Non metallic denture base material / dental crown & bridge courses

NON-METALLIC DENTURE
BASE MATERIAL
INDIAN DENTAL ACADEMY
Leader in continuing Dental Education
www.indiandentalacademy.com

CONTENTS
 Introduction
 History
 Disadvantages of earlier denture base materials
 Polymers
-Definition and use
-Chemistry-Addition polymerization
 Requisites for dental resins
-Biological compatibility
-Physical properties
-Manipulation
-Aesthetic properties
-Economic consideration
-Chemical stability
 Types of denture base resins
1 Conventional heat cured Polymethyl methacrylate

2 Cold cure /Autopolymerizing Polymethyl methacrylate (Pour resins).
3 High impact –resistant Acrylic
4 Injection molded polymers
5 Rapid heat polymerized polymers
6 Microwave- Polymerized polymers
7Light activated polymers
8 Fiber Reinforced polymer
 Review of literature
 Recent advancement
 Conclusion
 References

INTRODUCTION
All through the history of the making of dentures,we find a constant
struggle of the dentist to find a suitable denture base material

Definition : According to GPT - VI, Denture
Base is defined as the part of Denture that rests
on the foundation tissue and to which teeth are
attached. Denture Base Material is any
substance of which denture base may be made

HISTORY
 Skillfully designed dentures were
made as early as 700 BC.and
 Talmud a collection of books of
hebrews in 352-407 AD mentioned
that teeth were made of gold
,silver,and wood.
 Egypt was the medical center of
ancient world, the first dental
prosthesis is believed to have been
constructed in egypt about 2500 BC.
Hesi-Re Egyptian dentist of about
3000 BC

ront and back views of mandibular fixed bridge, four natural incisor teeth and two carved ivory teeth
ound With gold wire found in Sidon-ancient Phoenicia about fifth and fourth century BC.

 During medieval times dentures were seldom considered ,when
installed they were hand carved and and tied in place with silk
threads.
 Those wearing full denture had to remove them before eating.
 Upper and lower teeth fit poorly and were held together by steel
springs.
 Earlier pictures of dental prosthesis are delivered to us by ABUL-
CASIM an Arab born in Cordova Spain.
Persian dentist of late eighteen
century
Indian surgeon of mid nineteenth century

WOOD
 For years, dentures were fashioned from wood .
 Wood was chosen
-readily available
-relatively inexpensive
-can be carved to desired shape
 Disadvantages
-warped and cracked in moisture
-esthetic and hygienic challenges
-degradation in oral environment

Wooden denture believed to be carved out of box wood in 1538 by Nakoka Tei a Buddist priestess
Wooden dentures

Bone
 Bone was chosen due to its availability, reasonable cost and
carvability .
 It is reported that Fauchard fabricated dentures by measuring
individual arches with a compass and cutting bone to fit the arches .
 It had better dimensional stability than wood, esthetic and hygienic
concerns remained.

IVORY
 Denture bases and prosthetic teeth were fashioned by carving this material
to desired shape
 Ivory was not available readily and was relatively expensive.
 Denture bases fashioned from ivory were relatively stable in the oral
environment
 They offered esthetic and hygienic advantage in comparison with denture
bases carved from wood or bone.
Carved ivory upper denture retained in the mouth by springs with natural human teeth cut off at the
Neck and riveted at the base. www.indiandentalacademy.com

 Since ancient times the most
common material for false teeth
were animal bone or
ivory,especially from elephants or
hippopotomus.
 Human teeth were also
used,pulled from the deceased or
sold by poor people from their own
mouths.
 Waterloo dentures
 1788 A.D. Improvement and
development of porcelain dentures by
DeChemant.
G.Fonzi an italian dentist in Paris invented the
Porcelain teeth that revolutionized the construction
Of dentures.Picture shows partial denture of about
1830,porcelain teeth of fonzi’s design have been
Soldered to a gold backing.

CERAMICS
 Porcelain denture bases were relatively expensive
 During subsequent years secrets of porcelain denture became
known and it became common and inexpensive.
 ADVANTAGES over wood, bone , ivory were
-Could be shaped using additive technique rather than
subtractive (carving).
-Additive technique facilitated correction of denture base surface.
-this permitted more intimate contact with underlying soft tissues.
-Could be tinted to simulate the colors of teeth and oral soft
tissues.
-stable in oral environment.
-Minimal water sorption, porosity, and solubility.
-Smooth surface provided hygienic properties.
 Among the drawbacks BRITTLENESS was most significant,
fractures were common, often irreparable.

One piece porcelain upper denture crafted by Dr John
Scarborough,Lambertville,New Jersey 1868.

