Assoc. prof. T. Uzunov, PhD

THE RESINS ARE

POLYMERS

The term "polymer" derives from the Greek word πολύς (polus,

meaning "many, much") and μέρος (meros, meaning "part"), and

refers to a molecule whose structure is composed of multiple

repeating units, from which originates a characteristic of high

relative molecular mass and attendant properties.

CHEMICAL REACTION

THE RESINS ARE

POLYMERS Synthesis of polymers

A classification of the polymerization reactions: Step-growth, Chain-growth and others.

THE RESINS ARE


STEP-GROWTH POLYMERIZATION

In step-growth (or step) polymerization, each step may

involve the combination of two polymer molecules of any

lengths to form a longer polymer molecule.

The average molar mass increases slowly and long chains

are formed only late in the reaction.

Step-growth polymers are formed by independent reaction

steps between functional groups of monomer units, usually

containing heteroatoms such as nitrogen or oxygen. Most

step-growth polymers are also classified as condensation

polymers , since a small molecule such as water is lost

when the polymer chain is lengthened.

THE RESINS ARE


CHAIN-GROWTH POLYMERIZATION

In chain-growth (or chain) polymerization, the only chain-extension

reaction step is the addition of a monomer to a growing chain with

an active center such as a free radical or ion.

Once the growth of a chain is initiated by formation of an active

center, chain propagation is usually rapid by addition of a sequence

of monomers. Long chains are formed from the beginning of the

reaction. Chain-growth polymerization (or addition

polymerization) involves the linking together of molecules

incorporating double or triple carbon-carbon bonds. These

unsaturated monomer have extra internal bonds that are able to

break and link up with other monomers to form a repeating chain,

whose backbone typically contains only carbon atoms.

THE RESINS ARE


Step-growth versus chain-growth

polymerization

1. CONDENSATION POLYMERIZATION

A condensation polymerization is a form of step-growth polymerization.

Small molecules react with each other to form larger structural units while

releasing smaller molecules as a byproduct, such as water or methanol.

THE RESINS ARE


CHEMICAL REACTION

large polymerization shrinkage

2. ADDITION POLYMERIZATION

An addition polymer is a polymer that forms by simple linking of monomers without the

co-generation of other products. Addition polymerization differs from condensation

polymerization, which does co-generate a product, usually water. Addition polymers

can be formed by chain polymerization, when the polymer is formed by the sequential

addition of monomer units to an active site in a chain reaction, or by polyaddition,

when the polymer is formed by addition reactions between species of all degrees of

polymerization.

THE RESINS ARE


CHEMICAL REACTION

less

polymerization

shrinkage

INITIATORS

HEAT IONIZING

RADIATION

ULTRAVIOLET RAYS

CHEMICAL REACTION

MONOMER POLYMER

INITIATED POLYMERIZATION

INITIATORS

Benzoyl peroxide

(С6Н5СОО)2 HEAT

ACTIVATOR

DMPT

BENZOILS AND

PHENYLS

FREE RADICALS


CHEMICAL REACTION

1. Activation of monomer molecules by active

radicals

2. Growth of the polymer chain by

attachment of other activated monomer

molecules

3. Complete polymerization by saturating the

end of the polymer chain with another active

radical


The degree of polymerization

The degree of polymerization, or DP, is the number of

monomeric units in a macromolecule or polymer or oligomer

molecule.

Increasing degree of polymerization correlates with

higher melting temperature, higher mechanical strength

and better biological properties.

DEGREE OF

POLYMERIZATION

MECHANICAL

PROPERTIES

BIOLOGICAL

PROPERTIES


DEGREE OF

POLYMERIZATION MECHANICAL

PROPERTIES

Increasing degree of polymerization correlates with

higher melting temperature, higher mechanical strength

and better biological properties.


Increasing degree of polymerization correlates with the

speed of polymerization.

