4. Direct and Indirect Retainers Flashcards by J L

Direct Retainer

 The component of a PRDP used to retain and prevent ____ consisting of a clasp assembly or attachment

dislodgement

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Intracoronal - attachment placed into a crown NOT on the outside; often
incorporated into
provisional bridges &amp; are
nice bc they don’t show
clasps.

2 Systems- indicative of how tight attachment
connects to crown:

\_\_\_\_ - fits v tightly /
not loose; designed NOT
to release stress.
KC3 - bc it’s entirely
supported by abutment
teeth

____ - these
attachments “give” more Sometimes made w a ring + nylon (e.g. for
overdentures, we want
these prosths to be
supported/retained by the attachment BUT don’t
want it to torque the
abutment tooth.)

precision

semiprecision

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Extracoronal - attachment is on outside of the crown (e.g. a ring soldered to the ____ aspect of a crown w an attachment that fits into it)

Retentive class
assembly - most
\_\_\_\_; fits around
the tooth; 2 types
indicating where bulk
of clasp is located:

\_\_\_\_ ⿞
(clasp is above
height of contour
except the
retentive tip,
which flexes over
to engage)
\_\_\_\_ ⿞
(below HOC)

distal
common
suprabulge
infrabulge

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Clasp Assembly

The part of a PRDP that acts as a ____ for a prosthesis by ____ encompassing or contacting an abutment tooth

direct retainer

partially

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Terminology
Suprabulge
 the surface of a tooth that is occlusal of the ____

Infrabulge
 the surface of a tooth that is ____ of the height of contour

height of contour

gingival

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Types of Clasp Assemblies
 Suprabulge
 ____ or circumferential
 Approaches ____ from the occlusal (____ height of contour)

 Infrabulge
 ____ or bar
 Approaches undercut from the ____ (____ height of contour)

Aker’s
undercut
above

roach
gingival
below

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Clasp
That component of a clasp assembly that engages a portion of the tooth surface and either engages an undercut or remains above height of contour

Composition
 Cast ____
 Wrought wire

 Configuration
 \_\_\_\_ 
 Bar
 Combination
 Circumferential and bar
 Cast clasp arm and wrought wire clasp

Primary function
 ____
 Bracing (____)

Directional approach to
the undercut
 ____
 Infrabulge

metal
circumferential
retention
stabilizing
suprabulge

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Retention
Resistance to ____ dislodging forces
Provided by the retentive clasp arm
 Divided into three parts:
 Proximal 1/3 (shoulder)- must be ____ and located ____ the survey line
 Middle 1/3- must be ____ and ____ the survey line
 Terminal 1/3- must be ____ and engage retentive ____ on tooth ____ the height of contour

vertical
rigid
above
ridgid
traverses
flexible
undercut
below

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Retention
Should be the ____ necessary to resist dislodging forces
Retentive areas on ____ side of the arch should be opposed by retentive areas similarly placed on the ____ side of the arch

minimum
one
other

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Retention
To be retentive, the terminal end of the retentive clasp must be engaged in ____ area
 Counteract dislodging forces that unseat the PRDP at ____ angles to the occlusal plane during function

undercut

right

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Retention

 Amount of retention depends on:
1. \_\_\_\_
2. Flexibility of the clasp
arm
3. \_\_\_\_ of the undercut
4. Length
-
– amount of clasp arm extending \_\_\_\_ the height of contour
5. \_\_\_\_

material
degree
below
shape

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Flexibility of a Clasp Arm
Influenced by:
The cross-sectional form
 ____ clasp has greater flexibility than half round clasp with the same diameter

Diameter (cross-sectional size)
 The smaller the diameter of the clasp, the greater the ____

round

flexibility

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Flexibility of a Clasp Arm
Influenced by:

