The Indian Dental Academy is the Leader in continuing dental education , training dentists in all aspects of dentistry and
offering a wide range of dental certified courses in different formats.for more details please visit
www.indiandentalacademy.com
ICT Role in 21st Century Education & its Challenges.pptx
Designing/ dental implant courses
1. Designing in Removable partial
dentures
INDIAN DENTAL ACADEMY
Leader in continuing Dental Education
www.indiandentalacademy.com
2. Introduction
• Authorities in the field of removable partial
denture design may differ on their approach
in developing the design of each individual
prosthesis.
• There is however, complete agreement that
the correct design incorporates proper use
and application of mechanical and biologic
principles.
www.indiandentalacademy.com
3. • Simple mechanical principles have to be
understood and applied in designing of the
removable partial denture.
• Machines are classified into 2 categories as
simple and complex.
• Complex machines are combinations of
many simple machines.
www.indiandentalacademy.com
4. Simple machines
• Lever, wedge,
screw, wheel and
axle, pulley and
inclined plane.
www.indiandentalacademy.com
5. • Of all simple machines lever and inclined plane
principle is involved in partial denture design.
• A lever is a rigid bar supported somewhere along
its length.
• Support point of the lever is called the fulcrum.
www.indiandentalacademy.com
8. Location of stabilizing and retentive
components in relation to the horizontal
axis of rotation
• An abutment tooth will better tolerate off
vertical forces if these forces occur as near
as possible to the horizontal axis of rotation
of the abutment.
www.indiandentalacademy.com
9. Tooth Vs tooth- tissue supported.
• Manner in which each is supported.
• Method of impression registration.
• Need for some indirect retention.
• Denture base material. Acrylic/metal.
• Difference in clasp design.
www.indiandentalacademy.com
10. Forces acting on partial denture
• The all tooth supported RPD is rarely subjected to
induced stresses ,because leverage-type forces are
not involved and there are no fulcrums around
which the partial denture may rotate.
• The distal extension partial denture is subjected to
rotation around 3 principal fulcrums.
www.indiandentalacademy.com
11. • During the formulation of design these
fulcrums and the movement that may take
place around them must be kept in mind and
components positioned to counteract the
movement.
www.indiandentalacademy.com
12. Horizontal fulcrum line.
• It is in the horizontal
plane extending through
two principal abutments.
• Controls rotational
movement of denture in
sagittal plane (towards or
away from the ridge.)
www.indiandentalacademy.com
13. • Magnitude of rotational
movement is greatest around
this fulcrum but not the most
damaging.
• Difficult to control
movement around this
fulcrum line
• Resultant forces are in the
apical direction.
www.indiandentalacademy.com
14. Forces activated
by
Resultant force Counteracted by
Sticky foods Vertical lift Retention.
Tongue and
muscle forces.
Vertical lift adequate denture base
coverage
Gravity(maxillary) Vertical lift Indirect retainers
Denture tooth placement.
Gravity(mandibular)
Occlusal load Movement
toward the
residual ridge.
Occlusal,cingulam,and
incisal rests.
Adequate denture base
coverage
Choice of connector
www.indiandentalacademy.com
15. Fulcrum on sagittal plane
• Extends through the occlusal
rest on the terminal abutment
and along the crest of the
residual ridge on one side of
the arch.
• Controls the rotational
movement in vertical
plane(rocking,or side to side
movements).
www.indiandentalacademy.com
16. • Movements are easier to control around this
fulcrum.
• They are of lesser magnitude.
• More damaging forces as direction is
horizontal.
www.indiandentalacademy.com
17. Forces
activated by
Resultant
force
Counteracted by
Occlusal force
on one side of
the arch causes
lifting forces on
the contra lateral
side of the arch.
Twisting,tilting Rigid connectors
Direct retainer design
Denture base coverage.
Denture tooth placement.
Contour of the denture
base.
www.indiandentalacademy.com
18. Vertical fulcrum line
• Located in midline
,lingual to anterior
teeth.
