The document discusses the principles and philosophies of cast partial denture design, including stress equalization, physiologic basing, and broad stress distribution. Stress equalization aims to balance stresses on abutment teeth and residual ridges through the use of stress breakers like hinges or flexible connectors. Physiologic basing involves compressing tissues during the impression to position prosthetic teeth above the occlusal plane at rest. Broad stress distribution advocates distributing forces over many teeth and soft tissues through additional clasps and broad denture bases. The philosophies aim to prevent trauma to remaining structures by managing stresses.

1. PRINCIPLES AND PHILOSOPHY
OF CAST PARTIAL DENTURE DESIGNING
DR. AAMIR GODIL
DEPT. OF PROSTHODONTICS
M.A.R.D.C.

2. CONTENTS
 PRINCIPLES OF DESING
 PHILOSOPHY OF DESIGN
 Stress breakers and equalization
 Physiologic basing
 Broad stress distribution
 Summary
 References
 Exam oriented questions

3. 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)

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

5. STRESS EQUALIZATION
1

6. STRESS BREAKERS AND DIRECTORS
 A stress breaker is defined as " A device which relieves the abutment
teeth of all or part of the occlusal forces"— GPT.
 “ A stress director is a device that allows movement between the
denture base and the direct retainer which may be intra-coronal or
extra-coronal."

7. 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. It can be adjusted to control the amount of vertical movement.

8. TYPES OF STRESS BREAKERS
STRESS BREAKER
MOVABLE TYPE
movable joint is placed between the direct
retainer and denture base
Hinge
(Dalbo, Crismani,
ASC 52)
Ball-socket Sleeve- cylinder
FLEXIBLE TYPE
flexible connection between the direct
retainer and the denture base
Wrought wire
connector
Split major
connector

9. MOVABLE TYPE STRESS BREAKER
Distal extension CPD using hinge stress breaker

10. FLEXIBLE TYPE STRESS BREAKER
Distal extension CPD using split major connector

11. STRESS EQUILIZATION
1
• The alveolar support of the abutment teeth is preserved as the
stress acting on the abutment teeth are reduced.
2
• The stress on the residual ridge and the abutment teeth are
balanced.
3
• Weak abutment teeth are well splinted even during the
movement of the denture base.
4
• Abutment teeth are not damaged even if relining is not done
appropriately (after the denture wears out).
5 • Minimal requirement of direct retention.
6
• Movement of the denture base produces a massaging effect on
the soft tissues.This avoids the frequent need for relining and
rebasing.
ADVANTAGES

12. STRESS EQUILIZATION
1 • Design is complicated and expensive.
2
• The assembly is very weak and tends to fracture easily.
Distorts to rough handling and it is difficult to repair.
3
• It can be used only to counter the vertical forces on the
denture. Inability to counteract lateral stress acting on the
ridge leads to ridge resorption.
4 • Reduced stability against horizontal forces.
5 • Reduced indirect retention.
6
• The split major connector tends to collect food debris at
the area of split.
DISADVANTAGES

13. PHYSILOGIC BASING
2

14. PHYSIOLOGIC
BASING
oThat there is a
significant disparity
between the apical
displaceability of teeth
and compressibility of
the soft tissues.

15. PHYSIOLOGIC BASING
PHYSIOLOGIC BASING
displacing or depressing the
ridge mucosa during the
impression making procedure
by relining the denture base
after it has been constructed

16. 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.
A rigid metal
framework
Functional
occlusal rests
Indirect retainers
to provide
additional
stability
Well-adapted,
broad coverage
denture bases

17. PHYSIOLOGIC
BASING
ALTERED CAST IMPRESSIONS
 Anatomic impression of teeth
 Functional impression of
residual ridge using
framework

18. PHYSIOLOGIC BASING
• Physiologically based dentures compress
tissues even at rest. Hence, during
occlusal loading, the tissues cannot be
compressed further.
• The already compressed tissues offer
greater resistance to compression
equivalent to that of the periodontal
ligament thereby preventing stresses
within the denture.

19. PHYSIOLOGIC BASING
1 • Good adaptation of the denture base.
2 • Simple design and economical.
3
• Minimal direct retention decreases the functional
stress on the abutment tooth.
ADVANTAGES

20. PHYSIOLOGIC BASING
1
• Decrease in the number of retentive components
provides less stability.
2
• The denture tends to lift at rest.This leads to premature
contacts.
3
• Indirect retention is decreased due to vertical movement
of the denture due to tissue rebound at rest.
DISADVANTAGES

21. BROAD STRESS DISTRIBUTION
3

22. 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.

23. BROAD STRESS DISTRIBUTION
BROAD STRESS
DISTRIBUTION
additional rests and
clasps assemblies
broad coverage
denture bases

24. BROAD STRESS DISTRIBUTION
1
• This design with multiple clasps acts as a form of
removable splinting.
2
• It increases the health of the abutment teeth (due to
splinting action).
3 • Easier to construct and economical.
ADVANTAGES

25. BROAD STRESS DISTRIBUTION
1 • Less comfortable
2 • Difficult to maintain adequate oral hygiene
DISADVANTAGES

26. SUMMARY

27. REFERENCES

28. EXAM ORIENTED QUESTIONS
I) LAQ:
1. Discuss in detail the principles and philosophies of cast partial denture
design.
II) SAQ:
1. Stress equalization or stress breakers in cast partial dentures

29. THANK YOU