2.
COMPOSITE RESIN IS THREE DIMENSIONAL
COMBINATION OF TWO OR MORE
CHEMICALLY DIFFERENT MATERIALS WITH
A DISTINCT INTERFACE BETWEEN THEM.IN
COMBINATION, THE PROPERTIES ARE
SUPERIORE TO THOSE OF INDIVIDUAL
COMPONENTS.
3.
1955 –BUONOCORE– ACID ETCH TECHNIQUE
1956—BOWEN FORMULATED BIS – GMA RESIN
1962– SILANE COUPLING AGENTS INTRODUCED
- MACRO FILLED COMPOSITES DEVELOPED
1979 – FIRST PHOTOCURED COMPOSITES USING UV LIGHT
1972 – VISIBLE LIGHT CURING UNIT INTRODUCED
1976 – MICRO FILLED COMPOSITES DEVELOPED
EARLY 1980– POSTERIOR COMPOSITES INTRODUCED
MID 1980– HYBRID COMPOSITES DEVELOPED
1990 - SECOND GENERATION INDIRECT COMPOSITES
2002 – NANO FILLED COMPOSITES
2005 – SILORANE COMPOSITES BY WEINMANN
4.
BASED ON THE MEAN PARTICLE SIZE OF THE MAJOR FILLER
1.
TRADITIONAL COMPOSITES ---
2.
SMALL PARTICAL COMPOSITES – 1 – 5um
3.
MICROFILLED COMPOSITES ----
-0.04 – 0.4 um
4.
HYBRID COMPOSITES -------
0.6 – 1 um
BASED ON FILLER PARTICLE SIZE AND DISTRIBUTION:-
1.
MACROFILLERS ---- 10
TO 100 um
2.
MIDIFILLERS
----- 1
TO 10 um
3.
MINIFILLERS
----- 0.1
TO 1
4.
MICROFILLERS ----- 0.01 TO 0.1 um
5.
NANOFILLERS
8-12 um
um
----- 0.005 TO 0.01 um
5.
BASED ON METHOD OF POLYMERIZATION
1.
SELF CURED , AUTO CURED , OR CHEMICALLY CURED COMPOSITES
2.
LIGHT CURED COMPOSITES
I.
UV LIGHT CURED
II.
VISIBLE LIGHT CURED
3. DUAL CURED COMPOSIES – BOTH LIGHT&SELF CURING MECHANISMS
4. STAGED CURING COMPOSITES – INITIAL SOFT START POLYMERIZATION
FOLLOWED BY COMPLETE
BASED ON MODE OF PRESENTATION
1.
TWO PASTE SYSTEM
2.
SINGLE PASTE SYSTEM
3.
POWDER LIQUID SYSTEM
. BASED ON USE
1.
ANTERIOR COMPOSITES
2.
CORE BUILD UP COMPOSITES
3.
POSTERIOR COMPOSITES
4.
LUTING COMPOSITES
6.
BASED ON THEIR CONSISTENCY
1.
LIGHT BODY COMPOSITES – FLOWABLE COMPOSITES
2.
3.
MEDIUM BODY COMPOSITES – MEDIUM VISCOSITY COMPOSITES
LIKE MICRO FILLED , HYBRID , MICRO HYBRID COMPOSITES
HEAVY BODY COMPOSITES – PACKABLE COMPOSITES
7.
Dental composite is composed of a resin matrix and filler materials.
Coupling agents are used to improve adherence of resin to filler
surfaces.
Activation systems including heat, chemical and photochemical
initiate polymerization.
Plasticizers are solvents that contain catalysts for mixture into resin.
Monomer, a single molecule, is joined together to form a polymer, a
long chain of monomers.
Physical characteristics improve by combining more than one type
of monomer and are referred to as a copolymer.
Cross linking monomers join long chain polymers together along the
chain and improve strength.
9.
BIS-GMA resin is the base for composite. In the late 1950's, Bowen
mixed bisphenol A and glycidylmethacrylate thinned with TEGDMA
(triethylene glycol dimethacrylate) to form the first BIS-GMA resin.