 In 1794 John Greenwood began to swage gold bases for dentures. Made
George Washington's dentures.
George washington’s last dental prosthesis. The palate was swaged from a sheet of gold and ivory teeth riveted
To it.The lower denture consists of a single carved block of ivory. The two dentures were held togther by steel
Springs.

 In 1839 an important development took place CHARLES GOODYEAR
discovered VULCANIZATION of natural rubber with sulphur(30%) and was
patented by Hancock in england in 1843.
 NELSON GOODYEAR (brother of charles goodyear) got the patent for
vulcanite dentures in 1864.
 . They proceeded to license dentists who used their material, and charged a royalty
for all dentures made. Dentists who would not comply were sued.
 The Goodyear patents expired in 1881, and the company did not again seek to
license dentists or dental products.
 Vulcanite dentures were very popular until the 1940s, when acrylic denture bases
replaced them.

A set of vulcanite dentures worn by Gen. John J.
(Blackjack) Pershing, commander of the American
Expeditionary Forces in France during the First World
War
Set of complete dentures having palate of swaged
Gold and porcelain teeth set in vulcanite.

 In 1868 John Hyatt, A US Printer,
discovered the first plastic molding
compound, called celluloid. He
made it by dissolving nitrocellulose
under pressure
 In 1909, another promising
organic compound was found.
This was phenol formaldehyde
resin discovered by Dr. Leo
Backeland .
Celluloid upper denture 1880,celluloid as a
Substitute for vulcanite was unsuccessful as
It absorbs stains and odors in the mouth,
Gradually turns black and was flammable.

 In 1937 Dr. Walter Wright gave dentistry its very useful resin.
 It was polymethyl methacrylate which proved to be much
satisfactory material tested until now.
Dentures made of polymethyl methacrylate

Disadvantages of different denture base
1. Vulcanite :
In 1839 Vulcanized rubber was discovered and
introduced as a Vulcanite and Ebonite.
For the next 75 years Vulcanite rubber was the principal
Denture base Material. But failed because of following
reasons :
Disadvantages
It absorbs Saliva and becomes unhygienic due to
bacterial proliferation.
Esthetics were poor.
Dimensionally unstable.
Objectionable taste and odor

2. Celluloid
Although it was having tissue like color but
having principal disadvantages like
Disadvantages
 Lack of stability
 Unpleasant taste
 Unpleasant odor
 Stainability
 Flammable

3. Bakelite
It was formed by heating and compressing a
mixture of phenol and formaldehyde.
Disadvantages
 Lack of uniform quality
 Variable strength
 Variable color
 Dimensional unstability.

POLYMERS
Chronology of events
 Charles Goodyear discovery of vulcanized rubber in 1839.
 John hyatt discovered celluloid in 1868
 Dr Leo Bakeland discovered phenol-formaldehyde resin (Bakelite).
 In the 1930’s Dr Walter Wright and the Vernon brothers working at the
Rohn and Haas company in Philadelphia developed
Polymethylmethacrylate (PMMA), a hard plastic.
 Although other materials were used for dental prosthesis, none could come
close to PMMA and by the 1940;s 95% of all dentures were made from this
acrylic polymer.

 Natural polymers include:
 Proteins (polyamides or polypeptides) containing the chemical
group (-Co-NH-); this is known as an amide or peptide link.
 Polyesoprenes such as rubber and gutta percha.
 Polysaccharides, such as starch, cellulose, agar and alginates.
 Polynucleic acids, such as deoxyribonuclei acids (DNA) and
ribonucleic acids (RNA).
 Synthetic polymers are produced industrially or in the laboratory, by
chemical reaction.
Synthetic polymer : Defined as a non metallic compound
synthetically produced (usually from organic compounds) which can
be molded into various useful forms and then hardened for use.

DEFINITION: A polymer is a long chain organic molecule .It is produced by the
reaction of many smaller molecules called monomers,or mers.
 If reaction occurs between two different but compatible monomers the
polymeric product is called a COPOLYMER.
 Resin : A broad term used to describe natural or synthetic substances that
form plastic materials after polymerization (GPT-7th
edition).
USES IN DENTISTRY
 Denture bases and artificial teeth.
 Denture liners and tissue conditioners.
 composite restorative and pit and fissure sealent.
 Impression materials
 Custoum trays for impression
 Temporary restoratives.
 Mouthguards.
 Maxillofacial prosthesis.
 Space maintainers.
 Veneers.
 Cements and adhesives.

CHEMISTRY OF POLYMERIZATION
 Monomers react to form polymer by a chemical reaction called
polymerization.
 The most common polymerization reaction for polymers used in dentistry is
addition polymerization.
ADDITION POLYMERIZATION
 INDUCTION
 PROPOGATION
 CHAIN TRANSFER
 TERMINATION
INDUCTION
1)ACTIVATION
2)INITIATION

ACTIVATION Free radicals can be generated by activation of radical producing molecule
using.
 Second chemical
 Heat
 Visible light
 Ultraviolet light
 Energy transfer from another compound that acts as a free radical.

