undercut (redirected from unusable undercut)

undercut,

1 the part of a tooth or artificial crown that lies between the height of contour and the gingivae, only if that part has a smaller diameter than the height of the contour.

2 the contour of a cross section of a residual ridge that would prevent the placement of a denture or other prosthesis.

3 the contour of flasking stone that interlocks so as to prevent the separation of parts.

4 the part of a prepared cavity that creates a mechanical lock or area of retention. It may be desirable in a cavity to be filled with gold foil or amalgam but is undesirable in a cavity prepared for a restoration to be cemented.

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undercut,

n 1. the portion of a tooth that lies between its height of contour and the gingivae, only if that portion is of less circumference than the height of contour.
2. the contour of a cross-section of a residual ridge of dental arch that would prevent the placement of a denture or other prosthesis.
3. the contour of flasking stone that interlocks to prevent the separation of parts.
4. the portion of a prepared cavity that creates a mechanical lock or area of retention; may be desirable in a cavity to be filled with gold foil or amalgam but is undesirable in a cavity prepared for a restoration to be cemented.

undercut gauge,

n See gauge, undercut.

undercut, retentive,

n an area of the abutment surface suitable for the location of a retentive clasp terminal, which in order to escape the undercut would be forced to flex and thus generate retention.

undercut, soft tissue,

n an undercut in a residual ridge or soft-tissue covering of a dental arch that would prevent or influence the placement of a removable denture.

undercut, unusable,

n the area of an abutment tooth or soft tissue across which a unit of the removable partial denture must pass without interference and hence must be blocked out (filled with wax or clay) before the master cast is duplicated. Use of a surveyor produces a surface that is parallel to the proposed path of a placement and removal.

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undercut

in the preparation of a tooth cavity for restoration, a cavity under the edges of the opening which is intended to aid in retention of a filling.