Step 3 In RPD Design: Rest Preparation
Posted on 10/24/2011
After surveying and designing the RPD, the next step is to prepare the teeth in the mouth. While chairside preparation in advance of the fabrication of the RPD is recommended, many pracitioners who do not prescribe RPD frameworks regularly, prefer to have the lab prepare the teeth on the model - and they work to replicate the preparation in the mouth. Either way, the first preparation to consider is the creation of the rests.
Rests are defined as rigid extensions of a partial denture that contacts a remaining tooth (or teeth) to dissipate functional forces.*
The goals of the rests are to:
- Prevent movement in a cervical direction which would damage the mucosa
- Maintain retentive portions of clasps in their desired positions
- Distribute occlusal loads over several teeth
- Direct food away from tooth contacts and embrasures
A few notes about rests:
Rests must be located in a prepared occlusal, cingulum or incisal recess. They should avoid common contact areas and attempt to mimic the natural occlusal surface. Sufficient metal thickness is essential to prevent breakage. According to Tsao (1970), the minimal metal thickness is 1.38mm for cobalt-chromium partials and 1.43mm for cast gold based on a 80kg occlusal load.
*This post was 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. Page 19.
Rests are defined as rigid extensions of a partial denture that contacts a remaining tooth (or teeth) to dissipate functional forces.*
The goals of the rests are to:
- Prevent movement in a cervical direction which would damage the mucosa
- Maintain retentive portions of clasps in their desired positions
- Distribute occlusal loads over several teeth
- Direct food away from tooth contacts and embrasures
A few notes about rests:
Rests must be located in a prepared occlusal, cingulum or incisal recess. They should avoid common contact areas and attempt to mimic the natural occlusal surface. Sufficient metal thickness is essential to prevent breakage. According to Tsao (1970), the minimal metal thickness is 1.38mm for cobalt-chromium partials and 1.43mm for cast gold based on a 80kg occlusal load.
*This post was 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. Page 19.
