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2. Philosophy of design.
There are three basic, underlying
approaches to distributing the forces
acting on a partial denture between the
soft tissue and the teeth.
1.Stress equalization
2.Physiologic basing.
3.Broad stress distribution
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4. Disadvantages
The stress director is comparatively
fragile, and its construction is complex and
costly. It requires constant maintenance and
may be difficult or impossible to repair.
Although attempts are usually made to
strengthen the hinge to prevent lateral
movement of the denture base, its lack of ability
to prevent damaging lateral stresses from
occurring on the edentulous ridge can result in
rapid resorption of bone.
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5. Stress Equalization
The resiliency of the tooth secured by the
periodontal ligament in an apical direction is not
comparable to the greater resiliency and
displaceability of the mucosa covering the
edentulous ridge. Because of this great disparity,
forces are transmitted to the abutment teeth as the
denture bases are displaced in function.
A rigid connection between the denture bases
and the direct retainer on the abutment teeth is
damaging and that some type of stress director or
stress equalizer is essential to protect the vulnerable
abutment teeth.
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7. The treatment of the partially
edentulous
patient
requires
the
knowledge and the skill of the dentist in
almost every phase of dental practice.
Decisions relative to teeth to be
retained, surgical procedures to be
employed, and types of restorations to be
placed must be made with the ultimate
design of the prosthesis in mind.
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8. Advantages
The stress director design usually calls for minimal
direct retention, because the denture base operates
more independently than in a conventional denture.
Theoretically, at least, the stress director eliminates
the tipping strain on the tooth, thus preventing bone
resorption about the tooth.
Sum of its resiliency and that of the periodontal
ligament is equal to the resiliency of the mucosa. Thus
forces are distributed equally between the teeth and
the soft tissue.
Intermittent pressure against the mucosa caused by
the movement of the bases has a massaging or
stimulating effect www.indiandentalacademy.com
on the underlying bone and soft
tissue.
9. Disadvantages
The stress director is comparatively
fragile, and its construction is complex and
costly. It requires constant maintenance and
may be difficult or impossible to repair.
Although attempts are usually made to
strengthen the hinge to prevent lateral
movement of the denture base, its lack of ability
to prevent damaging lateral stresses from
occurring on the edentulous ridge can result in
rapid resorption of bone.
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10. Philosophy of design.
There are three basic, underlying
approaches to distributing the forces
acting on a partial denture between the
soft tissue and the teeth.
1.Stress equalization
2.Physiologic basing.
3.Broad stress distribution
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11. Principles of Design
by A.H. Schmidt in 1956.
1. The dentist must have a thorough knowledge of
both the mechanical and biologic factors involved in
removable partial denture design.
2. The treatment plan must be based on a complete
examination and diagnosis of the individual patient
3. The dentist must correlate the pertinent factors and
determine a proper plan of treatment
4. A removable partial denture should restore form and
function without injury to the remaining oral
structure.
5. A removable partial denture is a form of treatment
and not a cure www.indiandentalacademy.com
12. Physiologic Basing
This philosophy of design denies the necessity
of using stress directors to equalize the disparity of
vertical movement between the tooth and mucosa.
The belief is that the equalization can best and most
simply be accomplished by some form of physiologic
basing, or lining, of the denture base.
The physiologic basing is produced either by
displacing or depressing the ridge mucosa during the
impression making procedure or by relining the
denture base after it has been constructed
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13. It seems obvious that the artificial teeth of a
removable partial denture constructed from a tissue
displacing impression will be positioned above the
plane of occlusion when the denture is in the mouth
and not in function. To permit vertical movement of
the partial denture from the rest position to the
functioning position, the direct retainers or retentive
clasps must be designed with minimal retention and
the number of direct retainers must be limited.
The occlusal rests and direct retainers will
also be slightly unseated at rest.
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15. Advantages
The intermittent base movement that occurs
as occlusal loads are applied and removed has a
physiologically stimulating effect on the underlying
bone and soft tissue, which is said to reduce the
frequency of the need to reline or rebase the
prosthesis to correct for tissue change cause by
resorption.
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16. Disadvantages
Because of the artificial teeth are always
slightly above the occlusal plane when the denture is
not in function, there will always be slightly premature
contacts
between the opposing teeth and the
denture teeth when the mouth is closed.
By the time the indirect retainer engages a rest
seat to prevent the denture base from being
dislodged, the direct retainer will have lost contact
with the abutment tooth.
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17. Broad stress distribution
Advocates of this school of partial denture
design believe that excessive trauma to the
remaining teeth and residual ridge can be
prevented by distributing the forces of occlusion
over as many teeth and as much of the available
soft tissue area as possible. This is accomplished
by the use of additional rests, indirect retainers,
clasps, and broad coverage denture bases.
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18. Advantages
Lateral forces may be distributed over as many
teeth as possible.
Clasps may be used on some teeth not for
retention but to aid in lateral stability.
Because of the increased stability and
decreased movement, the broad stress distribution
partial denture does not require relining as frequently
as the other types because the residual ridge does
not bear as much of the occlusal plane.
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19. Disadvantages
An increased amount of tooth surface
coverage
philosophy.
is
associated
with
this
design
Preventive dental programs to
monitor caries must be instituted and carefully
followed for each patient.
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20. DESIGN PROCEDURE
Color-coding
A color coding system for the various parts of the
removable partial denture as well as for other
items of information that should be included on the
diagnostic casts helps prevent confusion on the
part of a dental laboratory technician or anyone
trying to understand the design being proposed.
Red, blue, and brown crayon pencils and a black
lead pencil, two H or three H hardness, are used.
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21. The brown crayon pencil is used to outline the
metallic portion of the partial denture; the blue
crayon pencil, to outline the acrylic resin portion of
the prosthesis. Rest seats are drawn in solid red.
The black pencil and the carbon marker in the
surveyor are used to denote survey lines, tripod
marks, soft tissue undercuts, and other information
that must be included such as the type of tooth
replacement or the use of wrought wire for retentive
clasps.
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22. Step-by-Step Procedure
1. Examine the occluded diagnostic casts.
2. Indicate with a pencil using the following symbols,
the type of tooth replacement desired.
Denture teeth on a denture base - no symbol
Tube tooth - T
Facing - F
Metal pontic - M
Reinforced acrylic pontic - RAP
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23. 3. Place the cast on the cast holder at a horizontal
tilt. Examine the teeth to be clasped for favorable
retentive undercuts examine anterior edentulous
area for esthetic considerations. Examine proximal
and lingual tooth surfaces for guiding planes.
