This document discusses removable partial dentures (RPDs). It begins by defining an RPD and its functions, which include aesthetics, supporting artificial teeth, and stimulating underlying tissues. It then discusses the ideal requirements of RPD materials, including biocompatibility, strength, stability, and polishability. Several RPD materials are described, including heat-cured acrylic resin and metallic alloys like cobalt-chrome and titanium. The advantages and disadvantages of acrylic and metallic denture bases are compared. Finally, it discusses different types of artificial teeth used in RPDs, such as acrylic, porcelain, and metal teeth.

2. Introduction
A removable partial denture
(RPD) is a denture for a
partially edentulous patient
who desires to have
replacement teeth for functional
or aesthetic reasons
and who cannot have
a bridge (a fixed partial denture)
for any number of reasons
such as a lack of required teeth
to serve as support for a bridge
(i.e. distal abutments) or
financial limitations

3. The part of a denture that rests on the foundation tissues
and to which teeth are attached
FUNCTIONS OF TOOTH SUPPORTED DENTURE BASE
Provide desirable esthetics.
Support the artifial tooth .
Prevent vertical & horizontal migration of remaining natural
teeth.
Eliminate undesirable food entrapment.
Stimulate the underlying tissues.

4. FUCTIONS OF DISTAL EXTENSION DENTUREBASE
Contributes to the support of the denture & improves stability
of the prosthesis .
Esthetics by attaching the teeth & restoring the lost facial contours
Stimulation of the underlying tissues.
Cleanliness maintenance.
Secondary retention by intimate contact between the denture base & the
major connector with the underlying tissues

5. IDEAL REQUIREMENTS
OF RPD
Bio-
compatible
Accurately adapt
to the underlying
tissues
Adequate
Physical &
Mechanical
properties
-Sufficient
strength to resist
distortion &
fracture
Dimensional
stability
Low specific
gravity
Good thermal
conductivity
Easy to finishing
& polishing
Should not
absorb oral fluids
Insoluble in
oral fluids.
Ease of fabrication
& repair
Potential for future
relining , rebasing.
Esthetically
acceptable
color stability
Odourless
tasteless
Easy to clean the
prosthesis
Long shelf
life
Cost effective

6. Heat Activated Denture Base Resin
Composition
DENTURE BASE MATERIALS
Acrylic resinMetallic
POWDER
1)Poly(methyl methacrylate)
2) Initiator- Benzoyl peroxide-0.5- 1.5%
3)Plasticizer- Dibutyl pthalate
4) Pigments
5) Opacifiers
6)Inorganic particles- glass fibers & alumina.
LIQUID
Non polymerized methyl methacrylate
Inhibitor – Hydroquinone 0.003%-0.1%.
Cross linking agent – Glycol dimethacrylate-1 to
2% by volume.

7. Modifications of Activated Resin
HIGH IMPACT
STRENGTH
MATERIALS
• Reinforced
with butadiene
styrene rubber
• The rubber
particles are
grafted to
methyl
methacrylate
to bond to the
acrylic matrix
POUR TYPE
RESIN
• Composition
similar
• particle size
smaller
RAPID HEAT
POLYMERIZED
RESIN
• Altered
initiator system
LIGHT ACTIVATED
• Urethane dimethacrylate
matrix with acrylic
copolymer
• Microfine silica fillers
• Photo initiator –
Comphorquinone
• Polymerized with a visible
light of 400 to 500 nm

8. Modifications of Activated Resin
FIBER –REINFORCED POLYMER
• Glass, carbon/graphite,aramid and ultrahigh molecular
wt polyethylene have been used as fiber reinforcing
agents.
• Metal wires like graphitehas minimal esthetic qualities.
• Fibers are stronger than matrix polymer thus their
inclusion strengthensthe composite structure.
• The reinforcing agent can be in the form of unidirectional,
straight fiber or multidirectional weaves.

