P a g e | 1

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

Ru

le 1

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

Ru

le 2

If the third molar is missing and not to be

replaced, it is not considered in the

classification

Ru

le 3

If the third molar is present and to be used

as an abutment, it is considered in the

classification

Ru

le 4

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

Ru

le 5

the most posterior edentulous area (or

areas) always determines the classification

Ru

le 6

Additional edentulous areas other than

those determining the class are referred to

as modification spaces and are designated

by their number

Ru

le 7

the extent of the modification is not

considered, only the number of additional

edentulous areas

Ru

le 8

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

Mech

an

ical 1- Direct retainers

2-Indirect R.

3-Frictional fit

4-Parts of the denture engaging tooth and

tissue

Ph

ysi

cal

1-Adhesion

2-Cohesion

3-Interfacial s.t

4-At. Pressure

6-Gravity

Ph

ysi

olo

gic

al 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

MED

UIM

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

DIA

GO

NA

L

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

HIG

H

Near to the occlusal surface

Wrought wire occlusally app.

Back action or reverse back action

commonly in inclined teeth

Bracing Arm

LO

W 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

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

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

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.

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:

BA

RS

•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 ST

RA

PS

• 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

PA

LA

TA

L P

LA

TES •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.

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.

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)

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

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

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

" اللهم اجعهل لوهجك خالصا وال

جتعل فيه نصيبا لغريك والتب هل

القبول والنفع اي هللا.."