this presentation includes details about composite resins which are tooth colored filling materials used in dentistry. it also includes various recent advances in this field.

2. COMPOSITE RESINS
Dr Meenal Atharkar
MDS
Dept of Conservative Dentistry and Endodontics

3. CONTENTS
• Introduction
• History
• Evolution of composite resins
• Terminologies
• Applications
• Classification

4. CONTENTS
• Indications
• Contraindications
• Advantages
• Disadvantages
• Composition of composite
resins
• Properties

5. CONTENTS
• Properties
• Finishing and polishing of composites
• Repair of composites
• Description of various composites
• Composites according to curing procedure
• Curing lights
• Innovations in dental composites
• Conclusion
• References

6. INTRODUCTION
• Composite resins have made it possible to provide
patients with highly conservative and esthetic
restorations.
• Coupled with acid etching and bonding to tooth
structure, composite resin presently enjoy universal
application.
• Today, optimization of formulations, improvement in
properties and new techniques for placement have made
composite restorations more predictable.

7. INTRODUCTION
• The search for an ideal esthetic material for
restoring teeth has resulted in significant
improvements in both esthetic materials and
techniques for using them.
• Composites and the acid-etch technique
represent two major advances

8. • In 1959, Skinner wrote, "The esthetic quality of a
restoration may be as important to the mental
health of the patient as the biological and
technical qualities of the restoration are to his
physical or dental health."

9. HISTORY

10. HISTORY
• First half of 20th century- SILICATES
( now used only for deciduous teeth because they
become eroded within few years)

11. • Later in 20th century- ACRYLIC RESIN
(poor wear resistance and tended to shrink
severely during curing, which caused them to
pull away from the cavity walls, thereby
producing crevices or gaps that facilitate leakage
within the gaps, excessive thermal expansion
and contraction caused further stresses to
develop at the cavity margins when hot or cold
beverages and foods were consumed)

12. • PMMA based composites (polymethylmethacrylate):
(filler particles simply reduced the volume of polymer
resin without being bonded to the resin. Thus defects
developed between the particles and surrounding
resin, which led to leakage, staining and poor wear
resistance).

13. • 1962- BOWEN-Bisphenol A glycidyl
dimethacrylate (BIS-GMA):
• A monomer that forms a cross linked matrix that
is highly durable and a surface treatment
utilizing an organic silane compound called a
coupling agent to bond the filler particles to
resin matrix.

14. • 1970s- a category of now known as traditional
composites(conventional/ microfilled
composites) was developed.
(roughening of surface as a result of selective
abrasion of softer resin matrix surrounding the
harder filler particles)

15. EVOLUTION OF
COMPOSITES

16. TERMINOLOGIES
• Dental composite:
Highly cross-linked polymeric materials
reinforced by a dispersion of amorphous silica,
glass, crystalline, mineral, or organic resin filler
particles and/or short fibers bonded to the
matrix by a coupling agent

17. TERMINOLOGIES
• According to SKINNER:
• A composite material is a compound of two or
more distinctly different materials with
properties that are superior or intermediate to
those of the individual constituents.

18. TERMINOLOGIES
• According to PHILLIPS:
• Dental resin-based composites are structures
composed of three major components: a highly
cross-linked polymeric matrix reinforced by a
dispersion of glass, mineral, or resin filler particles
and/or short fibers bound to the matrix by coupling
agents. Such resins are used to restore and replace
dental tissue lost through disease or trauma and to
lute and cement crowns and veneers and other
indirectly made or prefabricated dental devices.

19. • According to DCNA:
• Composite resin is a three dimensional
combination of two or more chemically different
materials with a distinct interphase between
them.

20. • MARZOUK states that:
• Composites are all reinforced materials with
- A continuous (dispersion/ reinforced) phase
- An interrupted (dispersed/reinforcing) phase

21. • The continuous phase – Consists of the synthetic resin
macromolecules, i.e. it is a reaction product of Bisphenol A
and glycidyl methacrylate.
Other substitutes for BIS-GMA are :
• Modified BIS-GMA – by elimination of OH group.
• Urethane dimethacrylate.
• TEG-DMA.
Polymerization of this continuous phase brings about hardening
of the material which is in turn brought about by the initiators
and activators.
21

22. The Interrupted Phase
This may consist of either one or combination of the following :
• Macro- Ceramics.
• Colloidal And Micro-ceramics.
• Fabricated macro reinforcing phases with colloidal micro-
ceramic component bases.
22