Diluents are added to increase flow and handling characteristics or
provide cross linking for improved strength. Common examples are:
RESIN:- BIS-GMA bisphenol glycidylmethacrylate
DILUENTS:- MMA methylmethacrylate
BIS-DMA bisphenol dimethacrylate
UDMA urethane dimethacrylate
CROSS LINK DILUENTS
TEGDMA triethylene glycol dimethacrylate
EGDMA ethylene glycol dimethacrylate
10.
Fillers are placed in dental composites to reduce shrinkage upon
curing.
Physical properties of composite are improved by fillers, however,
composite characteristics change based on filler material, surface,
size, load, shape, surface modifiers, optical index, filler load and
size distribution.
Materials such as strontium glass, barium glass, quartz, borosilicate
glass, ceramic, silica, prepolymerized resin, or the like are used.
11.
Coupling agents are used to improve adherence of resin to filler
surfaces.
Coupling agents chemically coat filler surfaces and increase strength.
Silanes have been used to coat fillers for over fifty years in industrial
plastics and later in dental fillers. Today, they are still state of the art.
Silanes have disadvantages. They age quickly in a bottle and become
ineffective. Silanes are sensitive to water so the silane filler bond
breaks down with moisture.
Water absorbed into composites results in hydrolysis of the silane bond
and eventual filler loss.
Common silane agents are:
vinyl triethoxysilane
methacryloxypropyltrimethoxysilane
13.
ADDED TO PREVENT SPONTANEOUS
POLYMERIZATION OF THE MONOMERS BY
INHIBITING THE FREE RADICALS
BUTYLATED HYDROXY TOLUENE 0.01 % IS
ADDED AS INHIBITOR IN COMPOSITE
RESINS
14.
METAL OXIDES – MINUTE AMOUNT – PRODUCE DIFFERENT
SHADES TO COMPOSITES
ALUMINIUM OXIDE & TITANIUM OXIDE – OPACITY TO
COMPOSITES
ALL OPTICAL MODIFIERS AFFECT LIGHT TRANSMISSION
THROUGH THE COMPOSITES RESINS. SO DARKER SHADES
AND GREATER OPACITES HAVE A LESSER DEPTH OF
CURING THAN LIGHTER SHADES
15.
Following are the imp physical properties:1) Linear coefficient of thermal expansion (LCTE)
2) Water Absorption
3) Wear resistance
4) Surface texture
5) Radiopacity
6) Modulus of elasticity
7) Solubility
16.
One of the requirements of using a composite as a posterior
restorative is that it should be radiopaque.
In order for a material to be described as being radiopaque, the
International Standard Organization (ISO) specifies that it should
have radiopacity equivalent to 1 mm of aluminium, which is
approximately equal to natural tooth dentine.
However, there has been a move to increase the radiopacity to be
equivalent to 2 mm of aluminium, which is approximately equal to
natural tooth enamel.
A majority of the composites described as all-purpose or universal
have levels of radiopacity greater than 2 mm of aluminium
17.
1) Class-I, II, III, IV, V & VI restorations.
2) Foundations or core buildups.
3) Sealant & Preventive resin restorations.
4) Esthetic enhancement procedures.
5) Luting
6) Temporary restorations
7) Periodontal splinting.
18.
1) Inability to isolate the site.
2) Excessive masticatory forces.
3) Restorations extending to the root surfaces.
4) Other operator errors.
5) high caries incidence and poor oral hygiene
19.
1) Esthetics
2) Conservative tooth preparation.
3) Insulative.
4) Bonded to the tooth structure.
5) repairable.
6) command set
7) can be polished
8) low thermal conductivity
20.
1) May result in gap formation when restoration extends to the root
surface.
2) Technique sensitive.
3) Expensive
4) May exhibit more occlusal wear in areas of higher stresses.
5) Higher linear coefficient of thermal expansion.
21.
1) Local anaesthesia.
2) Preparation of the operating site.
3) Shade selection
4) Isolation of the operating site.
5) Tooth preparation.
6) preliminary steps of enamel and dentin bonding.
7) Matrix placement.
8) Inserting the composite.
9) Contouring the composite.
10) polishing the composite.
22.
