This document discusses dental polymers, including their classification, properties, and uses. It provides information on the basic nature of polymers and how they are formed through polymerization reactions. Key points include: - Polymers are formed from monomers through chemical reactions, creating large molecular weight macro molecules. Their form determines if they are fibers, rigid solids, or elastomers. - Common dental polymers include polymethyl methacrylate (PMMA), which is used in denture bases and other prosthetic appliances. - Polymers have various desirable properties for dental applications, including being biologically compatible, strong, dimensionally stable, and easy to handle. - Polymer properties depend on factors like molecular

1. Dental Polymers

2. Contents
 Introduction
 Basic nature of polymers
 Classification of polymers
 Polymerization and Types
 Stages of polymerization
 Prosthetic dental polymers
 Properties of polymers
 Uses of polymeric materials
Types of polymers
Molecular
weight
Structure of polymer

3. Intoduction
Before introduction of acrylic polymers to dentistry the principle polymers used
was vulcanized rubber.Polymers introduced in 1937 included vinylacrylics and
poly acrylic acids.
The primary use of polymers has been construction of prosthetic appliances such
as denture base.
However they are also used in artificial tooth,restoration,cements,elastics,inlay
patterns,implants,impression materials,dies,temporary materials,endodontic
filling etcs.
Polymers are formed through chemical reactions that convert large number of low
molecular weight(LMW) molecules known as monomers into a large very high
molecular weight chain macro molecules known as polymers.
The form and morphology of this macro molecule determines whether the
material is a fiber,a rigid solid or an elastomer.

4. • DENTURE - An artificial substitute for missing natural teeth and adjacent
tissues
• DENTURE BASE - the part of a denture that rests on the foundation tissues
and to which teeth are attached
• DENTURE BASE MATERIAL - any substance of which a denture base may be
made up of.
• Polymeric molecules may be prepared from a mixture of different types of
monomers.
• Homopolymer-If it contains one type of constitutional repeating chemical
molecules.
• Eg-A-A-A-A-A.
• Terpolymers-If more than three chemical molecules.
• Stereo specific-Sometimes polymers is produced having “mer” units with a
special spatial arrangement with respect to adjacent unit.

5. EVOLUTION
• Materials used before 18th century
1. Wood
2. Bone
3. Ivory
• Materials used in the 18th century
1. Gold
2. Porcelain
• Materials used in the 19th century
. Tortoise Shell (1850)
2. Gutta Percha (1851)
3. Vulcanite (1851)
4. Cheoplastic (1856)
5. Rose Pearl (1860)
6. Aluminum (1867)
7. Celluloid (1870)
Materials used in 20Th century
1. Bakelite (1909)
2. Stainless steel (1921)
3. Cobalt Chromium (1930)
4. Vinyl Resin (1932)
5. Acrylic Resin (1937)
6. Self cure Acrylic Resin
7. Epoxy Resin (1951)
8. Polystyrene (1951)
9. Nylon (1955)
10. Polycarbonates(1967)
11. High impact acrylic (1967)
12. Polysulphones(1981)
13. Visible L.C.(1947)Acrylic (1986)
14. Pure Titanium (1998)
PMMA most accepted for use in dentistry
Khindria S K, Mittal S, Sukhija U. Evolution of denture base materials. J Indian Prosthodont Soc 2009;9:64-9

6. Desirable properties
BIOLOGICAL-
• should be tasteless, odourless, non-toxic,non-irritating to the biological
structures.
• impermeable to biological structures
• discourage the microbial growth.
PHYSICAL –
• must have adequate strength and resilient to resist masticatory, impact
and wear forces.
• must have dimensional stability and resistance to
thermal changes.
• low specific gravity for less bulkiness.
ESTHETICS-
• must have sufficient translucency and should allow coloring and
pigmentation.
• must not change colour over time.
HANDLING-
• must not produce toxic fumes or dust.
• must be easy to mix, insert, shape and cure.
• Should not change in presence of oxygen,saliva and blood
contamination.
• must be easy to polish and repair.
ECONOMIC-
• cost of the material and processing should be practical and feasible.