9. MECHANICAL PROPERTIES
PMMA&PVA posses adequate tensile & compressive strength .
Transverse strength is the combination of tensile & compressive strength proportional limit,
elastic modulus .
PVA has 7to 10%of Elongation ,is an indication of toughness & permit larger
deformation .
Proportional limit should be sufficiently high to withstand masticatory
forces.
Impact strength
Rubber reinforced acrylic more impact strength.
Rubber reinforced acrylic resin possesses adequate fatigue strength to withstand the
smaller cyclic stresses during mastication.
Fracture toughness of rapid heat cure resin is better than conventional & high impact
resin.
Hardness KHN of denture base acrylic is low so care should be taken while polishing,
cleaning.

10. ADVANTAGES
Easy adjust & polish.
Reling & rebasing is possible .
The weight & bulk is more than cast
alloys.
Denture base contours for functional
tongue & cheek movements.
In mandibular arch weight of the
denture contributes for retention.
Esthetics, tinting..
Processing
low Cost
DISADVANTAGES
Adaptation not as accurate
as cast metal alloy.
Abrasion resistance..
Acrylic resin bases tend to
accumulate mucinous
deposits
So meticulous cleanliness
maintenance required.
Thermal conductivity
Weight & Bulk
It should be min. 2mm in
thickness to obtain
adequate rigidity &
strength

12. 2- METALLIC DENTURE BASE MATERALS REMOVABLE
PARTIAL DENTURE
High Noble casting alloys
• Au- Ag- Cu -Pd
Predominantly base metal alloys
• Co-Cr-Mo
• Co- Cr –W
• Ni-Cr –Mo
• Ni-Cr –Mo-Be
• Cp-Ti
• Ti-Al-V
As early as 1949 it was estimated that nearly 80% of all
partial denture appliances were cast from Co-Cr alloys.
Principle elements –Cr, Co, Ni -82 to 92%.
COBALT-CHROMIUM-ALLOYS - Cobalt- 60%   -
Chromium -25% to 30%
OTHER COMPONENTS : Mo,Al,W,Fe,Ga, Cu, Si, C, Pl.

13. Figure 1 Chrome Cobalt upper RPD
• Co-50% - Cr-25% - Ni-19%
• Other constituents
• Mo-3.7% - C -0.2%
COBALT-CHROMIUM-NICKEL :
• Ni - 70% - Cr - 16%
• Other constituents
• Al –2% - Be –0.5% - Mo,W, Mg, Co, Si, C.
NICKEL CHROMIUM- MOLYBDENUM ALLOYS :
• Tarnish and corrosion resistance and stain less properties.
Chromium :
• In general cobalt and nickel are interchangeable .
Cobalt and nickel :
Cobalt increases the elastic modulus ,strength and
hardness morethan Nickel does.

15. Figure 2 Carbon
OTHER
ALLOYING
COMPONENTS :
• Carbon : increases the hardness of Co based alloys.
• Molybdenum : (3% to 6% ) Contributes to the strength of the alloy.
• Aluminium : Forms a compound with Ni ,which increases the tensile and
the yield strength of the alloys.
• Berylium : About 1% lowers the fusion temperature range of the alloy by
about 100 degrees C.
• Silicone and Manganese : Increase the fluidity and castability of these
alloys.
• Nitrogen : If present contributes to the brittle qualities of these alloys .

16. High purity titanium (99 wt %) with O,C ,N,H atoms dissolved interstitially.
It undergoes an allotropic transformation from hexagonal to
body centered crystal structure when the temperature is raised
to 882 +/ 2 degree.
4 types: Alpha
Near alpha
Alpha – Beta
Beta
Cp Ti available in 4 different grades
(ASTM)
Titanium alloy- Ti- 6V – 4Al
Vanadium is the beta phase stabilizer with the BCC structure.
Al alpha phase stabilizer
Most commonly used is alpha – beta alloy. [strength > Cp Ti.]

