Handout of R.P.D for O6u

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Handouts of R.P.D
Dr. Hesham Borg’s Lectures
Edited by
MO’men Gamal AboDaif

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Introduction & Classifications
Terminology
Prosthesis: Is an artificial replacement of an
absent part of the human body
Dentulous Patients: Patients having a complete
set of natural teeth
Edentulous Patients: Patients having all their
teeth missing
Treatment: COMPLETE DENTURE
Partially Edentulous Patients: Patients having one
or more but not their entire natural teeth missing.
Treatment: fixed Bridge – Implant - Removable
Partial Denture (R.P.D)
Removable Partial Denture (RPD): •Removable
dental prosthesis (appliance) replacing one or
more natural teeth and associated oral structures
Types of Edentulous Area
Free End (Distal extension): An edentulous area,
which has an abutment tooth on one side only
Bounded: An edentulous area, which has an
abutment tooth on each end
Abutment: A tooth, a portion of a tooth, or that
portion of a dental implant that serves to support
and/or retain prosthesis
OBJECTIVES
1. Preservation of the Remaining Tissues
A- Preservation of the health of the remaining
teeth
B- Prevention of muscles and TMJ Dysfunction
C-Preservation of the residual ridge
D- Preservation of the tongue contour and space.
2. Replacement of lost teeth to prevent
a. Migration of teeth into the edentulous area
following the loss of the natural dentition
b. Change the pattern of mandibular closure as a
result of loss of some teeth
3. Restore the Continuity of the Dental Arch to
Improve Masticatory Function
4. Improvement of Esthetics, and Providing
Support to the Paraoral Muscles, Lips and Cheeks
5. Enhance psychological comfort
*Restoration of anterior teeth improves and
restores appearance
*RPD should provide socially acceptable esthetics
6. Restoration of Impaired speech (D, T TH, F)
INDICATIONS
1- No abutment tooth posterior to edentulous
space (Free end edentulous area)
2- Long edentulous bounded span, too extensive
for fixed restoration
3- Periodontally weak teeth not sufficiently sound
to support fixed- partial denture.
4- With excessive loss of residual bone, the use of
labial flange or need to restore lost tissues as
space is seen under the pontic.
5- After recent extraction, usually done only to
improve esthetics, or for patient satisfaction.
6- Need of bilateral bracing (cross arch
stabilization)
7- Young age (less than 17 years) who has a high
pulp horn

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8- Enhancing esthetics in anterior region, by the
use of translucent artificial teeth instead of dull
fixed partial denture pontic
9- Economic considerations, attitude and desire of
the patient.
HAZARDS OF IMPROPERLY DESIGNED PARTIAL
DENTURES
*Stagnation of food  causes tooth decay
*Induce stresses on abutment teeth and tissues
 PM destruction, Inflammation & Bone
resorption
*Improper occlusion  causes T.M.J. disorders.
*Ill-fitting denture Inflammation, ulceration,
gingival recession, bone resorption
ADVANTAGES OF REMOVABLE PARTIAL DENTURE
OVER FIXED PARTIAL DENTURE
1- RPD constructed for any case whilst FPD are
confined to short spans bounded by healthy teeth
and with a normal occlusion.
2- Cheaper than fixed partial denture
3- They are more easily cleaned
4- They are more easily repaired
5- No tooth reduction is required
CLASSIFICATION OF PARTIALLY EDENTULOUS
ARCHES
Classifications are important to facilitate
communication between the dentist and the
laboratory technician
Requirements of an Acceptable Classification:
1- Permit immediate visualization of the type of
partially edentulous arch
2- Permit immediate differentiation between
bounded and free extension RPD.
3- It should be universally accepted
1- According to the Extension:
I. Unilateral RPD (Removable Bridge)
*long clinical crown of abutment tooth
*buccal and lingual surfaces of the abutment
tooth must be parallel to resist tipping forces
*Retentive undercuts should be available on both
the buccal and lingual surfaces of each abutment
Unilateral RPD (Removable Bridge) should be
used with caution, as the chance of the denture
becoming dislodged and aspirated is too great
II. Bilateral RPD: which restore missing teeth and
extended on both sides of the dental arch
2- According to the type of support:
1- Tooth and Tissue Supported RPD (Tooth and
tissue borne)
2- Tooth Supported RPD (Tooth borne) removable
partial denture
3- Tissue Supported RPD (Tissue borne)
3- According to the most posterior edentulous
span or spans Kennedy’s Classification
Class I: Bilateral edentulous areas located
posterior to the remaining natural teeth.
Class II: Unilateral edentulous area located
posterior to the remaining natural teeth.

