| crown of tooth | The portion of a tooth covered with enamel. Synonym: corona dentis, anatomical crown. (05 Mar 2000) |
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| crown of Venus | Papular lesions of secondary syphilis on the forehead near the hair margin. See: collar of Venus. (05 Mar 2000) |
| crown-rump length | In utero measurement corresponding to the sitting height (crown to rump) of the foetus. Length is considered a more accurate criterion of the age of the foetus than is the weight. The average crown-rump length of the foetus at term is 36 cm. (12 Dec 1998) |
| crown tubercle | Tubercle of cuneate nucleus, the bulbous rostral extremity of the fasciculus cuneatus corresponding to the position of the cunate nucleus, lying lateral to the clava and separated from the tuberculum cinereum on its lateral side by the posterior lateral sulcus. Synonym: tuberculum nuclei cuneati, tuberculum cuneatum, wedge-shaped tubercle. (05 Mar 2000) |
| tooth crown | The upper part of the tooth, which joins the lower part of the tooth (tooth root) at the cervix (tooth cervix) at a line called the cementoenamel junction. The entire surface of the crown is covered with enamel which is thicker at the extremity and becomes progressively thinner toward the cervix. (12 Dec 1998) |
| activated resin | Autopolymerizing resin, any resin that can be polymerised by chemical catalysis rather than by the application of heat; used in dentistry for dental restoration, denture repair, and impression trays. Synonym: activated resin, cold cure resin, cold-curing resin, quick cure resin, self-curing resin. (05 Mar 2000) |
| anion exchange resin | <chemistry> A resin with fixed cationic groups which is used in chromatography to separate anionic molecules. A High molecular weight, insoluble polymers that contain functional anionic groups capable of undergoing exchange reactions. These resins are used for ion exchange chromatography, as gastric antacids, hypocholesteraemics, etc. (14 Aug 2000) |
| autopolymer resin | Autopolymerizing resin, any resin that can be polymerised by chemical catalysis rather than by the application of heat; used in dentistry for dental restoration, denture repair, and impression trays. Synonym: activated resin, cold cure resin, cold-curing resin, quick cure resin, self-curing resin. (05 Mar 2000) |
| cation-exchange resin | See: cation exchange, cation exchanger. (05 Mar 2000) |
| cation exhange resin | <chemistry> An insoluble resin with fixed anionic groups which is used in chromatography to separate cationic molecules. (16 Mar 1998) |
| resin | Any one of a class of yellowish brown solid inflammable substances, of vegetable origin, which are nonconductors of electricity, have a vitreous fracture, and are soluble in ether, alcohol, and essential oils, but not in water; specif, pine resin. Resins exude from trees in combination with essential oils, gums, etc, and in a liquid or semiliquid state. They are composed of carbon, hydrogen, and oxygen, and are supposed to be formed by the oxidation of the essential oils. Copal, mastic, quaiacum, and colophony or pine resin, are some of them. When mixed with gum, they form the gum resins, like asafetida and gamboge; mixed with essential oils, they frorm balsams, or oleoresins. <chemical> Highgate resin, a fossil resin resembling copal, occuring in blue clay at Highgate, near London. <botany> Resin bush, a low composite shrub (Euryops speciosissimus) of South Africa, having smooth pinnately parted leaves and abounding in resin. Origin: F. Resine, L. Resina; cf. Gr. Rhtinh. (10 Mar 1998) |
| resin acids | A class of organic compounds derived from various natural plant resins; diterpenes containing a phenanthrene ring system; e.g., abietic acid, pimaric acid, ester gums. Synonym: resinic acids. (05 Mar 2000) |
| resin cement | A monomer or monomer/polymer system used as a dental luting agent; used in cementation of restorations or orthodontic brackets to the teeth. (05 Mar 2000) |
| resin cements | Dental cements composed either of polymethyl methacrylate or dimethacrylate, produced by mixing an acrylic monomer liquid with acrylic polymers and mineral fillers. The cement is insoluble in water and is thus resistant to fluids in the mouth, but is also irritating to the dental pulp. It is used chiefly as a luting agent for fabricated and temporary restorations. (12 Dec 1998) |
| melamine resin | A plastic material mixed with plaster of Paris for casts. Such a cast is lighter and stronger than one made with plaster of Paris alone. Synonym: melamine formaldehyde. (05 Mar 2000) |