 Commonly employed initiator is Benzoyl peroxide which is activated
rapidly between 50 degree and 100 degree C to release two free radicals
per benzoyl peroxide molecule.
 Second type is chemically activated ,consists of two reactants when mixed
undergo reaction eg tertiary amine (the activator) and benzoyl peroxide (the
initiator). Amine forms a complex with benzoyl peroxide which reduces the
thermal energy (and thus the temperature) needed to split it into free radicals.
 Third type is light activated .The visible light light cured dental
restoratives,camphorquinone and an organic amine
(dimethylaminoethylmethacrylate) generate free radicals when irradiated by
light in the blue to violet region.
 Light with a wavelength of about 470nm is needed to trigger this reaction.

INITIATION

The resulting free radical monomer complex acts as a new free radical center
which is approached by another monomer to form a dimer, which also becomes
a free radical.
PROPOGATION

CHAIN TRANSFER
 The active free radical of a growing chain is transferred to another molecule
(eg monomer or inactivated polymer chain) and a new free radical for further
growth is created termination occurs in the latter.

TERMINATION
 Can occur from chain transfer.
 Addition polymerization reaction is terminated by
-Direct coupling of two free radical chains ends
-Exchange of hydrogen atom from one growing chain to another.

INHIBITION OF ADDITION REACTION
 Addition of small amount of Hydroquinone to the monomer inhibits
spontaneous polymerization if no initiator is present and retards the
polymerization in the presence of an initiator.
 Amount added is 0.006% or less
 Methyl ether of hydroquinone is generally present.
COPOLYMERIZATION
 When two or more chemically different monomers each with desirable
properties can be combined to yield specific physical property of a
polymer .eg small amount of ethyl acrylate may be co-polymerized with
methyl methacrylate to alter the flexibility and fracture resistance of a
denture.

METHYL METHACRYLATE
 The acrylic resins are derivative of ethylene and contains a vinyl group
(-c=c-)
 Polyacids tends to imbibe water, due to polarity related to carboxyl group.
 Water tends to separate the chain and cause softening and loss of strength.
 Methyl methacrylate is a transparent liquid at room temp.
 Physical properties
-Molecular wt=100
-Melting point=-48 C
-Boiling point=100 C
-Density=0.945g/ml at 20 C
-Heat of polymerization=12.9 Kcal/mol
Methyl methacrylate
molecule

POLYMETHYL METHACRYLATE
 Transparent resin, transmits light in uv range to a wavelength of 250
nm.
it has got remarkable clarity.
 Hard resin ,knoop hardness no of 18 to 20.
 Tensile strength is 60 MPa
 Density is 1.19 g/cm cube.
 Modulus of elasticity 2.4 GPa(2400 MPa)
 It is chemically stable and softens at 1250
C
 It can be molded as a thermoplastic material between 125 and 200
C
 Depolarization takes place at approx 450 C .
 Absorbs water by imbibition
 Non crystalline structure possess high internal energy.
 Polar carboxyl group can form hydrogen bridge to a limited extent
with water.

REQUISITES FOR DENTAL RESINS
(I)BIOLOGICAL COMPATIBILITY
 Tasteless
 Odorless
 Nontoxic, non-irritating
 Insoluble in saliva or any other fluids taken into the mouth.
 Impermeable to oral fluids.
MONOMER TOXICITY
A review of clinical studies and patients reports on reaction to acrylic resin
dental prosthesis by William M. Goebel in Feb 1980 have shown the
following facts
 Fischer patch tested groups of patients with heat cured and
autopolymerizing acrylic resin disks, monomer, powdered polymer, and
patients own acrylic resin prosthesis. From the results he concluded that
methyl methacrylate monomer is a sensitizer which can cause an allergic
contact eczematous reaction on skin and oral mucoa
He also concluded when completely polymerized it is no longer a sensitizer

Or elicitor of allergic reaction.
 Crissey also concluded that stomatitis venenata is a possible but
uncommon result of monomer allergy.
 Danielewicz- A. stysiak found similar results leading to conclusion that
denture sore mouth caused by hypersensitivity is possible but rare.
 Axelsson and Nyquist performed a longitudinal study to determine the
biological effect of the leaching of monomer on the oral mucosa.
Deliberately under cured dentures were followed for up to 3 years . Clinical
examination revealed what was determined to be hyperkeratosis during
the first week with no signs of inflammation,it resolved by end of one month
Investigations concluded that results did not
substantiate the opinion that residual monomer plays an essential role in
denture sore mouth.
 Spealman and associates performed cutaneous sensitization tests for
monomer on 50 medical students, one third developed mild erythema at the
site of contact due to local irritation, when tested 10 days later evidence of
allergic sensitivity was obtained in 20% of the subjects. This demonstrated
that monomer can be both a local irritant and an allergic sensitizer.

