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Dent Station Exam fall 2015 > RPD > Flashcards

RPD Flashcards

1
Q

Components of an RPD

A

Each component has a name that is descriptive of its function:

major connector, minor connector, rests, direct retainers/clasps, indirect retainers, guide planes, base supporting replacement teeth

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2
Q

RPD must have

A

1) support derived from the abutment teeth through the use of rests
2) from the residual ridge through well fitting bases
3) stabilized against horizontal movement through the use of rigid connectors, indirect retainers
4) sufficient retention to resist reasonable dislodging forces

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3
Q

RPD Max & Mand Frameworks

A
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4
Q

Properties of the major connector

A

rigidity

not impinge on soft tissue

not placed on movable tissue

cross arch stability

connects all components

resists flexure

provide a means for placement of one or more denture bases

makes sure that parts are unified and effective

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5
Q

Mandibular MC: Lingual bar, lingual plate

A

Sublingual bar, lingual bar with cingulum bar, cingular bar

labial bar

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6
Q

Lingual Bar

A

above the movable tissue in the floor of the mouth

below the gingival margin

half pear shaped: superior margin is tapered and the inferior is rounded 4mm below

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7
Q

Mandibular Connector

A

height of the floor of the mouth measurement:

tongue lightly touching vermillion border of the upper lip - raises the floow of the mouth

measurement can be transferred to the case - indicates location of the inferior border of major connector - 8 mm from free gingival margin to the elevated floor of the mouth

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8
Q

Lingual plate

A

lingual frenum is too high

space for the lingual bar is limited - the superior border of the bar would be too close to the gingival tissue

plate permits the inferior border to be placed superiorly - avoiding tongue or gingival irritation

half-pear shape as w/ the bar & thin as technically possible incisally & follow the contour of the teeth and embrasures

bracing & stabilizing effect for periodontally challenged mandibular anterior teeth

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9
Q

Lingual Bar vs. Lingual Plate

A

Bar: superior border of the bar 4 mm below gingival margin of anterior teeth.

Inferior border of bar should not impinge on the movable tissue of the floor of the mouth

Plate: if inferior border of the bar is impinging on the tissue fo the floor of the mouth

if mandible tori is present

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10
Q

Maxillary Major Connector

A

In contrast to the mandible, the maxilla has no movable tissue as in the floor of the mouth

tissue covering the palate has firm submucosal connective tissue and good blood supply

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11
Q

Variety of maxillary major connectors:

A

single palatal bar

single palaral strap

U-shaped

anterior-posterior bar

anterior-posterior strap

full palatal

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12
Q

Location of the Major Connector

A

Maxillary: superior border located at least 6mm below free gingival margin

8mm in width

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13
Q

Single palatal strap:

A

Kennedy Class III

short edentulous areas

needs additional bulk in thickness

interfere with speech 8 mm in width

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14
Q

Anterior-posterior strap

A

any kennedy class

flat min of 8mm in width

max torus interferes in placement

weak perio support

flexure is non-existent

anterior strap can be extended to support an anterior edentulous area

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15
Q

Palatal Plate

A

Kennedy Class I

anterior edentulous area

can be uniformly thin

reproduced the anatomic contour

more acceptable to the tongue

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16
Q

U-shaped

A

used in particular in case of torus palatinus

patient that has had u-shaped before

interferes with speech

less rigid therefore made thicker

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17
Q

Single Palatal Bar

A

less than 8 mm in width

made thicker for rigidity

poor patient acceptance

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18
Q

Anterior-posterior bars

A

not used frequently

requires bulk for strength - interferes w/ speech

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19
Q

Indications for Max MC

A

weak perio support of the remaining teeth-more of the palate uncovered: A-P strap

long span distal extension, need more rigidity: A-P strap

anterior teeth to be replaced: A-P strap, u-shaped, or complete palate

torus present: u-shaped

modifying factors: number & location remaining teeth, perio support, type of opposing occlution

