Principles of cast partial denture design Philosophy of design Basic guidelines for designing Kennedy's Class I-IV designs Indications of specific components in designing cast partial denture Distal extension CPD Clinical cases Exam oriented questions

1. CAST PARTIAL DENTURE DESIGNING
BASIC PRINCIPLES
DR. AAMIR GODIL
DEPARTMENT OF PROSTHODONTICS
M. A .R.D.C

2. STEPS IN PLANNING A CPD
Diagnosis &
Treatment Plan
Diagnostic Casts Surveying Designing
Mouth
preparation
FPDs for RPD
abutments (if
necessary)
Final Framework
Impression
Make two casts Surveying Designing
Wax up Casting Framework trial
Altered Cast
impression (if
needed)
Jaw relation
record
Try-in Processing Denture insertion

3. KENNEDY’S CLASSIFICATION (1923)

4. KENNEDY’S CLASSIFICATION (1923)

5. Applegate's Rules for Applying the
Kennedy Classification
Rule 1: Classification should follow rather than precede extraction.
Rule 2: If the 3rd molar is missing and not to be replaced, it is not considered in the classification.
Rule 3: If the 3rd molar is present and to be used as an abutment, it is considered in the classification.
Rule 4: If the second molar is missing and not be replaced, it is not considered in the classification.
Rule 5: The most posterior edentulous area determines the classification.
Rule 6: Edentulous areas other than those determining classification are called modification spaces.
Rule 7: The extent of the modification is not considered, only the number.
Rule 8: There is no modification space in Class IV.

7. SURVEYING

9. GENERAL
PRINCIPLES
OF CAST PARTIAL DESIGNING

10. General Principles
- Minimize framework elements (minimize minor connectors, plating, etc.) – more hygienic
- Obtain good base adaptation - better stress distribution; use altered cast for mandibular distal extensions
- Use what is present (e.g. existing rest seats)
- Plan for the future (e.g. designing for continued use of RPD framework if a critical abutment is lost; placing
rest seats, guide planes and undercuts on crowns to allow fabrication of an RPD later)
- Never plan an RPD using a single cast alone. You can’t assess abutment mobility, compressibility of mucosa,
the level of the floor of the mouth, prominent freni, or occlusion. Use mounted models and assess these
features intraorally as you plan and check your design.

11. General Principles
Occlusion – AVOID:
◦ o centric contacts on rests (also ensure no increase in OVD)
◦ o heavy buccal contacts on denture teeth– causes more movement of removable partial denture
When other dental treatment is planned, and an RPD will be made at the end of treatment – ALWAYS
PLAN THE RPD FIRST.
You will see which abutment modifications will be needed, and will ensure the planned RPD is feasible,
prior to beginning treatment

12. DIRECT RETAINERS
reciprocal armretentive arm
EMBRASSURE CLASP
Direct Retainers
Kennedy Cl III & IV (Tooth Borne)
◦ Clasp of choice: cast circumferential
◦ if can’t use cast circumferential next to edentulous space, use double embrasure clasp
◦ if abutment is severely tilted use (depending on location of undercut):
◦ Cast circumferential clasp with lingual retention
◦ Ring clasp with support strut
◦ Rotational path removable partial denture
CIRCUMFERENTIAL
CLASP

13. Direct Retainers
Kennedy Cl I & II (Tooth & Tissue Borne)
For posterior abutments, or any tooth needing stress release:
Clasp of choice: RPI (mesial rest, distal proximal plate and I-bar)
I BAR
T BAR
RPI CLASP
REVERSE
CIRCLET
CLASP

14. Direct Retainers
Kennedy Cl I & II (Tooth & Tissue Borne)
If can’t use an I-bar in vestibule, because of
◦ •frenum • shallow vestibule • deep soft tissue undercut
then use an RPA retainer (mesial rest, distal proximal plate and wrought wire clasp [Akers])
If can’t use a mesial rest because of:
◦ • rotation • heavy centric contact on mesial • large amalgam restoration on mesial
then use Combination Clasp (distal rest, buccal wrought wire retention,
lingual bracing)
for abutments adjacent modification spaces (use tooth borne retainers)
RPA CLASP
COMBINATION CLASP
wrought wire
retentive arm