 There are well documented reports of both hyper sensitivity reaction
and local irritation caused by methyl methacrylate monomer
.Autopolymerizing acrylic resin contains a higher concentration of
residual monomer and could cause chemical injury , sensitization or
allergic reaction in a previously sensitized individual.
 A Harrison and R Huggett in 1992 did a study to find out the effect of
the curing cycle on residual monomer levels of acrylic resin denture
base polymers. Levels of residual monomer were determined on a
homopolymer and co-polymer using Gas-liquid chromatography.
A wide range of recommended and short cut curing cycles
were investigated which produced values ranging from 0.56 to
18.46%.From the ranges examined an optimum cycle of 7hr at 70 C
and 1 hr at 100 C was established which was used to polymerize 23
available synthetic denture base polymers and only small difference
were found with the material tested with a range of 0.54 to 1.08% of
residual monomer.

CURING CYLES EMPLOYED IN THE STUDY
A Recommended curing cycles
overnight water-bath cures:
1) 7hr at 70 C
2) 14hr at 70 C
3) 7hr at 70 C +1hr at 100C
4) 14hr at 70C + 1hr at 100C
Short and reverse cures:
5) Boil water,insert flask , remove heat for 20 min return to boil for 10 min.
6) Boil water ,insert flask ,return to boil, boil for 10 min.
Dry heat cure:
7)temp in excess of 100C using dry heat system
B Short curing cycles
8) 7hr at 60C
9) 7hr at 60C +1 hr at 90C
10) Boil water, insert flask remove heat for 20 min return to 90 C hold at 90C
for 5 min
11) Boil water insert flask return to 90C hold at 90C for 5min.

RESIDUAL MONOMER CONTENT OF TREVALON POLYMERIZED BY 11
DIFFERENT CYCLES
CURING CYCLE RESIDUAL MONOMER(%)
I 2.91
2 2.14
3 0.79
4 0.82
5 1.32
6 3.97
7 0.91
8 15.65
9 1.39
10 2.01
11 17.72

CONCLUSION
1 A curing cycle of 7hr at 70C followed by a terminal boil at
1hr at 100C is the optimum curing cycle resulting in max
monomer conversion.
2 Short cut curing cycles are undesirable and result in
significantly raised levels of residual monomer.
3 The residual monomer levels of 23 available denture
base polymers cured using the optimum cycle ranged
from 0.54 to 1.08%.

(II)PHYSICAL PROPERTIES
 Should possess adequate strength and resiliency and resistance to
biting and chewing forces impact forces and excessive wear in oral
cavity.
 Should be dimensionally stable under all conditions of service including
thermal changes and variations in loading.
I) Specific gravity: It should have low value of specific gravity in order that
dentures should be as light as possible.
II) Thermal conductivity: It is defined as the number of calories per second
flowing through an area of 1cm2
in which the temperature drop along
the length of the specimen is 1°C/cm.
 It should have high value of thermal conductivity
 Radiopacity: It is the inhibition of passage of radiant energy.
 It should be ideally radiopaque

 Glass transition temperature:
 It is the temperature at which molecular motions become such that
whole chains are able to move. It is close to softening temperature.
At this temperature sudden change in elastic modulus occurs.
 Amorphous polymer below Tg behave as rigid solids while above Tg
they behave as viscous liquids, flexible solids or rubbers.
 Increased chain branching  Decreased Tg.
Increased number of cross links  Increased Tg
Effect of molecular weight on properties
In many polymers the chains are held together by secondary, or Vander
Waals forces and molecular entanglement. Materials of high molecular
weight have a greater degree of molecular entanglement, and have greater
rigidity and strength and higher values of Tg and melting temperature than
low molecular weight polymers.

Effect of plasticizers
 Plasticizers penetrate between the randomly oriented chains of
polymer as a result of which molecules are further apart and forces
between them are less. They soften the material and make it more
flexible by lowering its Tg. They lubricate the movements of polymer
chains and are sometimes added to help molding characteristics.
This principle is used in producing acrylic soft lining materials.
 Effect of fillers
 Modulus of elasticity and strength are generally increased.
 A degree of anisotrophy exist, that is the strength depends on the
orientation of fibres in the polymers.
 Viscoelasticity : Polymers show viscoelastic behaviour. Elastic
behaviour is caused by uncoiling of polymer molecules. Plastic
behaviour is caused by breaking of intermolecular Vander Waals
forces

(III) MANIPULATION
 Should not produce toxic fumes or dust
 Easy to mix, insert, shape and cure and short setting time
 Oxygen inhibition, saliva and blood contamination should have little or no
effect.
 Final product should be easy to polish and easy to repair in case of
breakage.
(IV) AESTHETIC PROPERTIES
 Should be translucent to match oral tissues
 Capable of pigmentation
 No change in color after fabrication.
(v)ECONOMIC CONSIDERATION
 Cost should be low
 Processing should not require complex and expensive instruments.