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20
Q

Minor connectors

A

primary function: connecting link between the major connector and the other components of the prosthesis (RPD)

distributes forces to the teeth and ridge tissues

rigid, at same time min bulk, conform to the interdental embrasure

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21
Q

Types of minor connectors

A

clasps assemblies

indirect retainers & auxiliary rests

denture bases

bar-type clasps

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22
Q

Rests

A

forces that are applied to an RPD must be transferred to the supporting teeth and tissue

rests are the components of an RPD that transfer the forces down the long axis of the abutment teeth

the prepared areas of the abutment teeth in which the rest fits is called the rest seat

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23
Q

Primary function of the Rests

A

maintains components in planned position

maintains established occlusal relationships prevents settling of the RPD

prevents impingement of soft tissue

directs and distributes occlusal (vertical) loads to long axis of abutment teeth

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24
Q

Types of Rests

A

occlusal rests - occlusal surfaces of posterior teeth

lingual or cingulum - lingual surfaces of anterior teeth

incisal - incisal edges of anterior teeth

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25
Q

Occlusal Rests

A

rounded triangular form w/ apex toward center of occlusal surface

should be as long as wide

marginal ridge is lowered for strength & rigidity at the rest-minor connector

floor of rest at the most internal is slightly deeper than the marginal ridge

angle formed between the rest & the vertical minor connector: <90 degrees

angle greater than 90 degrees - forces not transmitted down long axis

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26
Q

Lingual/Cingulum Rests

A

lingual rest is preferred to an incisal rest

closer to horizontal axis thus less tendency to tip

more esthetic

slightly rounded V

apex of the V is incisal

placed at the junction between the gingival & middle 1/3

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27
Q

Incisal Rests

A

placed at the incisal angles of anterior teeth

used indirect retainers

little less tooth structure removed

provide stabilization perio compromised tooth

floor inclination to long axis of abutment

least esthetic

select clinical situations

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28
Q

Direct Retainers/clasps

A

direct retainer: a component of the RPD that prevents/resists the displacement of the prosthesis during function

unit of the RPD that engages an abutment tooth in such a manner as to resist displacement of the prosthesis away from seat tissues (abutment teeth & soft tissue)

retention: quality inherent in a prostehsis acting to resist the forces of dislodgement along the path of placement

resists forces that want to dislodge a prosthesis during function

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29
Q

Direct retainer - extracoronal

A

uses mechanical resistance to displacement through components placed on or attached to the external surfaces of an abutment tooth -> clasp/direct retainer

most common method of extracoronal direct retention

clasp assembly of which the retentive element is the metal clasp arm with limited flexibility

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30
Q

requirement of the clasp assembly

A

retention: resists forces acting to dislodge RPD away from the supporting tissues
support: resists displacement of teh RPD apically
stability: resists displacement in a horizontal direction
reciprocation: counter acts lateral displacement of an abutment when the retentive arm passes over the hieght of contour
encirclement: prevents movement of the abutment away from the assembly
passivitiy: retentive arm is passive until a dislodging force is applied

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31
Q

clasp assembly

A

part of teh RPD that acts as a direct retainer and/or stabilizer for a prosthesis by partially encompassing an abutment tooth

components are: retentive arm, reciprocating arm, minor connector, rest

all components of the assembly should be passive

retentive part of the retentive arm is only activated in the presence of dislogement

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32
Q

clasp arm assembly

A
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33
Q

clasp assembly

A

components are:

retentive arm: B

reciprocating arm: C

minor connector: D

rest: A

demonstrates the location of the clasp components in relation to the crown or abutment thirds

buccal - retentive arm

lingual - reciprocating arm

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34
Q

encirclement

A

more than 180 degrees in the greatest circumference of the abutment must be engaged by the clasp assembly

35
Q

reciprocating arm - functions and requirements

A

intended to resist tooth movement in response to the deformation of the retentive arm as engages the height of contour

must be rigid

must contact the abutment tooth at or occlusal to the height of contour

when RPD is fully seated - reciprocating arm is passive

36
Q

height of contour

A

greatest convexity

guideline: used as a guide in the placement of retentive arms and reciprocating arms

area of cervical convergence: below the height of contour - retentive clasp components

area of occlusal convergence above the height of contour - reciprocating components

37
Q

types of clasp assemblies

A

suprabulge: retentive clasp that approaches the undercut from the occlusal or incisal
infrabulge: retentive clasp that approaches the undercut from the apical direction