Length of the clasp
 the longer the clasp, the greater the ____

The taper of the clasp
 The more the taper, the more the ____
 A ____ taper in both thickness and width is necessary
 Clasp terminal should be ____ as thick as origin

flexibility
flexibility
uniform
half

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Flexibility of a Clasp Arm
Influenced by:
The material (metal alloy used)
 Flexibility of the retentive clasp arm varies with different alloys used
 \_\_\_\_
 \_\_\_\_

cast metal

wrought metal

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Wrought Metal Clasps
 Their longitudinal structure allow for greater degree of ____ than the grain structure of cast metal clasp
Are placed in slightly ____ undercuts (____ inch) than are cast clasps

flexing
greater
0.02

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Wrought Metal Clasps
Applied by:
 Soldering it to the \_\_\_\_
connector
 Soldering it to the \_\_\_\_

minor

meshwork

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 The B-L depth of retentive undercut and therefore, the position of the terminus of a retentive clasp arm is determined using undercut gauges in a dental surveyor
 0.01” undercut: ____ metal clasp
 0.02” undercut: ____ clasp
 0.03” undercut: ____ used

cast chrome
wrought wire
rarely

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Support
Resistance to ____ seating forces (displacement of the clasp assembly in a gingival direction)
Provided by the ____
Prevents ____ to periodontal structures

vertical
rests
trauma

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Stability (Bracing)
Resistance to \_\_\_\_ components of masticatory force
Provided by
 \_\_\_\_ portions of clasps
 Other rigid components which contact vertical tooth surfaces
 Proximal 
 Facial
 Lingual

Note: Retentive clasp ____ does NOT contribute to ____

horizontal
rigid
terminus
stability

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Reciprocation
Resistance to ____ forces exerted on a tooth by an active clasp during ____ and unseating of the prosthesis
Each retentive clasp arm must be opposed by a ____ arm

horizontal
seating and unseating
reciprocal

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Reciprocation
Positioned on the ____ side of the tooth from the retentive arm
Should always contact tooth ____ the retentive clasp arm when the clasp is being ____ on the tooth

opposite
before
seated

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Adequate Encirclement
 Each clasp assembly must engage a minimum of ____° of circumference of abutment tooth to prevent tooth from moving out of contact with clasp assembly
 May engage ____ than 180°

180

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Adequate Encirclement
Prevent ____ tooth movement from within the confines of a clasp assembly
May incorporate a minimum of ____ widely separated points of contact

horizontal

three

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Passivity
A clasp assembly in place should be completely ____ (no active force on tooth)
Only when a ____ force (e.g. force in occlusal direction) is applied to the PRDP is the ____ function activated

passive
dislodging
retentive

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Requirements of a Clasp Assembly Retention- ____ necessary  Support- proper ____  Stability (bracing)- ____ portions of clasps and minor connectors  Reciprocation- ____ clasp arm  Encirclement- ____° or more to prevent tooth movement  Passivity- no ____ force by clasp in place

``` minimum rests rigid reciprocal 180 active ```

``` Commonly used Clasp Assemblies for Tooth- supported PRDP ____ clasp assembly (Akers) Embrasure clasp assembly Cast circumferential and cast bar clasp assembly  ____ clasp  Modified T bar  ____ bar  I bar ```

circumferential T bar Y

Cast Circumferential Clasp Assembly  Excellent support, bracing and retentive qualities  Encircles tooth ____ than 180°  More frequently on teeth ____ to modification spaces  usable undercut on the abutment tooth is located on the side of the tooth ____ from the edentulous area

more adjacent away

Cast Circumferential Clasp Assembly Retentive clasp arm  originates ____ height of contour  terminal 1/3 is positioned ____ (engages undercut) Reciprocating clasp arm  slightly ____ than the retentive clasp to promote rigidity

above below thicker

Additional Considerations for the Cast Circumferential Clasp  The ____ of the retentive clasp and the entire ____ of the bracing clasp should be located at the junction of the ____ 1/3 of the tooth occlusogingivally

proximal 2/3 length middle and gingival

Proper Position of Retentive Clasp Terminus  Should not contact the ____  Should be located at the ____ portion of the gingival 1/3 of the tooth occlusogingivally

free gingival margin | gingival

Embrasure Clasp Two ____ clasp assemblies originating from a common ____ connector Indicated on side of arch where there is no ____ space Must cross the marginal ridges of ____ teeth

circumferential minor edentulous two

Embrasure Clasp Occlusal rests on ____ teeth Two cast ____ clasps Two cast ____ clasps Must provide sufficient space for adequate thickness of metal  Prepare rest seats and marginal ridges adequately

both retentive reciprocating

Bar Clasps • Classified by shape of the ____  T bar, modified T bar,Y bar • T and Y bar clasp arms are the most ____ • Only ____ of clasp is needed to be placed in undercut area

retentive terminal misused terminal

Bar Clasps • In many cases the ____ portion of T or Y clasp arm may be removed because they are ____ the survey line and they become ____ T or Y bar clasp.

