Components of removable partial dentures - retention Flashcards
What is retention?
quality inherent in the denture that resits vertical forces of dislodgment (forces of gravity, adhesiveness of the food, forces associated with the opening of the jaws) directed away from mucosa
How is retention achieved?
clasps
Where do clasps engage?
just below bulbosity of tooth
cusp to expansion allows the cusp allows retention
What hap[pens when the tooth does not have an undercut for clasp?
composite addition
How do you locate where the undercut is?
surveyor
place clasp just below survey line
What part of the clap engages in the undercut?
terminal 1/3
How long is a standard clasp to allow it to be flexible?
15 mm long
what are the materials for claps?
co-cr (cast)
stainless steel (wrought)
gold (wrought)
tooth coloured (resin)
What is the horizontal depth of undercut engaged for the Cocr clasp?
0.25 mm
What are types of occlusally approaching clasps?
three-arm
ring
back of reverse action
What are types of gingivally approaching claps?
T
Y or U
L
I
What is a gingivally approacing clasp?
a clasp retainer whose body extends from a major connector or denture base, passing adjacent to the soft tissues and approaching the tooth from a gingivo-occlusal direction
What is an RPI system?
R: occlusal rest seat (mesial)
P: guide plane (distal)
I: I bar clasp
What is the purpose of the RPI system?
designed to allow vertical rotation of a distal extension saddle into the denture-bearing mucosa under occlusal loading without damaging the supporting structures of the abutment tooth
