rest and rest seats

Question 1

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

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 functions of rests

Answer 3

*direct forces down the long axis of teeth

-prevent cervical movement of RPD
-limit lateral movement of RPD
-maintain retentive arm in proper vertical relation
-improve occlusal plane

Question 4

if preventing cervical movement of RPD is not accomplished by rest,

Answer 4

underlying hard and soft tissues may be damaged

Question 5

guiding principles of rest seat preparation:

Answer 5

evaulate inter-occlusal/inter-incisal relationships in both static and excursive movements

Question 6

what are the 5 types of rests

Answer 6

occlusal
embrasure
cingulum
hooded
incisal

Question 7

location of occlusal rests

Answer 7

-mesial/distal pits of premolars and molars
-centered over marginal ridge whenever possible

Question 8

shape of occlusal rest seats:

Answer 8

-concave “saucer” “spoon shaped”
-ball and socket
-triangular in shape

Question 9

width of occlusal rest seats

Answer 9

• one-third the buccolingual width
• one-half the width between the cusp tups
  -do not undermine the triangular ridges

Question 10

depth of occlusal rest seats

Answer 10

-1-1.5mm reduction over marginal ridge
-1.5-2mm reduction at deepest portion
-deepest portion located in pit area

Question 11

the floor of rest seat should incline towards the axial center, forming an angle

Answer 11

less than 90 degrees

Question 12

rest seat preparation should be (wide/narrow) and (shallow/deep)

Answer 12

wide and shallow

Question 13

designed to ensure max bracing from the tooth. this rest would ensure that the forces are directed down the long axis of abutment and therefore the disto-occlusal rest would not have been needed

Answer 13

extended occlusal rest

Question 14

location of embrasure rest seats:
used when:

Answer 14

-two adjacent posterior teeth
-often used when no posterior modification space is present

Question 15

the embrasure rest seat follows the form of

Answer 15

of occlusal rest

Question 16

where are the occlusal rests are placed on

Answer 16

adjacent posterior teeth

Question 17

adequate tooth reduction for embrasure rest seats

Answer 17

1mm
-prepare “sluiceway” of around 2mm

Question 18

what requires additional marginal ridge preparation u-shaped trough to accomodate clasp assembly

depth: 1mm
width:

Answer 18

embrasure occlusal rest
depth 1mm
width: 2mm

Question 19

how is the occlusal clearance evaluated for embrasure rest seats

Answer 19

by placing two pieces of 18-gauge wire across the preparation

Question 20

indications for lingual rest seats

Answer 20

1. can be prepared in canines having gradual lingual slop
2. can be prepared in canines using composite resin
3. may be used on most anterior teeth if placed in cast restorations

Question 21

location and type of cingulum rest seats

Answer 21

1. thick well- defined cingulum enamel
2. maxillary- cut into enamel
3. mandibular- composite resin

Question 22

form of cingulum rest seats proximal view

Answer 22

-floor 1mm wide
-extends from marginal ridge to marginal ridge

Question 23

form of cingulum rest seats incisal view

Answer 23

“crescent” shaped
widest portion at the center

Question 24

form of cingulum rest seats lingual view

Answer 24

inverted V, chevron-shaped

Question 25

if rest is placed on inclined surfaces, what happens

Answer 25

displaces tooth and destroys bone

Question 26

with maxillary cingulum rest seats, what do you want to avoid

Answer 26

avoid opposing occlusion

Question 27

where are lingual cingulum rests primarily on

Answer 27

maxillary canines

Question 28

shape of lingual cingulum rests

Answer 28

chevron V shape

Question 29

lingual cingulum rest measurements

Answer 29

-rest seat slopes downward slightly: 90 degree angle with path of insertion -width of floor: 0.75-2.0mm -inciso-apical depth: 1.0-1.5mm

Question 30

mandibular canine does not exhibit a sufficient thickness of lingual enamel, so

Answer 30

must use lingual resin-bonded cingulum rest seat

Question 31

how is lingual resin-bonded cingulum rest seat made

Answer 31

-lingual cingulum area roughened with diamond and acid-etch -composite resin placed and shaped to resemble chevron rest seat -clinical studies report long-term success

Question 32

indications for hooded rests:

Answer 32

1. mandibular first premolars only 2. to provide for increased occlusal support 3. decreases torque(twisting) by lowering the center

Question 33

where are hooded rests not on with mand first premolars

Answer 33

not on distal abutment of distal extensions

Question 34

shape of hooded rest seats

Answer 34

1-1.5mm reduction extends from marginal ridge to marginal ridge

Question 35

least desirable of all rests -poor esthetics -occlusal interferences -increased torquing forces

Answer 35

incisal rests

Question 36

where are incisal rests primarily used on

Answer 36

mandibular canines

Question 37

what rest is primarily used an indirect retainer and/or auxillary rest

Answer 37

incisal rests

Question 38

how should incisal rest seat

Answer 38

appear as small, V-shaped notch located 1.5-2.0mm from the proximal-incisal angle of the tooth

Question 39

under preparation of rest seat, minimum of what reduction is needed to prevent rest fracture

Answer 39

1mm