| crown cavity | The space within the crown of a tooth continuous with the root canal. Synonym: cavitas coronalis, cavum coronale. (05 Mar 2000) |
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| crown flask | A sectional metal boxlike case in which a sectional mold is made of plaster of Paris or artificial stone for the purpose of compressing and curing dentures or other resinous restorations. Synonym: crown flask. (05 Mar 2000) |
| crown gall | Gall or tumour, found in many dicotyledonous plants, caused by the bacterium Agrobacterium tumefaciens. (18 Nov 1997) |
| crown gall plasmid | A plasmid, or type of circular DNA, found in the bacteria Agrobacterium tumefaciens which infects dicot plants. Part of the plasmid inserts itself into the plant genome and causes tumours to form in the roots or in the stems nearest the roots. The plasmid has been used by geneticists, minus the tumour-causing parts, as a vector towards the genetic engineering of plants. (09 Oct 1997) |
| crown gall tumour | A disease which afflicts dicot plants, caused by the bacteria Agrobacterium tumefaciens. The disease causes large tumours to form in the roots or in the stems nearest the roots, deforming the plant along its base (where it meets the ground). (09 Oct 1997) |
| crown glass | A compound of lime, potash, alumina, and silica; commonly used in lenses; has a low dispersion (52.2) relative to index of refraction (1.523). (05 Mar 2000) |
| crown-heel length | Length of an outstretched embryo or foetus from skull vertex to heel. See: Streeter's developmental horizon(s). (05 Mar 2000) |
| crown inclination | <dentistry> A tooth movement in which the root of the tooth is tipped toward cheeks (lips) or toward the lingual (palate) of the mouth. (08 Jan 1998) |
| crown lengthening | Technique combining controlled eruptive tooth movement and incision of the supracrestal gingival attachment to allow for proper restoration of a destroyed or damaged crown of a tooth. Controlled eruption of the tooth is obtained using orthodontic appliances. During this eruptive phase, repeated incisions are made at the junctional epithelium of the sulcus and the supracrestal connective tissue to prevent coronal displacement of the gingiva and of the attachment apparatus. (12 Dec 1998) |
| crown of head | The topmost part of the head. Synonym: crown of head. (05 Mar 2000) |
| crown of tooth | The portion of a tooth covered with enamel. Synonym: corona dentis, anatomical crown. (05 Mar 2000) |
| 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) |