PRINCIPLES OF REMOVABLE PARTIAL DENTURE DESIGN Flashcards
T/ F
the strategy of selecting component parts for a partial denture to help control the movement of the prosthesis under functional load has been
highlighted as as method to consider for
logical partial denture design
T
Who introduced 5 basic principles in designing of removable partial denture?
COLONEL ARTHUR H. SCHMIDT (1953)
5 basic principles in designing of removable partial denture:
(1) Dentist must have a working knowledge of both the mechanical and biological factors included in RPD design and construction
(2) Any plan of restoration must be based on complete examination and diagnosis of individual patient
(3) The dentist not the technician should correlate the pertinent factors and recommend a proper plan of treatment
(4) A RPD should restore form and function without injury to the tissue
(5) A RPD is a form of treatment not a care
tooth-supported, or Class III, removable partial denture, like fixed partial denture, is supported by ___
abutments
T/ F
Classes I, II, and IV removable partial dentures are subjected to greater stresses because their support is a combination of tooth and soft tissue
T
a removable partial denture in the mouth can perform the
action of two simple machines, the ___&___
lever and the inclined plane
if the lever rests against its ___ and a weight is applied at another point, rotation or movement will occur around the
support
support
(the support is known as the fulcrum and movement takes
place around the fulcrum)
fulcrum is in center
→ resistance is at one end
A. First-Class
B. Second-Class
C. Third-Class
A
→ effort or force is at opposite end
→ most efficient and easily controlled lever
A. First-Class
B. Second-Class
C. Third-Class
A
→ fulcrum at one end
→ effort at opposite end
A. First-Class
B. Second-Class
C. Third-Class
B
→ resistance in center
→ seen as indirect retention in removable
partial dentures
A. First-Class
B. Second-Class
C. Third-Class
B
→ fulcrum at one end
→ resistance at opposite
A. First-Class
B. Second-Class
C. Third-Class
C
→ effort in center
→ not encountered in partial dentures
A. First-Class
B. Second-Class
C. Third-Class
C
the ___ is the other simple machine to be concerned with
o forces against the inclined plane may result in deflection of that which is applying the force or may result in movement to the inclined plane
o neither of these results is desirable
inclined plane
is in distal extension removable partial dentures that the type
of prosthesis controlling stress is important
PROSTHESIS SUPPORT
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the all-tooth supported partial denture is mostly subjected to
induced stresses, because leverage-type forces are not involved and there are no fulcrums around which the partial denture may rotate
F
the all-tooth supported partial denture is RARELY subjected to
induced stresses, because leverage-type forces are not involved and there are no fulcrums around which the partial denture may rotate
T/f
inclined planes are also not a factor when the partial denture is tooth supported
T
T/F
the distal extension partial denture, on the other hand, is subjected to rotation around three principal fulcrums
T
T/f
horizontal fulcrum line passing between two principal
abutment teeth controls rotational motion of denture toward or away from supporting ridge
T
________ extends from occlusal rest on terminal abutment posteriorly along crest of residual ridge; this fulcrum controls rocking, or side-to-side, movement that takes place over crest of ridge; in a Class I arch there are two such fulcrums
second rotational fulcrum
third fulcrum is ____ and is located in midline lingual to anterior teeth; it controls movement of denture in horizontal plane
vertical
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a modified T bar or I bar engaging the distobuccal
retentive area results in action similar to second class lever; when downward pressure is applied to partial denture, the clasp tip will also have downward movement thereby minimizing lateral stress on the abutment tooth
T
T/ F
Intracoronal retainers change the contour of abutment teeth
F
extracoronal retainers change the contour of abutment teeth
T/F
lingual and palatal major connectors must be rigid to transmit lateral stresses to other parts of the partial denture
T
T/F
lingual and palatal major connectors must be rigid to transmit lateral stresses to other parts of the partial denture
T
T/f
The longer the edentulous area covered by the denture base, the greater the potential level action on the abutment teeth
T
T/f
Flat ridge will provide good support, poor stability
T
T/f
Sharp spiny ridge will provide poor support, poor to fair
stability
T
T/f
Displaceable tissue on ridge will provide poor support and