1. Smile Design
2. Color and Color Analysis
3. Tooth Color
4. Tooth Shape
5. Tooth Position
6. Esthetic Goals
7. Composite Selection
8. Tooth Preparation
9. Bonding Techniques
10. Composite Placement
11. Composite Sculpture and
12. Composite Polishing to properly restore anterior teeth with
composite:
23.
A dentist must understand proper smile design so composite
restoration can achieve a beautiful smile. This is true for extensive
veneering and small restorations.
Factors which are considered in smile design include:A. Smile Form which includes size in relation to the face, size of one
tooth to another, gingival contours to the upper lip line, incisal edges
overall to the lower lip line, arch position, teeth shape and size,
perspective, and midline.
B. Teeth Form which includes understanding long axis, incisal edge,
surface contours, line angles, contact areas, embrasure form,
height of contour, surface texture, characterization, and tissue
contours within an overall smile design.
C. Tooth Color of gingival, middle, incisal, and interproximal areas
and the intricacies of characterization within an overall smile design.
24.
Colour is a study in and of itself. In dentistry, the effect of enamel
rods, surface contours, surface textures, dentinal light absorption,
etc. on light transmission and reflection is difficult to understand and
even more difficult replicate.
The intricacies of understanding matching and replicating hue,
chroma, value, translucency, florescence; light transmission,
reflection and refraction to that of a natural tooth under various light
sources is essential but far beyond the scope of this article.
25.
Analysis of colour variation within teeth is improved by an
understanding of how teeth produce color variation.
Enamel is prismatic and translucent which results in a blue gray
color on the incisal edge, interproximal areas and areas of
increased thickness at the junction of lobe formations.
The gingival third of a tooth appears darker as enamel thins and
dentin shows through.
Color deviation, such as craze lines or hypocalcifications, within
dentin or enamel can cause further color variation.
Aging has a profound effect on color caused by internal or external
staining, enamel wear and cracking, caries, acute trauma and
dentistry.
26.
Understanding tooth shape requires studying dental anatomy.
Studying anatomy of teeth requires recognition of general form,
detail anatomy and internal anatomy.
It is important to know ideal anatomy and anatomy as a result of
aging, disease, trauma and wear.
Knowledge of anatomy allows a dentist to reproduce natural teeth.
For example, a craze line is not a straight line as often is produced
by a dentist, but is a more irregular form guided by enamel rods.
27.
Knowledge of normal position and axial tilt of teeth within a head,
lips, and arches allows reproduction of natural beautiful smiles.
Understanding the goals of an ideal smile and compromises from
limitations of treatment allows realistic expectations of a dentist and
patient.
Often, learning about tooth position is easily done through denture
esthetics.
Ideal and normal variations of tooth position is emphasized in
removable prosthetics so a denture look does not occur.
28.
The results of esthetic dentistry are limited by limitations of ideals
and limitations of treatment.
Ideals of the golden proportion have been replaced by preconceived
perceptions.
Limitations of ideals are based on physical, environmental and
psychological factors.
Limitations of treatment are base on physical, financial and
psychological factors.
29.
Esthetic dentistry is an art form. There are different levels of
appreciation so individual dentists evaluate results of esthetic
dentistry differently. Artistically dentists select composites based on
their level of appreciation, artistic ability and knowledge of specific
materials. Factors which influence composite selection include
A- Restoration Strength,
B- Wear
C- Restoration Color
D- Placement characteristics.
E- Ability to use and combine opaquers and tints.
F- Ease of shaping.
G- Polishing characteristics.
H- Polish and colour stability
30.
Tooth preparation often defines restoration strength.
Small tooth defects which receive minimal force require minimal
tooth preparation because only bond strength is required to provide
retention and resistance.
In larger tooth defects where maximum forces are applied,
mechanical retention and resistance with increased bond area can
be required to provide adequate strength.
31.
Understanding techniques to bond composite to dentin and enamel
provide strength, elimination of sensitivity and prevention of microleakage.
Enamel bonding is a well understood science. Dentinal bonding,
however, is constantly changing as more research is being done
and requires constant periodic review.
Micro-etching combined with composite bonding techniques to old
composite, porcelain, and metal must be understood to do anterior
composite repairs.
32.
Understanding techniques which allow ease of placement, minimize
effects of shrinkage, eliminate air entrapment and prevent material
from pulling back from tooth structure during instrumentation
determine ultimate success or failure of a restoration.