DEGREE OF POLYMERIZATION

SPEED OF POLYMERIZATION

1. HARD (glassy) /ACRYLIC RESINS /

2. ELASTIC (rubbery) /ELASTOMERS/

TYPES OF POLYMERS

According to the degree

of cross-linking and their mechanical properties:

TYPES OF POLYMERS

According to the mode of activation of the

Benzoyl Peroxide (the initiator):

SELF-CURING RESINS

HEAT-CURING RESINS

LIGHT-CURING RESINS

SELF/LIGHT-CURING RESINS

Type Class (manufacturing) Group (presentation form)

Type 1 Thermopolymerizable resins

(>65°C)

Group 1: bicomponent powder and liquid

Group 2: monocomponent

Type 2 Autopolymerizable resins (<65°C) Group 1: bicomponent powder and liquid

Group 2: bicomponent powder and

casting liquid

Type 3 Thermoplastic resins Monocomponent system grains in

cartridges

Type 4 Light-cured resins Monocomponent system

Type 5

Microwave cured resins

Bicomponent system

The classification of resins according to DIN EN ISO 1567

Since the mid-1940s, the majority of denture bases has been fabricated using polymethyl methacrylate resins.

ACRYLIC RESIN

Pure polymethyl methacrylate is a colorless transparent solid. To facilitate its use in dental applications, the polymer can be tinted to provide almost any color, shade, and degree of

translucency.

ACRYLIC RESIN

Polymethyl methacrylate denture base material is commonly supplied as a powder-liquid system.

• The liquid contains mostly nonpolymerized methyl methacrylate

• The powder contains predominantly prepolymerized polymethyl methacrylate resin in the form of micro-sized beads (or spheres).

ACRYLIC RESIN

HEAT-ACTIVATED ACRYLIC RESIN

Съдържат:

LIQUID POWDER

MAIN COMPONENT

Methyl ester of methacrylic acid – methyl

methacrylate / ММА/

MAIN COMPONENT

Polymethyl ester of methacrylic acid –

polymethyl methacylate (PMMA)

CROSS-LINKING AGENT 5-15%

ethyleneglycol dimethacrylate /EGDMA/

triethyleneglycol dimethacrylate /TEGDMA/

INITIATOR – 0,2-0,5%

benzoyl peroxide

INHIBITOR – 0,005%

hydroquinone

Plasticizer – 5%

dibutyl phtalate /DBPh/ - limits the cross-linking

of the polymer

OPACIFIERS (OPAQUERS) – 0,5 - 1,5%

zinc oxide, titanium dioxide

Color agents

organic

non-organic

ACRYLIC RESIN

1.SANDY

When the

liquid and powder are

mixed in the proper

proportions (3:1 )

workable mass is

formed. Upon

standing, the resultant

mass passes through

five distinct stages.


ACRYLIC RESIN

Stages of polymerization:


2. STRINGY


ACRYLIC RESIN

3. DOUGH-LIKE

On a molecular level, an

increased number of polymer

chains enter the solution. Thus,

monomer and dissolved

polymer are formed.



ACRYLIC RESIN

It is important to note that a large quantity of swollen,

but undissolved polymer also remains. Clinically, the mass

behaves as a pliable dough. It is no longer tacky and does

not adhere to the surfaces of the mixing vessel or spatula.



ACRYLIC RESIN

3. DOUGH-LIKE

The physical and chemical characteristics exhibited

during the later phases of this stage are ideal for

compression molding. As a result, the material

should be introduced into the mold cavity during the

latter phases of the doughlike stage.

4. RUBBERY

(ELASTIC)



ACRYLIC RESIN

5. STIFFY



ACRYLIC RESIN

COMPRESSION MOLDING TECHNIQUE


ACRYLIC RESIN

A cross-sectional

representation of the denture

flask and its contents.

As a rule, heat-

activated denture

base resins are

shaped via

compression

molding.



ACRYLIC RESIN

At this stage, the master cast and

completed tooth arrangement are

removed from the dental articulator

The lower portion of a denture flask

is filled with freshly mixed dental

stone, and the master cast is placed

into this mixture. Upon reaching its

initial set, the stone is coated with

an appropriate separator.