23. • Macro-Ceramics – Consists of silicate based materials (SiO4),
e.g. quartz, fused silica, silicate glasses, crystalline lithium
aluminium silicate, (Radio-opaque) Ba-Al-boro-Si etc.
• Colloidal and Micro-Ceramics : Originally these consisted of
colloidal silicate forms of silicic acid and filler particle are
replaced by larger sized pyrogenic silica.
• The colloidal silica (as silicic acid) – formulated by a chemical
process of hydrolysis and preparation colloidal form diameter
not more than 0.04 micrometers.
23

24. Pyrogenic state – diameter – 0.05 – 1 micrometer.
• Colloidal or micro-ceramics are introduced into partially
thermo-chemically polymerized spherical particles of a resin
system.
• The interphase between the continuous and interrupted
phase is the most crucial in determining the final behavior of
these composite systems
24

25. APPLICATIONS
• Dental applications for resin-based composites
include
• cavity and crown restoration materials
• adhesive bonding agents
• pit and fissure sealants
• endodontic sealants
• bonding of ceramic veneers and
• cementation for crowns, bridges, and other
fixed prostheses.

27. CLASSIFICATION
I} Composites are usually divided into three types
based primarily on the size, amount, and
composition of the inorganic filler:
• (1) conventional composites,
• (2) microfill composites, and
• (3) hybrid composites

28. II} Based on the mean particle size of the major
filler:
• Traditional/conventional/macrofilled(8-12 um)
• Small particle (1-5 um)
• Microfilled (0.04-0.4um)
• Hybrid (0.6-1um)

29. III} Based on the filler particle size and
distribution:
• Megafilled (very large fillers)
• Macrofilled (10-100 um)
• Midifilled (1-10 um)
• Minifilled (0.1-1 um)
• Microfilled (0.01-0.1 um)
• Nanofilled (0.005-0.01 um)

31. IV} Based on method of polymerization:
• Self cured
• Light cured- ultraviolet light cured
- visible light cured
• Dual cured
• Stage curing composites- initial soft start
polymerization followed by complete
polymerization.

32. V} Based on mode
of presentation:
• Two paste system
• Single paste
system
• Powder liquid
system

33. VI} Based on use:
• Anterior composites
• Posterior composites
• Core buildups
• Luting composites

34. VII} Based on consistency:
• Light body- flowable
• Medium body- microfilled, hybrid, microhybrid
• Heavy body- packable

35. VIII} Based on generations:
1.First Generation Composites:
• Consist of macroceramic reinforce phases.
• Highest surface roughness.
• Highest proportion of destructive wear clinically (due to
dislodging of large ceramic particles).

36. 2. Second Generation Composites:
• With colloidal and micro-ceramic phases in continous
resin
• Best surface texture of all composites.
• Strength and coefficient of thermal expansion are
unfavorable because of limited % age of reinforcers that
can be added without increasing viscosity beyond limits
of workability
• Wear resistance is better than first gen. due to dimension
proximity of dispersed particles to dispersion matrix
macromolecules .

37. 3. Third Generation of Composite:
• Hybrid composite.
• Combination of macro and microcolloidal ceramic
reinforced in ratio of 75:25.
• Properties are intermediate to 1st and 2nd generations.

38. 4. Fourth Generation of Composites :
• Also a hybrid composite.
• But instead of macro ceramic fillers they contain heat
cured, irregularly shaped highly reinforced composite
macro particles with a reinforcing phase of micro
ceramics.
• Fourth generation composites are very technique
sensitive.

39. 5. Fifth Generation Composites:
• Hybrid composite.
• Continuous phase is reinforced with micro ceramics and
macro, spherical, heat cured highly reinforced composite
particles.
• The spherical shape of these macro ceramics improves
their wettability and consequently their chemical bonding
to the continuous phase of the final composite.
• Different size sphere ;improve packing factor.
• Specific shape – improve workability

40. 6. Sixth Generation Composites:
• Hybrid type.
• Continuous phase is reinforced with a combination of
micro-ceramics and agglomerates of sintered
microceramics .
• best mechanical properties
• Least shrinkage , due to min. amount of continous phase

41. INDICATIONS:
• Class I, II cavities
• Class III,IV,V Cavities
• Class VI cavities
• Foundations or core buildups
• Esthetic enhancement procedures
• Luting cements
• Interim restorations
• Miscellaneous applications

42. CONTRAINDICATIONS
• High caries incidence and poor oral hygiene
• Heavy abnormal occlusal stresses
• Access and isolation difficulties
• Subgingival extensions
• Limited operator skill and knowledge

43. ADVANTAGES:
• Esthetics
• Conserve the tooth structure
• Adhesion
• Low thermal conductivity
• Universal application
• Command set
• Repairable
• Can be polished at the same appointment

44. DISADVANTAGES:
• Polymerization shrinkage
• Technique sensitivity
• Time consuming and expensive
• Difficult to finish and polish
• Increased coefficient of thermal expansion

45. COMPOSITION AND FUNCTION
• Dental composites are made up of three major
components:
• a highly cross-linked polymeric resin matrix
reinforced by a dispersion of glass, silica,
crystalline, metal oxide or resinreinforcing filler
particles or their combinations and/or short
fibers, which are bonded to the matrix by silane
coupling agents.