• Controls movement of
the denture in
horizontal plane (flat
circular movements of
the denture).
www.indiandentalacademy.com
20. Principles by A.H. Schmidt (1956).
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.
www.indiandentalacademy.com
21. 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.
www.indiandentalacademy.com
22. Philosophy of design of stress
breaking
• Of the various schools of thought , none are
backed by scientific research or statistics.
• They are ideas of dentists who by extensive
clinical experience have formulated rules by
which they produce a design .
• The challenge in design lies primarily in
class 1 and 2 arches and to some extent in
the class 4 arches.
www.indiandentalacademy.com
23. • There are 3 basic , underlying approaches to
distributing the forces acting on partial
denture between the soft tissues and teeth.
– Stress equalization
– Physiologic basing
– Broad stress distribution.
www.indiandentalacademy.com
24. Stress equalization
• Resiliency 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.
www.indiandentalacademy.com
25. • There fore , it is
believed that a a
type of stress
equalizer is needed
to replace the rigid
connection between
denture base and
direct retainer. With
non rigid connector
www.indiandentalacademy.com
26. • Most common type
is a hinge device
which permits
vertical movement
of the denture base.
it can be adjusted to
control the amount
of vertical
movement.
• Split major
connector
www.indiandentalacademy.com
27. Advantages.
1. Minimal direct retention is required- as
denture base acts more independently.
2. Has the massaging or stimulating effect on
the underlying bone and soft tissue.
Which minimizes tissue change and
resulting Rebasing procedures.
www.indiandentalacademy.com
28. Disadvantages.
1. Construction of stress director is complex
and costly.
2. Constant maintenance required.
3. Difficult or impossible to repair.
4. Lateral movements of base can lead to
rapid resorption of the ridges.
www.indiandentalacademy.com
29. Physiologic basing
• This school of thought too believes that
there is relative lack of movement in
abutment teeth in an apical direction.
• But it 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
www.indiandentalacademy.com
30. • The tissue surface is
recorded in functional
form and not anatomic
form.
• Rpd constructed from
tissue displacing
impression will be
above the plane of
occlusion when the
denture is not in
function.
www.indiandentalacademy.com
31. • To permit vertical movement from rest
position to functional position the retentive
clasps have to have minimum retention and
also their number has to be less.
www.indiandentalacademy.com
32. Advantages.
1. Intermittent base movement
has a physiologically
stimulating effect on the
underlying bone and soft
tissue.
2. Less need for relining and
Rebasing.
3. Simplicity of design and
construction because of
minimal retention
requirements.
www.indiandentalacademy.com
33. 4. Light weight prosthesis with minimal
maintenance and repair.
5. The looseness of the clasp on the
abutment tooth reduces the functional
forces transmitted to the tooth.
www.indiandentalacademy.com
34. Disadvantages.
1. Denture is not well stabilized against
lateral forces.
2. There will be always premature contact
when mouth is closed .
3. It may be uncomfortable sensation to the
patient.
4. It is difficult to produce effective indirect
retention.
www.indiandentalacademy.com
35. Broad stress distribution
• Advocates of this school of
thought believe that
excessive 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.
• Achieved by means of
additional rests,indirect
retainers,clasps and broad
coverage denture bases.www.indiandentalacademy.com
36. advantages
1. Teeth can be splinted .
2. Prosthesis are easier and less expensive to
construct.
3. No flexible or moving parts so less danger
of distorting the denture.
www.indiandentalacademy.com
37. 4. Indirect retainers and other rigid
components provides excellent horizontal
stabilization.
5. Less relining required.
www.indiandentalacademy.com
38. disadvantages
1. Greater bulk may cause prosthesis to be
less comfortable.
2. Increased amount of tooth coverage can
lead to dental caries
www.indiandentalacademy.com
39. Factors influencing magnitude of
stresses transmitted to abutment teeth
1. Length of span.
2. Quality of support of ridge.
3. Clasp.
1. Qualities
2. Design.
3. Length
4. Material.
4. Abutment tooth surface
5. Occlusal harmony.www.indiandentalacademy.com
40. Length of span
Factors
influencing
magnitude of
stresses
transmitted to
abutment
teeth
1. Length of span.
2. Quality of support
of ridge.