(VI) CHEMICAL STABILITY
 Conditions in mouth are demanding and only the most chemically stable and
inert materials can withstand such conditions without deterioration.
“No resin has yet met all of these ideal criteria”. Methacrylate
polymers fulfill the aforementioned requirement reasonably
well.

TYPES OF DENTURE BASE POLYMERS
1)CONVENTIONAL HEAT CURED POLYMETHYL METHACRYLATE
 Supplied as powder and liquid
POWDER
 Polymer of PMMA in the form of spheres or beads.
 Benzoyl peroxide is attached to it (initiator) 0.5%
 Plasticizer is incorporated (methacrylate or acrylate monomer).
 Coloring pigments cadmium/ organic dyes/ iron are added for
esthetics.

POLYMER POWDER OF ACRYLIC DENTURE BASE MATERIAL

LIQUID
 Methyl methacrylate monomer
 Cross linking agent Ethylene glycol dimethacrylate(5-15%).they are added
to avoid crack or craze produced by stresses during drying.
 Inhibitor Hydroquinone (trace) to avoid premature polymerization and
enhance shelf life.
 When MMA polymerizes it shrinks 21% by volume.
 Using a 3:1 powder liquid ratio it could be minimized to 6%.
 A correctly heat processed denture base could have as little as 0.3% to 2%
residual monomer.

 As a rule,heat activated denture base are shaped via compression
molding technique.
Polymer monomer interaction
When polymer and monomer are mixed it passes through following stages
 Sandy
 Stringy
 Dough like
 Rubbery or elastic
 Stiff
Dough forming time
 According to ANSI/ADA specification no 12 for denture base resins requires
that this consistency be reached in less than 40 min from start of mixing
time.
 In clinical use it is achieved in less than 10 min.
Working time
 Time that a denture base remains in a dough like stage.ANSI/ADA
specification no 12 requires the dough to remain moldable for 5 min.

2)AUTOPOLYMERIZING/COLD CURE POLYMETHYL
METHACRYLATE (POUR RESIN)
 Composition same as the heat cure version with following
differences
1)The powder contains beads of polymer that have a lower molecular
wt. and benzoyl proxide (initiator)
2) The liquid contains a chemical activator ,tertiary amine such as
dimethyl-para-toluidine.
 Upon mixing tertiary amine causes decomposition of benzoyl
peroxide.
 Dentures processed have more residual monomer (1-4%),but lower
dimensional change.
 Decreased transverse strength (residual monomer act as
plastisizer).
 Compromised biocompatibility (residual monomer)
 Color stability inferior (teriaty amine susceptible to oxidation),
stabilizing agents should be added

 Fluid resin and compression molding technique can be employed for the
fabrication of denture.
 Also used as repair material

3)HIGH IMPACT RESISTANT ACRYLIC
 Similar to heat cured material but less likely to be broken if dropped.
 Produced by substituting the PMMA in the powder with a copolymer.
 Copolymer of butadiene with styrene or methyl methacrylate are
incorporated into the beads.
 Phase inversion resulting in dispersion throughout the beads of tiny islands
of rubber containing small inclusions of rubber/PMMA graft polymer.
Electron micrograph of high impact denture
Base showing size and shape of polystyrene-butadiene
Rubber inversion phase.

4) Injection molded polymers
 These are made of Nylon or Polycarbonate.
 The material is supplied as a gel in the form of a putty .
 It has to be heated and injected into a mold
 Equipment is expensive.
 Craze resistance is low .
The SR-Ivocap system uses specialized flasks and clamping presses
to keep the molds under a constant pressure of 3000 lbs

5) RAPID HEAT POLYMERIZED POLYMER
 Same as conventional material except that they contain altered
initiation system.
 These initiator allow them to be processed in boiling water for 20
min.
 A problem with these is that areas of the base thicker than
approx.6mm have a high level of porosity.
 Short duration of heating also leaves a higher level of residual
monomer,3-7 times greater than conventional heat cured denture
base.

