Prosthodontic materials/prosthodontic courses

Prosthodontic
Materials
INDIAN DENTAL ACADEMY
Leader in continuing Dental Education
www.indiandentalacademy.com

Gypsum Products – Dental Plaster, Dental stone
Impression Materials - Impression Compound, Zinc
Oxide Eugenol, Hydrocolloids, Elastomers
Restorative Materials – Dental Amalgam,
Composite, Glass Ionomer
Resins
Waxes

The gypsum products used for different
purposes such as:
i) They are used to take imp of edentulous
mouths.
ii) To mount casts.
iii) Used as dental stone to form a die that
duplicates the oral anatomy when poured into
any type of impressions.
iv) As a binder for silica for Au casting
investments, for soldering investment &
investment for low melting Ni-Cr alloy.

Depending on the methods of calcination
diff. forms of hemihydrates are formed such
as :
1.)Dental plaster or beta hemihydrate
2.)dental stone or alpha hemihydrate
3.)improved stone or densite

1.Dental plaster
2.Dental stone
3.Improved stone
4.Impression plaster
5.Dental casting investment

CLASSIFICATION
ADA specification number 25
Type I – Impression plaster
Type II – Dental plaster
Type III – Dental stone of medium strength
stone
Type IV – Improved stone or high strength
stone
Type V – Dental stone, high strength, high
expansion.

Impression materials
Elastic
Chemical reactions
Irreversible
Alginate
Elastomers
Polysulphides
Polyethers
Condensation silicon
Addition silicon
Temperature change
Reversible
Agar hydrocolloid
Chemical reactions
Irreversible
Plaster of Paris
ZnO Eugenol
Temperature change
Reversible
Impression compound
Waxes
Rigid / Inelastic

ZINC OXIDE EUGENOL IMPRESSION PASTES
Used for edentulous mouths is a rigid or inelastic
impression materials that hardens by chemical
reaction
After chemical reaction a relatively hard mass is
formed that possess certain medical advantages
as well as mechanical usefulness in certain
dental operations.
Limitations
Inability to accurately record undercuts
Fracture when withdrawn from undercut
Gross distortions due to plastic flow if used in
undercut situationswww.indiandentalacademy.com

Uses
• Cementing medium
• surgical dressing
• Temporary filling materials
• Root canal filling
• Bite registration
• Temporary relining materials for dentures
• An impression materilas for edentulous
mouths

IMPRESSIONS COMPOUND
Also called as modelling plaster.It is a
thermoplastic materials ,it is a rigid,reversible
impression materials which sets by chemical
change.
Uses
- making an impression of the edentulous ridge.
-Stablizes matrix band.
-For single tooth impression

WAX AS AN IMPRESSION MATERIAL
wax is used in some corrective
impression techniques in partial and
complete denture prosthesis. Impression wax
are available with variety of softening
temperature.
Used for functional impression and also in
extending the border of the denture base
when necessary .

ELASTIC
Material susceptible to being stretched compressed
or distorted and then tending to resume the original
shape.
Elastic impression materials are capable of
accurately reproducing both the hard and the soft
structures of the mouth including the undercut
areas and interproximal spaces

ADVANTAGE OF ELASTIC IMPRESSION
MATERIAL OVER RIGID IMPRESSION
MATERIAL
Elastic impression material can be used in
both dentulous and edentulous cases with
undercuts.
The distortion of elastic impression
material when removed from an undercut is
minimal.

CLASSIFICATION OF ELASTIC
IMPRESSION MATERIAL
1. REVERSIBLE HYDROCOLLOIDS
# Agar
2. IRREVERSIBLE HYDROCOLLOIDS
# Alginate
3. ELASTOMERIC IMPRESSION MATERIAL
# Polysulphide
# Condensation polymerizing silicon
# Poly ether
# Addition polymerizing silicon

AGAR
Agar is a organic hydrophilic colloid
(polysaccharide) extracted from a certain type
of sea weed. It is a sulphuric ester of a linear
polymer of galactose.

IRREVERSIBLE HYDROCOLLOID-ALGINATE
The chief active ingredient is one of the soluble
alginates such as sodium potassium or
atriethonalamine alginate. When mixed with water
they form a viscous sol.
Calcium sulfate dihydrate is used as a reactor. It
reacts with the soluble alginate to form a
insoluble calcium alginate gel.

TYPES
1. Type I - fast setting
2. Type II - Normal setting

MODE OF SUPPLY
It is supplied as a powder that is packed
In bulk or in tins or in sachets.
In pre-weighed individual containers
A plastic scoop is supplied for dispensing the
bulk powder and a plastic cylinder is supplied for
measuring the water required for the bulk or the
pre-weighed alginate powder.

