This document discusses diagnosis, treatment planning, design, sequencing and mouth preparation for removable partial dentures. It covers various classifications of partial edentulism, components of partial denture design including major connectors, minor connectors, rests, retainers and indirect retainers. It provides guidelines for different types of clasps, their location and design rules. Support for distal extension bases and impression techniques are also summarized. The overall document provides guidance on the key clinical and technical steps for removable partial denture fabrication.
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Mouth Preparation and Removable Partial Denture Design
1. DIAGNOSIS, TREATMENT PLANNING,
DESIGN, TREATMENT SEQUENCING
AND MOUTH PREPARATION
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Study cast surveyor
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Diagnosis
Guiding and verify the appropriate tooth preparation
Mouth preparation goal
Support
Stabilization
! Retention
!
REMOVABLE PARTIAL
DENTURE
!
!
Harmonious occlusion
CHATCHAI KUNAVISARUT
CHANITA SUPA-AMORNKUL
DIAGNOSIS, TREATMENT PLANNING,
DESIGN, TREATMENT SEQUENCING
AND MOUTH PREPARATION
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Mouth preparation sequence
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Proximal tooth surfaces
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Occlusal rest seats
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Parallel to guiding plane
Direct occlusal force along the long axis
Spoon shape
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Retentive area
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DIAGNOSIS, TREATMENT PLANNING,
DESIGN, TREATMENT SEQUENCING
AND MOUTH PREPARATION
Take impression with alginate for ascertain the
contour of abutment
! Take another impression for master cast
! Master cast
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Survey
Draw RPD framework design
! Tripoding
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Reciprocal area
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Resist dislodging force
KENNEDY’S CLASSIFICATION
CLASSIFICATION OF
PARTIALLY EDENTULOUS
ARCHES
2. APPLEGATE’S RULE APPLYING THE
KENNEDY CLASSIFICATION
COMPONENT OF PARTIAL
DENTURE DESIGN
MAJOR CONNECTOR
Join the components on one side of the arch with
those on the other side
! Rigidity " Distribution force
! Not impingement subgingival
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MAJOR CONNECTOR
BORDER OF MAJOR CONNECTOR
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Design
Symmetrical
Cross midline at right angle
! Avoid torus
! Smooth and round contour
! Self cleansing
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3. PALATAL BAR
MAXILLARY MAJOR CONNECTOR
Palatal bar
Palatal strap
! Anteroposterior palatal bar
! Horseshoe
! Anteroposterior palatal strap
! Complete palate
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!
Narrow half oval with thickest point at the middle
Interim application
Uncomfortable
Little vertical support
All support derive from remaining teeth
Short span class III
Should not place anterior to second molar
PALATAL STRAP
ANTEROPOSTERIOR PALATAL BAR
Anterior bar = Palatal strap Posterior bar = Palatal bar
Wide – thin band of metal
Join two bar with flat longitudinal element
At least 8 mm. wide
Rigidity
Little interfere tongue
Minimized soft tissue coverage
Patient accept
Uncomfortable
Resistance to bending and twisting force
Little support from palate
Distribute stress
Not the first choice
Patient may complain of palatal coverage
Support is not major consideration
Widely separate abutment
HORSESHOE CONNECTOR
Thin metal band running along the lingual surface of remaining teeth
and extending (6-8 mm.) on to the palatal tissue
Symmetry
Replaced several anterior teeth
Prominent median palatal suture line
Inoperable torus
Tendency to flex or deform
Not good for cross arch stabilization
More rigid connector cannot be used
ANTEROPOSTERIOR PALATAL STRAP
Indicated when replace numerous teeth or present of palatine torus
Extensive length of border may irritation to tongue
Open area in palatal region at least 20x15 mm.
Good support from palate
Resistance to flexure
Uncomfortable
4. COMPLETE PALATE
Ultimate rigidity and support
INDICATION OF MAXILLARY MAJOR
CONNECTOR
Anterior border cover cingular of anterior teeth
Greatest amount of tissue coverage
Replaced all posterior teeth
Condition
Major connector
Weak periodontal support of
remaining teeth
-Wide palatal strap
Adequate periodontal support of
remaining teeth
-Palatal strap
Long span distal extension
Posterior border extend to hard and soft palate junction
-Ant.-post. palatal strap
-Complete palate
-Ant.-post. palatal bar
-Complete palate
Replaced anterior teeth
Periodontal compromised
-Ant.-post. palatal strap
-Complete palate
-Horseshoe
Distribution force to remaining teeth and tissue
Stabilization
Extensive tissue coverage
MANDIBULAR MAJOR CONNECTOR
Lingual bar
Lingual plate
! Double lingual bar
! Labial bar
Condition
Major connector
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Torus present
-Ant.-post. Palatal strap
!
