Design 2

Question 1

4 things to consider when designing a saddle

Answer 1

• extension (more the better, pref to retromolar pad)
• material of fit surface (usually acrylic)
• design of occlusal surface of saddle (number of teeth, look at opposing arch for articulation)
• relationship of saddle to abutment tooth (tight against tooth/point contact)

Question 2

what is the neutral zone

Answer 2

area of minimum conflict where tongue and cheeks relax –> would push denture out

Question 3

does the neutral zone affect the denture more in the upper or lower arch? explain

Answer 3

lower: cheeks and tongue
upper: cheeks only

Question 4

what material is most commonly used for saddles and why

Answer 4

acrylic: easily changed eg for more teeth
teeth stick easily

cobalt chrome expensive, fiddly, cant adjust

Question 5

when would metal saddles be used

Answer 5

over-erupted opposing arch –> no room for acrylic-mesh-acrylic-tooth

Question 6

what is a rest

Answer 6

metal projection as part of metal framework attached to a denture that extends to surface of tooth

Question 7

main and other functions of rest

Answer 7

main: support
other: indirect retention, deflect food away from saddle abutment junction, improved occlusal contacts when used as an onlay

Question 8

2 essential features of a rest

Answer 8

• rigid

- does not interfere with existing occlusion

Question 9

rule of free end saddles rest seat location

Answer 9

must be MESIAL to prevent theoretical overloading and improved stress distribution

Question 10

direct/indirect retainers

Answer 10

direct: applied to abutment teeth to prevent withdrawal of denture along POI
indirect: applied to teeth at distance from possible axis of rotation of denture

Question 11

3 ways to gain retention

Answer 11

• mechanical (clasps)
• muscular control
• physical (POI, saliva)

Question 12

2 types of clasp and where they are used

Answer 12

• occlusally approaching (molars)

- gingivally approaching (premolars, canines)

Question 13

4 design criteria for effective clasp

Answer 13

• flexible retentive arm
• reciprocation
• encirclement
• passivity

Question 14

5 factors affecting clasp retention

Answer 14

• material of clasp
• cross section of clasp
• length of clasp
• depth of undercut
• clasp design

Question 15

4 ways to decide what clasp to use

Answer 15

• position of undercut
• amount of bone support
• length of clasp (last 1/3 sits in undercut. any more of this causes wire to fracture)
• appearance

Question 16

4 devices used for mechanical retention

Answer 16

• clasps
• magnets
• precision attachments (but expensive and high maintenance)
• implants

Question 17

what do indirect retainers do

Answer 17

resist rotational forces

Question 18

what is bracing

Answer 18

resistance to horizontal/lateral forces when denture fully seated

Question 19

how is bracing achieved

Answer 19

rigid 2/3 portion of clasp arm or plate

Question 20

what is reciprocation

Answer 20

resistance to horizontal/lateral forces when denture is on the move over max bulbosity of tooth
otherwise would get orthodontic tooth movement

Question 21

define a saddle

Answer 21

part of the denture that rests on and covers the tissues of the alveolar ridge