15. RESTS
OCCLUSAL REST
CINGULUM REST
INCISAL REST
Incisal rests/rest seats
◦ don’t use : poor esthetics
◦ more tilting/torquing forces (long lever arm
from center of rotation)
Cingulum rests/rest seats
◦ use composite build up, if no prominent
cingulum (less dentinal sensitivity)
◦ size - min 1 mm (if deeper, chance of dentin
exposure)
◦ ensure sufficient clearance from opposing
occlusion for maxillary cingulum rests
Occlusal rests/rest seats
◦ size - 1/3 of B-L width of the tooth
◦ depth : 1.5 mm of clearance from opposing
occlusion (critical at junction of rest & minor
connector)
◦ line angle of the marginal ridge should be
rounded
◦ deepest part should be located centrally
(positive)

16. INDIRECT RETAINER
Indirect Retainers
◦ 90° from fulcrum line & as far away from primary abutment as possible
◦ none required on tooth borne (Cl III & IV) cases
◦ canine is usually the most anterior tooth used for indirect retention
◦ usually don’t use a lateral (root length) or central incisor (speech)
◦ also helpful for seating and support, but not always possible or necessary

17. Rest Seats/ Rests
Ensure sufficient depth, especially at junction of the rest & minor connector (1.5mm minimum)
◦ Tooth Borne (Kennedy Class I & II)
◦ place rests adjacent to edentulous space (both ends)
◦ Tissue/Tooth Borne (Kennedy Class I & II)
◦ mesial rest preferred (less torquing of abutment)
◦ distal rest preferred when:
◦ abutment is rotated (limited access for minor connector to mesial)
◦ plunger cusp/heavy centric contact on mesial
◦ large restoration on mesial
◦ no long guiding planes with distal rests - potential torquing
◦ if tooth is severely weakened periodontally – sometimes move rest to the next tooth anterior

18. MAJOR CONNECTORS (MAXILLARY)
PALATAL STRAP
BROAD PALATAL
COMPLETE PALATAL COVERAGE
ANTERO-POSTERIOR BAR
HORSE-SHOE
Maxillary Major Connectors
◦ No tissue relief
◦ Tooth borne (Class III & IV):
◦ Palatal Strap
◦ Tooth & Tissue borne (Class I & II):
◦ A-P Strap whenever possible
◦ better sensation, preferred (minor
salivary glands & taste buds)
◦ Full Palatal Strap
◦ periodontal involvement of abutments
◦ less than 6 teeth left
◦ displaceable mucosa (increased
coverage
◦ Anterior Strap (Horseshoe)
◦ only if inoperable torus is present
◦ NEVER for Class I or II

19. MAJOR CONNECTORS (MANDIBULAR)
LINGUAL BAR LINGUOPLATE
Mandibular Major Connectors
◦ Lingual Bar whenever possible (less tissue coverage - hygiene)
◦ Lingual Plate if:
◦ high floor of mouth
◦ tori
◦ frenum
◦ terminate at FGM
◦ Tissue relief – mandibular major connector (29-30 gauge relief) to avoid
tissue impingement

20. MINOR CONNECTOR
Minor Connector
connecting direct retainer to
major connector
Minor Connector
connecting denture base to major connector
Minor Connector
connecting auxillary rest to major connector

21. BIOMECHANICAL
CONSIDERATIONS
Forces acting on cast partial dentures
in function

22. BIOMECHANICAL CONSIDERATIONS
FORCE
Duration & magnitude
LEVER
Class I, II and III
FULCRUM
In all 3 planes

23. FORCE

24. LEVER

25. FULCRUM LINES
Horizontal fulcrum line passing between two principal abutment teeth controls rotational motion of denture towards
or away from supporting ridge

26. FULCRUM LINES

27. FULCRUM LINES

28. FULCRUM LINES

29. PRINCIPLES OF DESIGN
1) The dentist must have a thorough knowledge of both the mechanical and biologic factors involved in removable
partial denture design.
2) The treatment plan must be based on a complete examination and diagnosis of the individual patient.
3) The dentist must correlate the pertinent factors and determine a proper plan of treatment.
4) A removable partial denture should restore form and function without injury to the remaining oral structure.
5) A removable partial denture is a form of treatment and not a cure.
(A.H. SCHMIDT 1956)

30. PHILOSOPHY OF DESIGN
STRESS
EQUILIZATION
PHYSIOLOGIC
BASING
BROAD STRESS
DISTRIBUTION

31. STRESS EQUILIZATION
oResiliency of the tooth secured by the periodontal ligament in an
apical direction is not comparable to the greater resiliency and
displaceability of the mucosa covering the edentulous ridge.
oMost common type is a hinge device interposed between the
minor connectors of the abutment tooth and the denture base.
oIt permits vertical movement of the denture base when forces
are applied to the artificial teeth .
oIt can be adjusted to control the amount of vertical movement.

