1. Dental composite
History and development
Resins have certain qualities that justify their use as a
dental restorative material. The first resin system used in
dentistry were primarily poly (methylmethacrylate)and are
often referred to as acrylic resins.
Acrylic resin for anterior restoration was developed in
Germany in the late 1930,but not marked until 1940
because of the second world war .when first placed ,they
had excellent esthetic characteristic ,insolublein oral fluid
and had low molecular weight polymers and lacked the
reinforcement provided by the ceramic filler particles,so
2. the acrylic restoration were not strong enough to support
occlusal load and have a high polymerization shrinkage
,high coefficient of thermal expantion ,very poor
resistance to abrasion ,significant tendency to discolored
and are not anticariogenic.
In an effort to improve physical characteristics of unfilled
resin ,Bowen 1962 ,developed a polymeric dental
restorative material reinforced with silica particles which
become the bases of restorations that are generically
termed composite .
The development of filled resin or composite resulted in
higher mechanical properties ,lower coefficient of thermal
expantion ,lower dimentional changes on setting and
higher abrasion than unfilled resin.
Early composite contained a large spherical filler particles
(20-30Mm),following by products having filler particular
with diameter of 0.04 Mm.composite resins continue to
evolve with the development of smaller average particle
size fillers.Another direction in the development has been
to refine resin chemistory ,activation system,adhesive
agents to reduse polymrrization shrinkage and to improve
color stability ,polymerization homogeneity and depth of
cure.
3. The use of composite resin was generally to confined to
anterior or non stress bearing locations such as (class
1,5,4restorations).The improved strength ,hardness and
modulus of elasticity of some of newer compsoite resins
,with low thermal conductivity and superior esthetic
,indicate that they might serve as a suitable replacement
for amalgam in the restoration of occlusal surfaces in
posterior teeth (class1,2 restoration)when esthetic is
primary concern and the size of restoration is
conservative.
Composition
Composite restoration consist of three phases:
1-Matrix phase(oligomers)
4. The most common organic materials are based on
(dimethacrylate as Bis-GMSresin or Urethane
dimethacrylate)these oligomers viscous ,sticky materials
and require dilution ,so a lower molecular weight
monomers such as triethylene glycol dimethacrylate are
added to control the consistency of composite paste.
2-Dispersed phase(filler composition)
The effect of matrix resin system on occlusal wear was
smaller than the filler system .The( type, consentration,
particle size and distribution)of the filler composite
material are major factors affecting used in properties.
5. The advantages of incorporating filler:
1-To reduce coefficient of thermal expantion
2-To improve abration resistance
3-to improve optical properties
4-Mechanical properties such as compression
strength, tensile strength, modulus of elasticity are
also improved.
Current Composite Restorative Materials
Composite resin materials are currently available as
microfilled,
(micro)hybrid, and nanofilled composites. Their chemistry
is
typically based on bisphenol-a-glycidyl dimethacrylate
(Bis-
GMA); however, additive chemistry has been used to
reduce polymerization shrinkage or stress, and the addition
of various
sizes and types of fillers has altered physical and esthetic
properties.
Pre-polymerized clusters and increased filler load help
reduce
polymerization shrinkage and stress, and increasing filled
load also
6. results in a higher viscosity composite. Each composite
type offers
advantages specific to its chemistry. An understanding of
these is
necessary to select an appropriate material for clinical
procedures.
Microfilled Composite Resins
Microfilled composite resins contain crushed particles
ranging in
size from 0.04 to 1 micron. The filler particles are typically
prepolymerized
particles comprised of resin and fumed silica. Filler load
is lower in microfilled composite resins, and internal
bonding between
the matrix resin and the prepolymerized filler resin is weak,
resulting in lower strength. This is an important
consideration in
stress-bearing areas. The very small particle sizes in
microfilled
resins, however, offer excellent esthetics with high
polishability
and a long-lasting surface gloss.
Microhybrid/Hybrid Composite Resins
Microhybrid composite resins contain silicon dioxide filler
with
particles ranging in size from approximately 0.04 up to
0.1micron,
and glass particle fillers typically range in size from 0.4 to
0.6
micron (400 to 600 nm). These resins lose their high polish
over
7. time with the development of a rougher surface, reducing
their
suitability for esthetically demanding cases. They do,
however,
offer strong physical properties and are suitable for stress-
bearing
restorations. Hybrid resins have slightly larger filler sizes
than do
microhybrid resins and essentially behave in the same
manner.
Nanofilled Composite Resins
Nanofilled composite resins have a high filler load in order
to
obtain strength and wear resistance similar to that of
microhybrid
composite resins. Nanofilled composite resins contain
smaller particles of filler in the range of 0.02 to 0.1
microns.
