Clinical course of Partial Denture
3- Basic principles for designing the removable partial denture
a- Problems and General Principles Applied for Kennedy Class I
Unit-IV; Professional Sales Representative (PSR).pptx
3- Basic principles for designing the removable partial denture
1.
2.
3. Removal Partial Design
Dr. Amal Fathy KaddahDr. Amal Fathy Kaddah
Professor of Prosthodontic,Professor of Prosthodontic,
Faculty of Oral &DentalFaculty of Oral &Dental
Medicine, Cairo UniversityMedicine, Cairo University
6. • Forces acting on RPD and factors that influence
the magnitude of stresses transmitted to the
tissues.
Is the Planning of the form and extent
of RPD, after studying all the factors
involved
• Controlling the stresses by RPD
• Design concepts
Removable Partial Denture DesignRemovable Partial Denture Design
• Biomechanical aspect of RPD design
7. * Mechanical ----- related to forces and its
application to object----- looseness of teeth ,
bon resorption……etc
Removable Partial Denture DesignRemovable Partial Denture Design
• Biomechanical aspect of RPD design
* Bio ------ pertaining
to living systems-----
inflammation, Caries,
b. resorption….etc
9. Fibers of periodontal ligament are
arranged such that their resistance to
vertical forces is much greater
than that to horizontal forces
Tissues are adapted toTissues are adapted to
receive and absorb forcesreceive and absorb forces
within their physiologicalwithin their physiological
tolerancetolerance
13. • The Resistance to
Tissue Ward
Movement
Support
• Adequate Distribution of Forces Over the Supporting
Structure
• Transferring Occlusal
Stresses to the
Supporting Oral
Structures and
decrease forces / unit
area
14. • Adequate Distribution of Forces Over the
Supporting Sttructure
• Decrease forces/unit area
• The Resistance to Tissue Ward Movement
15. This Function Is Mainly Provided By:
Properly designed supporting
rests placed in rest seats,
which are prepared on the
abutment teeth,
Broad accurately fitting
denture bases in distal
extension partial dentures.
Rigid major
connectors that are
neither relieved from the
tissues nor placed on
inclined planes also provide
support
21. Horizontal forces developed when
the mandible moves from side to
side during function while the teeth
are in contact
Lateral movements
have a destructive
effect on teeth leading
to tilting, breakdown of
the periodontal ligament
and looseness of
abutment teeth.
24. ReciprocationReciprocation
Nullifying the effect of pressure on one side ofNullifying the effect of pressure on one side of
the teeth by application of pressure, equal inthe teeth by application of pressure, equal in
amount, but in an opposite direction, on theamount, but in an opposite direction, on the
opposite side of the teeth.opposite side of the teeth.
Retention distance ??????
Palatal view
Proximal view
?
25. RECIPROCATIONRECIPROCATION
RECIPROCATIONRECIPROCATION can be achieved by:can be achieved by:
Reciprocal clasp arms contacting theReciprocal clasp arms contacting the
tooth prior to or at the same time thetooth prior to or at the same time the
retentive tip crosses the survey line ofretentive tip crosses the survey line of
the tooth.the tooth.
Parts of the major connectors……..?????Parts of the major connectors……..?????
Proximal plates.Proximal plates.
Cross arch reciprocation should also beCross arch reciprocation should also be
provided.provided.
27. A rigid major connector.
Balanced contact between upper and lower
teeth and reduction of cusp slope..
Broad base coverage
This movement is counteracted by:
Providing adequate bracing
The use of additional rests on teeth other thanThe use of additional rests on teeth other than
the abutment tooth serves as, indirectthe abutment tooth serves as, indirect
retainers.retainers.
Cover rage of the sloping part of the palateCover rage of the sloping part of the palate
ant. (rugea area) acts as an indirect retainerant. (rugea area) acts as an indirect retainer
28.
29. When you realize you've made a mistake,
take immediate steps to correct it.
30.
31. The first step in a successfulThe first step in a successful
partial denturepartial denture is to designis to design
and plan the case veryand plan the case very
carefully.carefully. The more timeThe more time
taken with this important step,taken with this important step,
the more secure andthe more secure and
functional the resulting partialfunctional the resulting partial..
