retention and stability Flashcards
What is retention?
resistance to tissue-away forces
What re the physical factors that affect retention of denture?
- adhesion
- cohesion
- interfacial surface tension (similar to cohesion)
- atmospheric pressure (peripheral seal)
What is adhesion?
physical attraction of unlike molecules to each other
What are examples of adhesion?
- saliva to mucosa
- saliva to denture
What is cohesion?
physical attraction of like molecules for each other
What is an example of cohesion?
saliva
Is cohesion and adhesion related?
yes
What forces does peripheral seal resist?
vertical and lateral forces
What forces does adhesion resist?
lateral forces
What forces does cohesion resist?
lateral forces
What forces does interfacial surface tension resist?
lateral forces
What are the intra-oral factors and biomechanical considerations of denture retention?
- 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
What is the recommended arch size for retention of denture?
large arch size
What is the recommended harmony of arch size for retention of denture?
angle class 1
What is the recommended arch form for retention of denture?
square
What is the least favorable prognosis for arch form for retention?
tapered
What does a flat vault resist?
vertical displacement but it
provides little resistance to lateral displacement (retention is good)
What does a V-shaped vault resist?
- unfavorable for the retention of dentures
- provides no adaptation –> decrease adhesion and cohesion –> decrease retention –> increase resistance to lateral forces (good stability)