Fundamentals of RPD Design Flashcards
which kennedy classification cannot have a modification space
class IV
what are the tooth-tissue supported kennedy classifications
- kennedy class I (Bilateral distal extension)
- kennedy class II (unilateral distal extension)
what are the tooth supported kennedy classifications
- kennedy class III
- kennedy class IV (single edentulous area crossing the midline)
what is after determining the class of the RPD
- survey the cast and draw/carve orientation (tripod) lines
- draw heights of contour
- evaluate possible guide planes
- identify undercuts
what are the mandibular major connectors
- lingual plate
- lingual bar
what are the 5 reasons to lingual plate
- opposing a maxillary denture
- inadequate space for a bar (8mm needed)
- anticipate loss of additional teeth
- mandibular tori
- aid in lateral and rotational stability
what are the maxillary major connectors
- palatal strap
- anterior palatal strap
- A-P strap
- full palatal coverage
if the major connector is not plating the lingual surfaces of the max teeth the frame needs to be:
at least 6mm away from the gingival margin
the minor connectors are:
portion of the RPD framework that connects the major connector to the clasp assembly, indirect retainer, denture base
in a kennedy class III RPD the rests of the RPD are located where
toward the edentulous area on the teeth adjacent to the edentulous area
you need approximately _____ of inter occlusal clearance
1.5mm
RPD rests are ____ of the buccal/lingual width
1/3
RPD rests in an edentulous area bordered by teeth on anterior and posterior rests are located _____ the edentulous space
toward
where are RPD rests located in a free end distal extension
away from the edentulous area
how many retentive clasps would be used in a kennedy class I design
2
what are the number of clasps necessary for a kennedy class I
2
what are the number of clasps necessary for a kennedy class II
3
what are the number of clasps necessary for a kennedy class III and IV
4
how do you alter the retentiveness of a clasp
- clasp length
- clasp diameter
-clasp taper - 1/2 round or round
- material
- amount of undercut engaged
what are the two types of retentive clasps
- infrabulge
- suprabulge
what are the infrabulge clasps
- I-bar clasps
- T and 1/2 T clasp
- Y clasp
what are the suprabulge clasps
- cast circumferential clasp (1/2 round and round)
- wrought wire (combination clasp)
what are the advantages of infrabulge clasps and contra indications
- advantages: esthetic, more retentive
- contra indications: excessive soft tissue undercut, lack of vestibular depth (min 4 mm), inability to place the terminus at the gingival 1/3
where are infrabulge clasps best utilized
on a sound abutment tooth adjacent to a free end edentulous area provided the tooth is tall enough and provides relief (undercut) gingival to the distal guide plate
what are the circumferential suprabulge clasps
1/2 round or round cast
what are the best utilized suprabulge
1/2 round - tooth supported RPDs
- round - tooth/tissue supported RPDs
wrought wire clasps are also called
combination clasps
when are wrought wire clasps best used
on tooth/tissue supported RPDs when the abutment tooth is compromised and an ideal guide plane is not present
where will rest seats be with with tooth/tissue supported RPDs when the abutment tooth is comproised and an ideal guide plane is not present
toward the free end distal extension
what if you dont have any undercut
- surveyed crown
- place a divot
- place composite
what if you dont have a buccal undercut
lingual retentive clasps
when an RPD is completely seated what is the function of the reciprocal clasp
it serves no purpose when fully seated
what is the reciprocal used for
to counterbalance the forces applied by the retentive clasp as it passes over the height of contour
what is the action distance of sterm
the distance that in which the retentive clasp is reciprocated
- 3-5mm
where are reciprocal clasps located
on all teeth that have a retentive clasp
which kennedy classification will never have an indirect retainer
class IV
what are the types of indirect retainers
- occlusal
- incisal
- cingulum
where are indirect retainers located
on tooth tissue supported RPDs
indirect retainers are located _______ to the primary fulcrum line which extends through _________
anterior; the most posterior abutments
what is the purpose of the indirect retainer
resists the RPDs tendency to move or rotate in an occlusal direction
what are the RPD impression techniques
static and functional impressions
PDL of abutment has a vertical displacement of ______
0.25mm
the gingival tissue on the residual ridge has a vertical displacement of about _____
2mm
what are the RPD impression methods
- metal stock tray with alginate (never plastic)
- custom tray, border mold, PVS impression
- corrected (altered) cast impression
when are the altered cast impressions done
on mandibular kennedy class I and II
describe the impression technique
framework must fit the mouth and be passive
- add tray to framework
-1mm wax relief
- check seating on cast and in mouth
- after tray is added: rests must be fully seated also the major connector, no resistance to seating
- check peripheries
- border molding
impression tray must be _____ short of vestibular extend
2-3mm
no displacement when:
pulling on the cheeks and lips
- patient activates the tongue
border molding techniques are ______ for RPD as CD
the same
how do you do the corrected cast impression
- remove wax spacer
- coat tray with adhesive
- use light body impression material
- carefully load tray - no material under rests, guide planes, major connector
- seat with pressure only over the rests, not on the saddle
why dont you want pressure over the tray
will cause tissue compression
what should be inspected on the impression
- no material under rests or minor connectors- remove excess material if present
- impression detail is correct
what are the lab steps
- section cast- remove extensions
- place retentive grooves or holes in the master cast
- ensure no contact between impression material/tray and cast
- sticky wax framework in place against teeth
describe boxing technique
box the master cast with the RPD framework/impression attached and pour the new edentulous ridges in yellow stone
what do you add if the metal stops dont contact the cast
add duralay tissue stops to the framework
what are the potential problems with the corrected cast technique
- a framework not seated either during the impression (material under rest, plate) or when being poured will result in an RPD that wont fit properly on teeth/tissues
- stone leaking over teeth during pouring makes articulation impossible