suprabulge above modified

Bar Clasp Approach undercut from a ____ direction More ____ than a circumferential clasp

gingival | esthetic

Bar Clasp T bar  ____ undercut Modified T bar  ____ finger omitted (____)

DB nonretentive esthetics

Bar Clasp Y bar  ____ are high on M & D but low on ____ of abutment tooth I bar  on ____ of canines for esthetics

height of contours center DB

Here’s the T-bar in the ____ 1/3 picking up the undercut at 2 termini. This has been relieved (points in this green highlighted space); this is the approach arm. We don’t want this too high on the tooth.

gingival

Relationship of Bar Clasp to the Gingiva • The approach arm must not impinge on the ____ adjacent to the abutment • The approach arm should cross ____ to the free gingival margin

soft tissues | perpendicular

``` Contraindication to Bar Clasp • The clasp should not be located over a deep tissue ____ • A great deal of relief required may  form a ____  interfere with patient comfort  cause ____ to the mucosa of the lip or cheek ```

undercut food trap injury

Additional Design Considerations for the Bar Clasp • The minor connector that attaches the occlusal rest to the framework should  be ____  contribute to the overall ____ and stabilization of the prosthesis

rigid | bracing

Commonly used Clasp Assemblies for Extension Base PRDP ____ clasp assembly ____ (RPC) clasp assembly ____ and wrought wire circumferential clasp assembly (combination clasp)

RPI RPA cast circumferential

RPI Clasp Assembly/ RPA (RPC) Clasp Assembly  RPI:  Rest (____)  Proximal plate (____)  Cast ____ bar retentive clasp engaging ____ or mid-buccal ____  Proximal plate and minor connector provide ____

``` MO D I 0.01" MB undercut reciprocation ```

Mechanics of the RPI Clasp Assembly • Forces are transmitted through the PRDP components to the ____ rest directing mesial torquing and axial forces to the tooth • Occlusal force causes rotation in the area of ____ rest • I bar clasp arm and proximal plate ____ from the tooth during function and move in a ____ direction • The abutment tooth is braced mesially by an ____ tooth

``` mesial mesial disengage mesiogingival adjacent ```

Contraindication for the RPI Clasp Assembly • No tooth undercut • Severe tissue undercut  Clasp arm -no more than ____ mm from the soft tissue  Excessive relief may form food trap food, interfere with patient comfort or irritate the lip or cheek • ____ buccal or labial vestibule  I bar arm should not interfere with movable tissue  Superior border of the arm located at least ____mm from the gingival margin

2 shallow 3

Advantages of the RPI Clasp Assembly Proximal plate and I bar move ____ from the tooth during function to reduce torque Mesial minor connector and proximal plate provide ____ and eliminate need for a ____ arm (no need for lingual recontouring) I bar is more ____ Mesial rest eliminates class ____ lever

``` away reciprocation lingual esthetic I ```

RPI Clasp Assembly/ RPA (RPC) Clasp Assembly  RPA Clasp Assembly:  Rest (____)  Proximal plate (____)  ____ retentive clasp engaging ____ or mid-buccal undercut  Proximal plate and minor connector provide ____  Used where RPI clasp is contraindicated  severe tissue ____  ____ B vestibular depth

``` MO D akers 0.01" MB reciprocation undercut insufficient ```

Assembly and Mechanics of RPA Clasp * Forces are transmitted through RPD components to the ____ rest directing mesial torquing and axial forces to the tooth. * Rotation occurs in the area of ____ rest. * Circumferential clasp and proximal plate ____ from tooth during function. * The abutment tooth is usually braced by a mesial ____ tooth.

mesial mesial disengage adjacent

Combination Clasp ____ circumferential (reciprocal) clasp arm A ____ circumferential (retentive) clasp arm  Indications  on an abutment tooth adjacent to a distal extension space when the usable undercut is on the ____ surface  greater ____ of retentive arm is desired  ____ an advantage