18. Composition:
Au - 69% Ag – 12.5% Cu -10% Pd – 3.5%
Pt – 3% Zn,Sn,Fe,In,Gafor balace.

19. ALLUMINIUM ALLOY
Al – 99.95 wt % Mg – 3.5%

20. ADVANTAGES OF METALLIC DENTURE BASE
Accurate adaptation & permanence
of the form
Abrasion Resistance.
Comparative tissue response
Inherent cleanliness
greater density & bacteriostatic
activity contributed by the ionization
& oxidation of metal base
Thermal conductivity .
Better patient acceptance.
Weight & Bulk
Metal alloys can be casted much thinner..
Maintains & prolongs the health of supporting tissues.
DISADVANTAGES
Relining & rebasing difficult.
Difficult to adjust.
It cannot be used whenever restoring the
normal facial contours is required for esthetics.
Special equipment required.
More expensive.

22. 1) Risk of fractureof resin denturebase.
2)RARatrophy
2) More roomfor the tongue functioning is required.
3) Patient allergic to resin.
4) Satisfactorily healed ridges.
INDICATIONS:
THE METAL- ACRYLIC RESIN BASE
Consists of cast metal base thatfits the RAR & acrylic
resin attachedto it to retain the teeth.

23. TYPES OF MINOR CONNECTORS
1) Open construction
2) Mesh construction
3) Bead, nail head & wire constructions
CHEMICAL BONDING
Direct bonding of acrylic resin to metal framework.
Sections of metal frame work meant for supporting the replacement teeth is
roughened with abrasives & treated with vaporized silica coating.
Acrylic bonding agent is applied.
Thin film of acrylic resin applied to act as substrate for teeth replacement or
acrylic resin tissues replacement

24. Teeth replacement is important to reestablish
• the lost facial contours
• phonetics
• masticatory function
IDEAL PROSTHETICTOOTH SHOULD SATISFYFOLLOWING REQUIREMNT
Pleasing appearance to satisfy the esthetic requirement.
Easily adaptable to any edentulous space.
Easy forattaching to the prosthesis.
Easy to modify the shape & size as per requirement & repolish restore the original
polish.
Color stability
Resistance to blanching, distortion ,crazing.
It should have enough strength to bear occlusal load.
Adequate resistance to wear.

25. TYPE OF ARTIFICIAL TEETH
Acrylic resin
teeth
Porcelain teeth Metal tooth Acrylic resin teeth
with occlusal
restorations
Custom denture
tooth.
ACRYLIC RESIN TEETH
Strength adequate to withstand the occlusal load.
Chemical bonding with acrylic denture base.
Low abrasion resistance
Absorbs stain.
Impact resistance greater than porcelain.
Shape & size can be modified.
Easy to polish.
Dose not cause the wear of the opposing natural teeth or gold restorations.
Low heat distortion temperature .
Cold flow or permanent deformation under pressure below their elastic limit.

26. CHARECTERISTICSOF PORCELAIN TETH
More esthetics than acrylic resin teeth.
Strength more than acrylic teeth .
Brittle chips off or fractures easily
Good abrasion resistance
It can cause wear of the opposing natural teeth or gold restorations.
Impervious to stain
Clicking sound.
Difficult to trim & adjust so cannot be used in inadequate interarch space.
Mechanical bonding with the acrylic denture base so
percolation may occur
High heat distortion temperature .
No permanent deformation under forces of mastication
METAL TOOTH
It is the tooth of choice for posterior tooth replacement.
Strength more than any other prosthetic tooth.
The frame work is of the Co- Cr then tooth should not be occluded heavily
with the opposing gold restoration .
Indicated in  Edentulous space measuring about 3to8 mm.
Decreased mesio distal width by mesial drifting of 2nd molar

27. Porcelain or Resin tube teeth & Facings cemented directly to
Metal Bases
Gold
occlusal
surfaces.
Amalgam
occlusal
surfaces
Teeth are altered & set
prior to completion of
frame work.
Disadvantages
•Difficulty in obtaining the
satisfactory occlusion.
•Lack of adequate contours
for functional tongue &
cheek contact.
•Unaesthetic display of metal
at the gingivalmargin

28. References:
 McCracken’s Removable partial prosthodontics, 11th edition.
 Philip’s Science of Dental Materials, 11th edition.