46. • MATRIX:
• The resin matrix in most dental composites is
based on a blend of aromatic and/or aliphatic
dimethacrylate monomers such as
• BIS-GMA
• urethane dimethacrylate (UDMA)
• They form highly cross-linked, strong, rigid, and
durable polymer structures.
• This matrix forms a continuous phase in which
the reinforcing filler is dispersed.

47. • UDMA and bis-GMA are highly viscous (800,000
centipoise, similar to honey on a cold day) and are
difficult to blend and manipulate.
• Thus, it is necessary to use varying proportions of
lower-molecular-weight highly fluid monomers such
as
• triethylene glycol dimethacrylate (TEGDMA, 5 to
30 centipoise) and other lower-molecular weight
dimethacrylates to blend with and dilute the viscous
components to attain resin pastes sufficiently fluid
for clinical manipulation and for incorporating
enough filler to reinforce the cured resin.

48. • FILLER:
• strengthen and reinforce composites
• reduce curing shrinkage and thermal expansion.
• generally between 30% to 70% by volume or
50% to 85% by weight of a composite.

49. • These include so-called “soft glass” and
borosilicate “hard glass”, fused quartz,
aluminum silicate, lithium aluminum silicate
(beta-eucryptite, which has a negative coefficient
of thermal expansion), ytterbium fluoride, and
barium (Ba), strontium (Sr), zirconium (Zr), and
zinc glasses.
• The latter five types of fillers impart radiopacity
because of their heavy metal atoms

50. • Quartz had been used extensively.
• It has the advantage of being chemically inert but it
is also very hard, making it abrasive to opposing
teeth or restorations as well as difficult to grind into
very fine particles; thus, it is also difficult to polish.
• amorphous silica has the same composition and
refractive index as quartz;
• however, it is not crystalline and not as hard, thus,
greatly reducing the abrasiveness of the composite
surface structure and improving its polishability

51. • For acceptable esthetics, the translucency of a composite
restoration must be similar to that of tooth structure.
• Thus, the index of refraction of the filler must closely
match that of the resin.
• For bis-GMA and TEGDMA, the refractive indices are
approximately 1.55 and 1.46, respectively
• a mixture of the two components in equal proportions
by weight yields a refractive index of approximately 1.50.
• Most of the glasses and quartz used for fillers have
refractive indices of approximately 1.50, which is
adequate for sufficient translucency

52. • Most commonly used- barium glass
• Glass fillers containing metals of high atomic
number provide radiopacity, they are not as
inert as quartz, amorphous silica and are slowly
leached and weakened in acidic liquids.

55. • Functions of fillers:
• Reinforcement
• Reduction of polymerization shrinkage
• Reduction in thermal expansion and contraction
• Control of workability/ viscocity
• Decreased water sorption
• Radiopacity

56. • COUPLING AGENT:
• The chemical bond between the two phases of the
composite is formed by a coupling agent.
• this is a difunctional surface-active compound that
adheres to filler particle surfaces and also coreacts
with the monomer forming the resin matrix.
• A properly applied coupling agent can impart
improved physical and mechanical properties and
inhibit leaching by preventing water from
penetrating along the filler-resin interface

57. • Although titanates and zirconates can be used as
coupling agents, organosilanes—such as γ-
methacryloxypropyl trimethoxysilane—are used
most commonly.
• In the presence of water, the methoxy groups (–
OCH3) are hydrolyzed to silanol (–Si–OH)
groups, which can bond with other silanols on
the filler surfaces by forming siloxane bonds (–
Si–O–Si–).
•

58. • The organosilane methacrylate groups form
covalent bonds with the resin when it is
polymerized, thereby completing the coupling
process.
• Proper coupling by means of organosilanes is
extremely important to the clinical performance
of resin-based composite restorative materials

59. • Functions:
• Impart improved physical and mechanical
properties.
• Inhibit leaching by preventing water from
penentrating along the filler resin interface.