Elastomers refers to a group of rubber
polymers
which are either chemically or physically
crosslinked , easily stretched and rapidly
recover
to their original dimension when the applied
stress is released.
Chemically there are four kinds of
elastomers
Polysulfide
Condensation silicon
Polyether
Addition silicon

ADVANTAGES AND DISADVANTAGES OF
CONDENSATION SILICONES COMPARED
WITH POLYSULFIDE MATERIALS
ADVANTAGES
Adequate working and
setting time
Pleasant odor and no
staining
Adequate tear strength
Better elastic
properties on removal
Less distortion on
removal
DISADVANTAGES
Adequate accuracy if
poured immediately
Poor dimensional
stability
Potential for significant
distortion
Putty-wash method is
technique sensitive
 Slightly more expensive
Poor to adequate shelfwww.indiandentalacademy.com

Advantages and Disadvantages of Addition Silicones
Compared with Polysulfide Materials
ADVANTAGES DISADVANTAGES
Shorter setting time Hydrogen gas evolution in
some materials
Easy to mix-automatic
mixing devices
need careful handling and
a very dry field
Adequate tear strength more expensive, especially
with automatic mixing
device
Extremely high accuracy
Undetectable distortion
on removal
Dimensionally stablewww.indiandentalacademy.com

Advantages and Disadvantages of Polyethers Compared
with Polysulfides
Advantages Disadvantages
Fast working and
setting times
Adequate accuracy if
poured immediately
Adequate tear strength Poor dimensional
stability
Less hydrophobic-
better wetting
Clean but tastes bad
Less distortion on
removal
Stiffness requires
blocking undercuts
Long shelf life Slightly more expensive

Synthetic Resins

Synthetic resins are often called plastics. A plastic
material is a substance that a although dimensionally stable in
normal use was plastic at some stage of manufacture.
APPLICATIONS OF RESINS IN DENTISTRY
Synthetic resins are used in a variety of dental applications.
Typical uses include the following
•        Dentures (bases, liners, and artificial teeth)
•        Cavity-filling materials ("composites")
•        Sealants
•        Impression materials
•        Equipment (mixing bowls)
•        Cements (resin-based)

CLASSIFICATION
. Based on their thermal behaviour, they can be divided into
Thermoplastic
Thermosetting polymers
Depending on whether they soften when heated.A third group of
polymeric materials are the elastomers.

MMethyl Methacrylate
MMethyl methacrylate is a transparent liquid at room temperature with
the following physical properties:
•        Molecular weight = 100
•        Melting point = —48° C
•        Boiling point = 100.8° C
•        Density = 0.945 g/mL at 20° C
•        Heat of polymerization =12.9 kcal/mol
MMethyl methacrylate exhibits a high vapor pressure and is an excellent
organic solvent. Although the polymerization of methyl methacrylate can
be initiated by visible light, ultraviolet light, or heat, it is commonly
polymerized in dentistry by the use of a chemical initiator,
A A volume shrinkage of 21% occurs during the polymerization of the
pure methyl methacrylate monomer
.

Poly(methyl Methacrylate)
Poly(methyl methacrylate) is a transparent resin of remarkable
clarity; it transmits light in the ultraviolet range to a wavelength of
250 nm. It is a hard resin with a Knoop hardness number of 18 to 20.
It has a tensile strength approx-imately 60 MPa, a density of 1.19
g/cm3
, and a modulus of elasticity of approximately 2400 MPa.
It is chemically stable to heat and softens at 125° C, and it can be
molded as a thermoplastic material. Between 125° and 200° C,
depolymerization takes place. At approximately 450° C, 90% of
the polymer depolymerizes to form the monomer

Amalgam: its an alloy of mercury with other
metals.
Silver amalgam has a silvery grey metallic
appearance and mainly used for posterior
restorations.
Amalgam

Classification of amalgam alloys
1.According to particle shape
a.Spherical shaped
b.Irregular surface spheres (spheroidal shaped)
c. Non-spherical – irregular shaped (Lathe cut)
d.Dispersed (spherical + lathe cut)
1.According to particle size
a.Micro cut (less than 25μ)
b.Fine cut (less than 35μ)
c. Coarse cut

3.According to dispensing
a.Powder mercury system
b.Pellet mercury system
c. Disposable capsules
3.According to composition
a.Zinc containing alloys (Zn > 0.01%)
b.Zinc free alloys (Zn < 0.01%)
c. Pre-amalgamated alloy (Hg = 3%)
3.According to copper content
a.Low copper (Cu 0 – 6%)
b.High copper admixed (Cu 13%)
c. High copper uni-composition (Cu 13-26%)www.indiandentalacademy.com