7. Basic nature of polymer
• The term polymer means a molecule which is made up of many “mers”.Thus
PMMA is a polymer composed of many mers.polymers may be prepared from
a mixture of different types of monomers
• Eg-Polymethylmethacrylate is derived from methyl methacrylate.
Dental uses of polymers-
• The various use of polymers in dentistry are as follows:-
• • Prosthodontics: “Denture bases and teeth, delicate liners, custom plate,
impression materials, core build up materials, temporary restoratives,
establishing/luting materials, and maxillofacial prostheses”.
• • Operative Dentistry: “Dentin bonding agents, cavity fillings, resin and glass-
ionomer cements, pit and fissure sealants, bracing materials and veneers”.
• • Orthodontics: “Brackets, bracket holding adhesives and cements and
spacers”.
• • Endodontics: “Gutta-percha , root canal sealants and elastic dams”.
• • Equipment: “Mixing bowls and spatulas, mouth guards (athletic gear) and
defensive eyewear”.

8. Properties Of Polymers-
Fig-1-Rigidity,strength and melting temperature increases with increase with
molecular weight and chain length(courtesy-phillips science of dental
material)
• The mix of polymer composition, chain length, branching, cross linking and
atomic direction can deliver an assortment of properties. To address the
issues of different dental applications, these highlights are controlled to
create a balanced properties. These properties can be gathered into four
interrelated classifications: Mechanical, Rheological (Flow), Dissolution And
Thermal.

9. Mechanical Properties—Deformation and Recovery
• When forces are applied to the polymer
they produce stress which causes materials to
deform or stretch from its original shape and
size (i.e, undergo strain) via either elastic strain,
plastic strain or a combination of elastic plus plastic
strain.
• Plastic strain Plastic strain is irreversible distortion
that can't be recouped and brings about another,
perpetual shape as the after effect of slippage
(flow) among polymer chains.
• Elastic strain is a reversible,versatile strain that is
rapidly and totally recouped when the stress is
eliminated, as the result of polymer chains
uncoiling and then recoiling.
• Viscoelastic strain is a blend of both flexible and
plastic disfigurement, yet just the versatile part is
recouped when the pressure is reduced.

10. Rheometric properties-
• The rheometry or flow behaviour of rigid
polymers involves a mix of elastic and plastic
deformation followed by elastic recovery after
the stresses are removed.This combination of
elastic and plastic changes are called visco elastic
property.
• The length of chain,cross link
numbers,temperature and rate of force
application determines which type of behaviour
dominates.
• Plastic flow- Irreversible strain conduct that
happens when polymer chains slide more than
each other and gets moved inside material
bringing about perceptual distortion.
• Elastic recovery- reversible strain behaviour that
occurs in amorphous regions of polymers when
randomly coiled chains straighten and then recoil
like springs.

11. Solvation and Dissolution properties-
• Polymers are usually slow to dissolve.the sovation
characteristic are very sensitive to polydispersity,cross
linking,crystallinity and chain branching.the following
characteristic properties exhibited by polymer which is
relevant in dentistry-
• The longer the chains with high molecular weight the
less is the solubility of polymer.
• Polymers engross a solvent and soften, but they never
dissolve.
• The cross connecting of the chain forestalls chain
detachment and retards disintegration and
exceptionally cross connected chains can't be broken
down.
• Elastomers swell more effectively than plastics.
• Absorbed molecules spread the polymer chain within
the polymer thus facilitating the slippage of chains
and this property is called plasticization.
• Swelling of dental polymers affect the fit of dental
polymeric prosthesis.

12. Thermal properties-
• The property of a polymer changes with change
in temperature and composition ,structure and
molecular weight.Thus higher is the temperature the
softer and weaker the polymers become.polymers can
be formed into desired shapes using type of polymeric
material used.According to its thermal setting polymer
can be divided into thermoplastic polymers and
thermosetting polymers.
Thermoplastic polymers-
• Soften on heating and hardens on
cooling.Thermoplastic polymers are made up of
branched or linear chains and they soften when
heated above the “glass transition
temperature(Tg)”.Eg-polyamides (nylon), acetal resins,
epoxy resins,impression compound,polystyrene,
polycarbonate resins, polyurethane and acrylic.
Thermosetting polymers-
• Thermoplastic material undergoes a series of chemical
changes and hardens when heated above the glass
transition temperature.They don't soften again on re
heating.They usually are cross linked in this state and
don't melt.Eg-PMMA.

13. • Co polymers-If it contains two or more different chemical
molecules.It can be of two types-
Random
Block
When
monomer A is
mixed with
monmer B
A and b
monomeric units
is formed.
A-B-A-B-A-B
Sequence of a monomer
followed by another
sequence of another
monomer.
A-A-A-B-B-B

14. Molecular Weight
• One polymer consists of various
“mers” multiplied by number of “mers”
and many range from thousand to
millions of molecular units.(mers).