3. Clasp.
1. Qualities
2. Design.
3. Length
4. Material.
4. Abutment tooth
surface
5. Occlusal harmony.
• The longer the edentulous span
,the longer will be the denture
base and the greater will be the
force transmitted to the abutment
teeth.
www.indiandentalacademy.com
41. Quality of support of ridge
Factors
influencing
magnitude
of stresses
transmitted
to abutment
teeth
1. Length of span.
2. Quality of
support of
ridge.
3. Clasp.
1. Qualities
2. Design.
3. Length
4. Material.
4. Abutment tooth
surface
5. Occlusal
harmony.
• Large well formed ridges are
capable of absorbing greater
amounts of stress than are
small,thin,or knife-edged ridges
• broad ridges with parallel sides
permit the use of longer flanges
which help in stabilizing the
denture against the lateral forces.
• Type of mucoperiosteum also
influences the magnitude of
stresses transmitted to abutment
teeth.
www.indiandentalacademy.com
42. •Flat ridge will provide good
support,poor stability
•Sharp spiny ridge will provide
poor support,poor to fair
stability.
•Soft ,flabby displaceable tissue-
poor support, poor stability-
leads to vertical and lateral
instability and transmission of
stress to the adjacent abutment
tooth.
www.indiandentalacademy.com
43. Qualities of clasp
Factors
influencing
magnitude
of stresses
transmitted
to abutment
teeth
1. Length of span.
2. Quality of
support of
ridge.
3. Clasp.
1. Qualities
2. Design.
3. Length
4. Material.
4. Abutment tooth
surface
5. Occlusal
harmony.
• 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.
www.indiandentalacademy.com
44. Design of clasp
Factors
influencing
magnitude
of stresses
transmitted
to abutment
teeth
1. Length of span.
2. Quality of
support of
ridge.
3. Clasp.
1. Qualities
2. Design.
3. Length
4. Material.
4. Abutment tooth
surface
5. Occlusal
harmony.
• A clasp that is designed so that it
is passive when it is completely
seated on the abutment tooth
will exert less stress on the tooth
than one that is not passive.
• A clasp should be designed so
that during insertion or removal
of the prosthesis the reciprocal
arm contacts the tooth before the
retentive tip passes over the
greatest bulge of the abutment
tooth.
www.indiandentalacademy.com
45. Length of clasp
Factors
influencing
magnitude
of stresses
transmitted
to abutment
teeth
1. Length of span.
2. Quality of
support of
ridge.
3. Clasp.
1. Qualities
2. Design.
3. Length
4. Material.
4. Abutment tooth
surface
5. Occlusal
harmony.
• More flexible the clasp
less stress it will exert
on the abutment tooth.
• Flexibility can be
increases by
lengthening the clasp.
www.indiandentalacademy.com
46. • Clasp length may be
increases by using a
curved rather than a
straight course on
an abutment tooth
www.indiandentalacademy.com
47. Material used for clasp
fabrication
Factors
influencing
magnitude
of stresses
transmitted
to abutment
teeth
1. Length of span.
2. Quality of
support of
ridge.
3. Clasp.
1. Qualities
2. Design.
3. Length
4. Material.
4. Abutment tooth
surface
5. Occlusal
harmony.
• Crome alloy being
more rigid will exert
greater stress on the
abutment tooth.
www.indiandentalacademy.com
48. • Clasp arm of chrome
alloys are
constructed with a
smaller diameter
than a gold clasp
www.indiandentalacademy.com
49. Abutment tooth surfaceFactors
influencing
magnitude
of stresses
transmitted
to abutment
teeth
1. Length of span.
2. Quality of
support of
ridge.
3. Clasp.
1. Qualities
2. Design.
3. Length
4. Material.
4. Abutment tooth
surface
5. Occlusal
harmony.
• 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.
www.indiandentalacademy.com
50. Occlusal harmony.Factors
influencing
magnitude
of stresses
transmitted
to abutment
teeth
1. Length of span.
2. Quality of
support of
ridge.
