RP - retention and stability of complete dentures Flashcards
what is retention?
resistance of a denture to vertical movement away from the tissues
what is stability?
the resistance of a denture to displacement by functional forces
what are types of displacive forces?
gravity
muscle activity
sticky food
function
what is interfacial surface tension?
thin layer of fluid present between 2 parallel planes of rigid material - ability of fluid to wet the rigid material
due to an air seal around border of denture
pellicle layer from saliva coating acrylic
what is interfacial viscous tension?
the force holding 2 parallel plates together that is due to the viscosity of the interposed liquid (saliva)
when may interfacial viscous tension be compromised?
thick mucinic saliva is less able to flow and wet denture base and generate surface
how can you achieve optimum adaptation between denture and mucosa?
thin salivary film - close fitting denture
what is adhesion?
the physical attraction of unlike molecules for each other
saliva - mucous membrane
saliva - denture base
how is adhesion maximised?
bigger area covered greater adhesive force
extend denture over potential load bearing area as possible
what is cohesion?
physical attraction between similar molecules (salivary film)
what feature of a denture gives atmospheric pressure?
border seal
only achievable in maxillary prosthesis
what features should be considered to achieve optimum retention and stability with complete dentures?
fitting surface
polished surface
occlusal surfaces
what do we want the fit surface to cover? primary and secondary
primary supporting tissue - basal bone
secondary - soft tissue, rugae, tuberosities
how to achieve an optimum fit surface?
border in buccal sulcus - border mould
0.5mm thick at post dam
do not pass the vibrating line (soft palate muscles move)
what landmark marks the vibrating line?
palatine fovea
what is the anatomical name for lingual pouch?
retromylohyoid fossa
what undercuts in the mouth are useful for prosthetics?
labial undercut
bilateral soft tissue undercuts
bilateral boney undercuts
list factors that can make retention and stability difficult?
the atrophic ridge
damaged alveolar ridge - from trauma or surgery (bone replaced by fibrous tissue - flabby ridge)
tori
pt that cant tolerate base extension
insufficient saliva
what can you do for a pt that cannot tolerate base extension to try and recover retention and stability?
double post dam
can shorten palatal extension slightly
what is the neutral zone of tooth positioning?
outward forces from tongue balanced by inwards forces of teeth
what are aids to denture retention and stability?
denture adhesives and linings
what can be added to achieve a good base fit?
valves - act by sucking air out from under denture base
what are anchors?
2 implants to prevent rotation
