INTRODUCTION

HISTORY

USES

COMPOSITION AND STRUCTURE

POLYMERIZATION MECHANISMS

CLASSIFICATION

PROPERTIES

BIOCOMPATIBLITY

MANIPULATION

SPECIAL TECHNIQUES

ADVANTAGES

DISADVANTAGES

RECENT ADVANCEMENTS

WHAT ARE

COMPOSITES???

A SOLID FORMED,FROM TWO OR MORE DISTINCT PHASES THAT

HAVE BEEN COMBINED TO PRODUCE PROPERTIES SUPERIOR TO

OR INTERMEDIATE TO THOSE OF INDIVIDUAL CONSTITUENTS.

TOOTH ENAMEL AND DENTIN ARE ALSO SOME OF THE NATURAL

COMPOSITES PRESENT IN NATURE.

COMPOSITE

BA

1962

Bisphenol A glycidyl methacrylate- (bis-GMA) and organic silane coupling agent

PMMA + QUARTZ

1940-1950

PMMA

20TH CENTURY

SILICATES

1950 198019701960 1990 2000 2010

Originaldevelopment

MACROFILLEDSelf-cure

composites

MID-FILLEDComposites

MICROFILLEDComposites

MID-FILLEDComposites

MIDI HYBRIDComposites

FLOWABLE

PACKABLE

MINI HYBRIDComposites

LOW SHRINKAGEComposites

NANOFILLED &NANOHYBRIDComposites

Non bondedcomposites

Acid etching &Enamel bonding

Dentin bondedComposites

Self-cured

UV-cured

Visible light-cured

Composite refinements

Reviewing last 55 years

3 part,2 part,1 partDentin bonding system

USES

1.Direct and indirect restorative material

2.Fiber Reinforced composite posts

3.Luting agents

4.Core build up in post endodontic restorations

5.Pit and fissure sealants

6.Bonding of orthodontic brackets

7.Splinting of mobile teeth

BASIC COMPOSITION

MATRIX

FILLERS

COUPLING AGEN

MATRIX: Coupling Agent:Plastic resin Binds by adhesion filler and

matrix

Continous phase

FILLERS:Reinforcing fibers/particles

Dispersed Phase

•Activator-Initiator-Soft moldable material hard durable mass

•Pigments-Matching tooth color

•Inhibitor- storage time, working time in chemically activated

composites

•UV Absorbers- Color stability

Most widely used

Aliphatic/Aromatic dimethyl acrylate monomers like

Bis-GMA

TEGDMA UDMA

MOST RECENTLY USED ARE THE SILORANE

MONOMERS

• POLYMERIZATION SHRINKAGE

• CROSS LINKING INCREASED – IMPROVED PROPERTIES

• STRENGTH,RIGIDITY

BUT DUE TO HIGH DENSITY THESE MONOMERS ARE VISCOUS AND

DIFFICULT TO MANIPULATE

TEGDMA(Dilutent monomer) + BISGMA(Viscous) Decreases Viscosity

easy to manipulate and paste like consistency

IMPROVE THE MECHANICAL PROPERTIES

DECREASE POLYMERIZATION SHRINKAGE

DECREASE THERMAL EXPANSION AND

CONTRACTION

DECREASE WATER SORPTION

RADIO OPACITY

QUARTZ:•Chemically inert

•Very hard and difficult to grind

•Difficult to polish

•Abrades opposing tooth

SILICA:•Less harder than quartz

•Non crystalline structure

GLASSES WITH HEAVY METALS:•Radio opaque

•Less inert

•Slowly leach out

•Shorter lifetime

FLOURIDE RELEASING FILLERS:

•Ability to release flourides

•Ytterbium triflouride and Ba-Al-

flourosilicates

Effect of filler size and distribution

The COMPOSITE properties are IMPROVED to a

great extent by increasing the filler loading.

This can be achieved by PARTICLES SIZE and

DISTRIBUTION

PARTICLES SIZE DISTRIBUTION

VOIDS/GAP

S

FILLER SIZE

LARGER PARTICLES

SCATTERING OF LIGHT

OPACITY

DECREASED CURING DEPTH

ROUGH SURFACE TEXTURE

STAINS,PLAQUE ETC

SMALL PARTICLES

LESS SCATTERING OF LIGHT

LESS OPACITY

INCREASED CURING DEPTH

SMOOTH SURFACE TEXTURE

HIGHER AESTHETICS

PARTICLES SIZE IN REFERENCE TO WAVELENGTH OF VISIBLE

LIGHT

•These bond the filler particles to the matrix

•They improve properties of resin by transferring stresses

from plastic resin matrix to stiff filler particles

•Prevent Leaching

•Organosilanes are most commonly used coupling agents

•Gamma methacryloxypropyl trimethoxysilane

Gamma methacryloxypropyl trimethoxysilane

MECHANISM

FUNCTIONS:

1.Extend storage life

2.Increase working time

Free radical formed by

brief exposure to

light

Inhibitor + Free radical

Inhibits chain

propagation

Reaction termination

Inhibitor exhausted

MECHANISM:

BUTYLATED HYDROXYTOULENE 0.01 WT%

TO ACHIEVE NATURAL TOOTH LIKE APPEARANCE

MECHANISM:

GREATER TRANSLUCENY

GREATER LIGHT PASSES

THROUGH

APPEARS MORE DARKER

AS LIGHT IS NOT

REFLECTED BACK

OPACIFIERS ADDED

TITANIUM DIOXIDE

ALUMNIUM OXIDE(0.0001

TO 0.007 WT%)

CLINICAL SIGNIFICANCE:

Darker shades and greater opacities have decreased depth of curing so we should either increase exposure time or apply thinner layers of material while curing

ADDITION POLYMERIZATION

CHEMICAL ACTIVATED RESIN

ACTIVATOR-

AROMATIC TERTIARY AMINE

INITIATOR-

BENZOYL PEROXIDE

LIGHT ACTIVATED RESINS

PHOTOSENSITIZER-

CAMPHOR QUINONEINITIATOR-AMINE

ACTIVATOR-VISIBLE BLUE LIGHT

Types

COLD CURING/SELF CURING

SUPPLIED AS:

SELF CURE

BASE

TERTIARY AMINE

N-N DIMETHYL-P-TOLUDIEN

BENZOYL PEROXIDE

CATALYST

:

POLYMERIZATION:

ADDITION POLYMERIZATION

REACTION STARTS AS SOON AS THE TWO PASTES ARE MIXED

ADDITION POLYMERIZATION

INDUCTION

ACTIVATION INITIATION

PROPAGATION CHAIN TRANSFER TERMINATION

1.INDUCTION

2.PROPAGATION

3.CHAIN TRANSFER

4.TERMINATION

ADVANTAGES DISADVANTAGES

Convenience and simplicity Mixing causes air entrapment

leading to porosity which might

weaken the material and

increase staining

Long term storage stability Aromatic amine accelerators

Oxidize and turn yellow with

time i.e color instability

Manipulation of working/Setting

time by varying proportions

Difficult to mix evenly

Degree of cure equal through

out if mixed properly

Marginal stress build up during

curing is much lower than for

photocured due to slower cross

linking

LIGHT CURING/PHOTOCHEMICALLY ACTIVATED

RESIN

UV LIGHT CURED VISIBLE LIGHT CURED

UV LIGHT CURED:

USED BEFORE.

LIMITED PENETRATION OF LIGHT INTO RESIN.

LACK OF PENETRATION THROUGH TOOTH STRUCTURE

CAUSED DAMAGE TO RETINA

VISIBLE LIGHT CURED:

SINGLE PASTE

PHOTOINITIATOR

CAMPHORQUININONE

0.2 WT%

DIMETHYLAMINOETHYL-METHACRYLATE

0.15 WT %

AMINE ACCELARATOR

POLYMERIZATIO

N

Exposure to light

(Wavelength 400-500nm)

Excites photosensitizer

Photosensitizerreacts with

Amine

Free radicals formed

Addition polymerization

starts

Advantages and DIsadvantages

FACTORS INVOLVED IN PHOTO

CURING

FACTORS

CURING LAMPS

LED LAMPS

QTH LAMPS

PAC LAMPS

ARGON LASER LAMPS

DEPTH OF CURE AND EXPOSURE

TIME

SAFETY PRECAUTIONS

•Hand held devices which contain the light source and have a rigid light guide made

up of fused optical fibers.

•The most widely used light source is QUARTZ bulb with a Tungsten filament in a

Halogen enviroment.

•Four types of lamps are used:

1.Light emitting Diode lamps (LED)

2.Quartz-tungsten-halogen (QTH) lamps

3.Plasma arc curing lamps (PAC)

4.Argon laser lamps

LED lamps

These light sources emit radiation only in the blue part of the visible spectrum between

440 and 480 nm

do not require filters

LEDs require low wattage,can be battery powered,generate no heat and are quiet

because a cooling fan is not needed.

Produce lowest intensity radiation

The latest versions utilize two or more LED units to increase intensity and extend

wavelength range

Quartz-tungsten-Halogen (QTH) lamps

QTH lamps have a quartz bulb with a tungsten filament that irradiates both UV and

white light

Must be filtered to remove heat and all wavelengths except those in the violet blue

range (~450 to 500 nm)

Intensity diminishes with use.

Plasma arc curing (PAC) lamps

Use ionized xenon gas to produce plasma

High intensity white light is filtered to remove heat

Blue light is then emitted (400-500nm)

Argon lamps

Highest intensity

Emit at a single wavlength

Emit wavelength of 490nm.