32. STRESS EQUILIZATION
ADVANTAGES
• Minimal direct retention is required- as denture
base acts more independently.
• They are sometimes used in conjunction with
intra-coronal attachments ( true In case of
Kennedy class I and class II )
• They minimize the tipping forces on abutment
teeth, thereby limiting bone resorption.
DISADVANTAGES
• Construction of stress director is complex and
costly.
• Constant maintenance required.
• Difficult or impossible to repair.
• Lateral movements of base can lead to rapid
resorption of the ridges.
• If sufficient thickness of metal in the hinge is
used to prevent lateral movements, the
prosthesis becomes heavy, bulky and annoying
to the patient

33. PHYSIOLOGIC BASING
oThat there is a significant disparity between the apical
displaceability of teeth and compressibility of the soft
tissues.
oIt believes that stress equalization can be best achieved
by either
• displacing or depressing the ridge mucosa during the impression
making procedure
• or by relining the denture base after it has been constructed

34. PHYSIOLOGIC BASING
oThis theory believes that denture bases formed over
compressed tissue will show an increased ability to
withstand vertical forces.
oThey also recognize the prosthetic teeth and occlusal rests
will be positioned above the existing the occlusal plane
when the prosthesis is not in function.
oTo permit vertical movement of the partial denture from its
rest position to its functioning position , the number of
direct retainers must be limited.

35. PHYSIOLOGIC BASING
•Intermittent base movement has a
physiologically stimulating effect on the
underlying bone and soft tissue.
•Less need for relining and rebasing.
•Simplicity of design and construction
because of minimal retention requirements.
•Light weight prosthesis with minimal
maintenance and repair.
•The looseness of the clasp on the abutment
tooth reduces the functional forces
transmitted to the tooth.
ADVANTAGES
Denture is not well stabilized against lateral
forces.
There will be always premature contact when
mouth is closed
It may be uncomfortable sensation to the
patient
It is difficult to produce effective indirect
retention.
DISADVANTAGES

36. BROAD STRESS DISTRIBUTION
oAdvocates of this school of thought believe that trauma to the
remaining teeth and residual ridge can be prevented by
distributing the forces of occlusion over as many teeth and as
much of the available soft tissue area as possible.
oIt is achieved by means of additional rests and clasps assemblies
and broad coverage denture bases.

37. BROAD STRESS DISTRIBUTION
ADVANTAGES
• Teeth can be splinted .
• Prosthesis are easier and less
expensive to fabricate.
• No flexible or moving parts so less
danger of distortion of the denture.
• Indirect retainers and other rigid
components provides excellent
horizontal stabilization.
• Less relining required.
DISADVANTAGES
• Greater bulk may cause prosthesis to
be less comfortable.
• Increased amount of tooth coverage
can lead to complicated oral
hygiene.

38. FACTORS
INFLUENCING THE
STRESS TRANSMITTED
TO ABUTMENT TEETH
1. Length of edentulous span
2. Quality of support of ridge
3.Clasp.
1. Qualities
2. Design
3. Length
4. Material
4. Surface characterization of the abutment
5. Occlusal harmony

39. FACTORS INFLUENCINGTHE STRESS TRANSMITTED TO ABUTMENT TEETH
THE LENGTH OF THE EDENTULOUS SPAN
•Longer the edentulous span:
• Fulcrum: near occlusal rest at terminal abutment
• Load: applied to artificial teeth
• Length of lever arm: Denture base determines the amount of
force the abutments can withstand
•Thickness of mucosa over the ridge & area of ridge covered
by denture base.
•Efforts made to preserve the posterior abutment tooth.

40. FACTORS INFLUENCINGTHE STRESS TRANSMITTED TO ABUTMENT TEETH
THE QUALITY OF THE SUPPORTING STRUCTURES
•Large well formed ridges withstand greater loads than small ,thin or knife
edged ridges.
• Broad ridges absorb more of the occlusal load and permit the use of well
contoured denture flanges.
•Type and health of mucosa also influence the loads transferred to abutment.
•Soft, flabby tissue contributes little to the vertical support of the denture &
nothing to lateral stability: transmission of stress to adjacent abutment tooth.