38
Q

Three distinct segments of a suprabulge clasp

A

s: shoulder - originates from the minor connector
m: midsection - relatively flexible and approches the height of contour
t: terminus - crosses the height of contour and engages the undercut

39
Q

suprabulge

A

cast circumferential/Akers:

simplicity in design

disadv. - large amt of tooth structure covered
rules: originates from above the height of contour

retentive terminus should be directed occlusally

terminate at the distal or mesial line angle

40
Q

combination clasp

A

less stress on the abutment

wrought wire: soldered to the RPD versus cast as part of RPD

wrought wire: round

soldered to RPD framework

41
Q

factors influencing clasp retention

A

based on retention to deformation (must be in an undercut where the clasp is forced to deform on placement and removal)

retention is produced by:

tooth factors - undercut and how far clasp is placed into undercut

prosthesis factors - flexibility of the clasp arm, material of clasp arm

42
Q

Flexibility of the Clasp

A

the length-longer, the more flexible

the diameter-greater diameter, less flexible

cross-section - can limit flexibility e.g. half round one dimensional flexure v. round can flex in all directions

all cast metals have flexibility proportional to the bulk of metal and type of metal

wrought wire - flexes in all directions & greater flexibility w/out fracture due to tensile strength that is greater than cast clasp - increase flexure w/ less bulk

43
Q

wrought wire vs. cast clasp

A
44
Q

RPD Clasp - RPI

A

R - rest, P - proximal plate, I - “I” bar clasp (infrabulge)

used in a Kennedy Class I, II

case: moves fulcrum to mesial

less tipping force when denture base is in function

used also in other classifications

45
Q

RPI Clasps

A

Fulcrum: axis about which the denture will rotate when the denture base moves away from the residual ridge

RPI: the mesial rest of the clasp moves the fulcrum mesially

46
Q

Indirect Retainers

A

resists rotational displacement of the denture base away from the supporting tissues

*a Kennedy Class III - tooth supported/borne RPD has adequate support and retention to resist functional displacement - no indirect retainers needed

fulcrum: axis about which the denture will rotate when the denture base moves away from the residual ridge

Axis: passes through the most posterior rests on each side of the arch

47
Q

Levers

A

all levers consist of a rigid bar, fulcrum, an object to be moved, and an applied force

efficiency of the lever system depends on the arrangement of the fulcrum, object, and the force in relation to the bar

48
Q

Indirect retainer effectiveness

A

activated during rotation

distance from the fulcrum: the farther the indirect retainer is from the fulcrumm, the more efficient

rigidity

placed in a definite rest seat

49
Q

guide planes

A

2 or more parallel vertical surfaces of abutment teeth

these parallel surfaces direct the prostesis during removal insertion

gives positive direction during placement and removal

contribute to the retention of the prosthesis when the dislodging forces are other than parallel

eliminates gross food traps between abutment teeth and components of the RPD

50
Q

denture base

A

primary function:

supports the artificial teeth

receives the functional forces

transfers the forces to the supporting structures

the transfer of forces is most important for the distal extension prosthesis

51
Q

denture base 1

A

primary function is related to masticatory function

cosmetic effect of the replacement particularly in the anterior area - natural effect as to contour & shade

stimulation of the underlying tissues - tissues under functional stress w/in their physiologic limits maintain their form and tone better

52
Q

denture base 2

A

primary retention of an RPD is mechanical by direct and indirect retainers

secondary retention is by intimate contact w/the underlying tissues by adhesion and cohesion

adhesion: attraction of saliva to the denture and to underlying tissue
cohesion: attraction of the saliva molecules to each other

53
Q

Finishing lines

A

junction - between the major connector and the minor connector

90 degree butt type joint

forms interface between major connector & denture base material

54
Q

tissue stops

A

master cast with relief wax and tissue stop drawn on cast

refractory cast with tissue stop drawn on cast

RPD wax pattern on refractory cast w/ tissue stop waxed in as it was drawn prior

tissue stop in contact with the ridge and a space under framework where relief wax had been