Outline in red-pencil those surfaces that will
require re-contouring or reshaping to produce the
desired result.
4. Tripod the cast
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24. 5. Place a carbon marker in the vertical arm of the
surveyor and scribe the survey line on the teeth
that will be contacted by the partial denture.
6. with a red pencil draw in the extent of rest areas
to be prepared in the mouth.
7. Outline the exact position and extent of the
denture base area. Blue pencil indicates acrylic
resin denture base; brown indicates a metal
denture base.
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25. 8. With a brown pencil, outline the framework
design
to
harmonize
and
join
the
major
connectors, rest areas, indirect retainers, minor
connectors, denture bases, and replacement
teeth. Use the carbon marker to outline soft
tissue undercuts that will influence the design
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26. 9. Replace the carbon marker with the appropriate
undercut gauge. (For most clasps of chrome, cobalt
alloy a O.OIO-inch undercut is adequate. For
wrought wire retentive clasps, 0.020 inch is usually
indicated).
10. With the brown pencil, draw the clasp arms to
the actual shape size and location desired. If
wrought wire clasps are to be used, place the
symbol WW on the soft tissue below the tooth.
11. Re-examine the design for accuracy and clarity.
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27. The Various Principles Involved in the
Functioning of a Removable Partial
Denture
Different forces acting on a denture in the mouth.
The response of the denture to the forces acting
on it.
Design methods, which help to limit the effects of
these harmful forces
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28. Different Forces Acting on the Denture
Inside the Oral Cavity
Occlusal force - It acts on the occlusal
surface of the denture. It is of very high
magnitude. This force pushes the denture on
to the tissues on the edentulous ridge.
Excessive occlusal forces can produce
residual ridge resorption.
Forces from the tongue - The tongue tends to
push the denture buccally and labially.
Excessive force from the tongue can displace
the denture frequently during function.
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29. Forces from the surrounding musculature (lip
and cheek muscles)- These forces compensate
the forces of the tongue. Excessive forces tend to
displace the denture .A balance is usually
maintained between the buccinator and the tongue.
This balance results in a 'dead zone of nil force'.
This zone is called neutral zone or zone of minimal
conflict or zone of equilibrium .Artificial teeth on the
denture should be placed on this zone to achieve
good stability for the denture.
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30. Response of the Denture to Various
Forces Acting on it
Generally tissue supported partial dentures
respond like a lever or like an inclined plane
when a force is applied on them. Tooth supported
partial dentures (Kennedy's Class III) are not
supported by resilient structures, and they
transmit all the forces acting on the prosthesis
along the long axis of the abutment tooth.
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31. A tooth supported partial denture is rarely
subjected to induced stresses because Leverage type of forces are not involved.
There is no fulcrum line around which the partial
denture can rotate.
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32. Lever- "A lever is a long bar with a single
support around which it rotates when a load is
applied to any one of its ends." The support
around which the lever rotates is called as the
fulcrum.
Levers can be of three types namely:
1st - order levers
IInd - order levers
IIIrd - order levers
Each lever modifies the intensity of the force
acting on the denture to a different degree.
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33. Ist order lever: In this lever the fulcrum is in the
center, resistance is at one end and effort (force)
is at the other .These levers are more efficient
and easily controlled. This type of lever can occur
in patients with distal extension partial dentures.
The direct retainer will be the fulcrum, effort end
lies on the point where the denture takes up the
occlusal load (area where the artificial teeth are
located) the load is the region of the anterior end
of the major connector .
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34. IInd order lever: In this lever, the fulcrum is at one
end, effort is at the opposite end and resis-tance or
load is the center. This type of lever action occurs in
indirect retention of a removable partial denture.
When a displacing force tends to lift a denture from
one end (effort), the anterior most point of the major
connector will act as the axis of rotation (fulcrum),
the intermediate zone of the denture, which is lifted
by the force, will form the resistance (load) of the
lever.
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37. IIIrd order lever: In this lever, the fulcrum is at one
end, resistance is at the opposite end and effort is
at the center e.g. tweezers. This type of lever action
does not occur in partial dentures.
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38. Lever action
prosthesis:
in
a
Kennedy's
Class
I
In a distal extension partial denture rotation
occurs around 3 principal fulcrums. They are:
•Horizontal fulcrum line passing between two
principal abutment teeth: It acts along the x-axis
of the denture. This controls the rotational motion
of the denture towards or away from the
supporting soft tissues. Forces across this lever
produce the most deleterious effect on the
supporting tissues and the abutment teeth .
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40. Second rotational fulcrum line (Sagittal):
It extends posteriorly from the occlusal rest of the
terminal abutment. It passes along the alveolar
crest till the posterior extent of the residual ridge
on the same side. It acts along the z-axis of the
denture. This fulcrum controls rocking or side-toside movement of the denture that takes place
over the crest of the residual ridge . In a Class I
condition, there are two such fulcrums extending
posteriorly from each primary abutment to the
respective retromolar pads. These forces also
have severe effects on the soft tissues.
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42. Third fulcrum line (Vertical): It is vertical and is
located on the midline, lingual to the anterior
teeth. It acts along the y-axis of the denture. It
controls the movement of the denture around the
y-axis).
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43. Inclined plane
Inclined plane is nothing but two inclined
surfaces in close alignment to one another. The
direct retainers and the minor connectors slide
along the guide planes of the teeth and can act
as inclined planes if not prepared correctly.
When a force is applied against an inclined
plane it may produce two actions:
• Deflection of object, which is applying the
force (Denture).
• Movement of the inclined plane itself (tooth).
These results should be prevented to avoid
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damage to the abutment teeth.
45. Designing an RPD to Limit the Effects of
Harmful Forces
Factors influencing magnitude
transmitted to abutment teeth
of
stresses
The various factors that control the amount of
stress transmitted to the abutment are:
1. Length of edentulous span.
2. Quality of support of ridge.
3. Response of oral structures to previous stress.
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46. 4. Occlusal relationship of the remaining
teeth and orientation of the occlusal plane.
5. Qualities of a clasp.
6. Clasp design.
7. Length of clasp.
8. Material used in clasp construction
9. Abutment tooth surface
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47. Length of edentulous span: The longer the
edentulous span, the longer will be the denture
base and the greater will be the force transmitted to
the abutment tooth. Posterior teeth should be
preserved as far as possible to reduce the length.
Quality of support of ridge : Large,
well-formed"
ridges are capable of absorbing greater amounts
of stresses than small, thin, or knife edged ridges.