60. • ACTIVATION/INITIATION SYSTEM:
• Both monomethacrylate and dimethacrylate
monomers polymerize by the addition
polymerization mechanism initiated by free
radicals.
• Free radicals can be generated by chemical
activation or by external energy activation (heat,
light, or microwave).

61. • INHIBITOR:
• minimize or prevent spontaneous or accidental
polymerization of monomers.
• Inhibitors have a strong reactivity potential with free
radicals.
• If a free radical is formed, for example, by brief exposure
to room lighting when the material is dispensed, the
inhibitor reacts with the free radical faster than the free
radical can react with the monomer.
• This prevents chain propagation by terminating the
reaction before the free radical is able to initiate
polymerization.
• After all of the inhibitor is consumed, chain propagation
can begin.

62. • A typical inhibitor is butylated hydroxytoluene
(BHT), which is used in concentrations on the
order of 0.01% by weight.
• BHT and similar free radical scavengers are also
used as food preservatives to prevent oxidation
and rancidity.
• Thus, inhibitors have two functions:
1. to extend the resin’s storage life and
2. to ensure sufficient working time.

63. • OPTICAL MODIFIERS:
• For a natural appearance, dental composites
must have visual shading and translucency
similar to the corresponding properties of tooth
structure.
• Shading is achieved by adding various pigments,
usually consisting of minute amounts of metal
oxide particles.
•

64. • For example, if a class IV incisal area is
reconstructed, the translucency of an
unmodified composite might allow too much
light to pass through the restoration.
• As a result, less light is reflected or scattered
back to the observer, who perceives the incisal
edge as too dark.
• This deficiency can be corrected by adding an
opacifier

65. • However, if an excessive amount of opacifier is
added, too much light may be reflected and the
observer then perceives that the restoration is “too
white,” or more correctly, “too high in value”.
• To increase the opacity, the manufacturer adds
titanium dioxide and aluminum oxide to composites
in minute amounts (0.001% to 0.007% by weight).
• It is important to realize that all optical modifiers
affect light transmission through a composite.

66. • Thus, darker shades and greater opacities have a
decreased depth of light-curing ability and
require either an increased exposure time or a
thinner layer when cured.
• Studies have shown that for optimal
polymerization, resins with darker shades and
opacifiers should be placed in thinner layers.
• This consideration has added importance when
a bonding agent covered by a composite layer is
being cured.

67. PROPERTIES

68. 2. MATRIX CONSTRAINT:
• the presence of filler particles bonded to the matrix
via coupling agents reduces thermal expansion and
contraction of the composite.
• When thermal stresses arise, the interfacial bond
and the presence of a filler with a lower coefficient of
thermal expansion (nearly zero in some cases)
prevents or reduces the contraction or expansion of
the matrix.
• Thus, during expansion, while the space occupied by
the filler tries to increase, the filler with lower
coefficient of expansion does not—and since the
filler is chemically bonded to the matrix, it prevents
the space from getting larger and hence prevents or
reduces the expansion

69. • Conversely, during cooling, the matrix contracts
and decreases the space occupied by the filler,
but since the filler occupies that space,
contraction is prevented or reduced.
• Thus the filler particles not only lower thermal
expansion and contraction by simply occupying
space that polymers, which are susceptible to
thermal expansion, would otherwise have
occupied but also constrains the interfacial bond
from expanding thermally

70. • This constraint does have its limits.
• During expansion, the composite can fracture within
the matrix because of the added tension caused by
the nonexpansion of the filler particle, within the
filler particle, or at the interfacial bond, depending
on whether the interfacial bond is stronger than the
fracture toughness of the filler or the matrix.
• In contraction, the composite can fracture within
the matrix or within the filler particle, depending on
which is weaker

71. 3. TOUGHNESS:
• The strength of composites is highly dependent on the
ability of the coupling agent to transfer stresses from the
weak matrix to the strong filler particles.
• Without the coupling agent, the filler particles cannot
absorb stresses in the matrix and act as if they were
voids, thereby weakening instead of strengthening the
matrix.
• Thus a crack traveling through the matrix simply
bypasses the particles.
• The energy required to detour around noncoupled
particles is low because the lack of coupling at the
particle-matrix interface makes this interface behave the
same as an already existing “crack.”
• Consequently, in a true composite, the matrix and filler
are chemically bonded.

72. • As the crack propagates to a bonded filler
particle, the crack must pass around the particle,
since it is stronger than the matrix and the
interfacial bond.
• Thus the path the crack must take and the total
new surface area that the crack must form is
increased; therefore the energy needed for the
crack to propagate is increased.
• This makes the composite tougher.