-Ant. -post. Palatal bar
-Horseshoe
•Very sparing use horseshoe connector
•Palatal bar is rarely indicated
LINGUAL PLATE
LINGUAL BAR
Half pear shape and thin piece of metal
Indicate for all tooth support unless insufficient space
Scallop appearance
At least 8 mm. between gin. margin and floor of mouth
Always support by rests
Minimum contact with teeth and soft tissue
Insufficient vertical space for lingual bar
Half pear shape
Splinting
Simplicity
Decrease plaque accumulate
Need extreme care for design and construction
Existing of mandibular tori
Exceptional rigidity
More comfortable than lingual bar
Extensive coverage
5. DOUBLE LINGUAL BAR
Characteristics of both lingual bar and plate
Join 2 bars with rigid minor connector
Contact with remaining anterior teeth indicated
Marginal gingival receives natural stimulation
Horizontal stabilization
Tendency to trap debris
Not comfortable
LABIAL BAR
MANDIBULAR MAJOR CONNECTOR
Run across the mucosa on facial surface
Indicated in the presence of a gross uncorrectable interference
Condition
Mandibular major connector
Tooth support
Lingual bar
-Insufficient space
Lingual plate
-Inoperative torus
Half pear shape
-High lingual frenum attachment
Swing-lock
-Reduced periodontal support in
anterior teeth
-Modified lingual plate
Tipped remaining mandibular teeth
-Large interproximal space
-Double lingual bar
(step back design)
Poor patient acceptance
Distort lower lip
Discomfort
Condition
Mandibular major connector
Replace all posterior teeth
Lingual plate
• Labial bar is rarely indicated
MINOR CONNECTOR
6. MINOR CONNECTOR
TYPE OF MINOR CONNECTOR
Join the remaining component of RPD to the
major connector
! Distribute force to supporting teeth and oral
tissues
! Rigidity
!
!
JOIN CLASP TO MAJOR CONNECTOR
Join clasp to major connector
Join direct retainers or auxiliary rest to major
connector
! Join denture base to major connector
! Serve as approach arms for bar- type clasp
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JOIN INDIRECT RETAINERS OR AUXILIARY REST
TO MAJOR CONNECTOR
Right angle with the major connector
Rigid
Gently curve junction
Locate on proximal surface
Positioned in lingual embrassure
Broad buccolingually but thin mesiodistally
JOIN DENTURE BASE TO MAJOR CONNECTOR
OPEN CONSTRUCTION FORM LADDER LIKE NETWORK
Strong enough to anchor denture base
Open construction form ladder like network
Mesh construction
Bead, wire or nail head components on metal base
Distal extension
In maxillary arch, extend as far posterior as practical
In mandibular arch, extend two thirds the length of edentulous ridge
7. SERVE AS APPROACH ARMS FOR BAR- TYPE CLASP
Not required to be rigid
Must not cross tissue undercut
RESTS AND REST SEAT
PRIMARY REST
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A rest that is part of a retentive clasp is referred
to a primary rest
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A rest that is responsible for additional support
or indirect retention is called an auxiliary rest or
secondary rest
AUXILIARY REST
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Prevent vertical movement
Transmit force to supporting tissue
! Ball and socket joints
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Indirect retainer in extension base
Place anterior or posterior to the axis of rotation
MAJOR FORM OF REST
Occlusal rest
Lingual or cingulum rest
! Incisal rest
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8. OCCLUSAL REST
OCCLUSAL REST
Floor of rest seat slightly inclined toward the center of the teeth
Triangular
Deepest portion located near the center
1/3 – 1/2 of mesiodistal diameter
At least 0.5 mm. thick at thinnest point
Approximate 1/2 of bucco lingual width
1.0-1.5 mm. thick at the marginal ridge
LINGUAL AND CINGULUM REST
INCISAL REST
Primarily used on maxillary canine
Frequently used in mandibular canine
V shape
Small V shaped notch
Ball and socket assembly
Located approximately 1.5 to 2.0 mm. from the proximal
incisal angle
DIRECT RETAINER
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Engage abutment and resist dislodging forces
Two type
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Intracoronal direct retainer
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DIRECT RETAINER
Precision attachment
Semiprecision attachment
Extracoronal direct retainer
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Retentive clasp
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Suprabulge
Infrabulge
Attachment
9. RETENTIVE CLASP ASSEMBLIES
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Structure of clasp assembly
Rest
! Retentive arm
! Reciprocal element
! Minor connector
RETENTION
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The quality of clasp that resists forces acting to
dislodge component from supporting tissue
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Depend on
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Type of clasp
Flexibility
! Undercut
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CLASP ARM FLEXIBILITY
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RECIPROCATION
Depend on
Length " increase
Cross-sectional diameter "circular
! Longitudinal taper
! Clasp curvature " single plane
! Metallurgical properties of alloy "gold , wrought
wire
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The quality of clasp that counteracts lateral
displacement of an abutment when retentive
clasp terminate
RECIPROCATION ELEMENT
ENCIRCLEMENT
Cast clasp
Lingual plate
! Combination of mesial and distal minor
connector