15. Spatial Structure
 Property of polymers is also determined by the spatial structure.
 Three basic types-
Linear
Branched
Cross linked
 Linear polymer has monmer unit of same type.the linear and
branched molecules are separate and discrete whereas cross linked
are network structure results in a giant molecule.

16. Classification
Based on their thermal behaviour-
a) Thermoplastic
b) Thermosetting
Based on polymerization
a) Addition
b) Condensation
Based on origin
a) Natural
b) Synthetic
Based on architecture
a) Linear
b) Branched
c) Cross linked
Based on chemistrty
a) Homopolymer
b) Co-polymer-random,block or graft

17. Poymerization and Types
• Polymers are prepared by a process
called polymerization where many no.
Of monomer undergo chemical
reaction and gets attached to itself by
cross linking and together form high
molecular weight macro molecule
called polymer.This series of chemical
reaction is called “polymerization”
• Polymerization takes place in 2
Types:-
a) Addition
b) Condensation

18. Addition polymerization
• Monomer unit add sequentially to the
end of growing chain.the chain grows
indefinitely untill all monomer is
exhausted.the process is simple but not
easily control.eg-Vinyl polymers and
MMA.
• The process occurs in two steps-
a) Carbon carbon double bond(c=c)
opens and joins to form single bond.
b) Ring open reaction in which 3 atom
ring is broken and joins with other
bond which again break to form single
bond.

19. Free radical polymerization
1. Initiator releases free radicals which bring about
polymerization reaction.
2. Eg-benzyl peroxide release free radicals to bring
polymerization in acrylic resins
Ring opening polymerization
1. Ring structure in the polymer chain is opened
and cross linking occurs.
2. Eg-polyether resins
Ionic
polymerization
1. Catalyst bring about exchange of ions
resulting in cross linked polymer
2. Eg-addition silicones

20. Stages in addition
polymerization
• Induction
a) Activation
b) Initiation
• Propagation
• Chain transfer
• Termination

21. Induction
First a free radical is formed denoted by R.
This free radical is a atom possesing unpaired electron.
Activation is the process of producing free radical.
Free radical is generated by
chemical agent-
benzoyl peroxide.
Heat-tertiary amine
Visible light
Uv light.
This free radical reacts with monomer and initiates the
polymerization reaction.
When at one end this initiation occurs the other end the remaining
molecule unpaired electron will make new molecule and free radical
which further will proceed the reaction.
Free radical converts monomer into polymer.the lower moleculer pair
with higher molecule resulting in atomic bonding.

22. Propagation
•Free radical are transferred to the
monomer which in turn reacts with other
monomer.
•M+M DIMER.
•This Process Continues With Evolution Of
Heat And Leads To Large No Of Polymer
Molecules.
•Increase in chain requires energy

23. Chain Transfer
• The active free radical is transferred
to another molecule and a new free
radical for further growth is created.
• Chain transfer occurs when a free
radical approaches a MMA molecule
and donates a hydrogen atom to
MMA.There forms a double bond and
free radical become inactive.
• A new nucleus growth is created.

24. Termination
• The chain reaction terminates by
direct coupling of free radical or by
exchange of hydrogen atom.
• Inhibition of addition polymerization
may also be due to impurities which
reacts with free radicals.eg-
hydroquinone.

25. Condensation
polymerization
• Also called step growth
polymerization.by products is formed.
• The formation of by product which
gradually evaporates is the reason for
step growth.
• Two molecules react to form a large
molecule with elimination of smaller
molecule such as water ,alcohol,halogen
acids and ammonia.
• The reaction proceeds in a step wise
fashion from monomer to dimer to trimer.
• The polymer formed is of low molecular
weight.

26. Requisite properties of polymers
• Strength and durability
• Satisfactory thermal properties
• Processing accuracy & dimensional stability
• Chemical stability ( unprocessed & processed)
• Insolubility in and low sorption of oral fluids
• Absence of taste and odor
• Biocompatible
• Natural appearance
• Color stability
• Adhesion to plastics, metals, and porcelain
• Ease of fabrication and repair
• Moderate cost

27. Poly methyl metha acrlyate
• The most popular material used for denture fabrication since its introduction
in 1937
• “Walter wright” introduced [PMMA]
• Clear and colourless polymer.
• polymer of methyl methacrylate, with chemical formula (C5H8O2)n
Belongs to the important acrylic family of resins.