ACRYLIC RESIN

The upper portion of the selected

denture flask is then positioned

atop the lower portion of the flask.

The dental stone is poured into

the denture flask. Care is taken to

ensure that the investing

stone achieves intimate contact with

all external surfaces of the

mounted teeth. The investing stone

is added until all surfaces

of the tooth arrangement and

denture base are completely

covered.



ACRYLIC RESIN

The lid of the flask is gently seated and the

stone is allowed to harden

After the stone has hardened, the record

base and wax must be removed from the

mold. To accomplish this task, the denture

flask is immersed in boiling water for 4

min.

The flask is then

removed from the water

and the appropriate

segments are

separated.



ACRYLIC RESIN

The record base and softened

wax remain in the lower portion

of the denture flask while the

prosthetic teeth remain firmly

embedded in the investing

stone of the remaining

segment.

The record base and softened wax are carefully removed

from the surface of the mold. Residual wax is removed from

the mold cavity using wax solvent. The mold cavity is

subsequently cleaned with a mild detergent solution and

rinsed with boiling water.



ACRYLIC RESIN

The placement and

adaptation of denture

base resin within

the mold cavity are

termed packing.

In a doughlike state, the resin is removed from its

mixing container and rolled into a ropelike form. Monomer

is painted over the necks of the denture teeth to promote

bonding to the denture base. Subsequently, the resin form is

bent into a horseshoe shape and placed into the portion of

the flask that houses the prosthetic teeth



ACRYLIC RESIN

The flask assembly is placed

into a specially designed flask

press and pressure is applied

incrementally.

Slow application of pressure

permits the resin dough to flow

uniformly throughout the mold

space.

Excess material is displaced

eccentrically. The application of

pressure is continued until the

denture flask is fully closed.



ACRYLIC RESIN

The flask is transferred to a

flask carrier.

The flask carrier maintains

pressure on the flask assembly

during denture base

processing.



ACRYLIC RESIN

The heating process used to control polymerization is termed

the polymerization cycle or curing cycle. This process

should be carefully regulated to avoid the effects of

uncontrolled temperature rise.



ACRYLIC RESIN

PURPOSES OF HEAT POLYMERIZATION:

1. OPTIMAL ACTIVATION OF THE INITIATOR - 60 – 80 °C

2. THE EXOTHERMIC PROCESS SHOULD NOT CAUSE

BOILING OF THE MONOMER /ABOVE 100,3 °C /

3. ADDITIONAL HEAT POLYMERIZATION OF THE

REMAINING FREE MONOMER AFTER THE EXHAUSTION OF THE

BENZOYL PEROXIDE

Chemical activation is accomplished through the

addition of a tertiary amine, such as dimethyl-

para-toluidine, to the denture base liquid (i.e.,

monomer). Upon mixing of the powder and liquid

components, the tertiary amine causes

decomposition of benzoyl peroxide. As a result,

free radicals are produced and polymerization is

initiated.

SELF-CURING ACRYLIC RESIN

ACRYLIC RESIN

Used for:

Denture Repairs


ACRYLIC RESIN


Съдържат:

LIQUID POWDER

MAIN COMPONENT

Methyl ester of methacrylic acid – methyl

methacrylate / ММА/

MAIN COMPONENT

Polymethyl ester of methacrylic acid –

polymethyl methacylate (PMMA)

CROSS-LINKING AGENT 5-15%

ethyleneglycol dimethacrylate /EGDMA/

triethyleneglycol dimethacrylate /TEGDMA/

INITIATOR – 1,5%

benzoyl peroxide

INHIBITOR – 0,005%

hydroquinone

Plasticizer – 5%

dibutyl phtalate /DBPh/ - limits the cross-linking

of the polymer

ACTIVATOR – 0,75%

Dimethyl par toluidine /DMPT/

OPACIFIERS (OPAQUERS) – 0,5 - 1,5%

zinc oxide, titanium dioxide

Color agents

organic

non-organic

ACRYLIC RESIN

As might be expected, denture bases

fabricated using chemically activated

resins and heat-activated resins are quite

similar.