poor stability
T
elastic impression materials use for IMPRESSION REGISTRATION
*irreversible hydrocolloid (alginate)
*mercaptan rubber base (thiokol)
*silicone impression materials (both condensation and addition reaction)
* polyethers
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The supporting form of the soft tissue underlying the distal
extension base of the partial denture should be recorded so that firm areas are used as primary stress-bearing areas and readily displaceable tissues are not overloaded
T
T/f
no single impression material can satisfactorily fulfill both of the previously mentioned requirements
→ recording the anatomic form of both teeth and supporting tissue will result in inadequate support for the distal extension base this is because the cast will ot represent the optimum coordinating forms, which necessitates that the ridge be related to the teeth in a supportive form
T
T/f
a fifth point of difference between the two main types of removable partial denture lies in their requirements for direct retention
T
arising from the body fo the clasp and approaching the undercut from an occlusal direction
Circumferential Type
arising from the base of the denture and approaching the undercut area from a gingival direction
Bar Type
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in the combination tooth- and tissue-supported removable partial dentures, because of this tissue ward movement, those elements of a clasp that lie in an undercut area mesial to the fulcrum for a distal extension (as is often seen with a distal rest) must be able to flex sufficiently to dissipate stresses that otherwise would be transmitted directly to the abutment tooth as leverage
T
produced on a cast by a surveyor making the greatest prominent of contour in relation to the planned path of placement of a restoration (GPT 7)
SURVEY LINES
marks the height of contour of the tooth
SURVEY LINES
Blatterfein divided the buccal and lingual surfaces in to two halves and described them as:
Near Zone
Far Zone
area closer to the edentulous space
Near Zone
area away from the edentulous space
Far Zone
survey lines can be classified as:
A. High Survey Line
B. Medium Survey Line
C. Low Survey Line
D. Diagonal Survey Line
→ line passes from the occlusal third in the near zone to the occlusal third in the far zone
→ undercut will be deep
A. High Survey Line
B. Medium Survey Line
C. Low Survey Line
D. Diagonal Survey Line
A
a wrought wire clasp which is more flexible should be used
A. High Survey Line
B. Medium Survey Line
C. Low Survey Line
D. Diagonal Survey Line
A
→ line passes from the occlusal third in the near zone to the middle third in the far zone
→ aker’s or roach clasp is used
A. High Survey Line
B. Medium Survey Line
C. Low Survey Line
D. Diagonal Survey Line
B
→ closer to the cervical third of the tooth in both near and far zone
→ a modified t-clasp is used
A. High Survey Line
B. Medium Survey Line
C. Low Survey Line
D. Diagonal Survey Line
C
runs from occlusal third in the near zone to cervical third of far zone
A. High Survey Line
B. Medium Survey Line
C. Low Survey Line
D. Diagonal Survey Line
D
a reverse circlet clasp is used
A. High Survey Line
B. Medium Survey Line
C. Low Survey Line
D. Diagonal Survey Line
D
originating from a distal occlusal rest on the terminal abutment tooth and engaging a mesio-buccal retentive undercut should not be used on a distal extension removable partial denture
CIRCUMFERENTIAL CAST CLASP
→ the terminal of this clasp reacts to movement of the denture base toward the tissue by placing a distal tipping, or torquing, force on the abutment tooth
→ this particular force is the most destructive force a retentive clasp can exert; this clasping concept must be avoided at all costs
CIRCUMFERENTIAL CAST CLASP
approaching a distobuccal undercut from mesial occlusal surface, may be acceptable for a distal extension partial denture. As the denture base moves toward the tissue, the retentive clasp tip will tend to move into an area of greater undercut (arrow). This action releases torquing forces that can damage an abutment tooth.
reverse circlet clasp
used on the terminal abutment tooth on a distal extension partial denture when the retentive undercut is located on the distobuccal surface
vertical projection, or bar, clasp
as the denture base is loaded toward the tissue, the retentive tip of the T-clasp rotates gingivally to release the stress being transmitted to the abutment tooth
VERTICAL PROJECTION, OR BAR, CLASP
→ it is never indicated when the tooth has a mesiobuccal undercut
→ the bar clasp functions in a manner similar to the reverse
circumferential clasp
VERTICAL PROJECTION, OR BAR, CLASP
releases torsional stress on the terminal abutment tooth.