28. METHYL METHACRYLATE
• METHYL METHACRYLATE is the methyl ester of methacrylic acid.
• It polymerizes easily to form polymethyl methacrylate.
• Colorless liquid with an acrid, fruity odor.
• Slightly soluble in water and floats on water.
• Vapors heavier than air.
• Boiling point 100.8 degree celcius

29. • The monomer tends to self-polymerize if subjected to
heat, polymerization catalysts , strong oxidizers, or
ultraviolet light.
• An inhibitor such as hydroquinone,is added to keep
the chemical from initiating polymerization
• Polymerize exothermically
• uses in the fields of medicine and dentistry to make
prosthetic devices and as a ceramic filler or cement.
• Vapors irritate the eyes and respiratory system.
• Studies have shown [european commission, esis; iuclid
dataset, methyl methacrylate (80-62-6) p.275 (2000
CD-ROM edition)] that dermal exposure is greater
than inhalational exposure and is excreted in urine, but
quantifiable analysis could not be made.

30. Polymer – Monomer
Interaction
• Sandy stage
• Stringy stage
• Dough like stage
• Rubbery or elastic stage
• Stiff stage

31. Synthetic resins are used in a variety of dental
applications:-
• Dentures (bases, liners and artificial teeth)
• Cavity-filling materials ("composites")
• Sealants
• Impression materials
• Equipment (mixing bowls)
• cements (resin-based)
• Dental resins used mainly to restore and
replace tooth structure and missing teeth
APPLICATIONS OF RESINS IN DENTISTRY

32. Applications of polymers in dentistry
Denture Base Material-
• Most denture bases and acrylic teeth are fabricated using (poly methyl
methacrylate) PMMA.pmma is frequently used due to its various
advantages like low cost,biocompatibility,ease of processing,stability in
oral environment and acceptable esthetics.How ever the properties of
pmma is enhanced by incorporating many fillers and fibers.
Soft Lining Materials-
• These are consistent materials which are placed between the denture
and the oral mucosa so as to diminish torment and distress brought
about by hard dentures. These materials are additionally applied in
maxillofacial reconstruction and as obturators. soft lining materials are
classed in two types: soft acrylics and silicone rubbers.
• Heat or room temperature polymerized methacrylates with included
plasticizers, hydrophilic acrylic polymers, silicones and
elastomer/methacrylate copolymers are ordinarily utilized as soft lining
materials. A basic prerequisite is a glass temperature beneath 37 °C, with
the end goal that the polymer stays delicate in the oral pit. The polymers
ought to be biocompatible, non aggravation to oral tissues, have
satisfactory mechanical quality and have low liquid take-up. soft acrylics
show great bond to PMMA denture bases true to form anyway the
joining of plasticizers adds to, the solidifying over some stretch of time
and they additionally experience the ill effects of enormous water take-
up. There is a developing worry about the utilization of Pthalate
plasticizers, because of their harmfulness. Silicones experience the ill
effects of absence of bond to the acrylic denture bases and have a low
protection from tear.

33. Some silicone delicate liners assimilate a lot of liquids and water take-up
of hydrosilanized silicone rubbers is affected by added substances,
for example, hydrophobic or hydrophilic silica and is identified with
the dissolvability of the added substance, more prominent solvency
offering ascend to a drawn out water take-up with bigger deviation
from traditional dissemination attributes.
Dental Composites-
• Dental composites are tooth hued filling materials made out of synthetic
polymers, particulate ceramic fillers, polymerization promoters and
coupling agents.They are progressively being utilized as restorative
materials set straightforwardly, in a roundabout way or as a cement,
inbonded restorations. Dental composites are supplied as single paste
formulations also termed visible light cure (VLC) materials and as two
pastes for the self-cure systems.