Manipulation
Selection of materials
Based on clinical requirement of restoration
1.Particle shape and size of the alloy
2.Presence or absence of Zinc
3.Composition as it is related to the elimination of
Gamma II phase
4.Physical and mechanical properties
5.Manipulative characters
6.Dispensing system
7.Mercury and its purity

Structural component of dental resin based
composite
1.Matrix- A plastic resin material that forms a
continuous phase and binds the filler particles.
2. Filler- Reinforcing particles and/or fibers that are
dispersed in the matrix
3. Coupling agent- Bonding agent that promotes
the adhesion between filler and resin matrix
4. Activator-initiation system- required to
convert resin paste from a soft moldable filling
material to a hard durable restoration
5. Optical Modifiers- help to match colour of tooth
structure www.indiandentalacademy.com

ACTIVATOR-INITIATOR SYSTEM
Both monomethacrylate and dimethacrylate
monomers polymerize by the addition polymerization
mechanism initiated by free radicals. The free
radicals can be generated by chemical activation or
by external energy activation (heat, light or
microwave).
CHEMICALLY ACTIVATED RESINS
supplied as two pastes
Initiator – benzoyl peroxide
Activator – N, N dimethyl –P-toluidine
Both the activator and initiator mixed together to form
free radicals and addition polymerization reaction is
initiated.

LIGHT-ACTIVATED RESINS:
Light-curable dental composites are supplied as
a single paste contained in a light-proof syringe. It
contains a photosensitizer and an amine initiator. As
long as these two components are not exposed to light,
they do not interact. However, exposure to light in the
blue region (wavelength of ~468nm) produces an
excited state of the photosensitizer, which then
interacts with the amine to form free radicals that
initiate addition polymerization.
photosensitizer- Camphorquinone (CQ)
Amine initiator-dimethylaminoethyl methacrylate
(DMAEMA)

DUAL-CURE RESINS:
One way to overcome limits on curing depth
associated with light curing is to combine chemical
curing and visible-light curing components in the
same resin. So-called dual-cure resins are
commercially available and consist of two light-
curable pastes. light curing is promoted by the
amine/CQ combination and chemical curing is
promoted by the amine/BP interaction.
Dual-cure materials are intended for any situation
that does not allow sufficient light penetration to
produce adequate monomer conversion, for
example, cementation of bulky ceramic inlays.www.indiandentalacademy.com

CLASSIFICATION OF COMPOSITES:
I. Classification given by Skinner:
Traditional or conventional composites
8-12 µ.m
Small particle filled composites
1-5 µ. m
Microfilled composites
0-04 –0.9 µ. m.
Hybrid composites
0.6-1 µ. mwww.indiandentalacademy.com

VI.GENERATIONS OF COMPOSITE RESTORATION
(Marzouk)
A. First Generation compositesA. First Generation composites
Consist of macro-ceramic reinforcing phase.
Has good mechanical properties.
Highest surface roughness
B. Second Generation compositesB. Second Generation composites
Consists of colloidal and micro-ceramic silica.
Low strength
Unfavourable coefficient of thermal expansion
Wear resistance better than first generation
Best surface texture.www.indiandentalacademy.com

C. Third Generation compositesC. Third Generation composites
Hybrid composite [combination of macro and micro
(colloidal) ceramics]
Ratio of 75:25
Good surface smoothness and reasonable
strength
D. Fourth Generation compositesD. Fourth Generation composites
Hybrid composite (heat-cured, irregularly
shaped, highly reinforced composite macro-
particles with micro (colloidal) ceramics].
Comparatively better surface characteristics and
mechanical propertieswww.indiandentalacademy.com

E. Fifth Generation compositesE. Fifth Generation composites
Hybrid composite (heat-cured, spherical, highly
reinforced composite macro. particles with micro
(colloidal) ceramics].
Improved workability
Surface texture and wear is similar to second
generation composites
Physical and mechanical properties similar to
fourth generation composites
F. Sixth Generation compositesF. Sixth Generation composites
Hybrid composite [agglomerates of sintered
micro (colloidal) ceramics and micro-ceramics]
Highest percentage of reinforcing particles
Best mechanical properties
Wear and surface texture similar to fourth
generation
Least polymerization shrinkage

VII. Classification according to Bayne and
Heyman:
CategoryCategory Particle sizeParticle size
Megafill - 1-2 mm
Macrofill - 10-100 µ.m
Midifill - 1-10 µ.m
Minifill - .01-.1µ. m.
Microfill - 0.04-0.4
Nanofill - .005-.01 µ.m.

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