32. OBJECTIVES OF REMOVABLE PARTIAL DENTURESOBJECTIVES OF REMOVABLE PARTIAL DENTURES
Preservation of thePreservation of the
Remaining TissuesRemaining Tissues
without injury of thewithout injury of the
remaining oralremaining oral
structures.structures.
Restore the form andRestore the form and
FunctionFunction
Enhance psychological
comfort
33. The prosthesis must be designed following
the most favorable biomechanical principles,
as the simple and proper design helps in
reducing the harmful effects on the
supporting structures
Therefore, forces falling on RPD
should be properly:
Directed vertically on both ridge
and abutment
Decreased , to reduce the force /unit
area within the physiological
tolerance of the tissues.
Distributed widely
34. Types of RPDTypes of RPD
Tooth SupportTooth Support
Mucosa supportMucosa support
Tooth-mucosa supportTooth-mucosa support
36. Tooth-mucosaTooth-mucosa
supportsupportSupport is derived from twoSupport is derived from two
different tissuesdifferent tissues ,, the non-
displaceable teeth and the
displaceable soft tissues
covering the residual ridge.
This results in vertical
movement of the denture
base either in tissue-ward or
tissue-away direction when
occlusal forces act on
38. Problems of support associated with free-end
saddles RPD is due to:
1. Lack of posterior abutment
2. Support is derived from both the
residual ridge and abutment teeth
3.Major support is obtained from the
residual ridge
4.If resorption occurs and relining of
the denture is neglected further
bone resorption occurs with
subsequent torque acting on the
39. This means that in class I RPDThis means that in class I RPD
there are problems of:there are problems of:
• Support (maimly)
• Retention
• Bracing and reciprocation
• Stabilization (tipping and
rotational movements)
41. These difficulties will lead to:These difficulties will lead to:
Ridge resorption is likely toRidge resorption is likely to
happen.happen.
The abutment teeth areThe abutment teeth are
subjected to torque in bothsubjected to torque in both
antero-posterior andantero-posterior and
buccolingual directions.buccolingual directions.
43. Problems of the distal
extension bases can be
controlled by
1. Reduction of the load.
2. Distribution of the load between
abutment teeth and residual
ridges.
3. Wide distribution of the load.
4. Providing posterior abutment
44. I- REDUCING THE LOAD
1.1. Broad tissue coverageBroad tissue coverage and maximumand maximum
extension of the denture base within theextension of the denture base within the
functional limits of muscular movements.functional limits of muscular movements.
2.2. Use ofUse of small and narrow teethsmall and narrow teeth to increaseto increase
the masticatory efficiency and reduce thethe masticatory efficiency and reduce the
mast. Loadmast. Load
3.3. Fitness andFitness and intimate adaptation of theintimate adaptation of the
denture basedenture base toto the tissue.the tissue.
4.4. Harmonious occlusion and reducing theHarmonious occlusion and reducing the
cusp anglecusp angle of artificial teeth.of artificial teeth.
5.5. Leaving aLeaving a tooth off the saddle.tooth off the saddle.
6-6- Improving the condition of the residualImproving the condition of the residual
ridgeridge e.g. correction of abusive conditione.g. correction of abusive condition
45. Total occlusal load applied may be reduced by using comparatively
smaller posterior teeth. less muscular force will be required to
penetrate food bolus with reduced occlusal table, thereby reducing
forces to supporting oral structures
46. • Varying the connection betweenVarying the connection between
the clasps and saddles: Throughthe clasps and saddles: Through
applying the stress-breakingapplying the stress-breaking
principleprinciple
• Functional basing.Functional basing. Muco-Muco-
compression impressioncompression impression
recording of the residual ridges.recording of the residual ridges.
• Placement of occlusal rests awayPlacement of occlusal rests away
from the saddle.from the saddle.
II- DISTRIBUTION OF LOAD BETWEEN
THE TEETH AND THE RIDGES
47.
48. 3. Wide distribution of the
load
a- By placinga- By placing additionaladditional
restsrests,, oror
b- by ab- by a splinting of onesplinting of one
or more teethor more teeth, either, either
by fixed partialby fixed partial
dentures or bydentures or by
soldering two or moresoldering two or more
individual restorationindividual restoration
together.together.
c- Using ac- Using a Kennedy barKennedy bar to distributeto distribute
the lateral load on multiple teeth.the lateral load on multiple teeth.