Broad ridges with parallel sides permit the use of
longer flanges on the denture base, which helps to
stabilize the denture against lateral forces. A
mucoperiosteum, which is approximately 1 mm
thick, gives good support compared to a thin
atrophic mucosa. www.indiandentalacademy.com
48. 3. Response of oral structures to previous stress.
The periodontal condition of the remaining teeth,
need for splinting and the amount of abutment
support remaining, are all a result of the previous
stress subjected on the oral tissues. These
factors affect the prognosis of the new prosthesis
too.
4. Occlusal relationship of the remaining teeth
and orientation of the occlusal plane.
Improper occlusal relationship and a steep
occlusal plane tend to increase the amount of
force acting on the denture.
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49. The force applied on natural teeth is 300 pounds and
the force acting on artificial teeth is about 30 pounds.
Poor occlusal relationship can lead to supra-eruption
of the opposing natural teeth.
The denture base area against which the occlusal
load is applied determines the amount of stress
transmitted to the abutment and the edentulous
ridge. The occlusal load should be applied on the
center of the denture bearing area both
anteroposteriorly and buccolingually (the second
premolar and first molar region). Artificial teeth
should be arranged so that the bulk of themasticatory
forces are concentrated here.
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50. 5. Qualities of a clasp A flexible retentive clasp arm
decreases the stress that will be transmitted to the
abutment tooth. Example: A wrought wire clasp is
more flexible than a vertical projection clasp, hence,
it decreases the forces acting on the abutment tooth
and
increases
the
forces
transferred
to
the
edentulous ridge. But it provides less horizontal
stability.
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51. 6. Clasp design A clasp should be passive when it
is completely seated on an abutment tooth. The
passive clasps will exert less stress on the teeth. If
a clasp is active throughout the period of denture
wear, it will produce injury to the abutment. When
the framework is completely seated, the retentive
clasp arms should become passive.
Disclosing wax can be used to test the proper
placement of a framework. A clasp should be
designed so that the reci-procal arm contacts the
tooth before the retentive tip passes over the
greatest bulge of the tooth during insertion and it
should be the last compo-nent to lose tooth
contact during removal of the prosthesis.
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52. 7. Length of clasp The flexibility of a clasp
depends on its length. Doubling the length
incre-ases the flexibility by five times. This
decreases the stress on the abutment tooth. Using
a curved rather than a straight clasp on an
abutment tooth will aid to increase the clasp length
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53. 8. Material used in clasp construction A clasp I
constructed of chrome alloy will exert more stress
on the abutment tooth than a gold clasp because
of its greater rigidity. To decrease the stress, the
chrome alloy clasps are constructed with smaller
diameter.
9. Abutment tooth surface The surface of a gold
crown or restoration will offer more functional
resistance to the movement a clasp arm than
enamel. Therefore, more stress is exerted on the
tooth restored with gold than on the tooth with
intact enamel.
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54. Controlling stress by design consideration
A removable partial denture will always have a
destructive effect within the oral cavity.
The following factors can be modified to reduce the
stresses developed within a denture.
1. Direct retention – the retentive clasp arm is
responsible for transmitting the destructive forces
to the abutment teeth. A removable partial denture
should be designed in such a way that the
retention obtained from the clasp is just enough to
provide
adequate
retention
to
prevent
dislodgement of the denture. It should also be
remembered that the retentive clasp should be
designed such that it is active only during insertion
and removal. www.indiandentalacademy.com
55. 2. Forces of adhesion and cohesion Adhesion is defined
as "The physical attraction of unlike molecules for one
another" - GPT. Here, Adhesion refers to the attraction of
saliva to the denture and the tissues. Cohesion is defined
as "The physical attraction of like molecules for one
another" - GPT. Here, Cohesion refers to the internal
attraction of the molecules of saliva for each other.
Forces of adhesion and cohesion can be increased by:
Recording an accurate impression so that the
denture base fits accurately to the supporting tissues.
Increasing the denture bearing area.
Atmospheric pressure may also contribute to retention.
Generally, major connectors are beaded at their margins
so that a tight valve seal is obtained.
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56. 3. Frictional control: Partial dentures should be
designed to have maximum number of guide
planes. Guide planes are flat surfaces on the teeth
that are created such that they are parallel to one
another and also to the path of insertion. As the
name suggests, guide planes help to guide the
denture during insertion.
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57. Preparation of guide planes on the proximal
surfaces of the teeth adjacent to edentulous
spaces will increase the retention by frictional
contact. These planes may be created on the
enamel surfaces of the restorations placed on the
teeth. During displacement, the components of the
denture produce frictional retention along the
surface of the guide planes.
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58. Kratochvil (1963) advocated an extension guide
surface preparation to eliminate space between
the guide plate and the abutment. Maximum
contact of the guide surface and the guide plate
was desired. A 2-3mm of metal foot extended
from the base of the guide plate onto the mucosa
of the residual ridge. Binding of the guide plate
against the abutment during function (movement
of the extension base toward the tissue when
biting force is applied over the base) was
prevented by physiologic relief of the metal at the
framework try-in stage
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60. Ten years later, Krol (1973) modified Kratochvil's
design and created the term RPI clasp (restproximal plate-I-bar). He recommended a much
smaller guide surface preparation (2 to 3 mm in
height; located in the occlusal third of the proximal
surface) and a guide plate that contacted only the
bottom 1 mm of the guide surface. Binding or
torquing of the abutment was prevented by
retaining a small space below the guide surface
(into which the guide plate could move during
function). The portion of the guide plate in contact
with the gingival tissue was relieved.
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61. Demer (1976) proposed another alteration in the
design. He concurred with Krol that a slight
undercut should be retained below the guide
surface. However, he felt that the more gingival
location of the guide plate would create the
potential for food entrapment between the occlusal
aspects of the abutment and the artificial tooth. He
recommended that the guide plate contact the
proximal surface of the abutment only at the top of
the guide surface. Demer also extended the guide
plate lingually far enough so that, in combination
with the minor connector of the mesial rest, it would
provide reciprocation and prevent lingual migration
of the abutment. www.indiandentalacademy.com
62. Research comparing the concepts noted has been
inconclusive. Excellent clinical success can be
expected using any of the three designs if certain
conditions are ensured.
First either by initial design or by way of
physiologic relief the guide plate must be
prevented from binding against the abutment
Second the mesial minor connector must have
freedom to move between the abutment and the
adjacent tooth during function
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63. Third. metal (e.g.. guide plate. plating) located
distal to the terminal rest must not be allowed to
extend above the height of contour .