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Class III: Unilateral edentulous area with natural
teeth, both anterior and posterior to it
Class IV: Single, bilateral edentulous area located
anterior to the remaining natural teeth.
•Additional edentulous areas are referred to as
modification spaces and are designated by their
number
•The numeric sequence of the classification
system is based on the frequency of occurrence of
each class
Class I being the most common while class IV is
the least common.
Kennedy's classification was then modified by
Applegate
Applegate's rules for applying Kennedy
classification
Rule1
Classification should follow rather than
precede any extraction, since further
extractions may alter the class
Ex. If the left molar is extracted class III
becomes class II
Rule2
If the third molar is missing and not to be
replaced, it is not considered in the
classification
Rule3
If the third molar is present and to be used
as an abutment, it is considered in the
classification
Rule4
If the second molar is missing and not to be
replaced, because the opposing second
molar is also missing, it is not considered in
the classification
Rule5
the most posterior edentulous area (or
areas) always determines the classification
Rule6
Additional edentulous areas other than
those determining the class are referred to
as modification spaces and are designated
by their number
Rule7
the extent of the modification is not
considered, only the number of additional
edentulous areas
Rule8
There can be no modification areas in class
IV arches, because if there is a posterior
edentulous area beside the anterior one, the
former will determine the class and the
anterior edentulous area will be a
modification to the class

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The Component Parts R.P.D
Denture Base
Artificial Teeth
Supporting Rests
Retainers: Direct retainers & Indirect Retainers
Connectors: Major Connectors & Minor
Connectors
1-Partial Denture Base
Definition: part of the removable partial denture
which rests on oral mucosa and to which teeth are
attached.
REQUISITES FOR IDEAL DENTURE BASE
•Accuracy of Adaptation to Tissues with Low
Volume Change
• Dense non irritating surface capable of receiving
& maintaining a good finish.
• Thermal conductivity
• Low specific gravity – Lightness in mouth
• Esthetics
• Biologically Compactable with tissues
• Dimensional stability
• Resist deformation
• Low Cost
• Self cleansing
• Potential for future relining
• Sufficient strength – Resistance to fracture
/distortion
Functions
• Esthetics
• Support and retain artificial teeth
• Assist in transfer of occlusal forces directly to
abutment teeth thru rests.
• Prevent vertical and horizontal migration of
remaining natural teeth.
• Eliminate undesirable food traps.
• Stimulates the underlying tissue.
Types of Denture Bases
A-according to the edentulous span
1-Bounded Partial Denture Bases (tooth-tooth
support)
2- Free-end Partial Denture Bases (Distal
extension Base) (Tooth-tissue support)
B -according to the materials
Metallic Gold - Co-Cr -Titanium - Vitallium
Non-metallic (Plastic) Acrylic - Polystyrene -
Valplast
THE METAL DENTURE BASE
INDICATIONS
1. A tooth supported edentulous space (class III or
IV & modifications) where further bone resorption
is not anticipated.
2. When a facing, tube tooth, metal pontic, or
metal reinforced denture tooth is to be used.
CONTRAINDICATIONS
1. Tooth-tissue supported edentulous space
(class I or II).

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2. Tooth supported edentulous space where bone
resorption is expected.
ADVANTAGES
1. Very rigid.
2. High thermal conductivity. (Thermal
conductivity may be decreased if plastic is
processed onto the metal base.)
3. Very stable form.
4. High abrasion resistance.
5. Less porous than plastic and easier to clean.
DISADVANTAGES
1. More difficult to adjust tissue surface than a
plastic base.
2. More difficult to reline the metal tissue surface.
3. Metal not esthetic.
Acrylic denture base
Indications
1. Extension base partial denture
2. Long span edentulous ridges
3. Relining
4. Contour restoration
5. Adequate bulk & strength
6. Junction of base & minor connector
Disadvantages
1- Weak, Have Low Tensile Strength, Brittle and
Are Liable to Fracture
2- To Attain Enough Strength, Resin Bases are
Made Bulky
3- Have Low Thermal Conductivity
4- The fitting surface is porous and not polished
bad oral hygiene, bad odor and inflammation of
the tissues
Valplast
• 1950,s
• Valplast – flexible base resin ideal for partial
dentures.
• Esthetic yet fully functional alternative to
traditional cast metal based removable partial
dentures.
• Biocompatible nylon and thermoplastic resin-
flexibility and stability.
• Color, shape and design of Valplast partials
blend seamlessly with natural appearance of
gingival making prostheses nearly invisible.
• Strength of valplast resin doesn’t require a metal
framework eliminates metallic taste.
• Enables partial to be fabricated thin enough with
non-metallic clasps.
• No tooth preparation required.
Combination Denture Base {metal & acrylic}
Indications
1-Free-end Saddle Cases
2-Increased Rate of Bone Loss as Diabetic Patients
or Patients on Steroid Therapy
3- Cases with Extreme Bone Loss. The Presence of
Acrylic Resin Is Necessary to Restore the Original
Contour