The vertical projection T-clasp
This releasing action is accomplished when the retentive clasp tip rotates gingivally into a greater undercut as tissueward forces are applied to the denture base (arrows). Rotation takes place around distal occlusal rest.
vertical projection T-clasp
(VERTICAL PROJECTION, OR BAR, CLASP )
→ one school of thought on the philosophy of removable partial denture design has advocated omitting the _____ occlusal rest from the terminal abutment in favor of a ___ rest when a bar clasp is used
→ advantage claimed for moving the occlusal rest more ___ is that the lever arm (the distance from the rest to the denture base) is ___, which causes the force directed toward the residual ridge to be more vertical and thus, better tolerated by the ridge
distal, mesial
anteriorly, increased
(VERTICAL PROJECTION, OR BAR, CLASP )
One advantage claimed for eliminating distal occlusal rest (A) and placing a mesial rest more anteriorly (B) is that lever arm, represented by ____ from rest to denture base, is increased.
distance
(VERTICAL PROJECTION, OR BAR, CLASP)
A ___ force is better tolerated by ridge than is a ___ oblique force
vertical, horizontal
when a mesiobuccal undercut exists on an abutment tooth adjacent to a distal extension edentulous ridge, the combination clasp can be employed to reduce the stress transmitted to the abutment tooth
COMBINATION CLASP
wrought alloy wire, by virtue of its internal structure, is more flexible than a cast clasp
COMBINATION CLASP
can flex in any spatial plane, whereas a cast clasp flexes in the horizontal plane only
COMBINATION CLASP
the wrought wire retentive arm has a stress-breaking action that can absorb torsional stress in both the vertical and horizontal planes
COMBINATION CLASP
how the tooth has responded to
previous stress)
bone index area
in a tooth- and tissue-supported partial denture, consideration must be given to:
- the quality of the residual ridge, which includes contour, quality of the supporting bone and quality of the supporting mucosa
- the extent to which the residual ridge will be covered by the denture base
- the type and accuracy of the impression registration
- the accuracy of the denture base
- the design characteristics of the component parts
of the partial denture framework - the anticipated occlusal load
in an entirely tooth-supported partial denture, the potential
support an abutment tooth can provide, consideration should be given to:
- periodontal health
- crown and root morphologies
- crown-to-root ratio
- bone index area (how the tooth has responded to
previous stress) - location of the tooth in the arch
- relationship of the tooth to other support units
(length of edentulous span - the opposing dentition
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major connectors must be rigid so that forces applied to
any portion of the denture can be effectively distributed to
the supporting structures
T
T/f
minor connectors arising from the major connector make it
possible to transfer functional stress to each abutment tooth through its connection to the corresponding rest and also to transfer the effect of the retainers, rests, and stabilizing components to the remainder of the denture and throughout the dental arch
T
T/f
retention is accomplished by mechanical retaining elements (clasps)
T
retention is accomplished by mechanical retaining elements (clasps), the key to selecting a successful clasp design for any given situation is to choose one that will:
- avoid direct transmission of tipping or torquing forces to the abutment
- accommodate the basic principles of clasp design
- provide retention against reasonable dislodging
forces - be compatible with undercut location, tissue
contour, and esthetic desires of the patient
T/F
the fourth step is to connect the retention units to the support
units
o if direct and indirect retainers are to function as designed,
each must be rigidly attached to the major connector
T
T/f
the fifth and last step in this systematic approach to design is to outline and join the edentulous area to the already established design components
T
ESSENTIALS OF PARTIAL DENTURE DESIGN
determine how the partial denture is to be supported:
A, 1st
B. 2nd
C. 3rd
D. 4th
E. 5th
A
ESSENTIALS OF PARTIAL DENTURE DESIGN
systematically developing the design for any removable partial denture is to connect the tooth and tissue support units
A, 1st
B. 2nd
C. 3rd
D. 4th
E. 5th
B
ESSENTIALS OF PARTIAL DENTURE DESIGN
the third step is to determine how the removable partial denture is to be retained
A, 1st
B. 2nd
C. 3rd
D. 4th
E. 5th
C
ESSENTIALS OF PARTIAL DENTURE DESIGN
is to connect the retention units to the support
units
A, 1st
B. 2nd
C. 3rd
D. 4th
E. 5th
D
ESSENTIALS OF PARTIAL DENTURE DESIGN
systematic approach to design is to outline and join the edentulous area to the already established design components
A, 1st
B. 2nd
C. 3rd
D. 4th
E. 5th
E
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to secure the maximum possible retention through the use of the forces of adhesion and cohesion, the denture base should cover the maximum area of available support and must be accurately adapted to the underlying mucosa
T
T/f
To enhance the quality of retention through adhesion and cohesion, the denture base must fit edentulous ridge accurately and must cover the maximum area of available support.