41. FACTORS INFLUENCINGTHE STRESS TRANSMITTED TO ABUTMENT TEETH
CLASP CONFIGURATION
Clasp flexibility
• More flexible the clasp less stress is transmitted to the abutment tooth.
• But at the same time it contributes less resistance to the lateral and
vertical stresses transmitted to the residual ridges.
Clasp design
• A clasp that is designed to be passive when it is completely seated on the
abutment tooth will exert less stress on the tooth than one that is not
passive.
Clasp length
• More flexible the clasp less stress it will exert on the abutment tooth.
• Flexibility can be increased by lengthening the clasp.
• Clasp length may be increased by using a curved rather than a straight
course on an abutment tooth
Clasp material
• Chromium based alloy being more rigid will exert greater stress on the
abutment tooth.
• Clasp arm of chromium alloys display a smaller diameter compared with
clasp arms constructed using gold base alloy.

42. FACTORS INFLUENCINGTHE STRESS TRANSMITTED TO ABUTMENT TEETH
SURFACE CHARACTERIZATION OF THE ABUTMENT
•Surface of gold crown or restoration offers more frictional resistance to clasp arm movement
than does the enamel surface of the tooth.
•Greater stress is exerted on a tooth restored with gold than on a tooth with intact enamel.

43. FACTORS INFLUENCINGTHE STRESS TRANSMITTED TO ABUTMENT TEETH
OCCLUSAL HARMONY
•Deflective contacts: leverage
•Ideally, the occlusal load should be applied in the center of the denture –bearing area, both antero-posteriorly and
bucco-lingually
•Partial denture constructed opposing a complete denture will be subjected to a much less occlusal stress than one
opposed by natural dentition.
◦ Force exerted by natural teeth –300 pounds per square inch.
◦ Complete denture – 30 pounds per square inch.
•Occlusal load applied to the distal end of denture base will result into more stress transmitted to the abutment

44. COLOR CODING
FOR CPD DESIGN
BROWN
for metal
components
Clasps
Connectors
Lattice /mesh
Rests
RED
for
preparations
Guide planes
Rest seats
Dimpling
BLUE
acrylic
components

45. CAST PARTIAL
DESIGNS FOR
DIFFERENT CLINICAL
SITUATIONS
• DESIGN CONFIGURATION
• TOOTH SUPPORTED VS TOOTH-
TISSUE SUPPORTED CPD
• KENNEDY’S CLASS I AND II
• KENNEDY’S CLASS III AND IV

46. DESIGN CONFIGURATION
Triangular Bilateral Quadrilateral Quadrilateral

47. SEQUENCE OF COMPONENT DESIGNING
1.DIRECT RETAINER
INDIRECT RETAINER
AUXILLARY RESTS
MINOR CONNECTOR
MAJOR CONNECTOR
DENTURE BASE AND ARTIFICIAL TEETH

48. TOOTH SUPPORTED VS
TISSUE SUPPORTED DENTURES
TOOTH SUPPORTED TOOTH-TISSUE SUPPORTED
SUPPORT
DERIVED
From abutment
teeth
Primarily from tissues
Secondarily from abutment teeth
IMPRSSION
TECHNIQUES
Static (anatomic)
impression
Functional impression for tissues
Anatomic impression for teeth
INDIRECT
RETENTION
Not needed Needed, depending on fulcrum line and axis
of rotation
BASE MATERIALS Generally metal
No need for reline
Generally acrylic
For ease of reline
STRESS
BREAKING
Not needed Recommended for long span
CLASS III mod 1
CLASS I

49. DISTAL EXTENSION CASES
KENNEDY’S CLASS I AND II
•Support from dentoalveolar
and muco-osseous segments
Displaceability of soft tissue
Rotation of prosthesis during
loading
Equitable distribution of
forces

50. SUPPORT FOR DISTAL EXTENSION
McCraken
1. Contour and quality of the residual ridge
2. Extent of residual ridge coverage by the denture base
3. Type and accuracy of the impression registration
4. Accuracy of the fit of the denture base
5. Design of the removable partial denture framework
6. Total occlusal load applied

51. KENNEDY’S CLASS I AND II
DESIGN CONSIDERATIONS: DIRECT RETAINER
RPA CLASP
COMBINATION CLASP
wrought wire
retentive arm
RPI CLASP
REVERSE
CIRCLET
CLASP
• For posterior abutments, or any tooth needing stress
release:
Clasp of choice: RPI (mesial rest, distal proximal plate and I-
bar)
• If can’t use an I-bar in vestibule, because of
• frenum • shallow vestibule • deep soft tissue undercut
then use an RPA retainer (mesial rest, distal proximal plate
and wrought wire clasp [Akers])
• If can’t use a mesial rest because of:
• rotation • heavy centric contact on mesial • large
amalgam restoration on mesial
then use Combination Clasp (distal rest, buccal retention,
lingual bracing)

