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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
Occlusal Rests
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
26
Lingual/Cingulum Rests
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
27
Incisal Rests
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
28
Direct Retainers/clasps
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
29
Direct retainer - extracoronal
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
30
requirement of the clasp assembly
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
31
clasp assembly
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
32
clasp arm assembly
33
clasp assembly
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
34
encirclement
more than 180 degrees in the greatest circumference of the abutment must be engaged by the clasp assembly
35
reciprocating arm - functions and requirements
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
height of contour
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
types of clasp assemblies
suprabulge: retentive clasp that approaches the undercut from the occlusal or incisal infrabulge: retentive clasp that approaches the undercut from the apical direction
38
Three distinct segments of a suprabulge clasp
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
suprabulge
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
combination clasp
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
factors influencing clasp retention
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
Flexibility of the Clasp
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
wrought wire vs. cast clasp
44
RPD Clasp - RPI
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
RPI Clasps
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
Indirect Retainers
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
Levers
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
Indirect retainer effectiveness
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
guide planes
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
denture base
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
denture base 1
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
denture base 2
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
Finishing lines
**junction** - between the major connector and the minor connector 90 degree butt type joint forms interface between major connector & denture base material
54
tissue stops
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
dental surveyor
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
dental surveyor
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
dental surveyor
58
Dental surveyor
59
dental surveyor components
60
surveyor steps for design
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
surveying steps: additional considerations
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
surveyor: analyzing
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
surveyor - analyzing rod
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
analyzing for parallelism
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) #5 distal proximal #12 distal proximal #15 mesial proximal
65
potential guide planes
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
abutment teeth
max #5, 12, & 15 mand #21, 28, 31
67
Tooth undercut
view of an undercut using an analyzing rod triangle formed: abutment tooth surveyor rod gingival tissue
68
undercuts gauges
2 sizes: .25 mm (.010 in.) .50 mm (.020 in.) undercits marked in **red**
69
measuring undercut
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 #12 undercut guage .25mm - mesial buccal
70
soft tissue/ridge analysis
analyzing rod evaluating edentulous ridge for undercuts and possible interferences with the denture base placements
71
tripoding
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
denture base
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
Good Basic Drawing Example
AP strap, guide planes, RPIs, Occlusal rests, cingulum rests, finish lines, tissue stops
74
drawing
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
dr geaman's drawing example
76
Lingual plate & guide planes
77
drawing - lingual bar
lingual bar (lingual plate option), retention wedding, tissue stops, cingulum, rests - indirect retainers, tripod marks
78
RPD drawing
maxilary minor connector, occlusal rest & tissue stop
79
survey lines, cingulum rest, occlusal rests, reciprocating arms, finish lines, retention wedding, tripod maring
80
guide plane
81
Tip should end slightly above undercut. I bar has retentive and stabilizing features
82
Akers Clasp (type of circumferential clasp): not position relative to survey line
83
Lingual retentive arm - buccal reciprocation is above survey

Dent Station Exam fall 2015 (18 decks)

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