DEPTH OF CURE AND EXPOSURE TIME

•Amount of photons absorbed by initiator depends on

Wavelength

Light intensity

Exposure time

•For maximum curing radiant energy influx should be 16,000 mJ/cm2

• Light absorbtion and scattering in resin composites reduce the degree of

conversion and depth of penetration so exposure time should be increased.

•Curing depth should be kept 2-3mm

•Exposure time depends on the intensity of curing units.

•Higher the intensity lesser will be the exposure time

•Light attenuation varies for different composites so manufacturers instructions

should be followed.

To maximize the degree of polymerization and clinical durablity clinician should

adjust curing time and curing technique to intensity of light source.

Light is also absorbed and scattered as it passes through tooth structure especially dentin ,causing incomplete curing so in critical areas like proximal box so here the exposure time must be increased to compensate for reduction in light intensity

•Light emiitted by curing units can cause retinal damage.

•Never look directly into light tip and reflected light for longer periods

•Wear protective eye glasses and shields that filter light both for operator and

patient.

A curing lamp with wavelength matching the absorbance range of

photoinitaiator must be selected.

Critical concentration of free radicals must be formed to initiate

polymerization

Intensity decreases with distance so lamp tip must be placed at minimum

distance through out exposure interval

Curing angle should be 90 degrees to resin surface to deliver maximum

intensity

Lamp intensity should be evaluated frequently.

Combination of light cure and self cure composites

dual-cure resins are commercially available and consist of two light-

curable pastes

One paste contains benzoyl peroxide and other contains aromatic

tertiary amine.

Chemical curing occurs by mixing the pastes and is accelerated on

command with the light source

light curing is promoted by the amine/CQ combination

and chemical curing is promoted by the amine/BP interaction.

Dual-cure materials are intended for any situation that does not allow

sufficient light penetration to produce adequate monomer conversion, for

example, cementation of bulky ceramic inlays.

ADVANTAGE:

•Complete curing throughout is the advantage

DISADVANTAGE:

•Porosity

•Colour instability

CLASSIFICATION

CLASSIFICATION OF COMPOSITES:

I. Classification given by Skinner:

Traditional or conventional composites

8-12 .m

Small particle filled composites

1-5 . m

Microfilled composites

0-04 –0.9 . m.

Hybrid composites

0.6-1 . m

II Philips and Lutz classification:

According to the mean particles size of the major fillers –

Traditional composite resins: (5.30 m earlier, 1.5m

current)

Hybrid composite resins: (1.5 m. earlier, 0.05-0.1m.

current)

Homogeneous microfilled composites: 0.05-0.1 .m

Heterogeneous micro filled composites: 0.05-01, 1-25

.m

III Classifications based on inorganic loading:

a. Heavy filled materials – 75% of inorganic loading by wt

b .Lightly filled material –66% of inorganic loading by wt.

IV. Based on method of curing

1. Chemical cured

2. Light cured

3. Heat cured

4. Dual cured

V Classification based on area used

Anterior composites

Posterior composites

VI.GENERATIONS OF COMPOSITE RESTORATION

(Marzouk)

A. First Generation composites

•Consist of macro-ceramic reinforcing phase.

•Has good mechanical properties.

•Highest surface roughness

B. Second Generation composites

•Consists of colloidal and micro-ceramic silica.

•Low strength

•Unfavourable coefficient of thermal expansion

•Wear resistance better than first generation

•Best surface texture.

C. Third Generation composites

•Hybrid composite[combination of macro and micro

(colloidal) ceramics]

•Good surface smoothness and reasonable strength

D. Fourth Generation composites

•Hybrid composite (heat-cured, irregularly shaped, highly

reinforced composite macro-particles with micro (colloidal)

ceramics].

•Comparatively better surface characteristics and

mechanical properties

E. Fifth Generation composites:

•Hybrid composite (heat-cured, spherical, highly reinforced composite macro. particles with micro (colloidal) ceramics].•Improved workability•Surface texture and wear is similar to second generation composites•Physical and mechanical properties similar to fourth generation composites

F. Sixth Generation composites:

•Hybrid composite [agglomerates of sintered •micro (colloidal) ceramics and micro-ceramics]•Highest percentage of reinforcing particles•Best mechanical properties•Wear and surface texture similar to fourth generation•Least polymerization shrinkage

VII. Classification according to Bayne and

Heyman:

Category Particle size

Macrofillers 10-100 m

Small/fine fillers 0.1-10 m

Midfillers 1-.10m

Minifillers 0.1-1m

Microfillers 0.01 – 0.1 m (agglomerated)

Nanofillers 005 - 0.1 m

Composite types

Traditional Composites

Conventional or macrofilled composites.