T
the partial denture should be designed so that guide planes are created on as many teeth as possible
FRICTIONAL CONTROL
term guiding plane is defined as two or more parallel, vertical surfaces of abutment teeth, so shaped to direct a prosthesis during placement and removal
FRICTIONAL CONTROL
Development of guide planes on proximal surfaces of teeth adjacent to edentulous spaces will increase retention of partial denture by ____. These guide planes may be created in enamel surfaces.
frictional contact
is indicated most often for Class III arches particularly when there is a modification space on the opposite side of the arch
QUADRILATERAL CONFIGURATION
a retentive clasp should be positioned on each abutment tooth adjacent to the edentulous spaces
o this results in the denture being confined within the outline
of the four clasps and leverage on the denture is effectively neutralized
A. QUADRILATERAL CONFIGURATION
B. TRIPOD CONFIGURATION
C. BILATERAL CONFIGURATION
QUADRILATERAL CONFIGURATION
is used primarily for Class II arches
o if there is a modification space on the edentulous side, the teeth anterior and posterior to the space are clasped
A. QUADRILATERAL CONFIGURATION
B. TRIPOD CONFIGURATION
C. BILATERAL CONFIGURATION
B
this design is not as effective as the quadrilateral configuration, but is most effective in neutralizing leverage in the Class II situation
A. QUADRILATERAL CONFIGURATION
B. TRIPOD CONFIGURATION
C. BILATERAL CONFIGURATION
B
most removable partial dentures fall into the bilateral distal extension group or Class I
A. QUADRILATERAL CONFIGURATION
B. TRIPOD CONFIGURATION
C. BILATERAL CONFIGURATION
C
the single retentive clasp on each side of the arch should be located near the center of the dental arch or denture bearing area
A. QUADRILATERAL CONFIGURATION
B. TRIPOD CONFIGURATION
C. BILATERAL CONFIGURATION
C
the clasps exert little neutralizing effect on the leverage-induced stresses generated by the denture base
A. QUADRILATERAL CONFIGURATION
B. TRIPOD CONFIGURATION
C. BILATERAL CONFIGURATION
C
part of the partial removable denture prosthesis that joins the components of one side of the arch to those on the opposite sid
A. MAJOR CONNECTORS
B. MINOR CONNECTORS
A
should be rigid necessary to provide proper distribution of forces to and from the supporting components
A. MAJOR CONNECTORS
B. MINOR CONNECTORS
A
must be supported by rests at each of anterior span
A. MAJOR CONNECTORS
B. MINOR CONNECTORS
A
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In the mandibular arch, the lingual plate major connector that is properly supported by rests can aid in the distribution of functional stresses to the remaining teeth.
T
T/f
In the maxillary arch, the use of a broad palatal major connector that contacts several of the remaining natural through lingual plating can distribute stress over a large area
T
T/f
In the maxillary arch, the use of a broad palatal major connector that contacts several of the remaining natural through lingual plating can distribute stress over a large area
T
the connecting link between the major connector or base of a partial removable denture prosthesis and the other units of the prosthesis such as the clasp assembly, indirect retainers, occlusal rests, or cingulum rests
A. MAJOR CONNECTORS
B. MINOR CONNECTORS
B
this close metal-to-enamel contact serves two purposes:
o offers horizontal stability to the partial denture against lateral forces on the prosthesis; the tooth with its supporting
bone helps dissipate these displacing stresses
A. MAJOR CONNECTORS
B. MINOR CONNECTORS
B
through the contact of the minor connector and the abutment tooth, the tooth receives stabilization against ____ stresses
lateral
component of a removable dental prosthesis used to retain and prevent dislodgement, consisting of a clasp assembly and precision attachment
Direct Retainer
the part of the removable dental prosthesis that acts as a direct retainer and/or a stabilizer for a prosthesis by partially encompassing or contacting an abutment tooth
Clasp Assembly
an interlocking device, one component of which is fixed to an abutment or abutments and the other is integrated to a removable dental prosthesis in order to stabilize and/or to retain it
Precision Attachment
retain the prosthesis against reasonable dislodging
forces without damage to the abutment teeth
A. TOOTH-SUPPORTED PARTIAL DENTURES
B. DISTAL EXTENSION PARTIAL DENTURES
A
to aid in resisting any tendency of the denture to be
displaced in a horizontal plane
A. TOOTH-SUPPORTED PARTIAL DENTURES
B. DISTAL EXTENSION PARTIAL DENTURES