3. Clasp.
1. Qualities
2. Design.
3. Length
4. Material.
4. Abutment tooth
surface
5. Occlusal
harmony.
• When deflective
occlusal contacts are
present between
opposing teeth
destructive horizontal
forces which are
magnified by leverage
are transmitted to the
abutment and ridge.
www.indiandentalacademy.com
51. • 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 teeth.
www.indiandentalacademy.com
52. • Ideally,the occlusal load should be applied
in the center of the denture –bearing area,
both antero-posteriorly and bucco-lingually
www.indiandentalacademy.com
53. Design considerations for stress control
1. Direct retention
• Adhesion ,cohesion
• Frictional
• neuromuscular
1. Clasp position
– Quadrilateral
– Tripod
– bilateral
1. Clasp design
• Circumferential clasp
• Bar clasp.
• Combination clasp
1. Splinting of abutments
5. Indirect retention
6. Occlusion
7. Denture base
8. Major connector
9. minor connector
10. Rests
www.indiandentalacademy.com
54. Design considerations for
stress control
1. Direct retention
• Adhesion ,cohesion
• Frictional
• neuromuscular
1. Clasp position
– Quadrilateral
– Tripod
– bilateral
1. Clasp design
• Circumferential clasp
• Bar clasp.
• Combination clasp
1. Splinting of abutments
2. Indirect retention
3. Occlusion
4. Denture base
5. Major connector
6. minor connector
7. Rests
• At present there is no way that
all forces can be totally negated
or countered.
• Long term clinical observations
have proved that a design
philosophy that strives to
control these forces within the
physiologic tolerance of the
teeth and supporting structures
can be successful.
www.indiandentalacademy.com
55. Direct retentionDesign
considerations
for stress
control
1. Direct retention
• Adhesion
,cohesion
• Frictional
• neuromuscul
ar
1. Clasp position
– Quadrilateral
– Tripod
– bilateral
1. Clasp design
• Circumferent
ial clasp
• Bar clasp.
• Combination
clasp
1. Splinting of
abutments
2. Indirect retention
3. Occlusion
4. Denture base
5. Major connector
6. minor connector
7. Rests
• The retentive clasp arm is responsible
for transmitting most of the destructive
forces to the abutment teeth.
• Clasp retention should be kept at the
minimum yet provide adequate
retention to prevent dislodgement of
the denture.
• Other components should be used to
contribute for the retention so that
amount of retention provided by clasp
can be reduces
www.indiandentalacademy.com
56. Adhesion and
Cohesion
Design
considerations
for stress
control
1. Direct retention
• Adhesion
,cohesion
• Frictional
• neuromuscul
ar
1. Clasp position
– Quadrilateral
– Tripod
– bilateral
1. Clasp design
• Circumferent
ial clasp
• Bar clasp.
• Combination
clasp
1. Splinting of
abutments
2. Indirect retention
3. Occlusion
4. Denture base
5. Major connector
6. minor connector
7. Rests
• For adhesion and cohesion to work
– Maximum area of available support should
be used.
– Denture base should be accurately adapted
to the underlying mucosa.
• Though peripheral seal cannot be
developed due to presence of teeth
.Atmospheric pressure helps in retention
of the maxillary partial denture when
metal casting is accurate and margins of
connector are beaded.
www.indiandentalacademy.com
57. Frictional controlDesign
considerations
for stress
control
1. Direct retention
• Adhesion
,cohesion
• Frictional
• neuromuscul
ar
1. Clasp position
– Quadrilateral
– Tripod
– bilateral
1. Clasp design
• Circumferent
ial clasp
• Bar clasp.
• Combination
clasp
1. Splinting of
abutments
2. Indirect retention
3. Occlusion
4. Denture base
5. Major connector
6. minor connector
7. Rests
• The partial dentures should be
designed so that guide planes are
created on as many teeth as
possible.
• These planes can be on enamel
surfaces of the teeth or in
restorations placed on the teeth.
www.indiandentalacademy.com
58. • The frictional contact of the prosthesis
against these parallel surfaces can contribute
significantly to the retention of the denture.
www.indiandentalacademy.com
59. Function of guide planes
1. To provide for one path of placement and
removal of the restoration.