73. • If the interfacial bond is weaker than the matrix, a
process of crack blunting occurs.
• As the crack propagates to the weak interface, a void or
tear opens up in front of the advancing crack because of
the stresses that the weak bond experiences.
• However, this void is perpendicular to the propagating
crack; thus when the crack arrives, the tip of the crack
has been blunted and significantly more stress is
required to propagate the crack.
• Note that the use of a cross-linked polymer matrix also
increases toughness, since it prevents the polymer chains
from being drawn and separated as the crack propagates.
• However, the material then becomes brittle.

74. 4. CURING SHRINKAGE AND
SHRINKAGE STRESS:
• Curing shrinkage arises as the monomer is
converted to polymer and the free space it
occupies reduces (approximately 20% less than
that among unreacted monomers).
• In turn, this polymerization shrinkage produces
unrelieved stresses in the resin after it reaches
the “gelation” point and begins to harden.

75. • The polymerization shrinkage and resultant
stress can be affected by the
• (1) total volume of the composite material,
• (2) type of composite,
• (3) polymerization speed, and
• (4) ratio of bonded/nonbonded surfaces or the
configuration of the tooth preparation (C-
factor).

76. • These stresses tend to develop at the
tissue/composite interface, weakening the bond,
and eventually producing a gap at the
restoration margins.
• Consequently the risk for marginal leakage and
the ensuing problems of marginal staining and
secondary caries are exacerbated.
• Undoubtedly this is one of the greatest problems
of composites used for class II and class V
restorations.

77. • Traditionally this problem has been combated in
two ways.
• First, larger monomers used to “dilute” the number
of double bonds that need to be reacted.
• Bis-GMA and UDMA have five times or more the
molecular weight of methyl methacrylate (MMA), so
the density of methacrylate double-bond groups is
approximately two-fifths as high in MMA.
• This reduces polymerization shrinkage
proportionately.

78. • Reduction of Shrinkage Stresses:
• light-activated resins have overcome many of the
deficiencies of chemically activated resins, including
lack of control over working time, color shift
(yellowing), and porosity from mixing the two-part
system.
• However, the internal pores in chemically cured
resins act to relax residual stresses that build up
during curing (the pores enlarge during hardening
and reduce the concentration of stresses at the
margins).

79. • Also, the slower curing rate of chemical
activation allows a larger portion of the
shrinkage to be compensated by internal flow
among the developing polymer chains before
extensive cross-linking occurs (i.e., before
gelation).
• After the gel point, stresses cannot be relieved
but instead continue to increase and concentrate
within the resin and the tooth structure adjacent
to the bonded surfaces

80. • Two general approaches have been followed in seeking
to overcome the problem of stress concentration and
marginal failure experienced with light-activated resins:
• (1) reduction in volume contraction by altering the
chemistry and/or composition of the resin system, and
• (2) clinical techniques designed to offset the effects of
polymerization shrinkage.
• The former is the more desirable solution, and intensive
research and development efforts are currently in
progress to develop resins with low shrinkage and low
thermal expansion.

81. • These techniques are associated with:
a)incremental buildup and
b)control of the curing rate

82. • A)Incremental Buildup and Cavity
Configuration:
• One technique attempts to reduce the C-factor,
which is related to the geometry of the cavity
preparation and represented as the ratio of
bonded to nonbonded surface areas.

83. • Residual polymerization stress increases directly
with this ratio.
• During curing, shrinkage leaves the bonded cavity
surfaces in a state of stress; the nonbonded, free
surfaces (i.e., those that reproduce the original
external tooth anatomy) relax some of the stress by
contracting inward toward the bulk of the material.
• A layering technique in which the restoration is built
up in increments, curing one layer at a time,
effectively reduces polymerization stress by
minimizing the C-factor.

84. • That is, thinner layers reduce bonded surface
area and maximize nonbonded surface area,
thus minimizing the associated C-factor.
• an incremental technique overcomes both
limited depth of cure and residual stress
concentration but adds to the time and difficulty
of placing a restoration

85. • B) Soft-Start, Ramped Curing, and Delayed Curing:
• Another approach that is used to offset
photopolymerization stress buildup is to follow the
example of chemically initiated systems by
providing an initial low rate of polymerization,
thereby extending the time available for stress
relaxation before reaching the gel point.
• This can be accomplished by using a soft-start
technique, whereby curing begins at low light
intensity and finishes with high intensity.