Five stages of changing consistency

They are not packed in gypsum molds

They polymerize without pressure


ACRYLIC RESIN

The fundamental difference between

heat-activated resins and

chemically activated resins is the

method by which benzoyl peroxide is

divided to yield free

radicals. All other factors in this

process (e.g., initiator and

reactants) remain the same.


ACRYLIC RESIN


ACRYLIC RESIN

The degree of polymerization achieved using

chemically activated resins is not as complete as

that achieved using heat-activated systems.

1. Initial hardening of the

resin generally will

occur within 30 min but

polymerization continues

for an extended period.

PROCESSING CONSIDERATIONS

Applied in limited areas –

denture repairs


ACRYLIC RESIN

Apparatus for hydro-pneumatic

polymerization

The polymerization is carried out in a

water bath at a pressure of 2-6 atm at

93-1150C for 10-15 minutes.

To ensure sufficient

polymerization, the

flask should be held

under pressure for a

minimum of 3 hours.


ACRYLIC RESIN

MECHANICAL, PHYSICAL AND

BIOLOGICAL PROPERTIES OF ACRYLIC

RESINS

OPTIMAL when:

1. The monomer-to-polymer ratio is correct

2. Using the resin in the dough-like stage

3. Strictly following the recommended heat-curing cycle

4. Maintaining the pressure on the gypsum molds during the

polymerization process

MECHANICAL PROPERTIES

Comparative analysis

HEAT

ACTIVATED

CHEMICALLY

ACTIVATED

DEGREE OF POLYMERIZATION 2500 1800

HARDNESS - ВН N 20 16

ELASTIC MODULUS - МРА 3800 2600

WEAR RESISTANCE HIGHER LOWER

PHYSICAL PROPERTIES

VOLUMETRIC CHANGES

WATER ABSORPTION (IMBIBITION)

INTERNAL STRESSES

SOLUBILITY

POROSITY

COLOR RESISTANCE

PHYSICAL PROPERTIES

VOLUMETRIC CHANGES

VOLUMETRIC CHANGES - SHRINKAGE

POSSIBLE INACCURACY OF THE PROSTHETIC CONSTRUCTIONS

MONOMER 0,945 g/cm2

POLYMER 1,16 – 1,18 g/cm2

relative density

MONOMER - POLYMER 21%

RESIN DOUGH - POLYMER 5%

If the resin is heat-activated or

hydropneumatically polymerized 0,5%

reduction up to

PHYSICAL PROPERTIES

VOLUMETRIC CHANGES

VOLUMETRIC CHANGES - SHRINKAGE

reduction up to

reduction up to

PHYSICAL PROPERTIES

VOLUMETRIC CHANGES


Water absorption is the property of materials to absorb liquids.

Imbibition is measured by the weight of the maximum amount

of water absorbed by a unit area of a given material and is

presented as WATER SORPTION in mg/cm2

PHYSICAL PROPERTIES

VOLUMETRIC CHANGES


The repeating change of

imbibition and drying causes

internal tension and fatigue of

the material.

Care should be taken for the

removable dentures.

PHYSICAL PROPERTIES

VOLUMETRIC CHANGES


Possibility for endogenic

discoloration

Compensates for the

shrinkage of resins.

Acrylic resins – expansion 0,04 %

PHYSICAL PROPERTIES

VOLUMETRIC CHANGES


INTERNAL STRESSES

DEFORMATIONS OF THE POLYMER STRUCTURE

Breaking of the covalent, hydrogen and

Van der Waals bonds

Fatigue /aging/of resins

PHYSICAL PROPERTIES

VOLUMETRIC CHANGES


INTERNAL STRESSES

REASONS

The difference in the thermal volumetric changes of the

resin and the volumetric changes of the metal and

porcelain elements of the prosthetic construction

PHYSICAL PROPERTIES

VOLUMETRIC CHANGES


INTERNAL STRESSES

SOLUBILITY

Solubility is the reduction of materials’ volume when they are in contact

with liquids – solvents.