2. To ensure the intended actions of
reciprocal,stabilizing, and retentive
components.
3. To eliminate gross food traps between
abutment teeth and components of the
denture.
www.indiandentalacademy.com
60. • Proximal guiding plane surfaces should be about
2/3rd
as wide as the distance between the tips of
adjacent buccal and lingual cusps or
about 1/3rd
of the buccal lingual width of the tooth.
Vertically it should extend 2/3rd
of the length of the
enamel crown portion of the tooth from the
marginal ridge cervically.
Care must be taken to avoid creating buccal or
lingual line angles.
www.indiandentalacademy.com
62. Neuromuscular control
Design
considerations
for stress
control
1. Direct retention
• Adhesion
,cohesion
• Frictional
• neuromuscul
ar
1. Clasp position
– Quadrilateral
– Tripod
– bilateral
1. Clasp design
• Circumferent
ial clasp
• Bar clasp.
• Combination
clasp
1. Splinting of
abutments
2. Indirect retention
3. Occlusion
4. Denture base
5. Major connector
6. minor connector
7. Rests
• The innate ability of the patient
to control the action of the lips,
cheeks, tongue can be a major
factor in the retention of a
denture.
• A properly contoured denture
base, however, can aid the
patient’s neuromuscular control
of the prosthesis.
www.indiandentalacademy.com
63. Clasp position
Design
considerations
for stress
control
1. Direct retention
• Adhesion
,cohesion
• Frictional
• neuromuscul
ar
1. Clasp position
– Quadrilateral
– Tripod
– bilateral
1. Clasp design
• Circumferent
ial clasp
• Bar clasp.
• Combination
clasp
1. Splinting of
abutments
2. Indirect retention
3. Occlusion
4. Denture base
5. Major connector
6. minor connector
7. Rests
• The position of
retentive clasp is more
important than the
number of retentive
clasp used in any
design.
• The number of clasps
used is determined by
classification.
www.indiandentalacademy.com
64. Quadrilateral configuration
Design
considerations
for stress
control
1. Direct retention
• Adhesion
,cohesion
• Frictional
• neuromuscul
ar
1. Clasp position
– Quadrilateral
– Tripod
– bilateral
1. Clasp design
• Circumferent
ial clasp
• Bar clasp.
• Combination
clasp
1. Splinting of
abutments
2. Indirect retention
3. Occlusion
4. Denture base
5. Major connector
6. minor connector
7. Rests
• Is indicated in class 3 arches
particularly when modification
space exists on the opposite side.
www.indiandentalacademy.com
65. • A retentive clasp is
positioned on each
abutment tooth
adjacent to the
edentulous spaces.
• In this design
leverage is
effectively
neutralized.
www.indiandentalacademy.com
66. • When no modification space exists the goal
should be to place one clasp as far posterior
on the Dentulous side as possible and one
as far anterior as space and esthetics permit.
www.indiandentalacademy.com
67. Tripod configuration
Design
considerations
for stress
control
1. Direct retention
• Adhesion
,cohesion
• Frictional
• neuromuscul
ar
1. Clasp position
– Quadrilateral
– Tripod
– bilateral
1. Clasp design
• Circumferent
ial clasp
• Bar clasp.
• Combination
clasp
1. Splinting of
abutments
2. Indirect retention
3. Occlusion
4. Denture base
5. Major connector
6. minor connector
7. Rests
• Used primarily for class 2 arches.
• If there is a modification space on
the Dentulous side .
www.indiandentalacademy.com
68. • If there is no modification space present .
One clasp on the Dentulous side of the arch
should be positioned as far posterior, and
the other, as far anterior as factors such as
interocclusal space, retentive undercut, and
esthetics considerations will permit.
www.indiandentalacademy.com
69. Bilateral configuration
Design
considerations
for stress
control
1. Direct retention
• Adhesion
,cohesion
• Frictional
• neuromuscul
ar
1. Clasp position
– Quadrilateral
– Tripod
– bilateral
1. Clasp design
• Circumferent
ial clasp
• Bar clasp.