86. • In delayed curing, the restoration is initially
incompletely cured at low intensity.
• The clinician then sculpts and contours the resin to
the correct occlusion and later applies a second
exposure of light for the final cure.
• This delay allows substantial stress relaxation to
take place.
• The longer the time available for relaxation, the
lower is the residual stress.
• Delayed curing and exponential ramp curing appear
to provide the greater reductions in curing stress but
do require more time.

87. • In response to this situation, care should be taken
when high-intensity lamps are used.
• Increased lamp intensity allows for shorter
exposure times for a given depth of cure in a
particular shade and type of resin.
• Curing depths equivalent to that of a 500-mW/cm2
QTH lamp (2 mm at 40 seconds) have been
demonstrated using an exposure time of 10 seconds
with certain PAC lights and 5 seconds with an argon
laser.
• Thus, these high-intensity lamps should, in
principle, provide substantial savings in chair time..

88. • However, a high-intensity short exposure time
causes an accelerated rate of curing, which
inevitably leads to substantial residual stress
buildup due to inherently less time for stress
relaxation mechanisms to take place.
• Because of these trade-offs, it would appear that
little advantage is to be gained by ramped,
delayed, or softstart curing techniques.

90. PROPERTIES:
• 1.DEGREE OF CONVERSION (DC):

91. 2. CURING SHRINKAGE AND
SHRINKAGE STRESS

92. Factors affecting stress development:

93. Polymerization shrinkage stress

99. C factor:

109. • Although wear rate differences of 10 to 20 µm/
year may seem small for posterior composites,
this wear rate still amounts to 0.1 to 0.2 mm
more than enamel over 10 years.
• Thus, it is important to be cautious in selecting
the clinical cases to be treated with posterior
composites.

110. 6. LONGEVITY OF COMPOSITES:
• The most commonly cited reasons for the failure
of composites in clinical studies are
• secondary caries,
• fracture,
• marginal deficiencies, and
• wear.

111. 7. PLACEMENT TIME OF COMPOSITES:
• Although the performance of posterior
composites has greatly improved during the past
decade relative to amalgams, the placement time
is significantly higher for composites.
• The placement time of ceramic and composite
inlays is significantly higher than that for either
amalgam or composite restorations.

112. 8. BIOCOMPATIBILITY OF COMPOSITES:
• Concerns about the biocompatibility of
restorative materials usually relate to the effects
on the pulp from two aspects:
(1) the inherent chemical toxicity of the material
(2) the marginal leakage of oral fluids.

113. • If a clinician attempts to polymerize too thick a
layer of resin or if the exposure time to the light
is inadequate (as discussed previously), the
uncured or poorly cured material can release
leachable constituents adjacent to the pulp.

114. • Bisphenol A Toxicity:
• Bisphenol A (BPA), a precursor of bis-GMA, has
been shown to be a xenoestrogen, a synthetic
compound that mimics the effects of estrogen by
having an affinity for estrogen receptors.
• BPA and other endocrine-disrupting chemicals
(EDCs) have been shown to cause reproductive
anomalies, especially in the developmental
stages of fetal wildlife.
• .

115. • 9. MECHANICAL PROPERTIES:
• MOE is lower for microfilled and flowable
composites than for hybrid composites.
• 10. LINEAR COEFFICIENT OF THERMAL
EXPANSION:
• They have higher COTE than that of tooth
structure. So they expand and contract more
than enamel and dentin when subjected to
temperature changes.

116. • This increases marginal gaps and effects of
polymerization shrinkage.
• As the filler content of composite resins
increases, the coefficient of thermal expansion
reduces.

117. • 11. WATER SORPTION:
• When resin content is high, the water sorption is
increased.
• Water sorption makes the resin matrix to swell
leading to filler debonding.

118. • 12. SOLUBITLITY:
• 0.5-1.1 mg/cm sq.
• 13. MARGINAL INTEGRITY:
• More if margins are on enamel and dentin.
• Less if margins are on root surfaces.
• 14. RADIOPACITY:
• It is due to glass fillers containing heavy metal
atoms like barium, strontium and zirconium.

119. FINISHING OF COMPOSITES
• The term finishing usually refers to the process of
adapting the restorative material to the tooth (e.g.,
removing overhangs and shaping occlusal surfaces),
whereas polishing refers to removing surface
irregularities to achieve the smoothest possible
surface.
• Residual surface roughness can encourage bacterial
growth, which can lead to a myriad of problems
including secondary caries, gingival inflammation,
and surface staining

120. • Research has been conducted to examine the
effect of several significant factors on the finish
and polish of a composite restoration:
• (1) environment,
• (2) delayed versus immediate finish,
• (3) the types of materials, and
• (4) surface coating and sealing

128. REPAIR OF COMPOSITES
• Composites can be repaired by replacing lost
material.
• This is a useful procedure for correcting defects
or altering contours on existing restorations.
• When a restoration has just been placed and
polymerized, it may still have an oxygen-
inhibited layer of resin on the surface.