Fourth, the mesial rest-I-bar-guide plate design
should be avoided on mesially inclined terminal
abutments because it is extremely difficult to
achieve any "releasing" capacity for the guide
plate .During function the guide plate will contact
the tooth and act as a rest on an inclined plane.
Efforts to prevent contact with physiologic relief
would create a significant space between the
abutment and the prosthesis.
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64. 4. Neuromuscular control The action of lips, cheeks and
tongue can be a major factor in the of the denture. A
properly contoured denture base can. aid to improve the
patient's neuromuscular control of the prosthesis. An
overextended denture will 'get constantly dis-placed due
to the neuromuscular action. Frequent displacement of
these denture~ will lead to excessive stress on the
abutment.
5. Clasp position. Position of the retentive clasp in relation
to the height of contour is more important in retention and
in controlling stresses than the number of clasps present
in the entire prosthesis. 'Consider the following example:
It is easier to pullout a pole immersed in sand from its tip
than at a point just above the level of the sand. Similarly,
a clasp located deep in the undercut will be more difficult
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to remove.
65. 6. Number and placement of clasps The number of clasps
used and their placement determine the type of stress
developed within a denture"
Removable partial dentures with four clasps are
described to have a quadrilateral configuration. Similarly
removable partial dentures with three and two clasps are
described to have a tripod and bilateral configuration
respectively. Quadrilateral configuration is the most
efficient in controlling the stresses developed within a
denture. Additional clasps are usually added to increase
the stability and force distribution of the partial dentures
with few clasps
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66. Quadrilateral configuration This design involves the
use of four clasps. It is used commonly for Kennedy's
class III arches particularly when there is a
modification space on the opposite side of the arch. A
retentive clasp should be positioned on each
abutment tooth adjacent to the edentulous spaces.
In a Kennedy's class III arch with no
modification, one clasp is placed as far posterior on
the dentulous side as possible and the other is I
placed as far anterior as possible depending on the
availability of space and aesthetics. This retains the
quadrilateral concept and is effective in controlling the
stress.
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68. Tripod configuration This design involves the use of
three clasps. It is used for Kennedy's class II arches. In
class II cases, rotational forces act on the prosthesis
producing stress over the terminal abutment tooth.
Adding two abutments on the opposite side helps to
stabilize and distribute the forces. One clasp is placed
on the posterior most abutment of the edentulous
space, and the other two are placed on the anterior
and posterior ends of the dentulous quadrant. If a
modification space is present, the anterior and
posterior teeth adjacent to the modification space are
clasped. If a modification space is not present, the
posterior clasp is placed as posterior as possible. The
placement of the anterior clasp is determined by the
availability of interocclusal space and aesthetics.
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70. Bilateral configuration: This design is used for a
Kennedy's class I partially edentulous arch. The
terminal abutment teeth are clasped. The clasps
have a very minimal neutralizing effect on the
stresses developed by leverage-induced forces
on the denture base. These stresses should be
controlled using other methods.
Additional clasps can be used at the anterior
end to convert the design into a quadrilateral
configuration.
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72. 7.Clasp Design
Circumferential cast clasp
The movement circumferential cast clasp
originating from a distal occlusal rest on the
terminal abutment tooth and engaging a
mesiobuccal retentive undercut should not be used
on a distal extension removable partial denture. The
terminal of this clasp reacts to movement of 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.
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74. The reverse circlet, a cast circumferential clasp that
approaches a distobuccal undercut from the mesial
surface of a terminal abutment tooth, , is acceptable.
The effect on the abutment tooth is reversed from
that of the conventional circumferential clasp.
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75. Vertical Projection, or Bar, Clasp.
The vertical projection, or bar, clasp is used on
the terminal abutment tooth on a distal extension
partial denture when the retentive undercut is
located on the distobuccal surface. It is never
indicated when the tooth has a mesiobuccal
undercut.
The bar clasp functions in a manner similar to
the reverse circumferential 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. The bar
clasp does not produce the wedging force
sometimes produced by the reverse circumferential
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clasp
77. One school of thought on the philosophy of
removable partial denture design has advocated
omitting the distal occlusal rest from the terminal
abutment in favor of a mesial rest when a bar clasp
is used. The belief is that a distal rest would cause
the fulcrum line around which the denture tends to
rotate to be distal to the retentive clasp terminal.
Theoretically the retentive tip could not
release if the denture base were to move toward the
tissue. Another advantage claimed for moving the
occlusal rest more anteriorly is that the lever arm
(the distance from the rest to the denture base) is
increased, which causes the force direct toward the
residual ridge to be more vertical and thus better
tolerated by the ridge.
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78. If the distal rest, or a rest adjacent to any
edentulous space, is omitted, a space is left
between the framework and tooth surface in
which food debris will collect and be trapped
against the most critical and sensitive area of the
tooth, the gingival crevice.
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79. Combination clasp
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.
Wrought alloy wire, by virtue of its internal
structure is more flexible than a cast clasp. It can flex
in nay spatial plane, whereas a cast clasp flexes in
the horizontal plane only. The wrought wire retentive
arm has a stress breaking action that can absorb
torsional stress in both the vertical and horizontal
planes. A cast circumferential clasp under the same
circumstances would transmit most of the leverage
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induced stress to the abutment tooth.
80. Splinting of Abutment Teeth
Adjacent teeth may be splinted by means of
crowns to control stress transmitted to a weak
abutment tooth. Splinting two or more teeth
actually increase the periodontal ligament
attachment area and distributes the stress over a
larger area of support.
Splinting is also indicated when the proposed
abutment tooth has either a tapered root or short
roots such that there is not an acceptable amount
of periodontal ligament attachment present.
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81. One of the most important and frequently
indicated needs for splinting is when the terminal
abutment tooth on the distal extension side of the
arch stands alone, that is, an edentulous space
exists both anterior and posterior to it. This
situation is most often seen in second premolars,
both maxillary and mandibular. Such a premolar is
potentially a weak abutment because of
the
rotational forces it must withstand. Splinting of this
tooth to the tooth anterior to it, usually the canine,
should be accomplished with a fixed partial denture.
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83. Splinting by means of clasps on the removable
partial denture is possible under some conditions.
This should not be attempted if fixed splinting is
possible because it is considered a compromise
form of treatment. It is indicated when no other
approach is feasible. The splinting consists of
clasping more than one tooth on each side of the
arch, using a number of rests for additional support
and stabilization, and preparing guiding planes on
as many teeth as possible to contribute to
horizontal stabilization of the teeth and the
prosthesis. The multiple clasps should not all be
retentive.