52. KENNEDY’S CLASS I AND II
DESIGN CONSIDERATIONS: INDIRECT RETAINER
◦ Tissue/Tooth Borne (Kennedy Class I & II)
◦ mesial rest preferred (less torquing of abutment)
◦ distal rest preferred when:
◦ abutment is rotated (limited access for minor connector to mesial)
◦ plunger cusp/heavy centric contact on mesial
◦ large restoration on mesial
◦ no long guiding planes with distal rests - potential torquing
◦ if tooth is severely weakened periodontally – sometimes move rest to the next tooth anterior
OCCLUSAL REST
CINGULUM REST
INCISAL REST

53. KENNEDY’S CLASS I AND II
DESIGN CONSIDERATIONS: MAJOR CONNECTOR
1. SUPPORT
o Maxillary: plate type design preferred over strap type
o Mandibular: Major connector does not provide support (no contact with edentulous
mucosa)
2. LOCATION OF EDENTULOUS AREA
o Must connect all edentulous areas
3. ANTICIPATED LOSS OF NATURAL TOOTH
◦ Plating lingual surfaces of natural teeth: ease of replacing in future
4. FUNCTIONAL DEPTH OF LINGUAL VESTIBULE
o Lingual bar (7-8 mm depth required) vs lingual plate
5. INCLINATION OF REMAINING TEETH
◦ Consider labial bar
6. TISSUE RESTRICTIONS
◦ Consider tori/ undercuts
7. PATIENT PREFERENCE
o Based on previous partial denture

54. MANDIBULAR KENNEDY’S CLASS I
Direct Retainer RPI: 34 44
Indirect Retainer and
Auxillary Rest
Should be provided as cingulum rests
with a common minor connector from
the mesial rest of 34 and 44 OR by giving
lingual plate
Minor Connector Lattice for 35 36 37 + 45 46 47
Connecting retainers and rest to major
connector
Major Connector Lingual bar

55. MAXILLARY KENNEDY’S CLASS I
Direct Retainer Combination clasp: 14 24
Indirect Retainer and
Auxillary Rest
Cingulum rest: 13 23
Minor Connector Lattice for 15 16 17 + 25 26 27
Connecting retainers and rest to major
connector
Major Connector Antero-posterior palatal bar (palatal torus)

56. MANDIBULAR KENNEDY’S CLASS II
Direct Retainer RPI: 34
Embrassure clasp: 46 47
Indirect Retainer and Auxillary Rest Mesial rest: 44
Minor Connector Lattice for 35 36 37
Connecting retainers and rest to major connector
Major Connector Lingual bar/ plate

57. MANDIBULAR KENNEDY’S CLASS II MOD 1
Direct Retainer RPA: 34
Simple circlet: 44 47
Indirect Retainer and
Auxillary Rest
Mesial rest: 44
Minor Connector Lattice for 35 36 37
Mesh for 45 46
Connecting retainers and rest to major connector
Major Connector Lingual bar

58. TOOTH SUPPORTED CPD
KENNEDY’S CLASS III AND IV
 Strap type major connectors for maxillary
 Support derived from dento-alveolar
segment
 Clasps with minimum tooth coverage to
reduce plaque accumulation
 Nail bead type minor connector for
smaller spans

59. KENNEDY’S CLASS III AND IV
DESIGN CONSIDERATIONS: DIRECT RETAINERS & MAJOR CONNECTORS
Circumferential clasp
(simple circlet clasp)
Embrassure clasp
Combination clasp
PALATAL STRAP ANTERO-POSTERIOR BAR HORSE-SHOE

60. MANDIBULAR KENNEDY’S CLASS III
Direct Retainer Ring clasp: 47
Simple circlet clasp: 44 36
Auxillary Rest Mesial rest: 34 (not needed)
Minor Connector Mesh for 45 46
Connecting retainers and rest to major connector
Major Connector Lingual bar

61. MAXILLARY KENNEDY’S CLASS IV

62. SUMMARY

63. EXAM ORIENTED QUESTIONS
I) LAQ:
1. Discuss the cast partial framework design for maxillary/ mandibular Kennedy’s Class I/II
II) SAQ:
1. Philosophy and principles of CPD designing
2. Stress equalization or stress breakers in cast partial dentures
3. Support for distal extension denture bases
4. Direct retainers for distal extension denture bases
5. Kennedy’s class III/IV design
6. Factors influencing stress transmission to abutment teeth in cast partial dentures
7. Difference between tooth supported and tooth-tissue supported cast partial dentures

64. THANK YOU