retention and stability

Question 1

What is retention?

Answer 1

resistance to tissue-away forces

Question 2

What re the physical factors that affect retention of denture?

Answer 2

• adhesion
• cohesion
• interfacial surface tension (similar to cohesion)
• atmospheric pressure (peripheral seal)

Question 3

What is adhesion?

Answer 3

physical attraction of unlike molecules to each other

Question 4

What are examples of adhesion?

Answer 4

• saliva to mucosa
• saliva to denture

Question 5

What is cohesion?

Answer 5

physical attraction of like molecules for each other

Question 6

What is an example of cohesion?

Answer 6

saliva

Question 7

Is cohesion and adhesion related?

Answer 7

yes

Question 8

What forces does peripheral seal resist?

Answer 8

vertical and lateral forces

Question 9

What forces does adhesion resist?

Answer 9

lateral forces

Question 10

What forces does cohesion resist?

Answer 10

lateral forces

Question 11

What forces does interfacial surface tension resist?

Answer 11

lateral forces

Question 12

What are the intra-oral factors and biomechanical considerations of denture retention?

Answer 12

• arch size
• disharmony of jaw sizes
• arch form
• ridge form
• vault form
• soft palate
• undercuts on basal seat
• interarch distance
• polished surface of denture
• gravity

Question 13

What is the recommended arch size for retention of denture?

Answer 13

large arch size

Question 14

What is the recommended harmony of arch size for retention of denture?

Answer 14

angle class 1

Question 15

What is the recommended arch form for retention of denture?

Answer 15

square

Question 16

What is the least favorable prognosis for arch form for retention?

Answer 16

tapered

Question 17

What does a flat vault resist?

Answer 17

vertical displacement but it
provides little resistance to lateral displacement (retention is good)

Question 18

What does a V-shaped vault resist?

Answer 18

• unfavorable for the retention of dentures
• provides no adaptation –> decrease adhesion and cohesion –> decrease retention –> increase resistance to lateral forces (good stability)

Question 19

What is the most recommended vault form for retention and stability?

Answer 19

u-shaped as it resists both vertical and lateral dislodging forces and goo adaptation

Question 20

What is the most favorable retention form of soft palate?

Answer 20

class I soft palate has a gentle curvature and demonstrates little muscular movement, hence it is the most favorable

Question 21

Are undercuts good for retention?

Answer 21

• no, it needs to be open flanges
• if only one undercut present, it increases retention (undercut is in path of removal and insertion)

Question 22

What are the uses of flexible resins?

Answer 22

• undercuts
• v-shaped palate (increased adaptation)
• sharp mylohyoid ridge

Question 23

What is the normal interarch distance?

Answer 23

2-3mm

Question 24

What is the interarch distance?

Answer 24

distance between maxilla and mandible (teeth and freeeway space) where denture is placed

Question 25

What is the interarch distance recommended for better retention and stability?

Answer 25

2-3mm (small interarch distance)

Question 26

What happens if the interarch distance is more than 2-3mm?

Answer 26

- longer teeth are used - lateral forces increase (alters stability and retention)

Question 27

What should the shape of polished surface be to be retentive?

Answer 27

concave (more muscle adaptation and stability)

Question 28

What should the shape of lingual surface be?

Answer 28

covex then concave to avoid formation of undercuts

Question 29

Does gravity aid upper denture?

Answer 29

no

Question 30

Does gravity aid lower denture?

Answer 30

yes

Question 31

What is stability?

Answer 31

resistance to rocking or lateral forces

Question 32

What is the most retentive shape for ridge form?

Answer 32

ideal form is a high ridge with flat crest and parallel or nearly parallel sides (square ridge)

Question 33

What ridge form provides most stability?

Answer 33

square

Question 34

What is the best arch form for better stability?

Answer 34

square

Question 35

What happens if mucosa is very low (hard bony areas)?

Answer 35

rocking and instability and pain

Question 36

What is the faorable prognosis for better stability for mucosa supporting prosthesis?

Answer 36

2-3mm

Question 37

What happens if the mucosa supporting denture is mpre than 10mm (flabby ridge)?

Answer 37

- rocking and instability - selective pressure impression technique

Question 38

What is the arrangement of teeth buccolingually?

Answer 38

on crest of the ridge to avoid cramped tongue

Question 39

What happens if teeth are arranged lingual to the crest of the ridge?

Answer 39

cramped tongue

Question 40

What happens if teth are arrangedbuccal to the crest of the ridge?

Answer 40

- cheek biting - rocking - instability

Question 41

What is the arrangement of teeth occlusogingivally?

Answer 41

below lateral borders of the tongue to allow lower denture stability

Question 42

What is the arrangement of teeth antro-posteriorly?

Answer 42

- away from retromolar pad (posterior) to avoid inclination of teeth (which might increase lateral forces leading to instabiliy)

Question 43

Does arrangement of teeth alter stability?

Answer 43

yes

Question 44

What should be done to flabby and bony ridges?

Answer 44

relieved

Question 45

What should the occlusion be for better stability?

Answer 45

even occlusion