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Methods of Attaching Artificial Teeth
a. Porcelain/ Resin Tube Teeth & Facings
Cemented Directly to Metal Bases
Some disadvantages of this type of attachment
are
1. Difficulties in obtaining satisfactory occlusion.
2. Lack of adequate contours for functional
tongue and cheek contact
3. Unaesthetic display of metal at gingival
margins.
4. Porcelain or resin tube teeth and facings
cemented directly to metal bases.
b. Metal posts
• Metal post may be casted with base or soldered
in it
• This mean of attachment for porcelain tube
teeth
c. Metal Teeth Cast With Frame Work
• Occasionally a second molar tooth may be
replaced as part of partial denture casting.
• Space too limited for attachment of an artificial
tooth.
• Because metal particularly a chrome alloy is
abrasion resistant area of occlusal contact should
be held to min to prevent damage to peridontium
of opposing tooth.
• Should be used only to fill a space and to
prevent tooth extrusion.
d. Chemical Bond
Recent developments-direct chemical bonding of
acrylic resin to metal frame works.
Investing alveolar and gingival tissue
replacement components can be attached without
the use of loops mesh or surface mechanical
locks.
-thin layer of
acrylic resin.
RESTS AND REST SEATS
Rest seat: The Prepared Recess in a Tooth or
Restoration Created to Receive Occlusal, Incisal, or
Lingual
Support: The Quality of the Prosthesis to Resist
Displacement towards Denture Supporting
Structures
NB: *Properly Prepared R.S. Help Control Stress by
Directing Forces Transmitted to Abutment Teeth
Down the Long Axis of Those Teeth.
*The Periodontal Ligament Is Capable of
Withstanding Vertical Forces of Far Greater
Magnitude than Off-vertical, (Near Horizontal) or
Torsional Force
Types of rests
1- Occlusal Rest 2- Incisal Rest 3- Lingual Rest
I- Occlusal Rest
A Rigid Extension of a RPD That Contacts the
Occlusal Surface of a Posterior Tooth or
Restoration, on a Rest Seat Specially Prepared to
Receive it
Forms and Requirements of Rest Seat Preparation
1- Should Be Rounded Triangular in Shape the
Base of the Triangle at the Marginal Ridge About
2.5 mm in Width, and Its Rounded Apex Is
Directed Towards the Center of the Tooth

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2-The Marginal Ridge Is Lowered Approximately 1
to 1.5 Mm of Teeth in Relation to a Vertical Line
(permit sufficient bulk)
3- The floor of the rest seat should be spoon
shaped
4- Spoon Shaped Inclined Apically As It
Approaches the Center of the Tooth
5- The angle between the minor connector and
the rest should be less than 90˚
Prevent Slippage of the Prosthesis Creating an
Orthodontic Like Force
To Direct the Forces along the Long Axis of the
Tooth
6- Rest Seats Are Prepared In Sound Enamel,
Existing Restorations or In Crowns and Inlays
7- If an Amalgam Restoration Is Present, It Could
Be Replaced By A Cast Restoration (Occlusal Rests
Can Be Prepared In an Old Amalgam Restoration
8- Preparations for the Occlusal Rest Must
Precede Making Master Cast And Follow Proximal
Preparation (Guiding Planes And Elimination Of
Undesirable Undercuts)
Requirements of the Occlusal Rest
1- O.R. must fit the tooth (minimize food
collection and preserve their location in relation
to the tooth
2- It must be strong enough to withstand the
loads without deformation
3-It must not raise the vertical dimension of
occlusion
Functions of The Occlusal Rest
1. Support
2. Transmitting Vertical Stress along the Long Axis
of the Tooth
3. Secure the Clasp in Its Proper Position
4. Distributing the Occlusal Load
5. Resistance to Lateral Displacement of the
Prosthesis
6- It May Act As Indirect Retention
Special Considerations
1. Tipped molar (Mesially inclined mandibular
molar)
a. An additional occlusal rest in the distal fossa
b. Molar with rest preparation extend from mesial
marginal ridge to distal triangular fossa
2. A casting is required such as full veneer crown
or onlay
3. Interproximal occlusal rest seats
4. Embrasure seats
(Embrasure  A Gap Between Two Molars)
II. Lingual Rests
A- Cingulum Rest (inverted V Rest)
I. V- Shaped 2 mm in width & 1- 1.5 mm in
depth
II. Half -Moon Shaped
*Adequate Tooth Preparation Directs Forces Down
Long Axis of Tooth
B. Ball Rest
1.5 Mm Deep - 2.5 Mm Wide
No sharp line angles

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C. Canine Ledge
A Step-like Preparation with 1.5 mm Depth
No Sharp Line Angles
III. Incisal Rest
•Used Predominantly As Auxiliary Rests or As
Indirect Retainers
•Rigid Extension
•More Applicable on Mandibular Teeth
•2.5 Mm Wide and 1.5 mm Deep
IV - Embrasure Hooks
•Placed in Embrasures between Teeth
•Act as Indirect Retainer
•Resistance to Lateral and Anteroposterior
Movement
•Splinting of Natural Teeth •Support
•Poor Esthetics and Wedging Action on Teeth