49.
50.
51. Metal base indicated in
bounded saddle cases
Acrylic baseAcrylic base
indicated in Free endindicated in Free end
saddle casessaddle cases
52. Free end saddle casesFree end saddle cases
Long span bounded S.Long span bounded S.
Diabetic patientDiabetic patient
Newly extractedNewly extracted
Young ageYoung age
?
54. 2. The metal part is designed either
in ladder-like configuration or in the
form of meshwork, to allow for
mechanical retention with acrylic
1-Denture base
55. 3. Attain maximum coverage
and extension within the
physiologic limits.
1-Denture base
56. 4. Either constructed over
mucosa in its displaced
functional form or in the
static form if the stress
breaking principle is applied.
5. Concave Polished surface
6. Open or closed design
1-Denture base
59. The neutral zoneThe neutral zone
conceptconcept is based on theis based on the
belief that the musclesbelief that the muscles
should functionally moldshould functionally mold
not only the border and thenot only the border and the
artificial teeth but also theartificial teeth but also the
entire polished surface.entire polished surface.
facial andfacial and linguallingual
forces generated by theforces generated by the
musculature of the lips,musculature of the lips,
cheeks and tongue arecheeks and tongue are
balancedbalanced
60. The tongue brings the food onto the occlusal plane, then it holds
the food between the upper and lower teeth by cooperating with
the buccinator muscle so that the food can easily crushed.
The food is held between the bucc. (its middle fibres) and
the tongue, and crushed.
61. Prepare the tray:Prepare the tray:
The purpose of the tray is to carry a uniformThe purpose of the tray is to carry a uniform
thickness of the final impression material to thethickness of the final impression material to the
mouth without exerting pressure on the mucosa.mouth without exerting pressure on the mucosa.
Altered Cast ProcedureAltered Cast Procedure
The purpose of this isThe purpose of this is
to obtain the maximum support possible from theto obtain the maximum support possible from the
edentulous area of the extension partial dentureedentulous area of the extension partial denture..
The mucosa is recorded in aThe mucosa is recorded in a
compressed form so that the degree ofcompressed form so that the degree of
tissue ward displacement is decreasedtissue ward displacement is decreased
intra-orallyintra-orally
62. The accuracy and type of impressionThe accuracy and type of impression
registration (anatomical orregistration (anatomical or
functional)functional)
Has greater area coverageHas greater area coverage
More stability under rotating and/orMore stability under rotating and/or
torquing forcestorquing forces
Maintain its occlusal relation with theMaintain its occlusal relation with the
opposing teeth.opposing teeth.
No rapid settling of the denture baseNo rapid settling of the denture base
Distribute the occlusal load equitablyDistribute the occlusal load equitably
and diminish the rotational movement.and diminish the rotational movement.
A denture base processed to theA denture base processed to the
functional form is generallyfunctional form is generally
63. Minor connectors forming denture basesMinor connectors forming denture bases
should include tissue stops and finishingshould include tissue stops and finishing
line:line:
Tissue stops:Tissue stops:
• Are essential parts in the fitting
surface of minor connectors.
They are usually two or three in
number that contact the cast.
• Stabilize the framework on the
master cast during processing as
acrylic resin is packed in the
retention spaces.
• Elevate the minor connectors,
forming the denture base, from
the ridge, by a space equal to the
thickness of acrylic bases.
• They are formed by making holes
in the relief wax placed over the
64. Finishing Lines:Finishing Lines:
Are butt joints created at the junctionAre butt joints created at the junction
of major connectors with the dentureof major connectors with the denture
bases.bases.
External finish lines: junction of major
connector and minor connectors at
palatal finishing line should be located 2
mm medial from an imaginary line that
would contacts lingual surfaces of
missing posterior teeth.
Incorrect: natural contours of palate will
65. 1.Smaller teeth and narrow bucco-
lingually are usually preferred to
reduce the occlusal load.
2.Teeth should exhibit sharp cutting
edges
3.Lower teeth should be placed over
the crest of the ridge to enhance
denture stability.
