34 Questions
What is the purpose of the prepared surface of the abutment tooth?
To receive a rest and provide vertical support
What is the primary purpose of rests in an RPD?
To provide vertical support for RPD
What is the function of a tooth-supported RPD rest?
To function similar to fixed abutment retainers
What occurs when a rest and tooth are in stable contact under occlusal loading?
The rest and tooth remain in stable contact
What is the characteristic of a rest in an RPD?
Rigid and receiving positive support from the abutment teeth
What is the role of remaining natural teeth in an RPD?
To resist functional forces
What occurs as the distance from the abutment increases in an RPD with one or more distal extension bases?
The RPD becomes more tissue-supported
What is the benefit of rests in controlling prosthesis movement?
They provide vertical support for the RPD
What is the primary function of rests in a removable partial denture?
To prevent movement of the prosthesis in an apical direction
What happens when rests prevent movement of the RPD in an apical direction?
The position of the retentive portion of the clasp arms is maintained in a designated relation to the tooth undercuts
Why is it important for the retentive portion of the clasp arm to remain in contact with the tooth?
To resist vertical dislodging forces
What is the consequence of RPD settling on the clasp arms?
The clasp arms stand away from the tooth, allowing vertical displacement
How do implants used as rests help to maintain vertical stability of the RPD?
By preventing compression of the supporting soft tissue
What is the function of an occlusal rest in a removable partial denture?
To transfer stress to the abutment tooth and resist movement of the prosthesis in a cervical direction
What is the benefit of using implants as rests in a removable partial denture?
Improved support and stability of the RPD
What is the role of the retentive portion of the clasp arm in a removable partial denture?
To resist vertical dislodging forces
What type of material should be avoided when restoring a Class II situation?
Glass Ionomer
What is the purpose of an Extended Occlusal Rest?
To stabilize a lone standing tooth
What is the minimum base width of the triangle-shaped occlusal rest seat for molars and premolars?
2.5 mm
Why is it necessary to lower the marginal ridge of the abutment tooth?
To permit sufficient bulk of metal for strength and rigidity of the rest
What is the recommended shape of the occlusal rest seat floor?
Concave
Why should sharp edges or line angles be avoided in the preparation?
To prevent stress concentrations
What is the ideal angle formed by the occlusal rest and vertical minor connector?
< 90 degrees
What is the purpose of the reduction of the marginal ridge?
To permit sufficient bulk of metal for strength and rigidity of the rest
When the angle between the occlusal rest and the vertical axis of the abutment tooth is more than 90 degrees, what happens?
Orthodontic-like forces are applied to the inclined plane of the abutment
What is the recommended labio-lingual width of the rest seat at the marginal ridge?
2.5 mm
What is the purpose of an extended occlusal rest seat in a Kennedy Class II Mod 1 and Kennedy Class III?
To minimize further tipping of the abutment and ensure forces are directed down the long axis of the abutment
What is the minimum recommended thickness of metal for the rest seat?
1 mm
What is the recommended width of the rest seat buccolingually in an extended occlusal rest?
1/3 of the tooth width
What is the purpose of a cingulum ledge in an anterior rest?
To provide a positive stop for the rest
When dentin is exposed and sensitive in an anterior rest, what may be needed?
A composite resin restoration
What should be avoided in the preparation of an extended occlusal rest?
Undercuts and sharp angles
What type of rest is created in a severely tilted abutment?
Onlay form
What is the recommended minimum extension of the rest seat in a Kennedy Class II Mod 1 and Kennedy Class III?
More than 1/2 of the mesiodistal width of the tooth
Understand the role of rests in controlling prosthesis movement, including the preparation of the occlusal rest seat and cingulum rest. Learn about the importance of rests in resisting functional forces and achieving functional stability in dentistry.
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