6) MICROWAVE POLYMERIZED POLYMERS
 Resins are the same as used with conventional material and are processed
in a microwave.
 Denture base cures well in Special polycarbonate flask (instead of metal).
 The properties and the accuracy of these materials have been shown to be
as good or better than those of the conventional heat cured material.
 Processing time is much shorter (4-5 min).
Microwave resin and non metallic microwave flask

7)Light activated denture base resins
 This material is a composite having a matrix of urethane dimethacrylate,
microfine silica and high molecular wt acrylic resin monomers
 Acrylic resin beads are included as organic fillers.
 Visible light is the activator, whereas camphorquinone serves as the initiator
for polymerization.
 Can be used as repair material and as custom tray material.
 Single component denture base is supplied as sheet and rope form in light
proof pouches.
Light curing unit for polymerizing
Dimethacrylate

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

REVIEW OF LITERATURE
 F.A. Peyton and D.H. Anthony(1963) evaluated and compared denture
bases of different types of materials as well as techniques of processing.
Materials selected were:
• 4 different self – cure type
• 7 heat cure acrylic resins
• 3 special injection products
• 2 chromium cobalt alloys
• 1 epoxy type of denture plastic
• 1 vulcanite denture material
• 1 all porcelain denture base -for purpose of comparison.
 . In this study comparisons of only three principal types of materials were
presented with results reported being primarily to maxillary dentures. After
the dentures were deflasked they were stored in water for 24hours at room
temperature before the measurements were recorded, to simulate interval of
time before delivery to the patient. The dentures were evaluated for
changes in contour and fit due to the effect of aging, influence of repair, the
effect of fracture along midline, effect on contour after repairs and effect on
contour due to processing time.www.indiandentalacademy.com

 Based on the observations they concluded that:-
- The most accurate dentures were of self- cure type, followed by the
heat- cure and then the injection molded group.
- The contours of heat cured and self- cured dentures after 20 months
of water storage as compared with 24 hours and 8 months of water
storage showed few changes in contour.
- The heat cure dentures exhibited considerable change in contour
after repair by heat – curing method, but few changes with self-
curing repair. Self – cure dentures showed no changes during
repairs by either method.

 M. Braden (1964) described the absorption of water by acrylic resins and
other materials. He enumerated the kinetics of water absorption to follow the
mathematical laws of diffusion. The effect of material thickness and
temperature of water, influencing the water absorption were studied.
Based on the observations they concluded that:-
- 1.The temperature had a marked effect on the diffusion coefficient (i.e. it
increased by factor of two to three) in temperature range of 22.5ºC to
37.4ºC, but had no effect on equilibrium water content.
2.The time required to saturate or dry- out an appliance depended
markedly on temperature.
3.The water absorption and desorption processes were shown to
obey the mathematical laws of diffusion.
The time for accompanying dimensional changes could be predicted.

J.M Berrong, R.M Weed, J.M. Young (1990)
 Studied the reinforcing effect of Kevlar (synthetic aramid) fibers
incorporated in processed poly(methyl methacrylate) resin samples
using 0%(control), 1%, and 2% by weight of the added fibers. The
samples were subjected to impact testing to determine the fracture
resistance, and sample groups were statistically compared using
ANOVA (analysis of variance)and Duncan’s multiple comparisons.
Impact strength of each reinforced sample was significantly greater
than the control (3.0 kg/cm) and 2% by weight (6.3 kg/cm) showed
the highest resistance to fracture. However the Kevlar fibers had the
following disadvantages
1.Yellowish color limits its use in esthetic regions
2. Difficulty to incorporate the fibers in middle of resin and its
subsequent exposure limited its polishability in that region.
3. An advantage was that Kevlar fiber reinforced resin when
fractured, the fracture ends were united which facilitated easy
repair.

John E.Ward et al in 1992 studied the effect of repair surface design
,repair material and processing method on the transverse strength of
repaired acrylic resin.
 Transverse strength (three point bend test) of heat cured acrylic
resin( lucitone) was tested after being repaired by
1.Autopolymerizing monomer and polymer
2.Autopolymerizing monomer and heat cured polymer
 Three repair joints were studied
1 Butt
2 Round
3 45 Degree bevel
 Three processing method were used
1 Bench cure
2 Hydroflask with hot water for 10 min
3 Hydroflask with hot water for 30 min

 The strength of the repairs made with round and 45-degree bevel joint
design were similar and significantly greater than those with a butt joint
design.
 the strength of the repairs processed in a hydroflask for 10 min and 30 min
were similar and significantly greater than those cured on bench top.
 There was no difference in the strength of repairs made with
autopolymerizing monomer and heat-cured polymer.
Andreas G and G L. Polyzois in 1994 Compared the repair strength of a
heat cured and a visible light cure denture resin with an autopolymerizing
(control) and four VLC resins used as repair material.
 Flexural properties were measured and revealed that the highest strength
and toughness of joint are obtained by autopolymerizing repair material.
 VLC material exhibited lower repair strength.and toughness.
 No interaction between base and repair material was detected which was
attributed to poor adhesive bonding created at the interface.