4.Position of the buccal cusp
favorably placed over the buccal
2- Artificial teeth and Occlusion for class I RPD2- Artificial teeth and Occlusion for class I RPD
66. 5- Centric occlusion of teeth should5- Centric occlusion of teeth should
coincide with centric relationcoincide with centric relation
Simultaneous bilateral contactsSimultaneous bilateral contacts of opposingof opposing
posterior teeth must occur in centric and eccentricposterior teeth must occur in centric and eccentric
occlusion. and in harmony with the remaining naturalocclusion. and in harmony with the remaining natural
teeth.teeth.
Contact of the anterior teethContact of the anterior teeth isis avoidedavoided
because such contact will lead to unfavorable forces tobecause such contact will lead to unfavorable forces to
maxillary anterior residual ridge and would be detrimentalmaxillary anterior residual ridge and would be detrimental
to the supporting tissues in this area. as well asto the supporting tissues in this area. as well as
enhances the instability of the denture.enhances the instability of the denture.
Artificial posterior teethArtificial posterior teeth shouldshould not benot be
arranged farther distallyarranged farther distally than the beginning ofthan the beginning of
sharp upward incline of residual mandibular ridge or oversharp upward incline of residual mandibular ridge or over
the retromolar pad, to avoid shunting the denturethe retromolar pad, to avoid shunting the denture
stability.stability.
67. Total occlusal load applied may be reduced by using
comparatively smaller posterior teeth
less muscular force will be required to penetrate food
bolus with reduced occlusal table, thereby reducing forces
to supporting oral structures
69. They are 2-4 mm
in height,
extending from the
marginal ridge to
the junction of the
middle and
gingival third of
the abutment
3- Proximal plates3- Proximal plates (Guiding Plates)(Guiding Plates)
70. A guide surface should be produced
by removing a minimal and fairly
uniform thickness of enamel, usually
not more than 0.5m.m., from around
the appropriate part of the
circumference of the tooth.
71. The bucco-lingual width of the
proximal plate is determined by
the proximal contour of the tooth
72. Contact approximately 1 mm of the gingival
portion of the guiding plane in distal
extension cases. a slight degree of
movement of the base and the clasp is
permitted without transmitting torsional
stress to the tooth
As the prosthesis is inserted and
removed, thus horizontal wedging is
eliminated
Vertically disengage with
extension base loading.
73. The proximal plate together with
the mesiolingually placed minor
connector provides stabilization
and reciprocation of the assembly
Lingual view
75. Rest seats should be carefully located and prepared
to avoid torque and allow transmission of stresses
along the long axes of abutment teeth
• Mesially placed
• Saucer-shaped
• The floor of the rest
seat should inclined
apically
• Fit
• Strong not raise the
vertical dimension of
occlusion.
4-Rests4-Rests
76. Positioning the occlusal rest on
the abutment teeth
changing the location
of the occlusal rest
from the distal fossa
to the mesial fossa
changes the character, direction and
often the magnitude of the forces that are
transmitted to the abutment tooth
77. Placing the occlusal rest away from the distal
extension base achieve mechanical adv. And
helps in favorable distribution 0f occ. Load bet.
Abut. t. and the ridge
1- By changing the direction of torque on the
abutment from the distal to the mesial side of the
tooth, the resistance to torque action will be applied
to the neighboring teeth (Buttressing effect )
?
78. Reverse Aker Clasp
F
2- Changing the stresses acting on the
saddle and Transfer the design from------ or
------ to favorable Class ?------Lever
79. Aker Clasp
when force is directed against unsupported end of beam,
cantilever can act as first class lever Torque on the abutment
tooth.
A cantilever design allows also excessive vertical movementA cantilever design allows also excessive vertical movement
80. Depression of the base disallowing harmful
engagement of the retentive clasp arm.
3- Clasp disengagement from the
tooth
81.
82.
83.
84. 4- lever arm, represented by distance from
rest to denture base, is increased. This
increase in length makes rotational action
caused by up-and down movement of denture
base in function more vertical. A vertical force
in better tolerated by ridge than is a
horizontal oblique force
85.
86.