34. Dentin Bonding Agents-
• Other than GIC bulk filling material do not adhere to tooth exclusively and
Dentine bonding agents provide a phenomenal attaching to tooth structures
as well as the new age materials likewise permit bonding between composite
resins and substrates, for example, base metal combinations, solidified
amalgam, cured composites and porcelain.adhesion to enamel isn't as
troublesome as to dentine inferable from the unpredictable and variable
arrangement of dentine. Dentine bonding agents can be considered to
include three segments:”a primer, a coupling agent and an unfilled resin”
significant so as to acquire a precise impression followed by its flexible
recuperation and mechanical quality.
• More recently, a therapeutic adhesive was synthesized that contained three
agents: “a QAM named dimethylaminododecyl methacrylate (DMADDM) with
antibacterial activity, nanoparticles of silver (NAg) and NACP for
remineralization”. There was no decrease in dentin bond quality from one day
to a half year of when placed in water, while the commercial control bonding
agent lost strength roughly 33% of its dentin bond quality at six months.This
bonding agent indicated a drawn out toughness in dentin bond quality.
Impression Materials-
• Numerous methods in restorative dentistry require an exact replica model of
the oral delicate and hard tissues so as to build appliances outside the
mouth; a few models being dentures ,crowns and bridges and orthodontic
appliances. Impression materials are presented in the oral cavity in a plastic or
fluid state which subsequently undergo a series of chemical reaction.The flow
properties are significant so as to get a precise impression followed by its
flexible recuperation and mechanical strength. Impressions are frequently
stored at room temperature and subjected to high tensile stresses on removal
from undercut areas. Eg-natural polymers agar –agar,silicone impression
material,polyethers,polysulphide.

35. Peek And Peak-
• PEEK (polyetheretherketone) is a synthetically manufactured
polymeric material and the most significant representative
of polyaryletherketone (PAEK). This is a partially crystalline,
thermoplastic high temperature- resistant, high-
performance plastic with a melting temperature of 334°C.
Therefore, PEEK can be used in pressurized compression
systems like “for 2 press” system, while the factory pressed
product can be processed with different cutters and used in
“CAD/CAM”technology.
• PAEK is a moderately new group of high temperature
thermoplastic polymers comprising of a fundamental sweet-
smelling aromatic molecular chain linked by “ketone and
ether”.The synthetic structure of polyaromatic ketones gives
stability at high temperatures (more than 300 ° C), making it
amazingly alluring for modern applications. Before the finish
of 1990, PEEK had developed as the fundamental
thermoplastic polymer and was utilized to supplant metal
parts in the orthopaedics.PEEK can without much of a
stretch be altered by including different materials carbon
fiber addition may build the elastic modulus to 18 GPa. The
carbon-fortified PEEK module is compared to the cortical
bone and the dentin. The elasticity of PEEK is like that of
bone, enamel and dentin subsequently making it an ideal
material for perpetual prosthetic rebuilding efforts.

36. Bio HPP-
• Bioactive PEEK with ceramic filler (Bio-High Performance Polymer) is a
part of the “PEEK” family and is applied in surgeries since a considerable
length of time. Because of its fantastic stability, its ideal polishing
properties and its low plaque affinity, BioHPP is generally excellent for
exact prosthetic reclamations manufacture. “The biopolymer has a
modulus of flexibility closer to the human bone and this reality improves
the masticating performances. BioHPP (High Performance Polymer) is an
innovative thermoplastic polymer dependent on PEEK”. It was made and
upgraded for dental use. It contains ceramic microparticles for better
polishing of the restorations. These ceramic fillers have a size of about
0.3-0.5 microns and possess 20% of the all out volume of BioHPP.
• BioHPP is as close as conceivable deep down, on account of its
coefficient of versatility (around 4 GPa). This is significant in implant
treatment in situations when winding powers may happen. The biting
pressure is transmitted as tenderly as could be expected under the
circumstances, and the danger of fracture is decreased, because of the
BioHPP modulus of flexibility near that of the spongiose bone.
• BioHPP is especially appropriate for patients with sensitivities on the
grounds that the solvency of the polymer in water is low <0.3
ìg/mm3.Studies exhibits high protection from abrasion.BioHPP can be an
option in contrast to chromium-cobalt dental alloys (Cr-Co) since it is
lighter and doesn't cause erosion. BioHPP developments can be built
utilizing both current CAD/CAM innovation and standard wax
substitution innovation.
• Application of Bio-HPP:-Removable Partial Dentures, Crown And Bridge
Fabrication, Individual Implant Abutments.

37. DENTURE
BASE RESINS
Dr.Rasmita Samantaray

38. Contents
• Introduction
• Some terminologies
• Types of denture base resins
Heat Cure
Self Cure
Light Cure
Techniques used in processing DBR.
Physical Properties Of DBR.

