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.