K.Vallitu in 1997 Did a study to analyze the preliminary results from a clinical
study of electrical glass (E-glass), partial fiber reinforcement ( PFR) of
acrylic resin removable denture base.
 E- glass fiber reinforcement was evaluated for 13 months after insertion of
the fiber
 12-CD, 10-RPD, with a history of recurrent fractures were selected.
 The PFR was incorporated at the time of repair..
 One CD and and one RPD fractured in the region of reinforcement during
examination period.
 Fractures were most likely caused by faulty placement of fiber
reinforcement.
 In six dentures new fracture occurred in region without PFR.
 Result revealed the importance of correct positioning of the partial fiber
reinforcement and use of accurate lab technique.

A study was done in our college Under The Able Guidance of Dr
N.P.PATIL to see the” effect of fiber reinforcement on the
dimensional changes of polymethyl methacrylate resin after
processing and after immersion in water”.
 Study was carried out to evaluate the effect of fiber reinforcement on the
dimensional changes of heat cure poly(methyl methacrylate) resins and to
compare the dimensional changes occurring in three types of heat cure poly
(methyl methacrylate) resins after processing and after immersion on water
 Thirty temporary denture bases of uniform thickness and peripheral
extensions in respective areas were fabricated on identical maxillary
edentulous cast for each of the three group.
 Denture bases of all three groups showed contraction in the intercanine,
intermolar, and canine to molar distances on right and left side after
processing.
 The dimensional changes observed in the three groups after processing are
in the following decreasing order- Fiber glass reinforced heat cure PMMA,
High impact heat cure PMMA, Non reinforced heat cure PMMA.

 The amount of space observed between the tissues was also in the above
order.
 The denture bases after immersion in water(17 days) of all the three groups
showed expansion this comensated partly for processing shrinkage.
 Fiber glass reinforcement can be used clinically since the magnitude of
change was less than one % which seems to have little clinical significance.

A STUDY WAS DONE IN OUR COLLEGE UNDER THE ABLE
GUIDANCE OF Dr N.P.PATIL TO SEE “ TRANSVERSE AND
IMPACT STRENGTH OF A NEW INDIGENOUS HIGH- IMPACT
DENTURE BASE RESIN DPI- TUFF AND ITS COMPARISON WITH
MOST COMMONLY USED TWO DENTURE BASE RESINS”
 Three heat cure denture base resins were compared;Three heat cure denture base resins were compared;
1.1. DPI – TUFFDPI – TUFF
2.2. Lucitone 199Lucitone 199
3.3. Conventional heat cure denture base resinConventional heat cure denture base resin
 Total of 120 samples were prepared using short and long curing cyclesTotal of 120 samples were prepared using short and long curing cycles
-- 73ºC and held for 90 minutes followed by boiling at 100 ºC for 30
minutes
- In the long curing cycle the temperature was slowly raised from
room temperature to 73ºC and held for 9 hours
 They were furher divided into samples tested under dry and wet conditions.

Conclusion drawn were
 The DPI- TUFF high impact denture base resin appears to be
comparatively superior to the other two resins compared with mean
transverse strength.
 The dry strength of the samples of the materials tested show that it
is greater than after immersion of the samples in water at 37ºC for 1
week.
 The long curing cycle shows considerably higher values of
transverse and impact strength as compared to short curing cycle.

Clinical Implications
 In the study it was observed that the dry strength of samples was
higher than that of the samples tested after immersion in water. This
could probably reduce the chances of fracture during accidental
dropping of the denture while polishing and before insertion of
denture.
 The denture may be more prone to fracture after use in mouth for
considerable period of flexing or accidentally dropped during or after
its removal from the mouth.
 Lastly, although the use of long polymerizing cycle is time
consuming, it results in dentures with more fracture resistance as
compared with the use of short polymerizing cycle.

RECENT ADVANCEMENT
 Modifications of acrylic resin materials designed to improve specific
properties included.
1 plasticization,
2 copolymerization,
3.cross linking and reinforcement.
 Internal plasticization by co-polymerization may improve strength
properties.
 Cross-linking is a special case of co-polymerization. In general cross-linking
lowers strength and flexibility but increases solvent resistance, softening
point and hardness

 One disadvantage of cross-linking is the reduction of bonding between
acrylic resin teeth and the base which may occur particularly with a cold
curing base material
 Reinforcement by glass fibers is easily accomplished. This is done by
mixing discrete fibers with dough or by combination with glass cloth.
 Specially primed glass is necessary to bring out good adhesion to the
resin and to maintain it particularly in wet conditions.
 In the dough fiber method, the percentage of glass which can be
incorporated is limited to about 20% by weight because of reduction of flow
of the dough.

