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REMOVABLE > direct retainers part 1 > Flashcards

direct retainers part 1 Flashcards

1
Q

resist disloding forces

A

RPD retention

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2
Q

mechanical from retaining elements on abutment teeth

A

primary retention

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3
Q

-intimate contact of minor connector with guide planes

-intimate contact of denture base and maxillary major connector with underlying tissues

A

secondary retention

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4
Q

RPD component used to retain and prevent dislodgement

A

direct retainer

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5
Q

two types of direct retainers

A

intracoronal
and
extracoronal

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6
Q

-internal precision attachment: key/keyway
-most esthetic
(type of direct retainer)

A

intracoronal direct retainer

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7
Q

disadvantages of intracoronal direct retainers

A

require crown
complex fabrication
high maintenance

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8
Q

-clasp assembly
-more commonly used
(type of direct retainer)

A

extracoronal

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9
Q

retentive arm approaches undercut from above the survey line

A

suprabuldge

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10
Q

type of suprabulge clasps:
type of infrabulge clasps:

A

suprabulge:
circumferential, akers, circlet

infrabulge:
bar clasps

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11
Q

retentive arm approach undercut from below survey line

A

infrabulge

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12
Q

properly constructed suprabulge or infrabulge clasp assembly must incorporate the following components:

A
  1. rest
  2. retentive clasp
  3. reciprocal clasp
  4. and one or more minor connector
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13
Q

6 clasp assembly components

A
  1. rest
  2. reciprocal components
  3. retentive clasp arm
  4. retentive terminal
  5. minor connector
  6. approach arm
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14
Q

this component lies on occlusal, lingual, incisal surface
-prevents tissueward movement of clasp

A

rest

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15
Q

4 types of rests

A
  1. occlusal rest
  2. cingulum chevron rest
  3. lingual ball rest
  4. incisal rest
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16
Q

-rigid component
-above height of contour
-reciprocal clasp, lingual plate, proximal plate, guide plate (minor connectors)

A

reciprocal component of clasp assembly

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17
Q

what part of the retentive clasp is in proximal 2/3, rigid portion, and above height of contour

A

retentive clasp arm

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18
Q

what part of the retentive clasp is in distal 1/3, flexible, below height of contour, and provides direct retention

A

retentive terminal (clasp tip)

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19
Q

part of clasp assembly that joins body of clasp to framework; rigid

A

minor connector

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20
Q

what clasp assembly component joins body of clasp to framework; rigid

A

minor connector

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21
Q

what clasp assembly component of bar clasp connects clasp to framework and is flexible minor connector (exception to the rule)

A

approach arm

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22
Q

6 requirements of clasp assembly

A
  1. support
  2. stability
  3. encirclement of more than 180 degrees
  4. reciprocation
  5. passivity
  6. retention
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23
Q

this requirement of clasp assembly resist vertical movement toward tissue
(rests)

A

support

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24
Q

this requirement of clasp assembly resists horizontal displacement, areas above the survey line, all rigid components of direct retainer

A

stability

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25
Q

this requirement of clasp assembly may be continuous or broken, minimum of 3 points used, prevents tooth from moving away from the clasp

A

encirclement of more than 190 degrees

26
Q

this requirement of clasp assembly
-reciprocal component contact tooth at the same time or sooner than retentive clasp
-remain in contact while retentive tip passes over height of contour
-resist retentive tip lateral forces
-requires parallel surface to path of insertion

A

reciprocation

27
Q

this requirement of clasp assembly components of direct retainer exert no force when fully seated

A

passivity

28
Q

this requirement of clasp assembly resists displacement of RPD away from supporting tissues, area below survey line: ideally in gingival 1/3 (clasp arm tip: terminal 1/3 below survey line)

A

retention

29
Q

this portion of the tooth must be undercut in relation to path of prosthesis insertion

A

retention portion

30
Q

retention factors:

A
  1. angle of convergence of the undercut
  2. depth of undercut
  3. flexibility of the retentive clasp
31
Q

when should the retentive clasps should become active

A

ONLY when disclosing forces are applied to them

32
Q

retentive clasp ability to provide retention is based on

A

the resistance of the metal to deformation

33
Q

retentive clasp flexibility factors
1
2
3
4
5

A
  1. length
    double length, 8x MORE flexible [increase length, curve clasp]
  2. diameter
    double diameter, 8x LESS flexible
  3. taper
    -clasp terminal 1/2 as thick as origin (1mm to 0.5mm)
    -clasp terminal 1/2 as wide as origin (2mm to 1mm)
  4. cross-sectional form
    round clasp more flexible than half-round
    -round flexes in all spatial planes
    -half round flexes in one plane
  5. material
    cast chromium<cast gold<wrought
34
Q

cross sectional shapes
1. this almost always as in circumferential clasps= flexes in only one direction
2. as in wrought wire clasps=flexes omnidirectionally and provides max flexibility