It causes the change in the shape, the dimensions and the properties of

dental materials in the mouth.

Solubility occurs during the materials’ contact with the oral fluids

(solvents) – saliva, gingival fluid, dentin fluid

PHYSICAL PROPERTIES

VOLUMETRIC CHANGES


INTERNAL STRESSES

SOLUBILITY

In water and saliva

the free monomer

the plasticizers

in organic solvents

acrylic resins are soluble

PHYSICAL PROPERTIES

VOLUMETRIC CHANGES


INTERNAL STRESSES

SOLUBILITY

POROSITY

Micropores exist even in the best processed and polished

acrylic resin:

1. They retain food particles and microorganisms

2. Cause exogenic discoloration

3. Increase with the aging of the resin

PHYSICAL PROPERTIES

VOLUMETRIC CHANGES


INTERNAL STRESSES

SOLUBILITY

POROSITY

The pressure applied during

polymerization reduces the resins’

porosity.

PHYSICAL PROPERTIES

VOLUMETRIC CHANGES


INTERNAL STRESSES

SOLUBILITY

POROSITY

COLOR RESISTANCE

EXOGENIC DISCOLORATION - DUE TO POROSITY

ENDOGENIC DISCOLORATION - OXIDATION OF THE ACTIVATOR (chemically-

activated resins)

)

BIOLOGICAL PROPERTIES OF ACRYLIC RESINS

TOXICITY

ALLERGENIC POTENTIAL

TOXICITY OF ACRYLIC RESINS

RESIDUAL MONOMER

RESINS FOR HYDROPNEUMATIC

POLYMERIZATION - 0,3 %

HEAT-ACTIVATED RESINS - 0,5 %

CHEMICALLY- ACTIVATED RESINS - 5 %

QUALITATIVE REACTION FOR DETECTION OF RESIDUAL

MONOMER EXCEEDING 3%


REMOVAL OF THE RESIDUAL MONOMER 1. Under flowing water


REMOVAL OF THE RESIDUAL MONOMER 1. Under flowing water

2. By additional heat polymerization


ALLERGENIC POTENTIAL OF ACRYLIC

RESINS:

RESIDUAL MONOMER

COLOR AGENTS / Cd- salts /

OPAQUERS

INITIATOR

ACTIVATOR

INHIBITOR

BENZOYL PEROXIDE, HYDROQUINONE

RESIDUAL MONOMER

SOFT DENTURE LINERS

SOFT DENTURE LINERS

Denture Reline

is a restoration of the

fitting surface between

the denture and the

mouth tissue. It’s an

effective way to improve

the fit and extend the life

of dentures. They

improve stability and

seal off space between

the mouth and the

denture from food

particles.

• Stable bonding to the denture base

• Preservation of their elasticity,

color and volume over time

• Smooth surface

Requirements:

• ACRYLIC

• VINYL SILICONE

• POLYPHOSPHAZENE

According to the chemical composition of the polymer

I. 30 up to 60 % plasticizer -

dibutylphtalate

II. Hydroxyethyl methacylate

/НЕМА/

ACRYLIC

- Have a strong chemical bond with the PMMA prosthetic base.

- Their elastic properties are rapidly reduced due to the solubility and

loss of plasticizer

- The material hardens, becomes highly porous, the accumulation of

dyes and bacterial plaque increases.

Coe-Soft Denture

Reline Material

ACRYLIC

- The linear polymer chain of polydimethylsiloxane is extended and partially

crosslinked by polymerization - the material acquires an elastic consistency.

- The connection to the prosthetic base is weak, mechanical and requires pre-

bonding and application of special adhesives.

- The surface of the silicone materials is very smooth and the elasticity

remains long.

SILICONE

SILICONE

Creation of mechanical retentions

Application of adhesive

Application of lining material

Compression of the prosthesis with

the lining material Cutting off excess material

Application of sealing varnish

SILICONE

POLYPHOSPHAZENE

Based on polyphosphazene (PNF)

synthetic rubber, NOVUS is

radiopaque, permanently resilient, and

absorbs energy from chewing.