55
Q

dental surveyor

A

to locate the most desirable path of placement & remove removal of an RPD

path of placement: direction in which the RPD moves from point of initial point of contact to terminal resting position with rest seats seated and denture base in contact w/ the supporting tissues

to locate path of removal: the reverse of placement

to identify tooth surfaces to act as guide planes

56
Q

dental surveyor

A

to locate and measure undercut areas of abutments to be used for the retentive arm of a clasp assembly

to determine whether teeth and/or soft tissue areas that could be an interference that need alteration or removal

to determine path of placement that will allow esthetic clasp placement

determine heights of contour

determine cast position for future references

locate soft tissue undercut areas

determine relative parallelism of proximal surfaces of all of the potential abutment teeth

57
Q

dental surveyor

A
58
Q

Dental surveyor

A
59
Q

dental surveyor components

A
60
Q

surveyor steps for design

A

RPD support: tooth or tooth-tissue

abutment teeth

potential guide planes

undercuts

heights of contour

tripoding

rests and potential clasps

indirect retainer

major connector

minor connectors

61
Q

surveying steps: additional considerations

A

occlusal plane approx. parallel to base of surveyor platform

retentive tooth areas - try for uniformity/balance

determine interferences - bone undercuts, malpositions teeth, etc…

will path in insertion satisfy esthetics?

62
Q

surveyor: analyzing

A

analyzing rod attachment for the surveyor spindle

analyzing rod in place to initiate evaluation of the cast

*analyzing rod perpendicular to the occlusal plane

63
Q

surveyor - analyzing rod

A

analyzing rod initial position perpendicular to the occlusal plane

visible black dot on ball joint indicates that analyzing rod is perpendicular to the occl. plane

64
Q

analyzing for parallelism

A

5 distal proximal

abutments #21, 28, & 31

potential path of placement

locating proximal surfaces of relative parallelism of and potential guide planes (proximal surfaces of abutment teeth adjacent to an edentulous area)

65
Q

potential guide planes

A

locating proximal surfaces of relative parallelism of proximal tooth surfaces and potential guide planes

proximal surfaces of abutment teeth adjacent to an edentulous area

66
Q

abutment teeth

A

max #5, 12, & 15

mand #21, 28, 31

67
Q

Tooth undercut

A

view of an undercut using an analyzing rod

triangle formed:

abutment tooth

surveyor rod

gingival tissue

68
Q

undercuts gauges

A

2 sizes:

.25 mm (.010 in.)

.50 mm (.020 in.)

undercits marked in red

69
Q

measuring undercut

A

12 undercut guage .25mm - mesial buccal

undercut present when:

shank of undercut gauge contacts height of contour

simultaneous contact of the lip of the undercut guage in the infrabulge area indicates definite degree of undercut and location

70
Q

soft tissue/ridge analysis

A

analyzing rod evaluating edentulous ridge for undercuts and possible interferences with the denture base placements

71
Q

tripoding

A

three lines on the lingual surface of the cast made w/ survey leadwith vertical arm in a locked position

relates cast to surveyor

lines should be in divergent areas

72
Q

denture base

A

tooth-tissue supported:

as the distance from the abutments increases, the ridge support increases in importance

knowledge of the limiting factors e.g. frenum & mylohyoid muscle

73
Q

Good Basic Drawing Example

A

AP strap, guide planes, RPIs, Occlusal rests, cingulum rests, finish lines, tissue stops

74
Q

drawing

A

remember - retentive forces need to be balanced. “retention must include one buccal retentive area on the right. Can not have L retention on one side and B on the other

75
Q

dr geaman’s drawing example

A
76
Q

Lingual plate & guide planes

A
77
Q

drawing - lingual bar

A

lingual bar (lingual plate option), retention wedding, tissue stops, cingulum, rests - indirect retainers, tripod marks

78
Q

RPD drawing

A

maxilary minor connector, occlusal rest & tissue stop

79
Q

survey lines, cingulum rest, occlusal rests, reciprocating arms, finish lines, retention wedding, tripod maring

A
80
Q

guide plane

A
81
Q

Tip should end slightly above undercut. I bar has retentive and stabilizing features

A
82
Q

Akers Clasp (type of circumferential clasp): not position relative to survey line

A
83
Q

Lingual retentive arm - buccal reciprocation is above survey

A

Dent Station Exam fall 2015 (18 decks)

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