129. • Additions of new composite can be made directly
to this layer because this represents, in essence,
an excellent bonding substrate.
• Even after the restoration has been polished,
adding more material can still repair a defect.
• A restoration that has just been cured and
polished may still have more than 50% of
unreacted methacrylate groups to copolymerize
with the newly added material

130. • As the restoration ages, fewer and fewer
methacrylate groups remain and greater cross-
linking reduces the ability of fresh monomer to
penetrate the matrix.
• The strength of the bond between the original
material and the new resin decreases in direct
proportion to the time that has elapsed between
polymerization and addition of the new resin.

131. USE OF COMPOSITES AS RESIN VENEERS
• The first resin veneers were mechanically
bonded to metal substrates using wire loops or
retention beads.

132. • Prosthetic resin-veneering materials have
several advantages and disadvantages compared
with ceramics.
• The advantages include
• ease of fabrication,
• predictable intraoral reparability, and
• less wear of opposing teeth or restorations.

133. • The drawbacks include
• low proportional limit and
• pronounced plastic deformation, which
contribute to distortion on occlusal loading.

134. • Leakage of oral fluids and staining below the
veneers, particularly those attached
mechanically, are caused by dimensional
changes from water sorption, heating, and
cooling.
• Surface staining and intrinsic discoloration tend
to occur with these resins

135. • The resins are used as preformed laminate
veneers, in which resin shells are adjusted by
grinding and the contoured facing is bonded to
tooth structure using the acid-etching technique
with either chemically activated, visible
light−activated, or dual-cure luting resin
cements.

136. DESCRIPTION OF COMPOSITES:
• 1)Conventional Composites:
• Conventional composites generally contain
approximately 75% to 80% inorganic filler by
weight.
• Particle size-8um.
• large size
• extreme hardness of the filler particles,
• rough surface texture.
• Wears at a faster rate.

138. • 2)Microfill Composites:
• In the late 1970s the microfill, or "polishable,"
composites were introduced.
• These materials were designed to replace the
rough surface characteristic of conventional
composites with a smooth, lustrous surface
similar to tooth enamel.
• contain colloidal silica particles whose average
diameter ranges from 0.01 to 0.04 um

139. • this small particle size results in a smooth,
polished surface in the finished restoration that
is less receptive to plaque or extrinsic staining.
• Typically, microfill composites have an inorganic
filler content of approximately 35% to 60% by
weight.
•

140. • physical and mechanical characteristics are
somewhat inferior.
• very wear resistant.
• low modulus of elasticity may allow microfill
composite restorations to flex during tooth
flexure, thus better protecting the bonding
interface.
•

141. • 3)Hybrid Composites:
• inorganic filler content of approximately 75% to
85% by weight.
• The filler is typically a mixture of microfiller and
small filler particles that results in a
considerably smaller average particle size (0.4 to
1 um) than that of conventional composites.

142. • Because of the relatively high content of
inorganic fillers, the physical and mechanical
characteristics are generally superior
• Hybrid composites currently are the
predominant direct esthetic restorative
materials used.

144. • 4)Small (Fine) Particle Composites:
• mean particle diameters between 0.1 and 10 µm
(minifiller and midifiller).
• cannot be polished to a high gloss.
• filler loadings are as high as or higher (77% to 88%)
than those of macrofilled composites, which
provides a high degree of hardness and strength but
also brittleness.
• Its excellent balance among polishability,
appearance, and durability make this category
suitable for general anterior use

146. • 5)Microfilled Composites:
• agglomerates of 0.01- to 0.1-µm inorganic
colloidal silica particles embedded in 5- to 50-
µm resin filler particles.
• Such a filler is made by a pyrolytic precipitation
process where a silicon compound such as SiCl4
is burned in an oxygen/hydrogen atmosphere to
form macromolecular chains of colloidal silica
resulting in amorphous silica

147. • However, these particles, because of their
extremely small size, have extremely large
surface areas ranging from 50 to 400 m2 per
gram.
• In addition, the pyrolytic process results in
particle “agglomeration” into long, molecular-
scale chains.