- It also has low water absorption

and resists fungal growth.

- NOVUS comes in individually

sealed “patties” with an

unlimited shelf life if refrigerated.

- During laboratory processing,

NOVUS chemically bonds to

fresh denture acrylics

THERMOPLASTIC RESINS

THERMOPLASTIC RESINS

Thermoplastic resins and co-polymers have many advantages

over conventional powder or liquid resin systems:

- Thermoplastic resins tend to have predictable long-term

performance

- They also exhibit high creep resistance and high fatigue

endurance as well as excellent wear characteristics and

solvent resistance.

- Thermoplastic resins typically have very little or almost no

free monomer in the material. A significant percentage of the

population is allergic to free monomer and these materials

offer a new safe treatment alternative for these individuals.

- Thermoplastic materials have almost no porosity, which

reduces biologic material build up, odors, and stains and

exhibit higher dimension and color stability.

INDICATIONS FOR THERMOPLASTIC RESINS At present, due to successive alterations in the chemical composition,

thermoplastic materials are suitable for manufacturing:

1. Metal-free removable partial

dentures

Dental Valplast Dentures

INDICATIONS FOR THERMOPLASTIC

RESINS

2. Partial denture frameworks

Zirlux Acetal is a semi-flexible, tooth colored material is ideal for partial denture

frameworks and other metal-free removable applications.

3. Complete dentures

4. Temporary or provisional

crowns and bridges

5. Orthodontic appliances,

flexible myofunctional therapy

devices

Zirlux Acetal - Temporary

provisional crowns and

bridges.

Flexite M.P.- complete dentures


RESINS

6. Splints

7. Mouth guards

8. Anti-snoring

devices


RESINS

CLASSIFICATION OF THERMOPLASTIC

RESINS

1. THERMOPLASTIC ACRYLIC

2. POLYCARBONATE RESINS

3. POLYAMIDES (NYLON) RESINS

4. POLYOLEFINS RESINS

5. POLYOXY-METHYLENE (ACETAL) RESINS

6. POLYETHERETHERKETONE (PEEK) RESINS

7. ) )

• Thermoplastic acrylic has poor impact resistance,

but has adequate tensile and flexural strength for a

variety of applications.

• The material is easy to adjust, handle and polish. It

is relineable and repairable at the chair-side.

• Like most thermoplastic resins, acrylic resin is also

strong, resists fracturing, and is flexible.



RESINS


- However, acrylic does not wear as well as acetal

during occlusal forces and consequently will not

maintain vertical dimension over long periods of

time.

- Thermoplastic acrylic is

available in both tooth

and gingival colors, and

has both translucency

and vitality, providing

excellent esthetics.


RESINS

Flexite M.P. contains fully

polimerized acrylate, its

base component is methyl-

metacrylate. This material

was developed for making full

dentures, it doesn’t behave elastic,

but being a bit elastic, it is

practically unbreakable. It can be

polished easily.

Flexite M.P. has a surface

hardness of 55-65, making it

popular for bruxism appliances as

well as dentures.



RESINS


Polycarbonate is a polymer chain of bisphenol-A

carbonate. It is a popular material and has been used

in dentistry for a long time as preformed temporary

crown shells.


RESINS

- Polycarbonate resin is very strong, resists fracturing, and is quite flexible.

- However, polycarbonate does not wear as well as Acetal during occlusal

force and consequently will not maintain vertical dimension as long.

- The material has a natural translucency and finishes very well, yielding

excellent esthetics.

- Polycarbonate is ideally suited for provisional crowns and bridges but not

suitable for partial denture frameworks.



RESINS

- Nylon is a resin derived from diamine and dibasic acid monomers.

- Because of its excellent balance of strength, ductility and heat

resistance, nylon is an outstanding candidate for metal replacement

applications. However, in dentistry, because of its inherent flexibility, it is

used primarily for flexible tissue born partial dentures.

- Nylon is specially indicated for patients allergic to methyl metacrylate,

being monomer-free.