39. Heat activated resins
• Activated by heat
• Above 60 degree celcius, benzoyl peroxide decomposes Free
radicals polymerization reaction initiated
• Unreacted monomer [0.2%-0.5%]
• Exothermic reaction
• Polymer to monomer ratio – 3:1
• Dough forming time – less than 40 min
manufacturers provide – less than 10 min
• Working time – 5min [extended via refrigeration]
• As a rule uses compression molding technique

40. composition
Powder
• Pre-polymerized poly (methyl methacrylate).
• Copolymers of of PMMA (5%) E.g.: Ethyl or Butyl methacrylates
• Initiator (0.2-1.5%) E.g.:benzoyl peroxide.
• Plasticizer E.g.: Dibutyl phthalate.
• Color pigments E.g: Mercuric sulphide, Cadmium
• Opacifiers E.g.: Zinc or titanium oxides
• Dyed synthetic fibers [nylon or acrylic]
• Inorganic particles E.g.: Glass fibers, zirconium silicate.
• Heavy metal compounds E.g.Barium, bismuth, etc.
Liquid
• Methyl methacrylate
• Co-monomers
• Inhibitor E.g.:Hydroquinone
(0.003%-0.1%).
• Plasticizers E.g.: Butyl
or Octyl methacrylate
• Dibutyl Phthalate.
• Cross-linking agent
E.g.: Ethylene glycol dimethacrylate

41. Compression Molding Technique

42. Dewaxing
• Immersed in boiling water for 4 min
• Appropriate parts of flask removed
• Softened residual wax removed using wax solvent or by dropping of
hot water.
• Mold cavity cleaned with mild detergent and rinsed with boiling
water
Packing

43. Injection molding technique

44. Compression vs injection
• Various studies suggest that the injection molding
technique produces dentures with higher dimensional
accuracy.
• It compensates the polymerisation shrinkage due to
high pressure and extra influx of resin for the unreacted
monomer
• Also called curing cycle
• Should be controlled to avoid effects of temp rise above
the boiling point of monomer [100.8 degree celcius]
• Boiling of monomer yields internal porosity
• Can control by heating the resin more slowly
Polymerization cycle
Also called curing cycle
Should be controlled to avoid effects of temp rise
above the boiling point of monomer [100.8 degree
celcius]
Boiling of monomer yields internal porosity
Can control by heating the resin more slowly

45. Research suggests 3 techniques:
1. DBR in constant temp. Of 74 degree
celcius for 8 hrs or longer, no terminal
boiling treatment
2. Processing in 74 degree celcius water
bath for 8 hrs and increasing temp. To
100 for 1 hr
3. Processing at 74 degree celcius for 2 hrs
and raise the temp to 100 for 1 hr.
• Cooling slowly
• Rapid cooling causes warping
• Thus bench cooling for 30 min, then
under cool tap water for another 15 min
• Denture stored in water till delivery to
the patient to avoid dimensional changes

46. Chemically activated
resins
Cold curing, self curing,
autopolymerising resins

49. • Degree of polymerisation incomplete
• Greater amount of unreacted monomer [ 3%-5%]
• Unreacted monomer acts as plasticizer – decreases
transverse strength
• Residual monomer – potential tissue irritant-
compromises biocompatibility
• Slightly less shrinkage than heat activated
• Greater dimensional accuracy
• Inferior color stability due to the presence tertiary
amines ready for oxidation
Two techniques used:-
• Compression molding technique
• Fluid resin technique

50. Fluid resin technique

52. Advantages
• Improved adaptation to underlying tissues
• Decrease probability of damage during deflasking
• Reduced material costs
• Simplified procedure
Disadvantages
• Shifting of prosthetic teeth
• Air entrapment
• Poor bonding of teeth to DBR
• Technique sensitivity
Light Activated Resins
• Composite – matrix of UDMA,microfine silica,
• high mol.wt. Monomer,resin beads as organic fillers,
• Visible light – activator,
• Camphorquinone – initiator
• Resin placed inside light chamber & polymerized
• Bluelight – 400-500 nm
• High intensity quartz-halogen bulbs
• Rotated continuously for uniform polymerisation

53. Advantages
• developed to surpass contact allergies,laboratory
vapours, and the traditional lengthy lost wax
technique of investing, flasking and boil-out used with
the conventional PMMA materials
• biocompatibility, ease of fabrication and
manipulation, low bacterial adherence, and ability to
bond to other denture base resins.
• use of UDMA was limited by the low impact resistance
and brittleness of the material [TRIAD]
• New MMA free material developed by dentsply
[ECLIPSE] – superior physical and mechanical
properties