It is important to incorporate proper instrumentation to allow ease of
shaping tooth anatomy and provide color variation prior to curing
composite.
In addition, a dentist must understand placement of various
composite layers with varying opacities and color to replicate
normal tooth structure.
33.
Composite sculpture of cured composite is properly done if
appropriate use of polishing strips, burs, cups, wheels and points is
understood.
In addition, proper use of instrumentation maximizes esthetics and
allows minimal heat or vibrational trauma to composite resulting in a
long lasting restoration.
34.
Polishing composite to allow a smooth or textured surface shiny
produces realistic, natural restorations.
Proper use of polishing strips, burs, cups, wheels and points with
water or polish pastes as required minimizes heat generation and
vibration trauma to composite material for a long lasting restoration.
35.
Composites are indicated for Class 1, class 2 and class 5 defects
on premolars and molars. Ideally, an isthmus width of less than one
third the intercuspal distance is required.
This requirement is balanced against forces created on remaining
tooth structure and composite material. Forces are analyzed by
direction, frequency, duration and intensity. High force occurs with
low angle cases, in molar areas, with strong muscles, point contacts
and parafunctional forces such as grinding and biting finger nails.
Composite is strongest in compressive strength and weakest in
shear, tensile and modulus of elasticity strengths. Controlling forces
by preparation design and occlusal contacts can be critical to
restorative success.
Failure of a restoration occurs if composite fractures, tooth
fractures, composite debonds from tooth structure or micro-leakage
and subsequent caries occurs. A common area of failure is direct
point contact by sharp opposing cusps. Enameloplasty that creates
a three point contact in fossa or flat contacts is often indicated.
36.
Tooth preparation requires adequate access to remove caries,
removal of caries, elimination of weak tooth structure that could
fracture, beveling of enamel to maximize enamel bond strength, and
extension into defective areas such as stained grooves and
decalcified areas.
Matrix systems are placed to contain materials within the tooth and
form proper interproximal contours and contacts. Selection of a
matrix system should vary depending on the situation (see web
pages contacts and contours in this section).
Enamel and dentin bonding is completed. Composite shrinks when
cured so large areas must be layered to minimize negative forces.
Generally, any area thicker than two millimeters requires layering.
In addition, cavity preparation produces multiple wall defects.
Composite curing when touching multiple walls creates dramatic
stress and should be avoided.
37.
Composite built in layers replicate tooth structure by placing dentin
layers first and then enamel layers.
Final contouring with hand instruments is ideal to minimize the
trauma of shaping with burs.
Matrix systems are removed and refined shaping and occlusal
adjustment done with a 245 bur and a flame shaped finishing bur.
Interproximal buccal and lingual areas are trimmed of excess with a
flame shaped finishing bur.
Final polish is achieved with polishing cups, points, sandpaper
disks, and polishing paste.
38.
Indirect laboratory composite is indicated on teeth that required large
restorations but have a significant amount of tooth remaining. It is used
when a tooth defect is larger than indicated for direct composite and
smaller than indicated for a crown. A common situation is fracture of a
single cusp on a molar or a thin cusp on a bicuspid. Force analysis is
critical to success as high force will fracture composite, tooth structure
or separate bonded interfaces. High force is indicated on teeth furthest
back in the mouth for example, a second molar receives five times more
force than a bicuspid. Orthodontic low angle cases and large masseter
muscles generate high force. Sharp point contacts from opposing teeth
create immense force and are often altered with enameloplasty.
Indirect composite restorations are processed in a laboratory under
heat, pressure and nitrogen to produce a more thorough composite
cure. Pressure and heat increase cure while nitrogen eliminates
oxygen that inhibits cure. Increased cure results in stronger
restorations. Strength of laboratory processed composite is between
composite and crown strength and requires adequate tooth support.
39.
Tooth preparation requires removal of existing restorations and
caries. Thin cusps and enamel are removed in combination of
blocking out undercuts with composite, glass ionomer, flowable
composite or the like.
Tooth preparation requires adequate wall divergence to bond and
cement the restoration and ideally, margins should finish in enamel.
The restoration floor is bonded and light cured.