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84. A
principal
advantage
of
splinting
with
a
removable prosthesis is cross arch stabilization.
The teeth on both sides of the arch, supported by
lingual plating, can be held together rigidly to
prevent damage from horizontal forces.
Other forms of removable prosthesis such
as the swing-lock partial denture can be used to
splint teeth effectively.
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85. Indirect retention
An indirect retainer is a part of the removable
partial denture that helps the direct retainer prevent
displacement of the distal extension denture by
resisting the rotational movement of the denture
around the fulcrum line established by the occlusal
rests. The indirect retainer is located on the
opposite side of the fulcrum line from the denture
base.
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86. The indirect retainer is essential in the
design of Classes I and II partial dentures. By
using the mechanical advantage of leverage, it
counteracts the forces attempting to move the
denture base away from the residual ridge by
moving the fulcrum farther from the force. In a
Class I prosthesis the fulcrum line would be
moved from the tips of the retentive clasp to the
most anteriorly located component, the indirect
retainer
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87. Because the indirect retainer resists lifting forces at
the end of a long lever arm, it must be positioned in
a definite rest seat so that the transmitted forces are
diverted apically through the long axis of the
abutment tooth.
The indirect retainer also contributes, to a
lesser degree, to the support and stability of the
denture.
The need for indirect retainers varies with the
type of removable partial denture.
In a class I arch indirect retention must always
be used. The indirect retainer or retainers must be
positioned as far anterior to the fulcrum line as
possible.
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88. Although indirect retention is not as critical in a
Class II arch as in a Class I arch, it is still required. If
a modification space exists on the tooth supported
side, abutment teeth on both sides of the space
should be selected. The fulcrum line will run
through the most posterior abutment on the tooth
supported side and the terminal abutment on the
distal extension side. The most anterior abutment on
the tooth supported side, with its rest and clasp
assembly, may be located far enough anterior to the
fulcrum line to serve as the indirect retainer.
However, a definite rest seat positioned even farther
anterior, if possible, may increase the effectiveness
of the indirect retention.
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89. If there is no modification space in the tooth
supported side of the arch, the most posterior
tooth on that side with favorable contours for
clasping should be used as one abutment. This
design places the fulcrum line in a posterior
position, allowing the indirect retainer to be placed
farther from the fulcrum line. To develop a good
triangular configuration of clasping, an additional
abutment tooth with suitable contours for clasping
should be selected as far anterior on the tooth
supported side as possible. this abutment tooth,
with its rest and clasp assembly, may serve as the
indirect retainer if it is located far enough anterior
to the fulcrum line.
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90. For the class III arch, indirect retention is not
ordinarily required because there is no distal
extension denture base to create a lever arm.
However, auxiliary rests may be needed to
provide additional vertical support for a long
lingual bar major connector or an extensive
palatal major connector. Auxiliary rests are
always indicated for support of a lingual plate
major connector.
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91. There are times when the contours of the
posterior abutment teeth of a Class II or III partial
denture are not suitable for retention and the
prognosis for the teeth may be such as not to
warrant construction of cast gold restorations.
These teeth, even with reduced periodontal support,
can usually provide support and stability for the
prosthesis. An occlusal rest and non retentive
stabilizing clasp should be designed for them.
Under these circumstances the clasp design for the
anterior abutment teeth need not be the same as for
the terminal abutments on a class I or II partial
denture, but indirect retention is required.
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92. The consideration for the Class IV arch is the
reverse of that for class I and Class II arches,
and the design of the partial denture, in order to
resist the rotational forces in the opposite
direction, must also be reversed. The lever arm
is anterior to the fulcrum line, so that indirect
retainer must be located as far posterior as
possible. Occlusal rests and clasp assembles
are placed on the most posterior teeth with
favorable contours for both direct retention and
support.
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94. Essential of Design
A. Classes I and II
Direct retention
a. Retention should not be considered the prime
objective of design
1. The main objectives should be the restoration of
function and appearance and the maintenance of
comfort, with great emphasis on preservation of the
health and integrity of all the oral structures that
remain.
b.
Close adaptation and proper contour of an
adequately extended denture base and accurate fit
of the framework against multiple, properly prepared
guide planes should be used to help the retentive
clasp arms retain www.indiandentalacademy.com
the prosthesis.
95. Clasps
a. The simplest type of clasp that will accomplish
the design objectives should be employed.
b. The clasp should have good stabilizing
qualities, remain passive until activated by
functional stress,
and accommodate a minor
amount of movement of the base without
transmitting a torque to the abutment tooth.
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96. c. Clasps should be strategically positioned in the
arch to achieve the greatest possible control of
stress.
1. A class I prosthesis usually requires only
two retentive clasp arms; one on each terminal
tooth.
a) If a distobuccal undercut is present, the
vertical projection retentive clasp is preferred.
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98. b) If a mesiobuccal undercut is present, a
wrought wire clasp is indicated. A cast of
circumferential type clasp should not be
used.
c)The reciprocal or bracing arm must be rigid.
This component of the clasp system can be
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replaced by lingual plating.
99. 2. A class II Prosthesis should usually have three
retentive clasp arms.
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100. a. The distal extension side should be designed
with the same consideration as for as Class I
prosthesis.
b. The tooth supported, or modification, side should
usually have two retentive clasp arms; one as far
posterior and one as far anterior as tooth
contours and esthetics permit. It a modification
space is present, it is usually most convenient to
clasp a tooth anterior and a tooth posterior to the
edentulous space.
1. The type of clasp and position of the retentive
undercut can be selected for convenience.
2. Rigidity is required for all bracing arms.
Lingual plating may be substituted.
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101. 3. Rests
a)Teeth should be selected for rest preparation to
provide maximum possible support for the
prosthesis.
b)Rest seats should be prepared so that stress will
be direct along the long axis of the teeth.
c) Rests should be placed next to the edentulous
space with few exceptions.
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103. 4. Indirect Retention
a)Indirect retention should be employed to
neutralize unseating forces.
1. The indirect retainer should be
located as far anterior to the fulcrum line
as possible.
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104. 2. Two indirect retainers should generally be used
in a Class I design, whereas one placed on the
side opposite the distal extension base may be
adequate in a Class II design.
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107. 3.The indirect retainers should be positioned in
teeth prepared with positive rest seats that will
direct forces along the long axis of the tooth.
b) Lingual plating can be used to extend the
effectiveness of indirect retention to several teeth.