• Combination
clasp
1. Splinting of
abutments
2. Indirect retention
3. Occlusion
4. Denture base
5. Major connector
6. minor connector
7. Rests
• Used in class 1 cases.
– In this configuration the clasps exert
little neutralizing effect on the
leverage induced stresses generated
be the denture base. These stresses
must be controlled by other means.
www.indiandentalacademy.com
70. The terminal
abutment tooth
on the each
side of the arch
must be clasped
regardless of
where it is
positioned.
www.indiandentalacademy.com
71. Circumferential clasp
Design
considerations
for stress
control
1. Direct retention
• Adhesion
,cohesion
• Frictional
• neuromuscul
ar
1. Clasp position
– Quadrilateral
– Tripod
– bilateral
1. Clasp design
• Circumferent
ial clasp
• Bar clasp.
• Combination
clasp
1. Splinting of
abutments
2. Indirect retention
3. Occlusion
4. Denture base
5. Major connector
6. minor connector
7. Rests
• Conventional circumferential
clasp originating from distal
rest and engaging mesiobuccal
retentive undercut should be
avoided at all cost in distal
extension removable partial
denture.
www.indiandentalacademy.com
72. • As denture base moves towards the tissue
the clasp puts distal tipping force on the
abutment tooth.
www.indiandentalacademy.com
73. Alternatives
• Reverse circlet clap
– Approaches a
distobuccal undercut
from the mesial surfaces
of a terminal abutment
tooth.
– As occlusal load is
applied, retentive
terminal moves
gingivally and loses
contact with the tooth
surface and no stresses
are transmitted.
www.indiandentalacademy.com
74. Disadvantage
It may produce wedging force between 2 teeth's-
can be countered by making rest on the
approximating surface too.
www.indiandentalacademy.com
75. Vertical projection or Bar
clasp.
Design
considerations
for stress
control
1. Direct retention
• Adhesion
,cohesion
• Frictional
• neuromuscul
ar
1. Clasp position
– Quadrilateral
– Tripod
– bilateral
1. Clasp design
• Circumferent
ial clasp
• Bar clasp.
• Combination
clasp
1. Splinting of
abutments
2. Indirect retention
3. Occlusion
4. Denture base
5. Major connector
6. minor connector
7. Rests
• It is used in distal extension partial
denture when retentive undercut is
located on the distobuccal surface.
• Never when tooth has a mesiobuccal
undercut.
www.indiandentalacademy.com
76. • Functions similar to the reverse
circumferential clasp with the advantage of
not producing any wedging forces .
www.indiandentalacademy.com
77. • One school of thought advocated omitting of
the distal rest in favour of a mesial rest for
the following reasons.
– As the fulcrum line is still distal to the clasp
terminal when distal rest is used .
– With use of mesial rest the lever arm is increases
and forces are directed to the ridge in more
vertical direction which are better tolerated by
the ridge.
www.indiandentalacademy.com
78. Disadvantage
• a space is created
between framework
and tooth surface
leading to food
trapment
www.indiandentalacademy.com
79. What is the consensus?
• Least unfavorable torque is when…..
…T clasp with distal -occlusal rest and a
rigid circumferential reciprocating clasp.
www.indiandentalacademy.com
80. Combination clasp
Design
considerations
for stress
control
1. Direct retention
• Adhesion
,cohesion
• Frictional
• neuromuscul
ar
1. Clasp position
– Quadrilateral
– Tripod
– bilateral
1. Clasp design
• Circumferent
ial clasp
• Bar clasp.
• Combination
clasp
1. Splinting of
abutments
2. Indirect retention
3. Occlusion
4. Denture base
5. Major connector
6. minor connector
7. Rests
• It is used when mesiobuccal undercut
exists on an abutment tooth adjacent to
a distal extension edentulous ridge.
• Only the retentive arm is wrought
metal.
• Reciprocation and stabilization against
lateral movement must be obtained
through the use of the rigid cast
elements that make up the remainder of
the clasp.
www.indiandentalacademy.com
81. • Wrought wire can flex in any spatial plane
and can absorb torosional stress in both the
vertical ad horizontal planes.