87. 5- As rest is moved anteriorly this will increase the
area of support (decrease the force /unit area)
6- Wide distribution of the load in an antero-posterior
direction. The bone near the abutment will thus
share the distal part of the ridge in bearing the
88. Advantages of Placing the occlusal rest away from
the distal extension base
1. By changing the direction of torque on the abutment from
the distal to the mesial side of the tooth, the resistance
to torque action will be applied to the neighboring teeth
(Buttressing effect
2. Achieving mechanical adv. By Changing the stresses
acting on the abutment and the saddle from the
cantilever action or class I lever to class II lever.
3. Clasp disengagement from the tooth during function
provide less stresses on the abutment.
4. The farther the ant. Placement of the rest, the more
vertical will be the forces, the less are the horizontal
components of force falling on the ridge.
5. As rest is moved anteriorly, will increase the area of
support (decrease the force /unit area) and hence less
stresses on the ridge and less torque on the abutments.
6. Wide distribution of the load in an antero-posterior
direction. The bone near the abutment will thus share the
89. The Lingual Rest is Preferred than
the Incisal Rest because:
1. It is placed closer to the
center of rotation of the
abutment tooth, thus it
will exert less leverage
and reducing its
tendency to tipping.
2. More esthetic, as it can
be discreetly hidden from
view.
3. It tends to be less
bothersome to a curious
90. Clasps Should be designed to:
1. Reduce torque to the abutment tooth.
The more flexible the
retentive arm of the clasp, the less stress is
transmitted to the abutment tooth.
2. Minimize interference with normal stimulation
of gingival tissue
3. Has good stabilizing qualities
4. Remain passive until activated by functional
stress
5-Direct5-Direct
RetentionRetention
91. Clasps with stress breakingClasps with stress breaking
actionaction
Gingivally approaching clasps
except Devan clasp
Occlusally approaching clasps
– Reverse Aker clasp
– Back action clasp
– Reverse back action clasp
– R.P.A.
– R L S
– Ring (bounded saddle, isolated molar)
Combination clasps (wrought wire +
94. The clasp should not interfere with
normal gingival stimulation and its
terminal should be away from the
The clasp should be
designed on biologic as
well as mechanical bases.
X
95. Fencepost is more readily
removed by application of force
near its top than by applying
same force nearer ground level
in B- abutment has been contoured to
allow rather favorable location of
retentive and reciprocal arms.
A
B
96. Strategic clasp positioning (Location of
clasps) as a method of stress control
Bilateral clasping
configuration is
required. Although this
configuration cannot
be considered ideal,
leverage must be
controlled by some
Leverage may be
partially controlled
by using triangular,
or tripod
configuration
(triangular pattern of
clasp placement).
97. Selection of Clasp formSelection of Clasp form
depends ondepends on
1-Position of the tooth1-Position of the tooth
2-Condition of the tooth.2-Condition of the tooth.
3-Position of the edentulous area.3-Position of the edentulous area.
4-Axial inclination of the4-Axial inclination of the
abutment.abutment.
5-Position of occlusal rest.5-Position of occlusal rest.
98. Position of retentivePosition of retentive
undercut:undercut:• If the abutment tooth exhibits an undercut on
the disto-buccal side, then a reverse circlet clasp
can be used.
• If the undercut is on the mesio buccal side, a
combination wrought wire clasp, RPI clasp or back
action can be used.
• If the undercut is on the distolingual side, RLS
clasp can be used.
• If precision attachments or rigid clasping are
used to retain a class I partial denture, a stress
breaker should be used.
99. Number of the claspsNumber of the clasps
The best retention is not
proportional to the number of
clasps. Satisfactory amount of
retention, is that required tois that required to
keep or just to retain thekeep or just to retain the
denture in its place duringdenture in its place during
101. (1) The I bar placed
on the distal cannot
move freely away from
the tooth thereby
producing a torquing
action
(2) Placement of the I
bar at the greatest
prominence or to the
mesial
(3) permits the I bar
under function to move
Occlusal view of
an RPI clasp.
1- R.P.I.
102.
103. Changing the position of the guiding plates changes
the center of rotation (
.
) indicates center of rotation
1- R.P.I.