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Retention of R.P.D
Support: • The resistance to tissue wards
movement
•Distribute the Forces over the Supporting
structure
• Transferring Occlusal Stresses to the Supporting
Oral Structures
Retention: Resistance to movement of the denture
away from its tissue foundation (resistance of a
denture to dislodgment)
Stabilization: the Resistance of Partial Denture to
Tipping (Rocking)
Retention
Mechanical
1- Direct retainers
2-Indirect R.
3-Frictional fit
4-Parts of the denture engaging tooth and
tissue
Physical
1-Adhesion
2-Cohesion
3-Interfacial s.t
4-At. Pressure
6-Gravity
Physiological
1-The physiologic molding of the tissues
around the polished surfaces
2-Neuromuscular control
Mechanical means of Retention
1-Indirect Retainers
2-Frictional fit
3-Parts of the denture engaging tooth and tissue
4- Direct retainers; I. Clasps
II. Attachments: • Intracoronal attachment
• Extracoronal attachment
Advantage of attachment
1. Esthetic.
2. Hygienic
3. Tolerated by the patient
4. Not affected by tooth contour.
5. Provide stabilization to the denture.
6. Provide stimulation to the tissues.
Disadvantage of attachment
1. Tooth preparation.
2. Complicated
3. Wear.
4. Difficult to repair
5. Excessive load on the abutment
6. Need long crown.
7. Expensive
Components of the Clasp Retainers
1. Minor connector 2. Rest
3. Reciprocal arm 4. Retentive clasp arm
Basic Principles of a Properly Designed Clasp
1- Encirclement; each clasp assembly must encircle
more than 180 degrees of abutment tooth
2- Retention; For a clasp to be retentive its arm
must flex as it passes over the height of contour
of tooth and engage undercut in infrabulge area
of the teeth
3- Support; Occlusal rest support prevents clasp
from being displaced in gingival direction.

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4- Reciprocation; each retentive terminal should
be opposed by a reciprocal arm to resist any
orthodontic pressure exerted by the retentive arm
5- Bracing & 6-Stabilization; all rigid parts of
clasps contribute to this property and resist
displacement of clasp in horizontal direction
7- Clasp arms should be placed at the lower part
of the middle third of the axial tooth surfaces.
While the retentive terminal should be placed at
the gingival third below the survey line
8- The clasp should be designed on biologic as
well as mechanical bases;
I. The clasp should not interfere with normal
gingival stimulation and its terminal should be
away from the gingival margin
II. There should be a minimum of 5-mm space
between any two neighboring minor connectors
9- Minor connector (or proximal plate) must
contact a definite guiding plane to dictate path of
insertion
10- Passivity; the retentive clasp arm should be
passive and should not exert any pressure against
the tooth until a dislodging force is applied.
Factors Determining the Retentive Force of a
Clasp
1- Depth of undercut used;
Uniform clasp retention depends on depth
(amount) of tooth undercut rather than on
distance below the height of contour at which
clasp terminus is placed
2- Angle of approach;
Gingivally approaching clasp gives better
retention
3- Flexibility of clasp arm;
*The more flexible the clasp arm, the less will be
the retention
*More rigid clasps can be used in tooth supported
partial dentures
The degree of Flexibility of the clasp arm depends
on the following factors
1. The length of the clasp arm
2. The diameter of the retentive arm
3. Tapering
“The greater the length and tapering and the less
the diameter, the greater will be the flexibility of
the clasp arm”
4. The cross sectional form
A round clasp arm is more resilient than half
round or oval cross section; that are difficult to
flex in certain directions
5. The material of alloy
Gold alloys are more flexible than cobalt chrome
alloys.
6. The type of alloy
The wrought form is more resilient than the same
alloy of identical diameter in cast form, because of
its internal structure
Types of the Clasp Retainers
I. Occlusally approaching clasp
1-Akers clasp (circlet) 0.01 of an inch
2-DOUBLE AKER (embrasure)
3- Circumferential `C` Clasp may be used when a
distofacial undercut exists, although it’s rarely
indicated, since the arm cover a large amount of
tooth structure

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4-R.P.A Provide bilateral bracing
Commonly used in tooth-mucosa borne partial
denture, where an “R.P.I” clasp cannot be used
because of bar clasp contraindications
5- Multiple Clasp
6- Extended arm clasp Abutment has no undercut
Adjacent tooth has a reasonable undercut
7- Half & Half clasp 2 M.C., 2 O.R. & 2 arms
Mainly indicated for dual retention commonly in
unilateral cases
8-RING CLASP Provides unilateral bracing
Used for single tilted molars
More flexible than aker because it is one arm
clasp
9-Back action clasp Single arm clasp
Minor connector starts mesiolingually
It engages mesiobuccal undercut
O.R. is located distally
Used in free end saddle.
10-Reverse Back action clasp M.C. originating
Mesiobuccally
Retentive arm engage Mesiolingual undercut
11-Mesio-Distal clasp •Used only in anterior teeth
•Depends on frictional resistance for retention
II. Gingivally approaching clasp
1-The I-bar clasp (Roach clasp arm); consists of
1. A retentive clasp arm
2. A rigid reciprocal clasp arm
3. An occlusal rest
4. A minor connector
*The tip of the retentive arm may be in the form I,
T, U, C or Y. One
* The base of the I bar should be 3mm away from
the gingival margin
Different forms of gingivally approaching clasps
I clasp - T clasp - Modified T clasp
2. R.P.I Provides unilateral bracing
Commonly used for tooth mucosa borne partial
dentures.
Contraindications for the use of gingivally
approaching clasps
I. Severe buccal or lingual tilting of the abutment
II. Severe tissue undercuts
III. Shallow buccal or labial vestibule
3. Devan clasp •More esthetic due to
interproximal position
•No distortion due to its proximity to denture
border
4. Wrought wire clasp
I. Simple circlet; Used for the teeth adjacent to the
edentulous space.
II. Jackson III. Split Crib IV. Half Jackson
5. Combination Clasp
•Buccal wrought wire retentive arm soldered to
the base
•Lingual casted bracing arm
The retentive arm is wrought wire and the
reciprocal arm is casted

