Rests and Rest Seats

Question 1

A rigid extension of a fixed or removable partial denture that transmits functional forces to the teeth and prevents movement toward the mucosa.

Answer 1

Rest

Question 2

The portion of a natural tooth or cast restoration prepared to receive an occlusal, incisal, lingual, internal, or semi-precision rest

Answer 2

Rest seat

Question 3

What are the 5 functions of rests?

Answer 3

• 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

Question 4

What are the 5 types of rests?

Answer 4

Occlusal 
Embrasure
Cingulum
Hooded
Incisal

Question 5

Where are the occlusal rests located on premolars and molars?

Answer 5

Mesial and distal pits centered over the marginal ridge

Question 6

The width of the occlusal rest seats should be ____ the BL width

Answer 6

1/3

Question 7

The width of the occlusal rest seats should be ____ the width between the cusp tips

Answer 7

1/2

Question 8

How much reduction for an occlusal rest should there be over a marginal ridge?

Answer 8

1-1.5 mm

Question 9

How much reduction for an occlusal rest should there be at the deepest portion in the pit area?

Answer 9

1.5-2 mm

Question 10

The floor of rest seat should incline towards the axial center, forming an angle ______ 90o

Answer 10

less than

Question 11

Should the rest prep be wide and shallow or narrow and deep?

Answer 11

Wide and shallow

Question 12

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

Answer 12

Extended Occlusal rest

Question 13

_______ 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

Answer 13

Embrasure rests

Question 14

For the embrasure occlusal rest, how wide and deep should the prep be?

Answer 14

1mm deep

2mm wide

Question 15

Occlusal clearance is evaluated by placing two pieces of ______ across the preparation.

Answer 15

18-gauge wire

Question 16

• 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

Answer 16

Lingual rest seats

Question 17

When doing rest seat preps, should you anesthetize the patient?

Answer 17

No

Question 18

Which tooth arch when doing a lingual rest seat do you need to use composite resin?

Answer 18

Mandibular

Question 19

Placement of rests on ____surfaces displaces the tooth and destroys bone.

Answer 19

inclined

Question 20

For lingual cingulum rests, how wide should floor be?

Answer 20

0.75-2mm

Question 21

For lingual cingulum rests, how deep should floor be?

Answer 21

1-1.5mm

Question 22

•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

Answer 22

Hooded rests

Question 23

What is the minimum amount of reduction needed for a rest seat to resist fracture of the rest?

Answer 23

1mm

Question 24

•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.

Answer 24

Incisal rest