| undercut | 1. That portion of a tooth that lies between the survey line (height of contour) and the gingivae. 2. The contour of a cross-section of a residual ridge or dental arch which would prevent the insertion of a denture. 3. The contour of a flasking stone which interlocks in such a way as to prevent the separation of the parts. (05 Mar 2000) |
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| undercut gauge | A device, used with a surveyor, to precisely locate areas for the placement of the retentive components of clasps when designing removable partial dentures. (05 Mar 2000) |
| a-form DNA | <molecular biology> One of several forms that can be assumed by a double helix. A-DNA is stable in dehydrated conditions. This form is less common than the dominant form found under physiological conditions -- beta-DNA. This form is also assumed by DNA-RNA hybrid helices and by regions of double-stranded RNA. It is a right-handed helix and is a more compact form than beta-DNA. (09 Oct 1997) |
| boat form | The less stable of two conformations assumed by 6-membered cyclic sugars (pyranoses) or cyclohexane derivatives, as opposed to chair form. See: Haworth conformational formulas of cyclic sugars. (05 Mar 2000) |
| cavity preparation form | The configuration or shape of a cavity preparation. (05 Mar 2000) |
| replicative form | An intermediate stage in the replication of either DNA or RNA viral genomes that is usually double stranded, the altered, double-stranded form to which single-stranded coliphage DNA is converted after infection of a susceptible bacterium, formation of the complementary ("minus") strand being mediated by enzymes that were present in the bacterium before entrance of the viral ("plus") strand. (05 Mar 2000) |
| resistance form | The shape given to a cavity preparation that enables the dental restoration to withstand masticatory forces. (05 Mar 2000) |
| retention form | The shape of a cavity preparation that prevents displacement of the dental restoration by lateral or tipping forces as well as masticatory forces. (05 Mar 2000) |
| chair form | The more stable of two conformations assumed by 6-membered cyclic sugars (e.g., the pyranoses) or cyclohexane derivatives, as opposed to boat form. See: Haworth conformational formulas of cyclic sugars. (05 Mar 2000) |
| wave form | The form of a pulse; e.g., an arterial pressure or displacement wave; or of the pacemaker pulse as demonstrated on the oscilloscope under a specified load. Synonym: waveshape. (05 Mar 2000) |
| wax form | A pattern of wax that, when invested and burned out or otherwise eliminated, will produce a mold in which a casting may be made. Synonym: wax form. (05 Mar 2000) |
| convenience form | The changes needed outside the basic outline form to enable proper instrumentation for the cavity preparation and insertion of a dental restoration. (05 Mar 2000) |
| myocardial infarction in dumbbell form | Infarction involving the septum along with both inferior and anterior walls to make an H-or dumbbell-shaped configuration. Synonym: Roesler-Bressler infarct. (05 Mar 2000) |
| posterior tooth form | The distinguishing contours of the occlusal surface of the various posterior teeth. (05 Mar 2000) |
| half-chair form | See: Haworth conformational formulas of cyclic sugars. (05 Mar 2000) |