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.02 - .03 inch undercut is used. It is indicated
when greater flexibility of retentive arm is desired.
Used when a vertical projection clasp is
contraindicated because of a soft tissue undercut
below tooth.
Types of Survey Line
MEDUIM
Midway between Occlusal surface & Gingival
margin in the Near zone
Nearer to gingival margin In the far zone
We can use occlusally or gingivally
approaching clasps
DIAGONAL
Near occlusal surface In the near zone
Near gingival margin In the far zone
Or Or Or Back action & Reverse back
C clasp
Ging.app. With T bar
HIGH
Near to the occlusal surface
Wrought wire occlusally app.
Back action or reverse back action
commonly in inclined teeth
Bracing Arm
LOW
Near the gingival margin
Extended arm clasp
• Devan clasp engaging proximal undercut •
Crowning of the tooth

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Clasp Aker Ring Back action Embrasure Half and half typeRPA Bar type
upportS excellent Excellent Fair to poor Excellent Excellent Good to
excellent
Excellent
racingB Excellent
(bi)
Excellent Poor Excellent Excellent Excellent Good
Retention Good(0.0
1-0.02)
Good(0.01
-0.02)
Poor Good(0.01-
0.02)
Good(0.01) Good(0.01
-0.02)
Excellent(0.01-
0.02)
eciprocatR
ion
good good Poor Good Good to
excellent
Good to
excellent
Fair to good
ncirclemE
ent
excellent Fair to poor Excellent Good to
excellent
Good
assivityP excellent good Pair to poor good good good Excellent
Occlusally Gingivally
Retention due to tripping action
Bracing  2 Arms above
survey line provide
bracing
Esthetics  less visible due to
gingival position
Tolerance Gingivally app.clasp arm relieved from gingiva
creating space accumulating food and causing
discomfort
Caries More tooth coverage
increasing the risk for
caries
Gingival
health
Trauma may occur due
to distortion or
inadequate relief

15. P a g e | 15
Indirect Retainers
Stabilization: the Resistance of Partial Denture to
Tipping (Rocking torsional forces)
Tipping (Rocking): the Rotation of Partial Denture
around a Fulcrum
*Movement of the distal extension base away
from tissues occur either as total displacement
prevented by direct retainers or as rotational
movement of the extension base around a
fulcrum line, this rotational movement is
prevented by the use of indirect retainers located
as far as possible from the extension base (or
fulcrum) affording the best possible leverage
advantage.
Indirect Retainer
Definition: Components of RPD that are used to
reduce Its Tendency to Rotate in an Occlusal
Direction about the Fulcrum Axis
*Supportive Elements Used to Retain Far Ends of
Partial Dentures
* A component that provides indirect retention is
that which resists rotation of the removable
partial denture in an anteroposterior direction
around the imaginary fulcrum line.
This Movement (Tipping) Is Related To:
1. Quality of the Tissue
2. Extent of Denture Base and Its Fit
3. The amount of Force Applied  Support
Indications
1. RPD having one or more distal extension bases
as in Kennedy class I, II, IV.
2. Kennedy class III where a long edentulous span
is bounded with one distal abutment
Fulcrum Line:
Definition: an imaginary line connecting principle
occlusal rests, around which a removable partial
denture tends to rotate under masticatory forces
*the Line Joining the Occlusal Rests Supported by
Principal Abutments
NB: The location of the fulcrum axis differs
according to:
1. The location of the edentulous area
2. The location of the principle abutments
Requirements (Mechanical factors) about the
Fulcrum line
1- The Indirect retainer in distal extension RPD
should be on the opposite side of the fulcrum
2- Should be more far away from the fulcrum to
↓loads on abutment
3- Should be perpendicular as much as possible
on the fulcrum line
4- Should be placed on a hard oral structure
(tooth surface or hard palate)
Factors Influencing the effectiveness of Indirect
Retainer
1. The effectiveness of the direct retainers;
2. Distance from the fulcrum line;
• Well-supported I. R. Should Be Placed As Far
From the Fulcrum Line As Possible. The Greater
the Distance, the More Effective Is the Indirect
Retention
•A Perpendicular Line Projecting Anteriorly From
the Fulcrum Axis Is the Most Effective Location of