It must always be supported by positive rest seats.
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108. 5. Major Connector
a. The simplest connector that will accomplish the
objectives should be selected.
1. The major connector must be rigid.
2. It must not impinge on gingival tissue.
b.
Support from the hard palate should be used
in the design of the maxillary major connector when it
would be beneficial.
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109. c.
Extension of the major connector onto the
lingual surfaces of the teeth may be employed
to increase rigidity, distribute lateral stresses,
improve indirect retention, or eliminate potential
food impaction areas. Lingual plating should
always be supported by adequate rest seats.
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110. 6. Minor Connectors
a)Minor connectors must be rigid.
b)Minor connectors should be positioned to enhance
comfort, cleanliness, and the placement of
artificial teeth.
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112. c. Artificial teeth should be selected and positioned
to minimize stresses produced by the prosthesis.
1.Smaller and / or fewer teeth, and teeth that
are narrower buccolingually maybe selected.
2. For mechanical advantage teeth should be
positioned over the crest of the mandibular ridge
when possible.
3. Teeth should be modified if necessary to
produce sharp cutting edges and ample escape
ways.
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113. 8. Denture base
a. The base should be designed with broad coverage
so that the occlusal stresses can be distributed over
as wide an area of support as possible.
1.The extension of the borders must not
interfere with functional movement of the
surrounding tissues.
b. A selective pressure impression should record the
residual ridge in a functional form.
c. The polished surfaces should be contoured to
enable the patient to exercise maximum
neuromuscular control.
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114. B. Class III
1. Direct retention
a. Retention can be achieved with much less
potential harmful effect on the abutment teeth than
with the Class I or II arch.
b. The position of the retentive undercut on
abutment teeth is not critical.
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115. 2. Clasps
a. The quadrilateral positioning of direct retainers
is ideal.
b. The type of clasp selected is not critical
1. Tooth and tissue contours and esthetics
should be considered, and the simplest clasp
possible selected.
2. If restorations are required to correct tooth
contours, the wax patterns must be shaped
with the surveyor.
c. Bracing arms must be rigid.
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117. 3. Rests
a. Rest seats should be prepared next to the
edentulous space when possible.
b. Rests should be used to support the major
connector and lingual plating.
4. Indirect retention
a. Indirect retention is usually not required
b. If one or both of the posterior abutment teeth are
used for vertical support alone without retentive
clasp arms, the entire design must be follow the
requirements of a Class II or II design.
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119. 5. Major and minor connectors
a. They must be rigid and meet the
requirements as for a Class I or II design.
same
6. Occlusion
a.The requirements for occlusion are the same as for
a Class I or II design
7. Denture base
a. A functional type impression is not required.
b. The extent of coverage of the residual ridge areas
should be determined by appearance, comfort and
the avoidance of food impaction areas.
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120. C. Class IV
1. The movements of this type of removable partial
denture and the resulting stresses transmitted to
the abutment teeth are unlike the pattern seen in
any other type of prosthesis.
2. The
esthetic
replacement
arrangement
teeth
may
of
the
anterior
necessitate
their
placement anterior to the crest of the residual
ridge, resulting in potential tilting leverage.
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121. a.Every effort should be made to minimize these
stresses. Some possibilities follow :
b. As much of the labial alveolar process should be
preserved as possible.
c. A central incisor or other tooth should be
retained to serve as an intermediate abutment or
as an over denture abutment.
1. A critical evaluation of each remaining tooth in
the arch should be made with the intent of
retaining as many teeth as possible. The shorter
the edentulous area, the less will be the harmful
tilting leverage. www.indiandentalacademy.com
122. 3. Strategic clasp position should be used. The
quadrilateral configuration, with the anterior clasps
placed as far anterior and the posterior clasps
placed as far posterior as possible, would be the
idea.
4. The major connector should be rigid, and broad
palatal coverage should be used in the maxillary
arch.
5. Indirect retention should be used as far posterior
to the fulcrum line as possible.
a. An ideal quadrilateral configuration of clasping
may preclude the need for an additional indirect
retainer.
6. A functional type of impression may be indicated
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if the edentulous area is extensive.
124. Denture Base
The denture base should be designed to cover the
maximum amount of soft tissue available.
The denture base should have long flanges in order
to stabilize the denture against horizontal
movements.
Distal extension denture bases must always extend
into the retromolar pad area in the mandible and
cover the entire tuberosity in the maxilla.
The denture base will displace the soft tissues on the
ridge during functional occlusal load. Hence, a
functional impression should be recorded to fabricate
the denture in order to improve its adaptation and
avoid excessive tissue displacement.
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126. Major connector
The major connector of choice in the maxillary arch
is the broad palatal major connector because it can
distribute stresses over a large area. In the mandibular
arch, a lingual plate with rests can aid to distribute
functional stresses to the remaining teeth. Functions of the
major connector include rigidity, retention, and stability.
Major connectors should be selected to best suit the
patient. It should distribute the occlusal load over a wide
area at the same time produce the least amount of stress.
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127. There are three important principles for design
exclusively used for a major connector. They
are
L-bar or L-beam principle.
Circular configuration
Strut configuration
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128. L-bar or L-beam principle
The L-beam or L-bar or linear beam theory
states that the flexibility of a
bar is directly
proportional to the length of the bar and inversely
proportional to its thickness. When a load is placed on
the bar or beam supported at its ends, maximum
stress is present in the centre and zero stress at the
supported ends.
A bar supported at both its ends can be divided
into two parts namely the parabolic and quartic parts.
The parabolic part forms the middle 2/4th of the
distance between the supports and the remaining
1/4th on the either sides of the bar form the quartic
part. The parabolic part shows maximum stress
concentration and the quartic part shows minimum or
zero stress concentration.
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130. Hence, if we design a bar such that it has a
smaller parabolic part and a larger quartic part it will
be less flexible. The material becomes more rigid
(less flexible) without adding bulk to the bar.
If we bend the bar on either side, the length of the
bar lying in the quartic part will increase.
Now apply this concept in the design of a major
connector. The palate has a flat vault and two
lateral slopes. If the slopes are shallow, the quartic
part of the major connector also decreases leading
to increased flexibility of the prosthesis under
occusal load. The major connector should be
located and designed such that it lies over the
steeper slopes in the plate
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131. Hence, broad palatal major connectors, palatal
strap major connectors can be fabricated with
lesser bulk of material (but with adequate rigidity)
because it extends in three planes (one central
vault and two lateral slopes) with the length of the
quartic part (the two lateral slopes) being greater
than the parabolic part.
