Rest Seat
From WikiDent
A rest seat is a preparation made in tooth structure to support a prosthesis and direct forces along a specified path (most often along tooth axis). Routinely used in RPD design, rest seats should ideally distribute force upon abutment teeth along their axis. Rests prevent displacement of the RPD toward the tissue and transfers the forces of mastication to the supporting teeth. All teeth adjacent to edentulous spaces need a rest.
Rest seats are prepared into teeth with the following guidelines:
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Occlusal Rests
- Triangular in shape with the base located at the marginal ridge.
- 1/3 - 1/2 the mesio-distal width.
- 1/2 the buccolingual width from cusp tip to cusp tip.
- Floor of the rest preparation must be inclined toward the center of the tooth.
- Thickness of the metal should be 1.0 -1.5 mm.
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Cingulum (lingual) Rests
- Usually used in maxillary canines.
- V-shaped in cross section.
- Crescent shaped when viewed from the lingual.
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Incisal Rests
- Usually used on mandibular canines.
- Small V-shaped rounded notch located 1.5-2.0 mm away from the proximal-incisal angle.
- Extended slightly onto the facial surface.