148. • In this way the overall inorganic filler content of the
final, cured composite is increased to about 50% by
weight

149. • However, a major shortcoming of these
materials is that the bond between the
composite particles and the clinically cured
matrix is relatively weak, facilitating wear by a
chipping mechanism.
• not generally suitable for use as stress-bearing
surfaces.

150. • .
• Microfilled composites are the resins of choice
for restoring teeth with carious lesions in
smooth surfaces (classes III and V) but not in
stress-bearing situations (classes II and IV).
•

151. • 6) nanofilled composites:
• Filler particle size-0.005-0.01 um.
• Fillers- zirconium, silica, nanosilica particles
• Filler distribution as high as 79.5% by weight.
• Lesser polymerization shrinkage of 1.5-2%.

152. • 7)Flowable Composites:
• A modification of the small-particle composite
and hybrid composite results in the so-called
flowable composites, which have become
popular since 1995.
• lower viscosity through a reduced filler loading,
which enables the resin to flow readily, spread
uniformly, intimately adapt to a cavity form, and
produce the desired dental anatomy.
•

153. • 8)Condensable (Packable) Composites:
• condensable composites (also known as
packable composites) were developed by
adjusting their filler distribution to increase the
strength and stiffness of the uncured material
and provide a consistency and handling
characteristics.

154. • Specifically the packable/condensable
characteristics are derived from the inclusion of
elongated, fibrous filler particles of about 100
µm in length and/or rough-textured surfaces or
branched geometries that tend to interlock and
resist flow.
• This causes the uncured resin to be stiff and
resistant to slumping yet moldable.
• larger than average filler particles (15 to 80 µm)
are used.

156. Composites based on curing
procedure:
Based on type of curing:
• Chemical cure
• UV light cured
• Visible light cured
• Dual cure
• Tri cure
• Heat and pressure cured

157. • 1) chemically cures composites:
• Self cure/ autocure composites.
• 2 paste- one- initiator- benzoyl peroxide
• other- activator- N.N. dimethyl P-
toluidine

158. • Light activation of composites:
• Single paste which has both photoinitiator and
activator.
• UV light< visible light curing

159. Difference between UV light and
visible light curing

161. Curing lights:

163. 1. High intensity quartz-tungsten- halogen (QTH )
lamps.
• Faster curing.
• Polymerization shrinkage –high
• Produce soft start polymerization and gradually
increase to maximum intensity through ramped
program.

164. 2. Plasma arc curing(PAC LIGHTS)
• 2 tungsten electrodes separated by a small gap,
between which high voltage is created.
• Spark ionizes xenon gas from environment to
produce conducive gas- plasma.
• Polymerize composites in 6-10 secs.
• Drawbacks- increased heat- rise in pulpal temp
• - expensive
• - increase polymerization shrinkage
stresses.

165. 3. Light emitting diodes(LED)
• Blue light(455-486nm)

166. • Argon laser curing:
• Emit blue light( 457-502 nm)

170. • Dual Cure composites:
• Consists of 2 light curable pastes
• BPO and aromatic tertiary amine
• Light curing – promoted by amine/CQ
combination
• Chemical- amine/BPO interaction
• APPLICATION:
• Cementation of bulky ceramic inlays

172. Recent advances in composite resins
Advances in direct composite
resin materials
Advances in indirect
composite resin materials
• Flowable composites
• Packable composites
• Ormocers
• Ion releasing composite resin
• Nanofilled composites
• Compomers
• Silorane composites
• Ceromer
• Single crystal modified
composites
• Fiber reinforced composites

173. INNOVATIONS IN COMPOSITES:

174. Nanofilled composites

192. Chitosan composites

194. • Single crystal modified composites:
• Symmetric shapes.
• Improved properties like:
1.High flexural strength
2.Increased fracture toughness
3.High modulus of elasticity
4.Increased hardness
• Used for inlay and onlay restorations.

195. • Fiber reinforced composites:
• 1998
• Fiber/ glass/ polyethylene and resin matrix is
coupled during the manufacture of composite
resins.
• Properties:
1. Very high compressive strength
2. High flexural strength

198. CONCLUSION
• Composites have acquired a prominent place
among filling materials employed in direct
techniques.
• It should not be forgotten that they are highly
technique sensitive, hence the need to control
certain aspects: correct indication, good
isolation, choice of right composite for each
situation, use of a good procedure for bonding to
the dental tissues and proper curing are
essential if satisfactory clinical results are to be
achieved.

199. REFERENCES
Art & science of operative dentistry- Sturdavent's
Dental materials – Phillips
Fundamentals of operative dentistry- Summit
Operative dentistry- Marzouk
Wikipedia
199