54. Microwave activated
resins
• Microwave energy
• Specially formulated resin [ethylene glycol dimethacrylate]
• Non metallic flask
• Conventional microwave oven
• Less time consuming
• Physical properties and dimensional accuracy is comparable with
conventional resins.
• cleaner, more time-efficient, more cost-effective, and less cumbersome
method of polymerisation of denture base resins
• Rapid heating may cause porosity
• minimal residual monomer levels attainable with the water bath system
were not achieved.
• Microwave curing at 70W for 25 min minimized porosity problems
associated with rapid heating in sections not thicker than 3 mm.
• offers no advantage in time saving over rapid water curing systems

56. POLYMERIZATION SHRINKAGE
MMA polymerises into PMMA, density changes from 0.94g/cm3 -1.19 g/cm3
Volumetric shrinkage -21%
Shrinkage is uniformly distributed
Clinically satisfactory denture
In presence of linear shrinkage, discrepancy in initial fit of a denture
TENSILE & COMPRESSIVE STRENGTH
Have adequate tensile & compressive strength
Fracture may happen accidentally or due to faulty fabrication & flexural fatigue.
Eg :-Heat cure DBR
ELONGATION
Elongation combined with strength indicates the toughness of the material.
Materials having low elongation are tough materials and vice versa
It is important as gives an idea about the workability of the materials
Mostly regarding alloys
Eg polyvinyl acrylics

57. PROPORTIONAL LIMIT
– Its a function of the rate of stress applied
– For a denture base it should be sufficiently high
– To prevent permanent deformation due to masticatory
forces
– This may result in loss of retention and/or loosening of teeth
from Denture base.

58. IMPACT STRENGTH
• It is the measure of the energy absorbed by a material when it breaks by a
sudden blow
• Addition of plasticizers increases impact strength
• But is followed by decrease in hardness, proportional limit, elastic modulus &
compressive strength
• Therefore , a DB cannot have excellent impact strength at the cost of other
properties
Eg : rubber reinforced acrylic has higher impact strength

59. FLEXURAL STRENGTH
• Closely represents type of loading in vivo
• When compared with metal the elastic moduli of all the plastics are low
FATIGUE STRENGTH
• It represents the no. of cycles before failure at a certain stress
• Eg : rubber reinforced has superior strength, pour type has the least.
FRACTURE TOUGHNESS
• It is a property which describes the ability of a material containing a crack to
resist fracture.
• Highest for rapid heat cured acrylic
• Lowest for pour type acrylic.
• Is higher when specimens are saturated with water rather than dry.
COMPRESSIVE CREEP
• Time dependant
• When DBR are kept under a load, it will deform with time
• Lowest – heat cure resins
• Higher - self cured resins
RECOVERY AFTER INDENTATION
• Recovery is greater in dry specimen [86%-89%] than wet specimen[84%-88%]
• Time allowed was 10 min
• Demonstrate viscoelastic properties.

61. THERMAL CONDUCTIVITY
• Poor conductors of heat and electricity
• Acts as insulators in mouth against hot & cold food
THERMAL COEFFICIENT OF EXPANSION
• describes how the size of an object changes with a
change in temperature.
• Temperature change from processing to room
temperature or mouth temperature indicates
importance
• High [71-81x10-6/degrees celcius]
• Addition of fillers may reduce this
HEAT DISTORTION TEMPERATURE
• Measure of ability of a plastic To resist dimensional
distortion by heat
• For PMMA – 71-91 degrees
• Repair temperature low
• Use self cure or light cure

62. Need for advancements
• Well fitting dentures which are repeatedly fracturing
• A complete denture opposing natural dentition
• Patients with heavy bites
• Implant supported over dentures
• Limited vertical space
• Thin dentures
• Technique sensitivity
• Denture Stomatitis [candida induced]
HIGH IMPACT REINFORCED RESINS
1000% strength increase over non-reinforced
greater impact strength and fatigue properties
Hence HIGH IMPACT
Reinforcements by :
1. Fibres [continuous parallel, chopped and woven]
2. Carbon / graphite fiber
3. Aramid fiber [aromatic polyamide/ kevlar]
4. Polyethylene
5. Glass fiber
6. E – glass fiber
7. Rubber [butadiene-styrene PMMA]
8. Metal

