Retainers Flashcards
This engages an abutment tooth to resist displacement of the RPD away from the tissues; keeps the RPD in place
direct retainer
This type of direct retainer is cast or attached totally within the contours of the abutment tooth
intracornal
What are the two types of intracoronal retainers
key and keyway
What is the ONLY advantage of an intracoronal retainer
esthetics
What are the 5 disadvantages of an intracoronal retainer
requires casting complicated clinical/lab difficult to repair additional expense may require the splinting of several teeth
This type of direct retainer resists displacement using components placed on or attached to the external surfaces of the abutment tooth
extracoronal
This is the type of extracoronal direct retainer that we will be using for this course
clasp type retainer
What are the four parts of a basic clasp
rest
retentive arm
reciprocating arm
guiding plate
Where would you like the arms of a cast circumferential to fall
in the middle 1/3 of the hight of contour
This is used to determine the path of insertion, HoC, and under cut
surveyor
What is the function of the occlusal rests
in order for the partial to not seat into the tissues and irritate them
This is used as a resistance to vertical dislodging forces
retentive arm
This counteracts the retentive force of the clasp
reciprocal arm
Which arm, the retentive or reciprocal, goes beneath the height of contour in a CC clasp
retentive arm
Resistance to vertical seating forces is provided by what
the occlusal rests
In which tooth surface is it best to keep rests in
enamel
What is the best type of rest for anterior teeth, specifically canines
cingulum rest
What is the best type of rest for anterior teeth, especially when using the cingulum is not practical
incisal rest
What is the indication for a CC clasp
Kennedy class III
What is the CC clasp excellent at
support
bracing
retentive properties
Where is the location of the occlusal rest of a CC clasp
adjacent to the edentulous space
mesial or distal
Where is the location of the guide plate of a CC clasp
adjacent to the edentulous space
mesial or distal
Where is the location of the retentive clasp of a CC clasp
usually on the buccal
wherever the undercut is
Where is the location of the reciprocating arm of a CC clasp
usually on the lingual
opposite of the retentive clasp
When is an embrasure clasp indicated
for a Kennedy class II, III or IV with no modification spaces on opposite of the arch to aid in clasping
Why are double occlusal rests needed with an embrasure clasp
to avoid wedging
What are the six requirements for every direct retainer or clasp assembly
support stabilization retention adequate encirclement reciprocity passivity SARRPS
This provides stabilization and unites the major connector with other components such as rests
minor connector
This component of the clasp provides stabilization
guide plates
What is adequate encirclement
greater than 180° encirclement around the tooth; engaging more than half the tooth
What is the passivity of the partial
there should be no active force on the tooth when the clasp is in place
This is the component of the RPD which contacts the oral much and to which the teeth are attached; made of pink acrylic and provides support
denture base
What are the three denture base retention designs
open lattice
mesh
nailhead (butt acrylic tooth)
Which denture base retention is used most frequently
open lattice denture base
What is the description of open lattice denture base retention
two longitudinal struts extending along the edentulous ridge, one strut buccal and the other lingual to the crest of the ridge
one strut between each replaced tooth (like the edentulous space)
A mesh denture base is thin, which would this be indicated
when there is not a lot of inner arch distance
In the bead, wire, or nailhead retention the cast is formed directly on the ridge so what occurs
so there is no acrylic packed underneath; making relining impossible
How is retention gain via the bead, wire, or nailhead retention base
by the metal projection on the metal surface
When is a bead, wire, or nailhead indicated for a butt acrylic tooth
in 1 or 2 teeth in the anterior kennedy class III or IV
The acrylic resin joins the metal at what
at the butt joint (finish line) to prevent over thinning of the acrylic
Where are the internal and external finish lines
internal on the tissue side
external on the outer aspect
Butt acrylic teeth are not indicated for what
Kennedy class I or II
What are the characteristics of the external finish line
should be sharp, definite, and slightly undercut to adhere to resin
angle or finish line with major connector should be less than 90°
What are the characteristics of the internal finish lines
formed from the margins of the relief wax, used over edentulous ridge to create space for the acrylic
This provides resistance which prevents the partial from being displaced toward the tissue; provided by the rests
support
This provides resistance to horizontal components of force; provided by the minor connector
stabilization
This provides resistance to dislodgment in a vertical or occlusal direction; provided by the retentive arm of the direct retainer; engaging the undercut
retention
This balances or counteracts the retentive force of the clasp; provided by the reciprocal arm
reciprocity
This is a component of a removable partial denture, located on the opposite side of the fulcrum line, that assist the direct retainer in preventing displacement of a denture base through mechanical leverage; prevents the lifting with sticky foods
indirect retainer
What is the purpose of the 2x2 tissue stop
prevents framework distortion during packing and processing of the acrylic resin
This type of direct retainer originates below the height of contour
infrabulge direct retainer
This type of direct retainer originates above the height of contour
suprabulge direct retainer
Kennedy class III uses which clasp design
CC clasp
Kennedy class I and II uses which clasp design
RPI and RPA
When is a wrought clasping system (combo included) indicated
when reduced force is desired upon the abutment; endo teeth and loss of bone support
This type of class is sometimes used when the available undercut is on the mesial lingual or mesial buccal of mandibular molars
ring clasp
Which clasp systems have a 0.02 undercut
wrought and combo clasp
What are four considerations when selecting the path of insertion
- amount of tooth structure to be removed on guiding surfaces
- correct location of undercut for clasping system selected
- absence of tissue undercuts that will prevent the seating of the RPD along the path of insertion
- patient’s ability to place the RPD along the path of insertion
Why must RPD clasps be configured regarding a Ken I or II
due to the lever system; rotation occurs due to differences between the tissue and the PDL
How can you counteract the class 1 lever system on a Ken I or II
move the occlusal rest to the mesial
What are the components of the RPI clasp
R - mesial rest
P - distal proximal plate
I - I bar
What are three things to watch for when fabricating an RPI clasp
tori
frenum
shallow vestibule
When is an RPI contraindicated
when there is a bony undercut below the bar or a high frenum attachment
How is reciprocation provided in the RPI clasp
minor connector to the rest
proximal plate or guide plate to DL line angle
What are the components of the RPA clasp
R - mesial rest
P - distal proximal plate
A - Akers clasp, just like the CC but the ENTIRE retentive arm is below the height of contour
The wrought wire has what proportion above the HoC
2/3
What is the fulcrum line
an imaginary line though the most posterior rest;indicates around which the denture tends to rotate under masticatory forces; involved with indirect retainers
What are the components of the combo clasp
wrought retentive arm
distal occlusal rest
lingual reciprocating arm
distal proximal plate
Which maxillary major connector is preferred for a Ken III
palatal strap
Which maxillary major connector is preferred for a Ken I, II, or IV
anterior-posterior palatal strap
At which distance from the FGM does the anterior-posterior palatal strap need to be located
5.0mm from FGM
What is the width of the anterior/posterior strap
8-10mm to prevent flexibility
What is the width of the lateral straps of the anterior-posterior palatal strap
7-9mm
What should the minimum width of the palatal strap connector be
8mm; should be determined by the width of the edentulous space
What is the approximate distance between struts
premolars; 7mm
molars; 10mm
What is the proper width of the struts
1.5-2mm
What is the proper distance between minor connectors
at least 5.0mm
For the RPI clasp, the proximal plate needs to extend where
to the distal lingual line angle for reciprocation