104. 2- Reverse Aker Clasp
F
Changing the stresses acting on the saddle
and Transfer the design from------ or ------ to
favorable Class ?------Lever
105. Properly designed RPA clasp showing movement
from occlusal forces. Proximal plate, C. drops
gingivally and slightly mesially as rotation occurs
around mesial rest with approximate center of
rotation, B. Rigid portion of retentive arm contacts
tooth only along survey line, A. and moves gingivally
and mesially. Retentive end of clasp arm moves
Buccal
view
Occlusal view
3- RPA clasp
106. 4- Combination clasp consists of cast reciprocal
arm and tapered, round wrought-wire retentive
clasp arm
Applicable when disto-buccal undercut cannot be
found or created, or tissue undercut contraindicate
placing bar type. It would be kinder to period.
Ligament than would a cast clasp.
107. I. R. are supportive elements,
designed to counteract
displacing rotational forces.
They may be in the form of
rests or palatal connectors.
Two I. Rs. one on each side are
generally used, they should be
located as far anterior to the
fulcrum axis as possible
6- Indirect Retention6- Indirect Retention
111. 3- Effectiveness of the Supporting
Structures
4- Rigidity of the Denture Frame
112. The prime requirement of any connector is rigidity
Maxillary Major connector used for distal extension removable
partial denture
Palatal strap
Anteroposterior palatal bars
Palatal plate
7-Maxillary Major connectors7-Maxillary Major connectors
113. The prime requirement of any connector is rigidity.
Plates sometimes used with the advantages of more strength,
less liability of food trapping, better tolerance, and broader
distribution of load (maximum support) in addition to providing
direct and indirect retention.
The strap or bar major connector has the advantages of
minimal encroachment on the oral muscles during
function.
A horseshoe-shaped palatal connector is used in cases in
which large torus palatinus or sharp median palatine raphe
exist
7-Maxillary Major7-Maxillary Major
connectorsconnectors
114. 8-Mandibular Major8-Mandibular Major
ConnectorsConnectors
Mandibular Major connector should be
relieved while Max MC should be
beaded??? Lingual bars with terminal rests
are preferred due to their
simplicity, limited coverage and
patient's tolerance.
A lingual bar connector should be
tapered superiorly with a half-pear
shape in cross section and should
be relieved sufficiently.
Lingual plates with terminal rests:
due to their rigidity, distribution of
lateral forces and due to improved
116. Interproximal spaceInterproximal space
9. Minor Connectors9. Minor Connectors
Minor connectors are designedMinor connectors are designed to connectto connect thethe
framework components either to the dentureframework components either to the denture
base or to the major connector.base or to the major connector.
Minor connectorMinor connector must be rigid.must be rigid.
Minor connector should be triangle in crossMinor connector should be triangle in cross
section, positioned to enhance comfort,section, positioned to enhance comfort,
cleanliness and placement of artificial teeth.cleanliness and placement of artificial teeth.
117. Ant. Modification spaces of class I areAnt. Modification spaces of class I are
preferably restored separately with fixedpreferably restored separately with fixed
bridge.bridge. This helps inThis helps in
• Simplifying the partial denture design.Simplifying the partial denture design.
• Saving the anterior ridge from resorption and the anteriorSaving the anterior ridge from resorption and the anterior
abutments from torque resulting due to movements of theabutments from torque resulting due to movements of the
anterior saddle occurring as a result of rotation of the posterioranterior saddle occurring as a result of rotation of the posterior
free end saddle.free end saddle.
Pier
abutment
??
??
119. Remember: to solve class I RPDRemember: to solve class I RPD
problemsproblems
Improve dentureImprove denture supportsupport. how. how
DecreaseDecrease torquetorque by using stressby using stress
equalization and placement ofequalization and placement of
the rests away from the saddlethe rests away from the saddle..
ImproveImprove bracing.bracing.
Need ofNeed of indirect retention.indirect retention.
Resin baseResin base to accept relining.to accept relining.
?
?
122. What we doWhat we do
for othersfor others
counts most incounts most in
lifelife......
Be Alert to give
Service.....