One nanofilled composite (Filtek Supreme Plus) contains
nanofiller particles that are approximately 0.02 microns in
diameter, sintered into nanoclusters of 0.6 to 1.4 microns
that
contain zirconia/silica particles, in order to improve
physical
characteristics
8. Latest Developments in Composite Resins
Recent developments in composite resin technology have
included
reductions in polymerization shrinkage and in
polymerization
stress. These have been achieved through increased filler
loads
and novel chemical technology. Polymerization shrinkage,
and
therefore stress, has been reduced through the use of
siloranering-
based chemistry as well as by increasing conversion rate
of the monomer.
Direct reduction of polymerization stress
has now also been achieved through the use of a
polymerization
9. modulator to reduce stress.
A recent development has improved
esthetics in a high-strength, esthetic nanofilled composite.
Changes in the synthesis of nanoclusters in nanofilled
composite
resin have demonstrated improved polish retention and
handling,
while maintaining wear resistance, in in vitro testing.
The
same material has fracture toughness equal to that of the
upper
range of other composites, as well as high flexural strength.
The cases below illustrate the use of this new nanofilled/
nanocluster composite for single-shade and multilayering
techniques.
10. Bacterial Considerations
A smooth, glossy appearance is also important to reduce
the potential
for bacterial adhesion and the accumulation of biofilm. In
vitro studies have found amalgam to be bactericidal and to
inhibit
the formation of biofilm.
The converse has been found with
resin-based restorative materials, although, interestingly,
the experimental
addition of microparticulate silver to composite resin
material has been found in vitro to have a bactericidal
effect as
well as to inhibit bacterial adhesion. These findings
increase the
11. importance of selecting a material that both achieves and
retains
a smooth surface.
In vitro studies on packable resin composites,
compomers (polyacid-modified composite resins), and
glass ionomer
cements found no antibacterial properties for these
materials,
while one found a minimal effect for a few days with
composite
resin.
In the case of the packable composites tested, newly
polymerized resin would actually support the development
of
biofilm, and one study found that bacteria formed a dense
biofilm on composite resin.
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Conclusions
Based on data from laboratory investigations,
it may be concluded that high quality
posterior restorations can be placed using
composite resins. However, the clinician
must be precise in the use of operative
techniques, meticulous in following the
manufacturers' directions for use for the
bonding system, and thorough in the
application of the selected technique for
i nsertion of the composite resin. Furthermore,
12. to be successful it is essential to
have an effective method of moisture
control. Clinical experience supports the
view that well-placed posterior composites
may be found to fulfil patients' needs for
esthetics and durable restorations. Longterm
clinical studies have revealed excellent
in-service behavior among composite
restorations. With an annual failure rate of
only 0.5% to 5.0%, posterior composites
may be found to perform as well as alternative
forms of direct restoration
Matrix Material
The importance of matrix material cannot be underestimated as
it
13. provides support for the fibres and assists the fibres in carrying
the loads. It also provides
stability to the composite material. Resin matrix system acts as a
binding agent in a structural
component in which the fibres are embedded.
Functions of a Matrix
In a composite material, the matrix material serves the following
functions:
• Holds the fibres together.
• Protects the fibres from environment.
• Distributes the loads evenly between fibres so that all fibres are
subjected to the same
14. amount of strain.
• Improves impact and fracture resistance of a component.
• Helps to avoid propagation of crack growth through the fibres
by providing
alternate failure path along the interface between the fibres and
the matrix.
• Carry interlaminar shear.
15. Properties of a Matrix
The needs or desired properties of the matrix which are important
for a composite
structure are as follows:
• Reduced moisture absorption.
• Low shrinkage.
• Low coefficient of thermal expansion.
• Good flow characteristics so that it penetrates the fibre bundles
completely and
eliminates voids during the compacting/curing process.
• Reasonable strength, modulus and elongation (elongation
should be greater than
fibre).
16. • Must be elastic to transfer load to fibres.
• Strength at elevated temperature (depending on application).
• Low temperature capability (depending on application).
• Excellent chemical resistance (depending on application).
• Should be easily processable into the final composite shape.
• Dimensional stability (maintains its shape)
Some of the physical properties of the matrix which influence the
behaviour of composites are:
• Shrinkage during cure,
• Modulus of elasticity,
• Ultimate elongation,
17. • Strength (tensile, compressive and shear).
.
General types of Matrix Materials
In general, following general following types of matrix materials
are available:
• Thermosetting material;
• Thermoplastic material;
• Carbon;
• Metals;
• Ceramics;
• Glass Matrix
18. Some of the significant differences between thermosets and
thermoplastics are
given below:
Thermosets Thermoplastics
• Resin cost is low. • Resin cost is slightly higher.
• Thermosets exhibit moderate
shrinkage.
• Shrinkage of thermoplastics is
low
19. • Interlaminar fracture toughness is
low.
• Interlaminar fracture toughness
is high.