Bonding agent is light cured to stabilize collagen fibers and avoid
collapse during restoration placement. A base of glass ionomer or
composite is used if thermal sensitivity is anticipated.
Restoration retention is judged by bonded surface area, number
and location of retentive walls, divergence of retentive walls, height
to width ratio and restoration internal and external shape.
Resistance form, reduction of internal stress and conversion of
potential shear and tensile forces is accomplished by smoothing
sharp areas and creating flat floors as opposed to external angular
walls.
40.
Impressions are taken of prepared teeth, models poured and composite
restorations constructed at a laboratory. Temporaries are placed and a
second appointment made.
At a second appointment, temporaries are removed and a rubber dam
placed. Restorations are tried on the teeth and
adjusted. Manufacturers directions are followed. In general, bonding is
completed on the tooth surfaces and bonding resin precured.
Matrix bands are placed prior to etching to contain etch within prepared
areas. Trimming of excess cement where no etching has occurred is
easier.
Composite surfaces are silinated and dual cure resin cement applied.
Restorations are seated, excess resin cement is wiped away with a
brush and then facial and lingual surfaces are light cured. Interproximal
areas are flossed and then light cured. Excess is trimmed with hand
instruments and finishing flame shaped burs.
The rubber dam is removed and occlusion adjusted. Surfaces are
finished and polished.
41.
There are several mechanisms of composite wear including
adhesive wear, abrasive wear, fatigue, and chemical wear.
Adhesive wear is created by extremely small contacts and therefore
extremely high forces, of two opposing surfaces. When small
forces release, material is removed. All surfaces have microscopic
roughness which is where extremely small contacts occur between
opposing surfaces.
Abrasive wear is when a rough material gouges out material on an
opposing surface. A harder surface gouges a softer surface.
Materials are not uniform so hard materials in a soft matrix, such as
filler in resin, gouge resin and opposing surfaces. Fatigue causes
wear. Constant repeated force causes substructure deterioration
and eventual loss of surface material. Chemical wear occurs
when environmental materials such s saliva, acids or like affect a
surface.
42.
Dental composite is composed of a resin matrix and filler materials.
The resin filler interface is important for most physical properties.
There are three causes of stress on this interface including: resin
shrinkage pulls on fillers, filler modulus of elasticity is higher than
resin, and filler thermo coefficient of expansion allows resin to
expand more with heat. When fracture occurs, a crack propagates
and strikes a filler particle. Resin pulls away from filler particle
surfaces during failure. This type of failure is more difficult with
larger particles as surface area is greater. A macrofill composite is
stronger than a microfill composite.
Coupling agents are used to improve adherence of resin to filler
surfaces. Modification of filler physical structure on the surface or
aggregating filler particles create mechanical locking to improve
interface strength. Coupling agents chemically coat filler surfaces
and increase strength. Silanes have been used to coat fillers for
over fifty years in industrial plastics and later in dental fillers. Today,
they are still state of the art.
44.
Hierarchical microstructures
- Dr H-X Peng
The properties of composite materials can be tailored through
microstructural design at different lengthscales such as the microand nano-structural level.
At the micro-structural level, our novel approach creates
microstructures with controlled inhomogeneous reinforcement
distributions.
These microstructures effectively contain more than one structural
hierarchy. This has the potential to create whole new classes of
composite materials with superior single properties and property
combinations.
Research also involves tailoring the nano-structures of microwires/ribbons for macro-composites.
45.
- Dr Ian Bond, Dr Paul Weaver
Research has shown that shaped fibres can be an effective means
of improving the through thickness properties.
A set of guidelines for fibre shape and a preferred ‘family’ of fibres
have been generated from qualitative analysis for the role of
reinforcing fibres in composites.
Methods have also been developed to produce such shaped fibres
from glass in order to form reinforced laminates in sufficient quantity
for materials property testing using standard methods.
Fibre shape has been shown to play a key role in contributing to the
bonding force between fibre and matrix, with significant increases in
fracture toughness possible. Results suggest that the shaped fibre
specimens have a greater throughthickness strength than the
circular fibre composites that are currently used.
46.