123. 1. Contour and quality of the residual ridge
(nature of the mucoperiosteun )
2. The Extent of area coverage by the denture
base
3. Accuracy and fitness of the denture base
4. The accuracy and type of impression
registration (anatomical or functional)
5. The Design characteristics of the
components parts of the partial denture Framework
124. 1- The Contour and quality of the1- The Contour and quality of the
residual ridge (nature of theresidual ridge (nature of the
mucoperiosteun )mucoperiosteun )
a- Tissue conditioning
b- Modify it by surgical intervention
2. The Extent of area coverage by the2. The Extent of area coverage by the
denture basedenture base
3. Accuracy and fitness of the denture3. Accuracy and fitness of the denture
basebase
. Materials and techniques that will ensure the greatest dimensional
stability should be selected.
. The better the base fits the denture foundation the less the degree of
• By using accurate impression technique to obtain maximum tissue
coverage for support.
• It should be based on biological and physiological tolerance of the
oral tissue.
• The broader the area of coverage, the greater the distribution of load,
the lesser the displacement; which results in less load per unit area.
125. 4. The accuracy and type of
impression registration (anatomical
or functional)
Has greater area coverageHas greater area coverage
More stability under rotating and/or torquing forcesMore stability under rotating and/or torquing forces
Maintain its occlusal relation with the opposingMaintain its occlusal relation with the opposing
teeth.teeth.
No rapid settelling of the denture baseNo rapid settelling of the denture base
Distribute the occlusal load equitabaly and diminisfDistribute the occlusal load equitabaly and diminisf
the rotational movement.the rotational movement.
A denture base processed to theA denture base processed to the
functional form is generallyfunctional form is generally
126. Problems of distal extension bases can be reduced by
a- Reducing the load
b- Stress equalization (distributing the load between
teeth and ridge)
C- Physiologic basing.
d- Broad stress distribution (dist. the load widely)
Type and accuracy of impression registration
(anatomical or functional) (Altered cast technique)
5. The Design characteristics of the components
parts of the partial denture Framework
127. 6. Total occlusal load applied
The more the load applied the higher
the degree of tissue displacement.
The magnitude of stresses can be assessed
through:
1. General musculature
2. Attrition and wearing of the remaining natural teeth
3. Type of opposing occlusion.
4. Use of fewer, narrower and more effectively shaped
artificial teeth.
5. Size and Degree of inclination of natural teeth and
cusps.
6. Sex.
7. General health of the patient.
129. Strain on the residual ridge is
minimized through
1. Broad tissue coverage and maximum extension of
the denture base within the functional limits of
muscular movements.
2. Fitness and intimate adaptation of the denture
base to the tissue.
3. Functional basing. Mucocompression impression
recording of the residual ridges.
4. Improving the condition of the residual ridge e.g.
correction of abusive condition of tori and
hyperplastic tissues.
130. 4. Use of small and narrow teeth to increase the
masticatory efficiency and reduce the mast. load
5. Harmonious occlusion and reducing the cusp angle
of art. teeth.
6. Leaving a tooth off the saddle.
7. Placing the artificial teeth on the anterior two-thirds
of the base (no 3rd
molar).
8. Placement of occlusal rests away from the saddle.
9. Providing Posterior Abutments
A- Using an implant at the distal part of the ridge.
B- Salvaging a hopeless badly decayed tooth
(an overdenture abutments)
131. 1. Correct choice of the abut. Tooth with
sufficient alveolar bone support and
crown and root morphology
2. Placement of occlusal rests away from the
saddl (6 benefits ????).
3. Correct choice of direct retainer (flexible
clasping).
4. Using stress equalizing design.
Strain on the abutment
teeth
is minimized through
132. 5. Wide distribution of the load over the teeth:
Strain on the abutment teeth is minimized through
a- By placing additional rests, or
b- by a splinting of one or more teeth,
either by fixed partial dentures or by
soldering two or more individual
restoration together.
6- Using a Kennedy bar to distribute the
lateral load on multiple teeth.
133. 7. Preparation and restoration of the abutment
teeth to accommodate the most ideal design of PD
this include
a- Proper form of occ. rest seats
b- Tooth prep. and modification to withstand the
functional stresses ( guiding planes, ………..)
8. Providing Posterior Abutments
a- Using an implant at the distal part of the ridge.
b- Salvaging a hopeless badly decayed tooth, an
overdenture abutment
The extension partial present a unique situation that it is relies upon
two entirely different sources of support. The tooth represent a relatively immobile support, but the mucosa are displaceable to varying degree. This factor must be fully understood and analyzed in planning the extension base RPD.