• Thermosets exhibit good resistance • Thermoplastics exhibit poor resistanceto
fluids and solvents. to fluids and solvents.
• Composite mechanical properties
are good.
• Composite mechanical properties are
good.
• Prepregability characteristics are
excellent.
• Prepregability characteristics are
poor.
• Prepreg shelf life and out time are
poor.
• Prepreg shelf life and out time are
excellent.
Types of resins
20. The different types of resin material are plastic resin, polyester resin,
polycarbonate resin, casting resin, polymer resin, acrylic resin, chemical resin,
and dry resin. Resin is a substance used in lacquers, adhesives, plastics, and
epoxies and is known for its translucent properties.Resin initially is in liquid form
but hardens to produce a solid coating.
21. Plastic resin material is a large category of resins and includes many types.
Plastic resins are manufactured using synthetic materials and are produced
when large hydrocarbon molecules are heated until they break into smaller
particles. The process, known as "cracking," is repeated until the hydrocarbons
are separated into different materials, such as ethylene and propylene, which can
then be used to form all kinds of products.
Resin Properties For composite
The choice of a resin system for use in any component
depends on a number of its characteristics, with the
following probably being the most important for most
composite structures:
1. Adhesive Properties
2. Mechanical Properties
3. Micro-Cracking resistance
4. Fatigue Resistance
5. Degradation from Water Ingress
22. A – Main properties:
Meyeb composites have three main properties that make them superior to
ceramics,
plastics, and organic composite materials:
• Meyeb composites have a higher heat tolerance than organic
composites. Tests conducted on a Meyeb resin showed that it will not
burn at all, even at 1200°C.
• Meyeb composites resist all organic solvents (and are only affected by
strong hydrochloric acid). The mechanical properties of GeopolymerMeyeb
composites are as good as those of organic composites (e.g.
phenolic fiber reinforced composites).
Meyeb composites are very easy to produce, with curing temperatures
in the range of 80° C and below.
Before the discovery of geopolymerization, these three critical properties had not been
23. incorporated into any composites.
Meyeb Composites are:
• fire resistant
• non flammable
• not producing combustion gases
• non toxic
• not emitting any smoke
• relatively good heat shields
• light weight .
Class II composite resin restoration
24. Class II cavities prepared in brass models and in extracted teeth were
restored with three light-cured composite resins. A transparent cone-
shaped device (Light-tip) at the end of the light source was pressed
into the filling material in the proximal ☐ for curing the resin. A second
layer was filled in the recess left by the cone and cured without the
cone. Controls consisted of fillings cured in two layers. In the brass
cavities the contraction gap was 10 μm (±10.6) with use of the cone
compared with 109.5 μm (±46.5) in control fillings (p< 0.001).
Extracted teeth were restored without etching of the enamel. Cervical
contraction gaps in control restorations were reduced by more than
half with the use of the transparent cone technique.
Difficulties with composite resin in Class II
1-open contact area.
2-pits and avoids in composite resins,espisialy toth preparation margin.
3-dificulty in finishing.
25. 4- post operative tooth sensitivity.Any d
PREVENTION POSTOPRATIVE TOOTH SENSITIVITY
1-PERFECT USE OF TOTAL ETCH SYSTEM
Many dentist use well known total etch concept on routine basis
>it is easy to ddry tooth much before apply the primer solution
>if the bonding solution are too thin .which can happen easily the
bonding resin will not cure properly because oxygen inhabitation.
2-improve total etch concept.
26. a-total desensitizing solution.
Tooth desensitizing solution can improve total etch
technique.these solution should use after etch is completed and
tooth surfaces are dried slightly.
Wetting the tooth surface provided by the hydroxy ethyl
methacrylate in desensitizing solution subsequent drawing of
bonding resin into dental canals to reduce tooth sensitivity.
One popular solution is GLUMA and microprime.
B-FLOWABLE RESINS
After placing and curing the bond ingredient of standered bonding
agent the practitioner places and cures a tthin layer of flowble
resin .
The resin layer is the thicker than the standered layer of bonding
agent.
The flowable resin provide buffer between the tooth ad
restorative material .it obtures any area of inadequate seal
between the previously placed bonding agent and acid etct
dentin.
c-High viscosity bonding agent.
d- Using multiple layer of bonding agent.
3- Self etch primer.
27. The bonding agent don’t remove the smear . the smear layer is
left in place and impregnated with a wetting agent and unfilled
resin.
The resultant combination of smear layer wetting agent and
unfilled resin creates plugs in the dentinal canals.
4-resin reinforced glass ionomer liners.
Many years ago , acombination of glass ionomer and resin was
introduced to be used as luting cement,liner and restorative
material ,it apply to deepest portion of class 1-2-5 tooth
preparation before bonding system.
5- combination of above technique.