- Dr Ian Bond
Impact damage to composite structures can result in a drastic reduction
in mechanical properties. Bio-inspired approach is adopted to effect
selfhealing which can be described as mechanical, thermal or
chemically induced damage that is autonomically repaired by materials
already contained within the structure.
Efforts are undergoing to manufacture and incorporate multifunctional
hollow fibres to generate healing and vascular networks within both
composite laminates and sandwich structures.
The release of repair agent from these embedded storage reservoirs
mimics the bleeding mechanism in biological organisms.
Once cured, the healing resin provides crack arrest and recovery of
mechanical integrity.
It is also possible to introduce UV fluorescent dye into the resin, which
will illuminate any damage/healing events that the structure has
undergone, thereby simplifying the inspection process for subsequent
permanent repair.
47.
- Dr Ian Bond and Professor Daryll Jagger
The material most commonly used in the construction of dentures is
poly (methyl methacrylate) and although few would dispute that
satisfactory aesthetics can be achieved with this material, in terms
of mechanical properties it is still far from ideal.
Over the years there have been various attempts to improve the
mechanical properties of the resin including the search for an
alternative material, such as nylon, the chemical modification of the
resin through the incorporation of butadiene styrene as in the "high
impact resins" and the incorporation of fibres such as carbon, glass
and polyethylene.
The use of self-healing technology within dental resins is a novel
and exciting approach to solve the problems of the failing dental
resins.
Methods are currently being developed to translate the self healing
resin technology into dental and biomaterials science.
48.
- Dr Bo Su
An electrospinning technique has been used to produce polymer,
ceramic and nanocomposite nanofibres for wound addressing,
tissue engineering and dental composites applications.
The electrospun nanofibres have typical diameters of 100-500 nm.
Natural biopolymers, such as alginate, chitosan, gelatin and
collagen nanofibres, have been investigated.
Novel nanocomposites, such as Ag nanoparticles doped alginate
nanofibres and alginate/chitosan core-shell nanofibres, have also
been investigated for antimicrobials and tissue engineering
scaffolds.
Zirconia and silica nanofibre/epoxy composites are currently under
investigation for dental fillings and aesthetic orthodontic archwires.
49.
- Dr H-X Peng
Carbon fibre composite components are susceptible to sand and
rain erosion as well as cutting by sharp objects.
The use of nanomaterials in coating formulations can lead to wearresistant nanocomposite coatings.
Work is developing novel fine-particle filled polymer coating
systems with a
potential step-change in erosion resistance and exploring their
application to composite propellers and blades.
These tailored materials also have potential applications in lightning
strike protection and de-icing.
The nano-structure of magnetic micro-ribbons/wires is being
investigated and optimised to obtain the Giant Magneto-Impedance
(GMI) effect for high sensitivity magnetic sensor applications.
50.
- Dr Ian Bond, Prof. Phil Mellor and Dr H-X Peng
The main aim of this work is to examine methods ofincluding
magnetic materials within a composite whilst maintaining structural
performance.
This has been achieved by filling hollow fibres with a suspension of
magnetic materials after manufacture of the composite component.
Research is continuing to tailor the magnetic properties of the
composite to other applications.
In another approach, magnetic microribbons and microwires are
being tailored and embedded into macrocomposite materials to
provide magnetic sensing functions.
51.
- Dr Fabrizio Scarpa
Auxetic solids expand in all directions when pulled in only one,
therefore exhibiting a negative Poisson’s ratio.
New concepts are being develope for composite materials, foams
and elastomers with auxetic characteristics for aerospace, maritime
and ergonomics applications.
The use of smart material technologies and negative Poisson’s ratio
solids has also led to the development of smart auxetics for active
sound management, vibroacoustics and structural health
monitoring.
52.
- Dr Paul May and Professor Mike Ashfold
Researchers in the CVD Diamond Film Lab based in the School of
Chemistry are investigating ways to make diamond fibre reinforced
composites.
The diamond fibres are made by coating thin (100 mm diameter)
tungsten wires with a uniform coating of polycrystalline diamond
using hot filament chemical vapour deposition.
The diamond-coated wires are extremely stiff and rigid, and can be
embedded into a matrix material (such as a metal or plastic) to
make a stiff but lightweight composite material with anisotropic
properties. Such materials may have applications in the aerospace
industry.