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Prepared parallel to path of insertion
The characteristic of clasp that prevent
movement of abutment away from associated
clasp assembly
! Contact over at least 180°
10. LOCATION OF RETENTIVE CLASP
TERMINUS
PASSIVITY
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Quality of clasp that prevent the transmission of
the adverse forces to the associated abutment
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Mesial or distal line angle
Facial surface better than lingual surface
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Length " Flexibility
Contraindicated in premolar
SIMPLE CIRCLET DESIGN (Aker’s clasp)
Widely used
REVERSE AKER DESIGN
Undercut located adjacent to edentulous area
Tooth support RPD
Engage undercut remote from edentulous area
Half round cross sectional
Disadvantages
- Increase circumference clinical crown
- Increase tooth coverage
MULTIPLE CIRCLET DESIGN
2 simple circlet clasp joined at the terminal aspect of their reciprocal
elements
Principle abutment is periodontal compromised
Disadvantage
- The same as simple circlet and reverse circlet
Infrabulge clasp is contraindicated
Kennedy class I ,II
Disadvantage
- Reduced strength
- Lack of rest adjacent to edentulous area
- Poor esthetic
EMBRASURE CLASP
2 simple circlet joined at bodies
Used on no edentulous area side
Insufficient tooth preparation results in
Inadequate cross sectional dimension
Compromised clasp strength
11. RING CLASP DESIGN
Indicated on tipped mandibular molar
Engage mesiolingual or mesiobuccal undercut
Auxiliary bracing arm
Distal and mesial –occlusal rest
Disadvantage
- Tooth coverage
- Difficult correction
Contraindication
- Limit vestibular depth
- Soft tissue undercut
Lingual
Buccal
C-CLASP DESIGN (Back action clasp)
WROUGHT WIRE CIRCUMFERENTIAL CLASP
“Fishhook” or “Hairpin” clasp
Combination clasp
- Occlusal rest
- Cast metal reciprocal arm
- Wrought wire retentive arm
Simple circlet clasp with loop back retentive arm
Circular cross sectional
Sufficient crown height
Kennedy class I and II
Disadvantage
- Insufficient flexibility
- Tooth coverage
- Esthetic compromised
Mesiobuccal undercut
Minimal tooth coverage
Disadvantage
-Breakage
-Minimal stabilizing
COMBINATION CLASP IN
INFRABULGE CLASP
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Bar type
Flexibility
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Length
Taper
More esthetics
T-clasp, modified T clasp, Y clasp and I bar
12. DESIGN RULES
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Disadvantage
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Food accumulate
! Flexibility ! " Horizontal stability "
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Approach arm
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must not impinge soft tissue
cross perpendicular to free gingival margin
Uniformly tapered " Flexibility
Terminate clasp positioned " Apically on the abutment
! Rigid minor connector " Bracing and Stabilization
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!
T-CLASP DESIGN
Kennedy class I and II
I-CLASP OR I BAR
Contact area
Undercut locate adjacent edentulous area
O.01’’ undercut
2-3 mm. in height
1.5-2 mm. in width
Contraindication
- Severe soft tissue undercut
- High of contour locate near occlusal surface
A = Approach arm
B= Vertical projection of approach arm
C= Location where B cross perpendicular to free gingival
D=Point of first tooth contact
E=Terminus of the retentive clasp
F= Encirclement portion
Mesial rest
Kennedy class I and II
RPI
- Mesial rest
- Proximal plate
- I bar
MODIFIED T-CLASP
Y-CLASP DESIGN
Equivalent to T-clasp
No retentive horizontal projection
Kennedy class I and II
Undercut locate near adjacent edentulous area
Canine and premolar
Advantage
- Improve esthetic compare with conventional T clasp
Mesial and distal projection terminate near occlusal surface
13. INDIRECT RETAINER
INDIRECT RETAINER
Framework component that resists rotational
displacement of an extension base from the
supporting tissue
! Require for Kennedy class I, II and IV
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EFFECT OF ROTATIONAL
MOVEMENT
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Occlusal dislodging forces
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Denture base move away from supporting tissue
Anterior segment of major connector impinge upon
underlining tissue
14. FACTOR DETERMINE INDIRECT
RETAINER
FORM OF INDIRECT RETAINER
Position on the opposite site of fulcrum line
Perpendicular and far from fulcrum line
! Canine and premolar
! Rest at each end of lingual plate
Auxiliary occlusal rest
Cingulum rest
! Incisal rest
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Distal Extension RPD
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Direct retainer design
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Indirect retainer
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15. SUPPORT FOR DISTAL
EXTENSION DENTURE BASE
Impression technique
Maximum border extension
Accurate border detail
! Primary supporting area
! Form of the ridge under function
Final impression with custom tray and
elastomeric impression material
! Altered-cast technique
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Miscellaneous
“Being excited about being wrong because
that means you’ve discovered something new”
Retentive arms should be on the same side
! Dimpling
! Treatment denture
! RPD drawing
- in paper
- on the cast
!
THANK YOU
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