Rests and Rest Seats Flashcards
A rigid extension of a fixed or removable partial denture that transmits functional forces to the teeth and prevents movement toward the mucosa.
Rest
The portion of a natural tooth or cast restoration prepared to receive an occlusal, incisal, lingual, internal, or semi-precision rest
Rest seat
What are the 5 functions of rests?
- Direct forces down the long axis of teeth
- Prevent cervical movement of the RPD
- Limit lateral movement of the RPD
- Maintain retentive arm in proper vertical relation
- Improve the occlusal plane
What are the 5 types of rests?
Occlusal Embrasure Cingulum Hooded Incisal
Where are the occlusal rests located on premolars and molars?
Mesial and distal pits centered over the marginal ridge
The width of the occlusal rest seats should be ____ the BL width
1/3
The width of the occlusal rest seats should be ____ the width between the cusp tips
1/2
How much reduction for an occlusal rest should there be over a marginal ridge?
1-1.5 mm
How much reduction for an occlusal rest should there be at the deepest portion in the pit area?
1.5-2 mm
The floor of rest seat should incline towards the axial center, forming an angle ______ 90o
less than
Should the rest prep be wide and shallow or narrow and deep?
Wide and shallow
Designed to ensure maximum bracing from the tooth. The extended rest would ensure that the forces are directed down the long axis of the abutment, and therefore the disto-occlusal rest would not have been needed
Extended Occlusal rest
_______ rests
•Two adjacent posterior teeth
•Often used when no posterior modification space is present
•Follows form of occlusal rest
•Occlusal rests are placed on adjacent posterior teeth
•Avoid eliminating the contact point
•Allow adequate tooth reduction:approximately 1 mm
•Prepare “sluiceway” of around 2 mm
Embrasure rests
For the embrasure occlusal rest, how wide and deep should the prep be?
1mm deep
2mm wide
Occlusal clearance is evaluated by placing two pieces of ______ across the preparation.
18-gauge wire
- Can be prepared in canines having a gradual lingual slope
- Can be prepared in canines using composite resin
- May be used on most anterior teeth if placed in cast restorations
Lingual rest seats
When doing rest seat preps, should you anesthetize the patient?
No
Which tooth arch when doing a lingual rest seat do you need to use composite resin?
Mandibular
Placement of rests on ____surfaces displaces the tooth and destroys bone.
inclined
For lingual cingulum rests, how wide should floor be?
0.75-2mm
For lingual cingulum rests, how deep should floor be?
1-1.5mm
•Mandibular first premolars only
•To provide for increased occlusal support
•Decreases torque by lowering the center of rotation
-Not on distal abutment of distal extensions
•1.0 -1.5 mm reduction
•Extends from marginal ridge to marginal ridge
Hooded rests
What is the minimum amount of reduction needed for a rest seat to resist fracture of the rest?
1mm
•Least desirable of all rests
•poor esthetics
•occlusal interference
•Increased torquing forces
•Primarily used on mandibular canines
•Primarily used as an indirect retainer and/or auxiliary rest
-It should appear as a small, V-shaped notch located 1.5 to 2.0 mm from the proximal-incisal angle of the tooth.
Incisal rest