63. Indication
• Indicated for patients who drop their dentures repeatedly e.g.
Parkinsonism.
• powder-liquid system
• processing is same as heat cure resins.
HYPOALLERGEN RESINS
• Polyurethane, Polyethylenterephthalate and
Polybutylenterephthalate [phthalate based], light activated
UDMA
• significantly lower residual monomer content
RESIN WITH MODIFIED CHEMICAL STRUCTURE
• hydroxy-apatite fillers increases fracture toughness
• Al2O3 fillers increases the flexural strength and thermal
diffusivity
• 2% quaternary ammonium compound polymerised with a
denture acrylic resin displays antiseptic properties
• Addition of ceramic or sapphire whiskers improves thermal
diffusivity
• Addition of Triphenyl Bismuth or uranium or organo-zirconium
compound impart radiopacity equivalent to that of aluminium.
PMMA MODIFIED HYDROXYAPATITE
• Hydroxyapatite whiskers added to [polymer matrix] reinforce acrylic
resins
• Better mechanical properties
• Clinical effectiveness yet to be studied

64. Thermoplastic Resins
• Thermoplastic Nylon (Polyamide)
• Thermoplastic Acetal
• Thermoplastic Acrylic
• Thermoplastic Polycarbonate
• Excellent Esthetics
• Very Comfortable For The Patient.
• Non-porous So No Growth Of Bacteria [It Still Retains A Slight Amount Of
Moisture To Keep It Comfortable Against Gums
Thermoplastic Nylon
• Polymide
• Rapid Injection System
• 1962 -- the first flexite thermoplastic
• injected at temperatures from 274 to 293 degrees Celsius.
• Valplast and flexiplast and lucitone
• 1992, The Flexite Company, developed and patented the first pre-
formed tooth colored clasps known as Clasp-Eze, made of nylon
material and is available in pink and clear shades.

65. LUCITONE-
• High grade microcrystalline polyamide
• Excellent stability, aesthetics
• Soft – doesnt fracture easily on falling
• High resistance to abrasion
• Resistant to stains and calculus
• Lacks color stability
• Become loose with long term use
• Cannot be relined or repaired
• Bonding with acrylic teeth is not good
THERMOPLASTIC ACETAL-
• Polyoxymethylene [POM]
• 1986, introduced as tooth colored clasps
• Superior aesthetics
• Available in about 17 shades
• Injection molding technique
• Acetal as a homo-polymer has good short-term mechanical
properties, but as a co-polymer has better long-term stability.
• Clasps & framework material
THERMOPLASTIC ACRYLIC-
• Commercially available as flexite MP
• Special blend of polymers – highest impact rating of any acrylic
• tooth and gingival colors & has both translucency and vitality,
providing excellent esthetics
• easy to adjust, handle and polish
• It is relineable and repairable at the chair-side
• very popular for bruxism appliances and denture bases

66. THERMOPLASTIC POLYCARBONATE
• polymer chain of bisphenol-A carbonate very strong, resists fracturing, and is
quite flexible
• does not wear well thus will not maintain vertical dimension long
• not suitable for full or partial dentures but ideal for provisional crown and
bridges
• natural translucency and finishes very well, yielding excellent esthetics
• Temporary and provisional restorations
• available commercially as Reigning.
DRUG RELEASING DENTURES
• Disks were prepared by grafting PNVP [poly(N-vinyl-2-pyrrolidinone)]
onto PMMA
• loaded with miconazole
• Quenched disks could also be charged with chlorhexidine that
displayed anticandidal activity.
• Long term management of candida induced denture stomatitis

67. References
• Craig’s 12 th edition, chapter-7,chapter 21.
• ANUSAVICE 11th edition, chapter 6,chapter-19.
• Progress in Natural Science: Materials International 2013;23(1):89–93.
• Vivek R, Soni R (2015) Denture base Materials: Some Relevant
Properties and their Determination. Int J Dent Oral Health 1(4)
• International Journal of Prosthodontics. May/Jun1990, Vol. 3 Issue 3,
p249-255. 7p.
• Dental Materials Volume 4, Issue 1, Pages 1-48 (February 1988)
• OHDM - Vol. 13 - No. 2 - June, 2014.
• R.Bhola et al, trends biomater. Artif. Organs, vol 23(3), pp 129-136 (2010)
biocompatible denture.
• Nogueira SS et al comparison of accuracy between compression- and
injection-molded complete dentures.J prosthet dent. 1999 sep;82(3):291-
300.