RPD Lecture 3 Flashcards
what are the 2 types of direct retainers?
extracoronal and intracoronal
what kind of attachment is commonly used?
extracoronoal attachment
_____ retainer: precision attachment. Prefabricated keys (in PRDP) and keyways (in abutment crown) with vertical parallel walls create frictional contact which limits the movements and resists displacement
intracoronal
How are the keyways of intracoronal retainers cast?
within the crown
what kind of contact do the vertical parallael walls create in intracoronal retainer?
frictional contact.
resistance to VERTICAL displacement?
retention
areas ___ the the heigh of contour are used for the placement of flexible (terminal third) retentive clasp components
apical for retention
resistance to HORIZONTAL forces applied to a tooth by an active retentive clasp during PRDP insertion and removal; counters the force of clasp deformation at the survey line.
reciprocation
these will be areas CORONAL to the heigh of contour and are for stabilizing (non retentive) reciprocating clasp components
can you place the full cusp below the height of contour?
no, ideally just the termnal third because this is flexible
resistance to horizontal components of MASTICATORY forces?
bracing.
MCs brace and stablaize
GPs also brace along with recirpocal clasp arms.
prevents horizontal tooth movement away from the confines of the clasp assembly; assist in bracing.
adequate encriclement.
more than 180 degrees should be engaged by clasp assembly at largest circumference of tooth
how much of the tooth should be engaged by the clasp assebmly?
more than 180 degrees with
does the contact of encirclement of clasp have to be continuous?
NO! it can be continous or discontinous
difference between cast circumferential clasp and bar type clasp?
bar type doesn’t circle around the entire tooth
resistance to vertical seating forces, occlusal forces
support — rests for example
direct forces parallel to the long axis of the abutment teth
the quality of inactivity or rest assumed by the teeth, tissues and prosthesis when a partial removable dental prosthesis is in place but NOT under masticatory pressure
passivity
where should the retentive arm be placed?
gingival third of the abutment tooth in a predetermined undercut of .01
where should the reciprocating arm be placed?
occlusal 1/3 of the abutment tooth
describe the properties of the retentive arms?
retention= the resistance to deformation of the retentive clasp tip when in undercut.
terminal 1/3 of clasp arm is in undercut area of tooth
what happens to the clasp tip as you insert and remove?
it flexes upon insertion and removal as it passes over survey line
what kind of alloy do you want of retentive arms?
elastic moduli
should recricprcal or retentive arm contact tooth first?
reciprocal arm should contact first.
what is the classic supra bulge clasp?
Cast circumferential clasp- it’s half round in X section (low flexibility).
classic supra bulge clasp.
other names for the C clasp?
akers, and circlet