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132. Circular configuration
The advantages of a circle is that is a continuous
unit without an end.
Any force acting on a circular bar can be easily
distributed all along the circumference. Hence, a
circular bar is more rigid than linear bar with the
same area of cross section. This concept can be
used to reduce the bulk of the major connector
with a circular configuration (anteroposterior
double palatal bar and close horse shoe).
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134. Strut Configuration
According to this configuration, a straight bar
bent at its ends near the support is more rigid
because, the bent slopes of the bar aid to transfer the
load acting on the horizontal portion. This is similar to
the linear bar theory (L-beam discusses stress
concentration but struts discuss stress distribution).
The major connector on a narrow vault is more rigid
than a major connector extending over a shallow
vault. In other words, the major connector extending
in two different planes has more rigidity. This concept
is seen in the anterior plate of the double palatal bar,
where, the slope of the rugae area acts as an
additional strut.
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136. Minor connector
The minor connector joins the major connector
to the clasp assembly and the guidance planes
located on the abutment tooth surface. The minor
connector should be designed such that it does not
interfere with the placement of the artificial teeth,
tongue etc. The minor connectors used for auxiliary
rest aid in indirect retention. It has the following
functions;
It provides horizontal stability to the partial denture
against lateral forces on the prosthesis.
The abutment tooth receives stabilization against
lateral forces by the contact of the minor connector.
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137. Rests
Rests help control stresses by directing the
forces acting on the denture to the long axis of the
abutment teeth. The floor of the rest seat should
be less than 90o to a tangent line drawn parallel to
the long axis of the tooth. In class I and Class II
partial dentures, the rest seat preparation must be
saucer shaped. Adding rests on additional teeth
decreases the amount of occlusal load on each
tooth and helps to distribute the occlusal load
equally to all the abutment teeth.
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138. I-BAR REMOVABLE PARTIAL DENTURES
The i -bar removable partial denture, a subject
of discussion since Kratochvil introduced a design in
1963. Has achieved considerable status as a
treatment modality in recent years.
Mesial rest, i-bar, and guide plane
Kratochivil addressed his attention to the tooth
mucosa junction and developed a system that
includes a mesial rest, i-bar retainer, and long guide
planes that extend onto the tooth tissue junction. The
i-bar retainer is one element in the design equation
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and as such has been overemphasized
140. Rests
The function of rests is to provide vertical support
against occlusal forces and control and relationship
of the prosthesis to supporting structures
The ideal anterior rest is the crescent shaped
cingulum rest, which places vertical force low on
the tooth and provides maximum stabilization. The
cingulum rest can be prepared directly in enamel
on bulky canines and maxillary central incisors or
can be implemented with a cast restoration. The
incisal is used on mandibular anterior teeth when
esthetics allows.
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143. Premolar rests are prepared in the marginal and the
triangular ridges and molar rests extent into the
central fossa. In distal extention cases the most
distal rests are placed on the mesial aspect of
the abutment teeth for the following two reasons
(kratochvil, 1963 ).
I. Anterior placement of the rest (fulcrum) helps
verticalize the forces occlusion on bearing
mucosa under the denture base extension.
II. The mesial rest directs tipping forces on the
abutment mesially and tends to move the
abutment tooth into firm contact with the support
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of the anterior teeth
144. Proximal plates
Parallel guide planes are prepared on all proximal
tooth surfaces adjacent to edentulous spaces. The
proximal plate covers the guide plane from marginal
ridge to the tooth tissue junction and extends onto the
attached gingiva for 2 mm. This configuration serves
many functions
1. Provides horizontal stability
2. Reunites and stabilizes the arch
3. Increases retention because of parallelism and
because dislodgement is limited to the part of insertion.
4. Protects the tooth tissue junction by preventing food
impaction and because of metal coverage in this area.
5. Provides reciprocation.
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6. Distributes occlusal force throughout the arch
145. Major connector
Major connectors are designed for maximum
rigidity and gingival health. The combination
anteroposterior strap is preferred for maxillary
partial dentures, and lingual bar is preferred for
mandibular
partial
dentures.
Maxillary
major
connectors are placed 5 to 6 mm away from tooth
tissue junctions, and mandibular major connectors
are placed on attached mucosa or at least 4 mm
away from the gingival crest.
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146. Minor connectors
Minor connectors connect rest, proximal plates, and
retainers to the major connector. They also help
provide horizontal stability.
Denture base connectors
One-millimeter relief is provided for retention, and the
retentive meshwork is placed on the lingual aspect of
the ridge and extends only to the crest of the ridge to
avoid interference with tooth placement on the facial
side of the ridge.
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148. Direct retention
The i bar provides retention against vertical
displacement, but this retention is augmented considerably
by the parallelism of guide planes that. In most situations
limit displacement to the path of insertion.
The i-bar is an infrabulge retainer with a configuration
designed to minimize the deleterious effect that over
contoured retainers have on the health of both tooth and
gingiva. The arm is long and tapering with a half round cross
section. The tip, which flexes, engages an undercut at the
height of mesiodistal contour or mesial to it. The position of
the i -bar in relation to the height of contour is essential to
this design because proper positioning allows the tip to move
passively into the mesial embrasure space when the
extension base receives occlusal loading. The retainer
engages the undercut www.indiandentalacademy.com vertical displacement.
area and resists
149. The following important advantages are gained
with the i-bar configuration:
1 . Because tooth contour is not altered, food
accumulation
against
the
tooth
surface
is
minimized
2. The i -bar is passive in its relationship to the
abutment tooth except against vertical displacing
forces
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150. The disadvantages of the i-bar are of consequences
only if the design concept is not fully deployed
I. Less horizontal stability than other retentive
elements.
2. Less retention.
When used in the tooth-borne situation, the i-bar
retainers can be placed for convenience relative to
retentive undercuts and esthetics. In extension
situations, the retentive i-bars are placed with
respect to the axis of rotation.
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152. Indirect retention
Indirect retention is provided by rests placed
on secondary abutments as far from the axis of
rotation and the edentulous area as possible to
stabilize the major connector. Although recent studies
have cast doubt on the effectiveness of indirect
retention against displacing force (frank and nicholls,
1977), the indirect retainer has been shown to be
effective in redistributing occlusal force more evenly
throughout the entire dent alveolar structure
(mcdoweii, 1978
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153. Design variations
Physical considerations and alternate components
Most problems in design application are related to tipped
abutment teeth, soft tissue contours or frenum
attachments.