16. P a g e | 16
I. R. And Affords the Best Resistance against
Vertical Dislodging Forces
3. Rigidity of the connectors joining the indirect
retainer & the Denture Frame
4. Effectiveness of supporting tooth surface;
• Should Never Be Placed on Weak Teeth or on
Inclined Surfaces
• I.R. In the Form of Rest Should Be Placed in a
Definite, Properly Prepared Rest Seat that Allows
Transmission of the Forces along the Long Axis of
the Tooth without Slippage of the Rest or
Movement of the Tooth
• The Minor Connector Joining the I. R. to the
Framework Should Be Rigid. Flexing of the
Connector multiplies rather than dissipates the
applied Forces
Types (Forms) of Indirect Retainers
A - Used In Mandibular Partial Denture
1 - Auxiliary Occlusal or Canine Rests
2 - Principal Occlusal Rest of Modification Area
3 - Embrasure Hooks
4 - Auxiliary Rests at the Terminal Ends of Ling
Plate or Kennedy Bar (Auxiliary extension rests)
NB: Modification areas: the occlusal rest on the
anterior abutment of modification space (which
acting as indirect retainer) opposite a unilateral
distal extension
B -Used in Maxillary Partial Dentures
1. Cummer Arm
2. Palatal Arm
3. Anterior Palatal Bar
In case of posterior extension base partial denture
4. Posterior Palatal Bar
Posterior palatal bar: Indirect retainer for Class IV
denture base.
5. Palatal Strap and Rugae Support
6. Direct - indirect Retainer (Full Palatal Coverage);
may give some form of indirect retention
7. Auxiliary Occlusal or Canine Rests
8. Principal Occlusal Rest of Modification Area

17. P a g e | 17
CONNECTORS
Minor Connectors
Definition: portion of denture base frame that
supports the clasp and occlusal rest
*Connects components to the major connector;
Direct retainer – Indirect retainer – Denture base
Functions
1. Unification and rigidity
2. Stress distribution
3. Bracing through contact with guiding planes
4. Maintain a path of insertion
5. Triangular shaped in cross section
6. Joins major connector at right angles
7. Relief placed so connector not directly on soft
tissue
8. Contact teeth above height of contour
9. Prevents wedging & tooth mobility
10. Must be at least 5mm of space between
vertical minor connectors.
Major Connectors
Definition: It Is That Unit Of The Partial Denture
To Which All Other Parts Are Directly Or Indirectly
Attached.
This Component Provides Cross-arch Stabilization
It Is The Component Of R P D That Connects The
Parts Of The Prosthesis Located On One Side Of
The Arch With Those On The Opposite Side
Functions of connectors
1. Join the component parts of RPD together.
2. Contribute to the support of the prosthesis, by
distribution of stresses applied to the prosthesis.
3. They may contribute to the functions of bracing
and reciprocation.
4. Contribute to retention of the prosthesis:
Palatal plates provide direct retention.
5. Connectors resting on prepared dental or firm
oral tissues provide indirect retention.
[1] Maxillary major connector
Biological and biomechanical principles in P.D
1- Must be properly located in relation to gingival
and moving tissues l .e 6 mm away from
gingival margin to allow self-cleaning and
prevent food trapping.
2- Must not impinge on gingival margin and
never depend on gingival for support.
3- Rigidity is necessary to transmit stress of
mastication from one side of the arch to the
other.
4- Finish lines should allow butt joint between
base and metal framework → smooth surface →
preventing saliva and debris accumulation.
5- Good peripheral seal along the border of major
connector to prevent food trapping under it also,
to prevent overgrowth of palatal tissues.
This can be accomplished by beading at the
border of major connector in the model (1 mm
wide and depth) and fades out as it approaches
gingival margin.

18. P a g e | 18
6- Should cover the least possible amount of
gingival tissues → to maintain normal stimulation
from tongue.
Requirements
•Rigidity is necessary to transmit stresses of
mastication from one side of the arch to the
other.
•Must be properly located in relation to gingival
and moving tissues and not impinge on the
marginal gingiva
•The borders are placed a minimum of 6mm. away
from gingival margins.
•Should be self-cleansing and not allow trapping
of food particles.
•Relief is avoided under maxillary major connector
except in the presence of palatal tori or prominent
median palatine raphe.
•Must be properly located in relation to gingival
and moving tissues and not impinge on the
marginal gingiva
•The borders are placed a minimum of 6mm. away
from gingival margins.
A minimum of 6mm away from gingival margins
•The borders should run parallel rather than
diagonal to the gingival margin and should be
crossed abruptly and at right angle to the margin
in order to produce the least possible soft tissue
coverage.
•All borders should be tapered slightly towards
the tissues, and should be smoothly curved.
Hence they are less detectable by the tongue and
not interfere with speech, and to minimizing
patient discomfort.
•Thickness of the metal should be uniform
throughout the palate. •Bony or soft tissue
prominences should be avoided. •The borders
should be beaded.
•The borders should be beaded $ Seal along the
border Preventing food from collecting under the
max M C and Preventing over growth of the
palatal tissues.
MAXILLARY MAJOR CONNECTORS
The Form of Maxillary Major Connectors Maybe:
BARS
•narrow, (6-8 mm)
• Half oval in cross section.
• Their margins are beveled and gently
curved
• Cover lesser amounts of tissues
• Require more bulk of to gain the required
rigidity, may interfere with proper speech
and may be untolerated by patients
STRAPS
• Wide and thin
• More than 8 mm in width to gain the
necessary rigidity
• Having a uniform thickness,
• Well tolerated
• Helps in distribution of stresses over a
wider area thus provides support
PALATALPLATES
•Cover half or more of the palate
•The maximum area coverage contributes to
Wide distribution of the stresses falling on
denture.
•Support and retention of the prosthesis.
•Horizontal stabilization of the prosthesis
a. Bar Types;
1. ANTERIOR PALATAL BAR
Indication: It is rarely used alone
Location and form: Anterior palatal region,
located 68 mm behind the gingival margin of
anterior teeth.