- Thermoplastic nylon is injected at temperatures from 274 to 293

degrees Celsius.



RESINS

- Nylon exhibits high physical strength, heat resistance and chemical

resistance. It can be easily modified to increase stiffness and wear

resistance.

- Nylon is a little more difficult to adjust and polish.

- The resin can be semitranslucent and provides excellent esthetics for

flexible tissue born partial dentures.

- It does not have enough strength to use for occlusal rest seats, and

won’t maintain vertical dimension when used in direct occlusal forces.

Removable partial

denture of polyamide

combined with metal



RESINS

Vertex ™ ThermoSens is a

thermoplastic material to be used

for dental prothesis. The product

is based on a compounded

mixture of Polyamide and

pigments. Because Vertex™

ThermoSens is on a

polyamide basis and to be used

as a thermoplastic in the injection

technique, the product is suitable

for people allergic for residual

monomer, since the product

doesn’t contain residual

monomer.



RESINS


This group includes thermoplastic materials such as polybutene,

polyethylene, polypropylene. These are flavorless, inodorous, amorphous,

non-toxic polymers.

- Due to their good mechanical and aesthetic qualities they are

popularly utilized in dentistry.

- The most used member of this group is polypropylene - a semi-

crystalline transparent polymer with stable colour, that does not absorb

liquid.

- Polypropylene has a

molecular weight between

75,000 and 200,000 and

has high wear resistance.

It is indicated for partial

removable dentures,

temporary dentures and

implant supported dentures.


RESINS

Partial dentures made with

iFlexTM can be very thin and

flexible yet durable and are

designed to give long term

performance under normal

usage. iFlex™ is biocompatible,

and ideal for patients that are

allergic to monomers found in

acrylic dentures.



RESINS

5. POLYOXY-METHYLENE (ACETAL) RESINS

Thermoplastic acetal is a poly(oxy-methylene)-based material,

which as a homopolymer has

good short-term mechanical properties but as a copolymer has

better long-term stability

Due to its resistance to wear and fracture,

combined with a certain amount of

flexibility, acetal resin is an ideal material

for:

- partial denture frameworks,

- preformed clasps for partial dentures,

- provisional bridges,

- occlusal splints ,

- implant abutments,

- artificial teeth for removable dentures

- orthodontic appliances


RESINS


Polyetheretherketone (PEEK) material is a polycyclic, aromatic,

thermoplastic polymer that is semi-crystalline and has a linear

structure.

- PEEK has good mechanical and

electrical properties such as

resistance to high temperature and

resistance to hydrolysis.

- When PEEK material and

components are examined, no

evidence has been shown of

cytotoxicity, mutagenicity,

carcinogenicity or immunogenicity in

the toxic form

- The most characteristic property

of PEEK material is that it has a

low elasticity modulus, close to

that of bone.


RESINS

- PEEK is used in dentistry as an

alternative to metal braces and

hooks in removable partial

prostheses.

- In comparison with chrome-

cobalt-based partial prostheses,

PEEK hooks have been shown to

have lower retentive strength.




structure.


RESINS

- They eliminate metallic taste and

allergic reactions, can be well

polished and have low plaque

retention.

- As PEEK is white in color and has

high resistance, it can be used in the

preparation of metal braces and

hooks.



structure.



RESINS

INJECTION TECHNIQUE IN MANUFACTURING

COMPLETE AND REMOVABLE PARTIAL DENTURES

The use of thermoplastic

resins in dental medicine is

continuously growing. The

material is thermally

plasticized and no chemical

reaction takes place.

The injection of

plasticized resins

into a mold represents a

new technology in

manufacturing complete

and removable partial

dentures.



Injected under HEAT

No Shrinkage /

No Distortion

The SR Ivocap system is

based on a special injection

technique that is capable of

compensating for chemical

shrinkage. Controlled

heat/pressure

polymerization

compensates for acrylic

shrinkage by pressure

feeding additional material

into the mould.



Assoc. prof. T. Uzunov, PhD

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Transcript of Assoc. prof. T. Uzunov, PhD