarose and a heterogeneous mixture of smaller molecules called agaropectin. It forms the supporting structure in the cell walls of certain species of algae and is released on boiling. These algae are known as agarophytes, belonging to the Rhodophyta (red algae) phylum. The processing of food-grade agar removes the agaropectin, and the commercial product is essentially pure agarose. Agar has been used as an ingredient in desserts throughout Asia and also as a solid substrate to contain culture media for microbiological work. Agar can be used as a laxative; an appetite suppressant; a vegan substitute for gelatin; a thickener for soups; in fruit preserves, ice cream, and other desserts; as a clarifying ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Neutral Zone (dentistry)
In dentistry, the neutral zone refers to that space in the oral cavity where the forces exerted by the musculature of the tongue are equal and balanced with the forces exerted by the buccinator muscle of the cheek laterally and the orbicularis oris muscle anteriorly. In other words, it is the ''potential space'' between the lips and cheeks on one side and the tongue on the other; where the ''forces'' between the two are ''equal''. Other synonyms include: zone of equilibrium, zone of minimal conflict, potential denture space and dead space. It is in this zone that the natural dentition lie, and this is where artificial teeth of complete dentures should be positioned. Complete dentures that are constructed in this way exhibit ''enhanced stability, retention and comfort''. The neutral zone is an important concept in prosthodontics, because prosthetic teeth generally must conform to the horizontal position determined by the neutral zone. Prostheses which set teeth outside this zone ri ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
