PARTIAL DENT - Design for Cobalt Chrome Dentures

Question 1

give 4 principles of design for cobalt chrome dentures.

Answer 1

• avoid gingival coverage
• good support from denture
• rigid connector
• keep it simple

Question 2

describe the 8 steps of design

SSRRRGC

Answer 2

1. saddle
2. support
3. retention
4. bracing/reciprocation
5. indirect retention
6. guide planes
7. connector
8. review the principles of design

Question 3

give 3 aesthetic reasons of replacing a tooth

Answer 3

• aesthetics match with other teeth
• prevent over eruption
• phonetics

Question 4

give 4 disadvantages of replacing a tooth

Answer 4

• contributes to plaque retention
• trauma to the tissues
• patient may not be tolerant
• cost

Question 5

2 types of saddle, describe it

Answer 5

bounded saddle - bound to teeth on either side

free ended saddle - bound to one side

Question 6

when replacing teeth, plaque is a disadvantage, what can plaque potentially lead to?

Answer 6

perio disease
caries
fungal infections

Question 7

trauma can be a factor of tooth replacement, what can be traumatised?

Answer 7

soft tissues
pulp - lead to pulpal necrosis

Question 8

why may the patient not be tolerant when replacing teeth?

Answer 8

gag reflexes
patient expectations may not be met

Question 9

what does replacing teeth cost?

Answer 9

time and money

Question 10

where do saddles extend to?

Answer 10

full extent of the denture bearing area

• to the sulcus functional depth
• lower arch - as far back as the pear shaped pad
• upper arch - as far back as hamualar notch

Question 11

why do saddles extend so far?

Answer 11

to decrease pressure in the underlying mucosa

Question 12

how is support provided?

Answer 12

rest seats

Question 13

how are rest seats positioned on bounded saddles and free end saddles?

Answer 13

bounded
- on nearest surface of each abutment tooth

free saddle
- on the mesial aspect of the abutment tooth

Question 14

why are rest seats placed mesially on the abutment tooth for free ended saddles?

Answer 14

• reduce torque on the abutment tooth
• aka reducing the force placed

Question 15

when placing rest seats, what must be checked?

Answer 15

the occlusion
- if its tight, deep rest seat may be required

Question 16

what can be made to assess the rest seat occlusions?

Answer 16

articulated study casts

Question 17

what is used for retention?

Answer 17

clasps

Question 18

how are clasps used to retain?

Answer 18

engage with the undercut

Question 19

what is the undercut?

Answer 19

the area below the survey line
- the line of maximum bulbosity on a tooth

Question 20

how is the retentive force determined?

Answer 20

by the horizontal depth of the undercut

Question 21

what are the 3 types of clasp?

Answer 21

occlusal approach
- 3-arm
- ring

gingival approach
- I-bar

Question 22

if there is no undercut on a tooth and we want to use that tooth for retention, how can we manage this?

Answer 22

add composite to gain an undercut

Question 23

what must each retentive clasp arm include?

Answer 23

reciprocations

Question 24

what is a indirect retainer and what does it aim to do?

Answer 24

a component which stops displaced rotation on the clasp when a free end saddle is pulled away from the mucosa

Question 25

how is indirect retention achieved?

Answer 25

place an occlusal rest on a tooth anterior to the clasp

as far from the clasp axis as possible

Question 26

what is a guide plane?

Answer 26

a prepared surface on the abutment teeth that helps the insertion and removal of a denture

Question 27

why may a guide plane be used?

Answer 27

• single path of insertion
• reciprocation
• indirect retention
• use with the RPI clasp system

Question 28

what is a unique way a guide plane can be made?

Answer 28

not perpendicular to the occlusal plane

so that the tooth has to be inserted in a particular angle and the denture can’t lift up

Question 29

what is a denture connector?

Answer 29

keeps all of the denture together and has shapes to suit the upper and lower arch

Question 30

how much of the gingival margin must be cleared from the connector?

Answer 30

3mm

Question 31

what are the 6 types of upper arch connectors?

Answer 31

anterior palatal bar
mid palatal
posterior palatal bar

horseshoe
palatal plate
ring

Question 32

what are the 5 types of lower arch connectors?

Answer 32

lingual bar
sublingual bar
lingual plate
dental bar
buccal bar

Question 33

show what a lingual bar looks like and its criteria

Answer 33

must have 6mm depth to the lingual sulcus to insert it

Question 34

show what a sublingual bar looks like and its criteria

Answer 34

must be a 5mm depth clearance for insertion

Question 35

how do you take an accurate impression of the sulcus

Answer 35

ask the patient to move the tongue around

Question 36

what does a lingual plate look like

Answer 36

Question 37

huge disadvantage of a lingual plate

Answer 37

PLAQUE RETENTION

Question 38

show what a dental bar looks like and its criteria

Answer 38

needs a long clinical crown

good because it doesn’t rely on sulcus depth

Question 39

show a buccal bar

Answer 39

Question 40

advantages of cobalt chrome

Answer 40

• easy cleaning
• distributes force onto PDL of existing tooth
• can mask alveolar bone helps aesthetic
• restore multiple teeth at a time
• rigid connector to distribute occlusal load
• less PRF than acrylic plates

Question 41

disadvantages of cobalt chrome

Answer 41

• metal aesthetics
• metal is hard to add onto
• expensive

Question 42

why is a class 4 hard to manage with a denture?

Answer 42

retention
path of insertion

Question 43

what is gum stripping?

Answer 43

Loss of normal gum tissue contour, the denture keeps sinking into the gum because it is not supported