• A cast clasp flexes in the horizontal plane
only.
• A short wrought wire arm can be
destructive element because of its reduced
ability to flex compared with a longer
wrought –wire arm.
www.indiandentalacademy.com
83. Splinting of abutments
Design
considerations
for stress
control
1. Direct retention
• Adhesion
,cohesion
• Frictional
• neuromuscul
ar
1. Clasp position
– Quadrilateral
– Tripod
– bilateral
1. Clasp design
• Circumferent
ial clasp
• Bar clasp.
• Combination
clasp
1. Splinting of
abutments
2. Indirect retention
3. Occlusion
4. Denture base
5. Major connector
6. minor connector
7. Rests
• Rationale
– It increases the periodontal ligament
attachment area and distributes the
stress over a larger area of support.
www.indiandentalacademy.com
84. Indications by crowns.
1. Loss of periodontal
attachment by disease
or therapy.
2. Abutment has tapered
or short roots
3. Second premolar as
abutment with
edentulous space
anterior to it- splinted
with canine by FPD.
www.indiandentalacademy.com
85. • Splinting by crowns
stabilizes the teeth in
mesiodistal direction.
• Splint should include
canine to achieve the
stabilization in
buccolingual direction
as well.
www.indiandentalacademy.com
86. • An extremely week
teeth should not be
splinted with a
strong teeth.
www.indiandentalacademy.com
87. Splinting by clasps
• Should not be done if fixed
splinting is possible.
• More tan one teeth are
clasped on each side of the
arch ,using a number of
rests for additional support
and stabilization of the
teeth and prosthesis.
• Most of the clasp arm will
not be retentive.
www.indiandentalacademy.com
88. Indirect retentionDesign
considerations
for stress
control
1. Direct retention
• Adhesion
,cohesion
• Frictional
• neuromuscul
ar
1. Clasp position
– Quadrilateral
– Tripod
– bilateral
1. Clasp design
• Circumferent
ial clasp
• Bar clasp.
• Combination
clasp
1. Splinting of
abutments
2. Indirect retention
3. Occlusion
4. Denture base
5. Major connector
6. minor connector
7. Rests
• Indirect retainer.
– The component of removable partial
denture that assists the direct retainer in
preventing displacement of the distal
extension denture base by functioning
through lever action on the opposite
side of the fulcrum line when the
denture base moves away from the
tissues in pure rotation around the
fulcrum line.
• Indirect retainer also contributes to a
lesser degree, to the support and
stability of the denture.www.indiandentalacademy.com
90. Class 1.
• It must always be
used and
positioned as far
anteriorly as
possible.
www.indiandentalacademy.com
91. Class 2
• its use is not as critical as in
class 1.
• If no modification space exists .
• An abutment tooth with suitable
contours for clasping should be
selected as far anterior on the
tooth-supported side as possible.
• This rest and clasp assembly,
may serve as the indirect
retainer if it is located far
enough anterior to the fulcrum
line.
www.indiandentalacademy.com
92. • If modification space exists.
• The most anterior abutment
on the tooth supported side,
with its rest and clasp
assembly, may be located far
enough anterior to the fulcrum
line to serve as the indirect
retainer.
• A definite rest seat positioned
even farther anterior,if
possible,may increase the
effectiveness of the indirect
retention.
www.indiandentalacademy.com
93. Class 3
• Indirect retention is not
ordinarily used.
• Auxillary rests must for
lingual plate major
connector.
• Auxillary rests may be
needed to provide additional
vertical support for a long
lingual bar major connector
or an extensive palatal major
connector.
www.indiandentalacademy.com
94. • If the contours of the posterior abutment
teeth in class 2 or 3 partial denture are not
suitable for retention
• In such case non retentive stabilizing clasp
are designed for posterior teeth and anterior
indirect retention is a must.
www.indiandentalacademy.com
95. Class 4
• The indirect retainer must be located as far
posterior as possible.
www.indiandentalacademy.com
96. Occlusion
Design
considerations
for stress
control
1. Direct retention
• Adhesion
,cohesion
• Frictional
• neuromuscul
ar
1. Clasp position
– Quadrilateral
– Tripod
– bilateral
1. Clasp design
• Circumferent
ial clasp
• Bar clasp.
