Steps in designing cast partial dentures

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

2. CONTENTS
• Steps in planning CPD
• Tooth supported vs tooth-tissue supported CPD
• CPD components: an overview
• CPD design
• General rules
• Kennedy’s class I
• Kennedy’s class II
• Kennedy’s class III and IV
• Summary

3. 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

4. KENNEDY’S CLASSIFICATION (1923)

5. KENNEDY’S CLASSIFICATION (1923)

6. SURVEYING

7. TOOTH SUPPORTED VS TOOTH-
TISSUE SUPPORTED CPD

8. 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

9. 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

10. COMPONENTS OF CPD

11. NEAR ZONE AND FAR ZONE

12. DIRECT RETAINERS
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
reciprocal arm
retentive arm
EMBRASSURE CLASP
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
◦ 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
◦ 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. CPD DESIGN RULES

22. 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.
When other dental treatment is planned, and an RPD will be made at the end of treatment – ALWAYS PLANTHE RPD FIRST.

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

24. COLOR CODING FOR
CPD DESIGN
BROWN
for metal components
(Clasps | Connectors | Rests)
RED
for preparations
(Guide planes | Rest seats | Dimpling)
BLUE
for acrylic components
(Denture base | Artificial teeth)

25. DESIGN CONFIGURATION
Triangular Bilateral
Quadrilateral

26. CPD DESIGN
KENNEDY’S CLASS I

27. MANDIBULAR KENNEDY’S CLASS I
Direct Retainer RPI: 34 44
Indirect Retainer and
Auxiliary 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

28. MAXILLARY KENNEDY’S CLASS I
Direct Retainer Combination clasp: 14 24
Indirect Retainer and
Auxiliary 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)

29. CPD DESIGN
KENNEDY’S CLASS II

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

31. MANDIBULAR KENNEDY’S CLASS II MOD 1
Direct Retainer RPA: 34
Simple circlet: 44 47
Indirect Retainer
and Auxiliary 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

32. CPD DESIGN
KENNEDY’S CLASS III AND IV

33. 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

34. 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

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

36. MAXILLARY KENNEDY’S CLASS IV
Direct Retainer RPI: 14 25
Simple circlet clasp: 17 27
Auxiliary Rest (Not needed)
Minor Connector Mesh/ lattice for 13 12 11 21 22 23 24
Connecting retainers and rest to major connector
Major Connector Antero-posterior strap / horse-shoe

37. SUMMARY

38. EXAM
ORIENTED
QUESTIONS
• I) LAQ:
1. Discuss the cast partial framework design for maxillary/
mandibular Kennedy’s Class I/II
• II) SAQ:
1. Support for distal extension denture bases
2. Direct retainers for distal extension denture bases
3. Kennedy’s class III/IV design
4. Difference between tooth supported and tooth-tissue
supported cast partial dentures

39. REFERENCES

40. THANK YOU