A
→ the prosthesis cannot move tissueward as the rest supports the
retentive components of the clasp assembly
→ there should be no movement away from the tissue and
therefore, no rotation about a fulcrum because a direct retainer
secures the retentive component
A. TOOTH-SUPPORTED PARTIAL DENTURES
B. DISTAL EXTENSION PARTIAL DENTURES
A
→ the clasp retainer must not impinge on gingival tissue and must
not exert excessive torque on the abutment tooth during
placement and removal
→ it must be located the least distance into the tooth undercut for
adequate retention and it must be designed with a minimum of
bulk and tooth contact
A. TOOTH-SUPPORTED PARTIAL DENTURES
B. DISTAL EXTENSION PARTIAL DENTURES
A
→ the bar clasp arm should be used only when the area for
retention lies close to the gingival margin of the tooth
→ with an excessive tissue undercut, recontouring the abutment and
using some type of circumferential direct retainer is advisable
A. TOOTH-SUPPORTED PARTIAL DENTURES
B. DISTAL EXTENSION PARTIAL DENTURES
A
____ (frictional) retainers are ideal for tooth-supported
restorations and offer esthetic advantages that are not possible
with extracoronal (clasp) retainers
intracoronal
____ (frictional) retainers are ideal for tooth-supported
restorations and offer esthetic advantages that are not possible
with extracoronal (clasp) retainers
intracoronal
the retainer should retain the prosthesis and also be able to flex or disengage when the denture base moves tissueward under function; thus, the retainer may act as a stress-breaker
A. TOOTH-SUPPORTED PARTIAL DENTURES
B. DISTAL EXTENSION PARTIAL DENTURES
B
→ the clasp arm must be freely flexible in any direction, as dictated by the stresses applied
→ bound, tapered clasp forms offer advantages of greater and more universal flexibility, less tooth contact, and better esthetics
A. TOOTH-SUPPORTED PARTIAL DENTURES
B. DISTAL EXTENSION PARTIAL DENTURES
B
explained stress breakers which automatically return the saddle to rest position following displacement
ALLISON G. JAMES (1955)
basic principle involved is that portion of appliance directly attached to the abutment teeth, the anterior part of palatal casting shall be rigid, and with __ motion possible allowed
between it and the abutment
minimum
the ___ will be attached to this rigid portion by a narrow
isthmus in the saddle casting as close as feasible to the midline of the palatal appliance
saddles
components of the partial removable dental prosthesis that assists the direct retainers in preventing displacement of the distal extension denture by functioning through lever action on the opposite side of the fulcrum line when the denture base moves away from the tissues in pure rotation around the fulcrum line
INDIRECT RETAINERS
→ it must be placed as far anterior from the fulcrum line
→ it must be placed on a rest seat prepared on an abutment tooth
that is capable of withstanding the forces placed on it
INDIRECT RETAINERS
cannot function effectively on an inclined tooth surface, nor on a single weak incisor tooth; either a canine or premolar tooth
should be used for the support of
indirect retainer
function:
o restrict movement of a distal extension base away from the basal seat tissue
o support for major connectors
INDIRECT RETAINERS
when the edentulous span is too large to ensure adequate support from the adjacent teeth, an ________ may be attached to the adjacent abutment teeth in such a manner that fixed splinting of the abutment teeth results, with a smooth, contoured bar resting lightly on the gingival tissue to support the removable partial denture
anterior splint bar
___ surfaces are minimally contacted by rounded form of lower portion of bar. Anterior and posterior slopes of splint bar must be compatible with path of placement of denture.
Tissue
differs from the splint bar in that the ____ provides both support and retention from the connecting bar
internal clip attachment
→ every consideration should be directed to preventing the need for a distal extension removable partial denture
→ in many instances, it is possible to salvage the roots and a portion of the crown of a badly broken-down molar through endodontic treatment
OVERLAY ABUTMENT AS SUPPORT FOR A DENTURE BASE
→ a ______ is a removable partial denture in which the framework is designed and fabricated in separate parts
→ the tooth support and tissue supported components are individually fabricated, and the two are joined with a high impact acrylic resin to become a single, rigid functioning unit
component partial