• Combination
clasp
1. Splinting of
abutments
2. Indirect retention
3. Occlusion
4. Denture base
5. Major connector
6. minor connector
7. Rests
• Occlusion which is in
harmony with
movements of TMJ
and neuromusculature
will minimize the
stress transferred to
the abutment teeth and
residual ridge.
www.indiandentalacademy.com
97. Design considerations
• The initial occlusal contact should always be
in the remaining natural teeth.
• Mandible should not be guided into protrusive
or lateral movements by the metal or artificial
teeth.
• Reduced buccolingual width of replaced teeth
reduces the stress transmitted.
www.indiandentalacademy.com
98. • if number of teeth replaced is reduced stress
transmitted will be less
• Sharp cutting surfaces and sluiceways can
help relive some unnecessary force during
mastication.
• Steep cuspal inclines on the artificial teeth
should be avoided because they tend to
introduce horizontal forces .
www.indiandentalacademy.com
99. Denture base
Design
considerations
for stress
control
1. Direct retention
• Adhesion
,cohesion
• Frictional
• neuromuscul
ar
1. Clasp position
– Quadrilateral
– Tripod
– bilateral
1. Clasp design
• Circumferent
ial clasp
• Bar clasp.
• Combination
clasp
1. Splinting of
abutments
2. Indirect retention
3. Occlusion
4. Denture base
5. Major connector
6. minor connector
7. Rests
• ….to reduce the stress to the
abutment teeth?
– denture base should cover
maximum area of the supporting
tissue as possible.
– Denture base flanges should be
as long as possible-to help
stabilize against horizontal
movements.
www.indiandentalacademy.com
100. Design considerations….
– Distal extension denture base should cover the
retro molar area and tuberosity of maxilla as
these structures better absorb stress.
– Overextension should be avoided as
interference with functional movements of
surrounding tissues will transmit stresses to the
remaining teeth.
– Accurate adaptation of denture base leads to
less tendency for movement during function.
– Contour of the polished surfaces also helps in
reducing the stress transmitted.
www.indiandentalacademy.com
101. Essentials of partial denture
design.
• It should be systemically developed and
outlined on an accurate diagnostic casts.
www.indiandentalacademy.com
102. First step
• Decide how the partial denture has to be
supported.
• If Tooth supported.
– Evaluate
1. Periodontal health
2. Crown and root morphologies
3. Crown to root ratio.
4. Bone index area.
5. Location of tooth in arch.
6. Length of edentulous span.
7. Opposing dentition.
www.indiandentalacademy.com
103. • If tooth and tissue supported.
• Also Consider
1. Quality and contour of supporting bone and
mucosa
2. Extend to planned coverage of ridge.
3. Type and accuracy of impression registration.
4. Accuracy of denture base.
5. Design characteristics of the component parts
of framework.
6. Anticipated occlusal load.
www.indiandentalacademy.com
104. • Denture base areas adjacent to abutment
teeth are primarily tooth supported.
• As we proceed away from abutment teeth,
they become more tissue supported.
www.indiandentalacademy.com
105. Second step
• Connect the tooth and tissue support units.
• These connection is facilitated by designing
and locating major and minor connectors in
compliance with the basic principles and
concepts.
www.indiandentalacademy.com
106. Third step.
• Determine how the partial denture is to be
retained.
• Selecta clasp design that will
1. Avoid direct transmission of tipping for torquing
forces to the abutment
2. Accommodate the basic principles of clasp design by
definitive location of components parts correctly
positioned on abutment tooth surfaces.
3. Provide retention against reasonable dislodging
forces.
4. Be compatible with undercut locations,tissue
contour,and esthetic desires of the patient.
www.indiandentalacademy.com
107. Fourth step.
• Connect the retention units to the support
units
www.indiandentalacademy.com
108. Fifth step.
• Outline and join the edentulous area to
already established design components.
www.indiandentalacademy.com