19. P a g e | 19
Disadvantages: -intolerable by patients as it
crosses the palatal rugae where tongue activity is
marked.
-Speech difficulties may be encountered.
-  Support & Retention
-  Bracing, Stability & Indirect Retention
2. MIDDLE PALATAL BAR
Advantages: *Comfortable, away from the rugae
area, well tolerated
*Support and Bracing are achieved
Disadvantages: Lacks rigidity unless made bulky
Contraindications: It cannot be used in cases
having large torus palatinus or prominent median
palatine raphe.
3. POSTERIOR PALATAL BAR
• Limited indications for use as single bar.
• Location and form: in close relation to the
junction of the hard and soft palate, or placed in
level with the second molar.
• Advantages: exhibits limited coverage and well
tolerated by the tongue it is not likely to affect
taste.
•Bracing, indirect retention for Kennedy class IV
cases.
Disadvantages: lacks of rigidity. It cannot be used
in with large torus palatinus.
4. ANTERO-POSTERIOR PALATAL BAR (Ring
Design, A-P bar)
Location and form: Anterior, Posterior bars and
Longitudinal bars: , the metal forming the
connector lies in two different directions giving
the connector strength and rigidity
Indication: in any design especially in the
presence of torus palatinus
Advantages: the most rigid bar major connector,
minimal soft tissue coverage
Disadvantages: Poor support, annoy the tongue
and are intolerable
Contraindications: high, narrow palatal vault. large
tori extending to the junction of the hard and soft
palate.
b. Strap Types;
1. ANTERIOR PALATAL STRAP
Horse shoe (U) shape
Location and form: in the valleys rather than the
crests of the rugae area.
Indications: a large torus or a hard prominent
median palatine raphe exists.
Advantages: some vertical support. Indirect
retention may be provided.
Disadvantages: a poor connector because it lacks
the rigidity,
2. ANTERIOR PALATAL STRAP
Disadvantages: a poor connector because it lacks
the rigidity, that causes movement or spreading
of the lateral borders of the connector when
vertical force is applied.
•Interfere with phonetics and might cause
discomfort
3. MIDDLE PALATAL STRAP
Advantages: •Rigid.

20. P a g e | 20
•Reduces gingival margin coverage to a minimum
•Well tolerated
•Away from the tactile receptors
•Rarely annoying to the patient.
•Relatively narrow
•Minimal interference with phonetics.
The most versatile and widely used maxillary
major connector
The strap lies on the central portion of the hard
palate
4. ANTRO-POSTERIOR STRAP
Location and form: a rigid connector; similar
location and structure to that of the a p bar
Indicated: in Kennedy class I or II partial denture
bases, when a large torus exists.
Advantages: Rigidity and strength of the
connector allow the metal to be used in thinner
sections.
Support due to wide palatal coverage.
Good retention and stability.
Extended palatal plate
Covers half or more of the palatal surface
May be:
-Metal plate -Resin plate
-Combination, metal, and resin plate
May be:
-Complete Palatal Coverage
-Covering two thirds of the palate
-A palatal plate connector covers half or more of
the palatal surface
NB: Anterior metallic part having provisions for
mechanical retention to attach an acrylic posterior
portion
-All Max. M. C. except single bar Provide
Rigidity, Support.
-All Max. M. C. except middle palatal MC
Provide indirect Retention
-All Max. M. C. except Bar major connectors
Provide Retention
-All Max. M. C.  Bracing is achieved by the
vertical parts of the connector
-All anterior Max. M. C.
Disadvantages: *intolerable by patients as it
crosses the palatal rugae where tongue activity is
marked.
*Speech difficulties may be encountered.
-ANTERIOR PALATAL STRAP
A poor connector because it lacks the rigidity,
Interfere with phonetics and might cause
discomfort
-MIDDLE PALATAL STRAP
Is the most versatile and widely used max. m. c.
-Extended Palatal PLATES
Provide Direct -indirect Retention (Full Palatal
Coverage)