``` cast wrought wire MB flexibility adjustability ```

Combination Clasp  Advantages:  may be used when a ____ projection clasp is contraindicated because of a soft tissue ____ below the tooth  can be placed in a ____ undercut area (____”)  ____ occlusal rest, distal proximal plate

``` vertical undercut deeper 0.02 distal ```

Mechanics of Cast Circumferential and Wrought Wire Clasp (Combination Clasp) Strategy – Reduce the effective Class ____ lever in distal extension partial by using ____ component in the resistance arm. • Consists of cast, reciprocal arm and tapered, round wire, retentive clasp arm • The retentive clasp is either ____ to a cast framework

I flexible cast or soldered

Mechanics of Combination Clasps • Rotation occurs at area where minor connector breaks ____ with tooth • Wrought wire retentive clasp tip moves ____ during function and directs a ____ torquing force on tooth • Magnitude of the torquing force is influenced by the ____ of the wrought wire clasp

contact occlusally distal flexibility

Advantages of Combination Clasps • Flexibility- used when maximum flexibility required  Abutment tooth adjacent to ____ extension base.  Weak abutment, when a ____ type retainer contraindicated. * Adjustability- when precise retentive requirements ____ and later on adjustment needed for retention. * Esthetics – less bulkier than cast clasp. Wrought wire small diameter thickness, stronger because ____ in structure. Light reflected in such a way that the appearance of metal less obvious. * Minimum tooth surface coverage – less ____ buildup

``` distal bar unpredictable round plaque ```

``` Disadvantages of Combination Clasps  Involves extra ____ in fabrication  Can be ____ by careless handling  won’t ____ tooth  It may distort with function and not engage tooth ```

step distorted stabilize

Ring Clasp Most often indicated on ____ molars ____ almost the entire tooth from its point of origin Entire clasp except for the ____ must be placed above the height of contour An ____ arm is needed to prevent excessive f lexing

tilted/tipped encircles retentive tip auxiliary bracing

Factors Determining the Selection of Clasp Assembly A. Distribution of Forces  ____ of forces to muco-osseous and dento- alveolar segments is required  ____ clasps minimize lateral torquing forces directed to abutment teeth  ____ clasps direct lateral torquing forces to the abutment teeth

distribution stress releasing non-stress directing

Factors Determining the Selection of Clasp Assembly A. Distribution of Forces  Commonly Used Non-stress Directing Clasp  ____ (circumferential) clasp  ____ clasp  Commonly Used Stress Releasing Clasp Assemblies  ____ (Rest, Proximal Plate, I-Bar)  ____ (Rest, Proximal Plate, Akers)  Cast circumferential and wrought wire circumferential (____) clasp

akers embrasure RPI RPA combination

Factors Determining the Selection of Clasp Assembly B. Location of Undercut  on ____ tooth will influence choice of retentive clasp arm C. Minimal tooth and minimal gingival coverage  Clasps which ____ these tissues are preferred  Reduce plaque accumulation ``` D. Esthetics  Influenced by visibility of clasp  Bar clasps • confined to ____ 1/3 of tooth and contact less tooth surface area • approach undercut from ____ direction • are less conspicuous than ____ clasp ``` E. Clasps on Previous Removable Partial Denture  May indicate esthetic awareness and demand of patient  May indicate amount of ____ necessary

``` abutment minimize gingival gingival circumferential retention ```

Indirect Retainer  “The component of a removable partial denture that assists the direct retainer (s) in preventing ____ of the distal extension denture base by functioning through ____ action on the opposite side of the fulcrum line when the denture base moves ____ from the tissues in pure ____ around the fulcrum line” (GPT, 1999)

displacement lever away rotation

Indirect Retainer Should be positioned on the ____ side of the fulcrum line (center of rotation) At ____ angles to and as far from the fulcrum line as possible

opposite | right

``` Indirect Retainer Forces causing vertical movement of the denture base away from the supporting ridge:  pull of ____ foods  forces created by ____ action  ____ ```

sticky muscle gravity

``` Indirect Retention ____ premolar  an ideal location for an indirect retainer (no opposing maxillary cusp that occludes into this fossa)  Anterior to ____ line (F)  Resists lifting of denture base ```

mesial fossa of mandibular first | fulcrum

Indirect Retention | Without an indirect retainer, the PRDP may ____

dislodge

Types of Indirect Retainers ____ ____ connectors and proximal plates Others  ____  Need rest seats prepared  Kennedy bar ____ connector

rests minor lingual plate major