Alternatives to methacrylate materials
 Most alternatives to polymethacrylate are vinyl acrylic, polysterene, acrylic
styrene, acrylonetrile copolymers .
NEW PLASTIC MATERIAL
 High impact methacrylates (IM): These are basically similar to standard
methacrylate but have a higher impact and fatigue strength.
 Epoxy resins (E): The general properties of these materials are strength,
hardness, toughness, low curing shrinkage and good adhesion to metals.
The disadvantages for dental use are the toxicity, the yellow colour which
darkens further, high water absorption, poor adhesion to vinyl polymers

 Nylon materials: They were found to be unsatisfactory for denture base
because of high molding shrinkage which led to warpage, high water
absorption and yellowing.

 High impact polystyrene (IS): This is an elastomer graft copolymer with
styrene. It is basically similar to polysterene and injection molded in a similar
way.
 High density polythene (DE): This is stiffer stronger variety of polyether.
 Polypropylene (PP): this is a hydrocarbon polymer similar to polyethylene
but stiffer and stronger.
 Polyacetal (A): Also called polyformaldehyde. It has lower water absorption
with good resilience and toughness, and resistance to fatigue

 Polycarbonate (PE): It is thermoplastic material with low water absorption
and very high impact strength and toughness.
 Chlorinated polyether: It has very low water absorption and low mold
shrinkage with excellent resistance to staining and chemical agents
 Eclipse prosthetic resin system is a new method of fabricating dentures
from Dentsply International. It is being marketed as an indirect build-up
method for fabricating dentures that is monomer-free and flask-free. Eclipse
is a light-cured system that does not contain any ethyl-, methyl-, butyl-, or
propyl-methacrylate monomers.
 System uses three resins to form the denture: Baseplate Resin, Set-up
Resin and Contour Resin. The resins were developed to handle like wax,
yet be cured into a denture base material – without investing and flasking.

 VALPLAST -
Valplast is a flexible denture base resin that is ideal for partial dentures and
unilateral restorations.
 The resin is a biocompatible nylon thermoplastic ,it eliminates the concern
about acrylic allergies.

Conclusion

REFERENCES:
 Kenneth j. Anusavice ; Phillips Science of dental material .Eleventh
edition, Elsevier,2004.
 Jack L. Ferracane ; Materials in Dentistry principles and application.
Second edition ,Lippincot williams, 1995.
 William J. O’Brien; Dental materials and their selection. Third edition,
quintessence Publishing co. 2002.
 Robert C. Craig John M. Powers, John C.Wataha ;Dental materials
properties and manipulation,. Eight edition,2004.
 Robert L.Engelmeier; The dental clinics of North America-complete
dentures, W B Saunders company jan 1996 vol.40 no.1
 J.W. Nicholson; The chemistry of medical and dental materials, First
edition RS.C 2002.
 Peyton F.A., Anthony D.H., 1963: “Evaluation of dentures processed by
different techniques”. J. Prosthet Dent.; March – April 13(2): 269-282.
 Braden M., 1964: “The absorption of water by acrylic resins and other
materials”. J Prosthet Dent.; March/April 14(2): 307-316
 Vallitu .P.K 1997 “Glass fiber reinforcement in repaired acrylic resin
removable dentures: Priliminary result of a clinical study.” Quintessence
Int;28:39-44.

 Patil N .P and Hedge VK 1996,”comparative evaluation of the effect of
palatal vault configuration on dimensional changes in complete dentures
during processing as well as after water immersion”.Dissertation submitted
to Rajiv Gandhi univ of health sciences,karnataka.
 John E .Ward et al; 1992; effect of repair surface design, repair material,and
processing method on the transverse strength of repaired acrylic resin.
 Andreas G.A and G.L.Polyzois,1994;”Repair of denture base resin using
visible light cured materials”.J Prostho Dent; 72:462-8
 Patil N P and Arundhati N Raj 2004 “ TRANSVERSE AND IMPACT
STRENGTH OF A NEW INDIGENOUS HIGH- IMPACT DENTURE BASE RESIN
DPI- TUFF AND ITS COMPARISON WITH MOST COMMONLY USED TWO
DENTURE BASE RESINS” Dissertation submitted to Rajiv Gandhi univ of health
sciences,Karnataka.
 Melvin E Ring ; ,An illustrated history of dentistry.1985

THANK YOU

Non metallic denture base material / dental crown & bridge courses

Empfohlen

Empfohlen

Weitere ähnliche Inhalte

Was ist angesagt?

Was ist angesagt? (20)

Andere mochten auch

Andere mochten auch (20)

Ähnlich wie Non metallic denture base material / dental crown & bridge courses

Ähnlich wie Non metallic denture base material / dental crown & bridge courses (20)

Mehr von Indian dental academy

Mehr von Indian dental academy (20)

Kürzlich hochgeladen

Kürzlich hochgeladen (20)

Non metallic denture base material / dental crown & bridge courses