Tipping of abutment teeth affects retention in several
ways. Buccolingual tipping frequently eliminates the
necessary retention in undercut or creates an excessive
undercut when tilting creates an excessive undercut, the
solutions include enameloplasty to reduce the undercut
or a cast restoration to provide ideal contours. When
lack of retention exists, the solutions are preparation of
an undercut or the use of a lingual undercut for
retention. Severe tipping is most effectively controlled
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with a cast restoration.
154. The attachment of the buccinator muscle
adjacent to mandibular molars will occasionally
obliterate the vestibule in this area. Lack of attached
gingiva further aggravates the problem of i-bar
placement. An alternative to placement of an i-bar in
an inadequate vestibule is again the use of a lingual
i-bar for retention and a buccal rest extension for
reciprocation
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155. RPI
Rest, proximal plate, and i-bar
In agreement with kratochvil’s basic design but unable
philosophically to accept the amount of tooth preparation that
is sometimes necessary to execute it, krol developed a
modification that studiously avoids tooth preparation the
stated emphasis in krol's system is stress control with
minimal tooth coverage and minimal gingival coverage the
clasp system includes the three elements of kratochvil's
system: mesial rest, proximal plate, and i -bar. Each element
however has undergone significant change to meet krol's
criteria. Rest preparations are less extensive in the rpi
system. The mesial rest extends only into the triangular
fossa, even in molar preparations, and canine rests are often
circular concave depressions prepared in the mesial
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marginal ridge.
156. The prepared guide plane is 2 to 3 mm high
occlusogingivally and the proximal plate contacts
only 1 mm of the gingival portion of guide plane.
The i-bar terminus is pod shaped to allow more
tooth contact and placement tends towards the
mesial embrasures space to achieve more efficiency
reciprocation from the diminutive proximal plate.
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158. Swing lock removable partial dentures
In the swing lock removable partial dentures first
described by Dr Joe .J. Simmons in the Texas dental
journal in February 1963, all or several of the
remaining teeth are used to retain and stabilize the
prosthesis against vertical displacement. The
prosthesis consists of a hinged buccal or labial bar
attached to a conventional major connector.
Retention and stabilization are provided by the bar.
The labial bar is generally designed with small
vertical projection arms that contact the labial or
buccal surfaces of the teeth gingival to the height of
contour. These vertical arms look like an i or t bar
and provide both retention and stabilization for the
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prosthesis.
161. Advantages
The primary advantages of the swing lock concept of
treatment is that it provides a relatively inexpensive
method of using all or most of the remaining teeth for
the retention and stabilization of a prosthesis because
the construction of a swing lock removable partial
denture is relatively simple and inexpensive, it can be
used in situations for which more conventional types
of treatment may appear hopeless.
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162. Disadvantages
A swing lock prosthesis can produce a relatively
poor esthetic result for patients with short of
extremely mobile lips.
A long distal extension base is likely to move
toward the tissue under the forces of occlusion.
This movement can tip the teeth grasped by the
prosthesis
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164. Indications.
1. Too few remaining natural teeth for a removable
partial denture of conventional design
2. Remaining teeth too mobile to serve as abutment
teeth for remaining teeth for conventional design.
3. Position of remaining teeth too mobile not
favorable for a conventional design.
4. To retain a prosthesis for patients who have lost
large segments of teeth and alveolar ridge
through traumatic injury
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168. Selection of metal for swing lock framework
Chrome alloy is the material of choice for the
metallic framework of a swing lock removable
partial denture. Gold is contraindicated because the
hinge and lock mechanisms show noticeable wear
in a relatively short time when gold is used and gold
component must be made fairly bulky compared
with chrome components to provide the necessary
rigidity and strength.
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169. Design
The swing lock removable partial denture consists
of a labial or buccal bar which is fastened to the
partial denture by a hinge at one end and a latch at
the other end. Reciprocation is achieved through a
lingual plate. The basic swing lock design
incorporates a lingual path of insertion. a hinge
connection of the labial bar to the framework with a
locking mechanism on the opposite end of the bar,
and a labial opening arch of the retentive bar with
struts and / or veneers contacting the infrabulge
area of the labial surface of the teeth.
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170. It braces and supports a natural tooth that is
being occlusally loaded by the contact of the
retentive labial struts and the lingual plate loaded by
the contact of the retentive labial struts and the
lingual plate on opposite sides of the tooth. Since a
rigid major connector is essential, a continuous
lingual plate or bar contacting the suprabulge region
of remaining anterior teeth and the height of contour
of the posterior teeth used for stabilization in both the
mandible and maxillae. In the maxillae the
connectional designs are used i.e. anterior- posterior
bar, or complete metal palate.
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172. Controlled direct retention and stabilization
on all or part of the remaining teeth resists
dislodgement of the swing lock removable partial
denture. This is accomplished by a labial bar, with
one end extending from the framework by a hinge,
and the other end of the bar terminating with a
latch attached to the framework. From the labial or
buccolabial bar, vertical struts similar to I-bar clasp
arms traverse the free margins o the gingivae (with
proper relief) and passively contact the teeth in the
gingival third.
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173. These struts are rigid since they swing into any
undercut by the hinged bar and act as both the
retentive and stabilizing elements To avoid torquing
forces on the anterior teeth in distal extension
situations, these struts are adjusted to incorporate
some freedom and allow for movement of the
denture base in friction. If exposure of the roots of
anterior teeth due to gingival recession or periodontal
surgery is an esthetic problem, a gingiva colored
acrylic resin veneer can be processed to the labial
bar with proper relief for the marginal gingiva.
Occlusal rest can be used to direct forces to the
abutment teeth if desired but they are not indicated in
most distal extension situations.
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174. CONCLUSION
A properly designed RPD in combination with a
well planned comprehensive treatment will
contribute to the preservation of the remaining
teeth, bone and gingiva by maintaining the
gingiva, tooth position and occlusion. It will also
improve mastication and speech and enhance
appearance.
The emphasis is on design as it is one of the
major weak link in the process of total care. The
results of a detailed clinical and radiographic
examination should dictate the ultimate design of
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175. REFERENCES :1.An Atlas of Removable Partial Denture Design
Russell J. Stratton Frank J. Wieblt
2.Partial Dentures
John Osborne George Alexander Lammie
3. Clinical Removable Partial Prosthodontics
Stewart Rudd Kuebker
4.Textbook of Prosthodontics
Deepak Nallaswamy
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