A
  1. half round
  2. round
35
Q

with increasing clasp flexibility, must use______ undercuts to obtain equal retention

A

deeper

0.010 cast chrome
0.015 cast gold
0.020 wrought

36
Q

what is the alloy used in casting the framework

A

usually ticonium (NiCr) or vitallium (CoCr)
-easy to fabricate

37
Q

this is produced by drawing metal through dies of smaller diameter and most flexible of all clasps

A

wrought wire

38
Q

the design of a retentive clasp arm should incorporate maximum clasp _____for optimal flexibility

A

length

39
Q

-approaches undercut from above the survey line
-Pulls toward occlusal to resist displacement

(retentive qualities for what type of clasp)

A

circumferential clasp

40
Q

-approaches undercut from below survey line
-pushes towards occlusal to resist displacement
-easier to seat, more difficult to remove than circumferential clasp

(retentive qualities for what type of clasp)

A

bar clasp

41
Q

this clasp must be rigid, shaped different than flexible retentive clasp, and not tapered

A

reciprocal clasp

42
Q

the means by which one part of the framework opposes the action of the retainer in function

A

reciprocation

43
Q

how may the reciprocation be achieved by

A

-rigid plating (lingual plate)
-minor connectors
-guid planes extended around the vertical line of abutments
-reciprocal clasp arms
-contact areas of proximal teeth

44
Q

this is the most logical clasp for tooth-supported RPD (kennedy class III)
-excellent stabilization, support bracing
-easiest to design and construct
-easier to repair

A

circumferential clasps

45
Q

what are the disadvantages of circumferential clasps

A

-covers more tooth surfaces: more conducive to caries
-increases tooth circumference: cause greater occlusal force exerted on teeth
-more difficult to adjust

46
Q

why keep the circumferential clasp as low on crown as survey line permits

A

-less torquing action on tooth
-less interference with occlusion
-if survey line too high, enamel surface must be recontoured to lower survey line

47
Q

if the survey line is too low

A

surveyed crown required

48
Q

this clasp is cast 1/2 round
-proximal 2/3 in middle 1/3 above survey line
-terminal 1/3 in gingival 1/3 below survey lines and tip curves to occlusal
*tapers from origin 2mm to tip 1mm

A

retentive clasp

49
Q

this clasp is cast 1/2 round
-entire clasp in middle 1/3 above survey line
-no taper: uniform width 1.5-2mm

A

reciprocal clasp

50
Q

what are the 4 types of circumferential clasps

A
  1. circlet
  2. embrasure clasp
  3. ring clasp
  4. combination clasp
51
Q

this circumferential clasp
-engage undercut remote from edentulous area
-choice of class III RPD

A

circlet

52
Q

this circumferential clasp
-2 circlet clasps joined at body
-used when retainer is necessary in dental area
-class III with no modification space
-class II with no modification space
-class IV
-requires heavy reduction of abutment teeth for adequate clasp bulk

A

embrasure clasp

53
Q

this circumferential clasp
indication: mesiolingually-tipped mandibular molar class III RPD
-engages mesiolingual undercut
-bracing arm for reciprocity
additional occlusal rest
-avoid if possible

A

ring clasp

54
Q

this circumferential clasp
indication: retentive undercut adjacent to edentulous space
-class III RPD
-tooth-tissue supported RPD (class I or II distal extension)
-1/2 T bar clasp preferred, if no tissie undercut at approach arm
-avoid if possible

A

reverse circlet clasp

55
Q

this circumferential clasp
-wrought round wire retentive clasp
-cast 1/2 round reciprocal clasp

A

combination clasp

56
Q

this circumferential clasp
indications: distal extension RPD (class I or II)
-mesial rest not possible, distal rest must be used
-mesiofacial undercut
-wrought wire soldered to framework

A

combination clasp

57
Q

RPC clasp assembly (RPA)

A

Rest (mesial), Proximal Plate, Circumferential (akers) clasp

58
Q

what are the indications for RPC clasp assembly

A

-class I or II RPDS
-mesiofacial retentive undercut

59
Q

for RPCs, the circumferential retentive clasp is ALWAYS:

except in periodontally compromised teeth and Kennedy I w/o modification: cast round

A

cast 1/2 round

60
Q

what are the reciprocations in RPCs

A

distal proximal plate and ML minor connector

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