Occlusal Rest Seat Preparation
Posted on 04/04/2012
Occlusal rest seats should be prepared in the tooth enamel only. If the dentin is touched, it is important to restore the tooth (usually with a composite or amalgam restoration) prior to placing the framework. Rests that penetrate the enamel will often lead to caries - so restorations are critical.
Occlusal rest seats should be prepared as follows:
1. Preparation should be made using a No. 4 or No. 6 round carbide bur or diamond stone.
2. Spoon shaped with no sharp edges or vertical walls
3. Buccal-Lingual width should be approximately half the distance between the buccal and lingual cusp tips.
4. Mesio-Distal length depends on occlusal surface morphology and axial inclination of tooth. Generally, length mesio-distally should be set so the deepest portion of the prep is located at the closest naturally occurring fossa (picture A below). If the abutment is tilted, the rest seat can extend to the center of the tooth (picture B below).
5. Marginal ridge should be reduced by 1.0 to 1.5mm
6. Center portion of the rest should be about 0.5mm deeper than the common plane of the rest.
*Portions of this post were adapted from the book: Atlas of Removable Partial denture Design by Dr. Russell J. Stratton and Dr. Frank J. Wiebelt published by Quintessence Publishing Co., Inc. in 1988. Pages 86-87.
Occlusal rest seats should be prepared as follows:
1. Preparation should be made using a No. 4 or No. 6 round carbide bur or diamond stone.
2. Spoon shaped with no sharp edges or vertical walls
3. Buccal-Lingual width should be approximately half the distance between the buccal and lingual cusp tips.
4. Mesio-Distal length depends on occlusal surface morphology and axial inclination of tooth. Generally, length mesio-distally should be set so the deepest portion of the prep is located at the closest naturally occurring fossa (picture A below). If the abutment is tilted, the rest seat can extend to the center of the tooth (picture B below).
5. Marginal ridge should be reduced by 1.0 to 1.5mm
6. Center portion of the rest should be about 0.5mm deeper than the common plane of the rest.
*Portions of this post were adapted from the book: Atlas of Removable Partial denture Design by Dr. Russell J. Stratton and Dr. Frank J. Wiebelt published by Quintessence Publishing Co., Inc. in 1988. Pages 86-87.