21. P a g e | 21
(2) MANDIBULAR MAJOR CONNECTOR
Beside gingival relation of the border (3 mm from
gingival margin), Rigidity and finish lines. As in
maxillary major connector
1- lingual embrasures and all soft tissue undercut
should be blocked out.
2- superior border must contact lingual surfaces
of teeth above survey line → to prevent food
entrapment.
3- superior border projections should be placed at
contact points.
4- superior border between projections should be
scalloped and should never be placed over the
middle 1/3 of teeth.
5- gingival margin should be relieved to avoid
gingival irritation.
6- superior border is made as thin as possible.
7- in free end saddle, it should have terminal
occlusal rests at each end to prevent labial
movement of teeth as it provide indirect retention
TYPES OF MANDIBULAR MAJOR CONNECTORS
I. PLATE: as LINGUAL PLATE
II. BAR: as
LINGUAL BAR - SUBLINGUAL BAR -
DOUBLE LINGUAL BAR (KENNEDY BAR)
CINGULUM BAR - LABIAL BAR
Structural Requirements for Mandibular Major
Connectors
1- Rigidity 2- Relief
3- A half-pear shape in cross section.
4- The superior border of the lingual bar should
be placed 3-5 mm
5-The lingual plate it should be extends to the
cingulae of the anterior teeth in which the
gingival margin should be relieved.
6- The borders should run parallel to the gingival
margin
7- The inferior border should be gently rounded
above the moving tissues of the floor of the
mouth.
8- Impingement of gingival tissues
1. LINGUAL BAR
-The inferior border should be gently rounded
above the moving tissues of the floor of the
mouth; to avoid irritation or injuring the
subadjacent tissues when the restoration moves
Half-pear shape in cross section, tapered
superiorly with the broader and thicker portion at
the inferior border.
The bar should be relieved sufficiently but not
excessively over the underlying tissues Lingual tori
are generously relieved when surgery is
contraindicated.
Function: The lingual bar functions only as a major
connector. It does not provide neither support nor
indirect retention.
Disadvantages: * May attain some flexibility,
specially if they are poorly constructed or
designed.
Contraindications: - Inadequate space

22. P a g e | 22
- Extreme lingual inclination of lower anterior
teeth.
- High lingual frenular attachment.
- Bilateral torus mandibularis
- Undercut on the lingual side of the ridge
2. SUBLINGUAL BAR
Location and form: • extending over and parallel
to the anterior floor of the mouth.
• It has a tear drop configuration whose base is
towards the base of the tongue.
Indications and Advantages:
• Insufficient depth of the anterior floor of the
mouth.
• Reduced height of the alveolar ridge,
• Highly attached lingual frenum.
• Well tolerated
• It permits exposure of the gingival tissue
• allows for proper cleaning.
• the underside of the tongue is sparsely provided
with tactile receptors.
3. THE DOUBLE LINGUAL BAR KENNEDY BAR
A lingual bar and a cingulum bar (Kennedy bar).
• Secondary lingual bar,
• Continuous bar or cingulurn bar.
Used to add to the strength and rigidity of the
denture
Kennedy bar is neither a major connector nor
indirect retainer by itself
• Allows natural stimulation
• Stabilization • rigidity
• Proper distribution of the stresses
• splinting. • I.R. through its terminal rests.
Disadvantages: Objectionable to the tongue
• collect food • Phonetic problems.
Contraindications: short clinical crowns or inclined
lingually
4. KENNEDY BAR
Two supporting rests must be placed one on each
end of the Kennedy bar. These rests prevent
settling of the bar during function, thus
preventing laceration of the gingiva and act as
indirect Retainers
5. CINGULUM BAR
• Indicated where there is insufficient room for
the lingual bar
• The teeth should have good mesiodistal contact
with sufficient crown length.
• Marked lingual inclination of the anterior teeth
prevents the use of cingulum bar

23. P a g e | 23
LINGUAL PLATE
Most rigid mand. M. c. Better bracing
Cross-arch stabilization
Splinting for weak teeth.
Form and location
Indications Disadvantages
LABIAL BAR
With extreme lingual inclination of mandibular
anterior teeth
When large lingual tori exist and surgery is
precluded. obviates the need for surgical
intervention
Form and Location:
• Thick and bulk than a lingual bar to counteract
the increased flexibility due to increased length.
• Half-pear shaped with bulkiest potion located
inferiorly,
• Runs across the labial and buccal mucosa.
• Superior border tapered to soft tissue located at
least 4 mm below the gingival margin.
• Must be relieved over the canine eminence.
Labial vestibular depth must be adequate
especially in the presence of gingival recession
lacks sufficient rigidity
The Swing Lock Partial Denture
‫وال‬ ‫خالصا‬ ‫لوهجك‬ ‫اجعهل‬ ‫للهم‬‫ا‬ "
‫هل‬ ‫تب‬‫ل‬‫ا‬‫و‬ ‫لغريك‬ ‫با‬‫ي‬‫نص‬ ‫فيه‬ ‫جتعل‬
"..‫هللا‬ ‫اي‬ ‫نفع‬‫ل‬‫ا‬‫و‬ ‫القبول‬