The traditional composites have comparatively large filler

particles.

This category was developed during the 1970

The most commonly used filler for these materials is finely

ground amorphous silica and quartz.

Although the average size is 8 to 12 μm, particles as large

as 50 μm may also be present.

Filler loading generally is 70 to 80 wt% or 60 to 70 vol%

Advantage

High stength

Disadvantage

rough surface

Poor wear resistance

Poor marginal integrity

Finishing produces a roughened surface

Discoloration due to rough textured surface to retain stain.

Small-Particle-Filled Composites

To improve surface smoothness and retain or improve the

physical and mechanical properties of traditional composites

inorganic fillers are ground to a size range of 0.1 to 10μm.

•Fillers were made by grinding quartz to small particle size smaller

than traditional.

Small-particle-filled (SPF) composites generally contain more

inorganic filler (80 to 90 wt% and 65 to 77 vol%) than traditional

composites.

High strength and high hardness

High polishiblity,durablity.

USES

Class 1 and class 2 restorations

Microfilled Composites

Agglomerates of 0.01 to 0.1 um inorganic colloidal silica

The problems of surface roughening and low translucency

associated with traditional and small particle composites can be

over come through the use of colloidal silica particles as the

inorganic filler.

1.Homogenous

2.Heterogenous

Homogenous

Silica compound

SiCL4

Pyrolyticprecipitation

Amorphous silica0.04 um or 40nmHighly polishable

Small size

Large surface area +

Agglomeration and long chains

Increased monomer viscocity

2 % wt produces a stiff paste

Decrease filler

loading

Inferior mech.

properties

Hetrogenous

SiO2 + silanetreated +

liquid monomer

Solid resin

Resin filler particles

(5-50micron)

CURE PULVERIZE

PRECURED RESIN FILLER + MONOMER + SILANE TREATED COLLOIDAL SILICA = HETROGENOUS COMPOSITE

•Inorganic filler loading is increased by50 %

ADVANTAGES

•High polishiblity•Less shrinkage

DISADVANTAGES:•Weak bonding between precured resinparticles and matrix•Increased wear•Decreased mechanical properties•Not suitable for stress bearing areas

They should be finished with diamond burs rather than carbide burs as they are very much prone to chipping

•Material of choice for smooth surface lesions like class 3 and class 5

SUBTYPES:

1. Splintered prepolymerized particle2. Spherical prepolymerized particle3. Agglomerated prepolymerized particle

This category of composite materials was developed in an

effort to obtain even better surface smoothness than that

provided by the large particle composites, while still

maintaining the desirable properties.

Hybrid composites contain two kinds of filler particles:

Most modern hybrid fillers consist of:

1.Colloidal silica

2.Ground particles of glasses containing heavy metals.

Constituting a filler content of approximately 75 to 80 wt%

Hybrid Composites

The glasses have an average particle size of about 0.4 to 1.0

μm.

Colloidal silica represents 10 to 20 wt% of the total filler

content.

The mechanical properties inferior to those SPF composites

Surface smoothness + good strength Anterior

restorations,including Class IV sites.

• High stress areas where aesthetics dominates

• Nanofillers are the filler particles.

• These particles are extremely small (0.005-0.01 nm) and virtually invisible

• Their particle size is below range of wavelength of light and thus they do not absorb or scatter visible light

• Aggregates are silane treated

NANOFILLED COMPOSITES

• Additionally the extremely small size of nanofillers allow the particles to fit into spaces between other particles in composite and effectively increase the overall filler level.

• Nanofiller permit overall filler level of 80 wt% that significantly reduce the effect of polymerisation shrinkage and dramatically improves physical properties

• Commercially available nanocomposites:Filtek supreme plus Tetric N Ceram

NANOHYBRIDS

•Like conventional hybrids in range of size of nano fillers

•Mechanical properties like conventional hybrids

•Aesthetics and polishiblity like microfilled composites

•They can be used for both anterior and posterior restorations

•Stronger than nanocomposites

FLOWABLE COMPOSITES

A modifications of the SPF and hybrid composites.

The reduced filler makes them more susceptible to wear, but

improves the clinician’s ability to form a well adapted cavity

base or liner, especially in Class II posterior preparations and

other situations in which access is difficult.

Decrease filler

loading

Decreased viscosity

Easy to flow

Adapt into cavity

Diifcultaccessiblityposterior

areas

Called dental caulk,as it can flow into small crevices along restoration margins

USES: Sealing gingival floor of the proximal box of Class II restorations. Class V cavities. Small Class III cavities. First increment of all deep restorations to prevent voids and porosities and

to get good seal. Small Class I cavities frequently referred to as ‘Preventive Resin

Restorations’. Blocking out cavity undercuts during inlay, onlay and crown preparations

ADVANTAGES:• Decreased microleakage• Increased marginal adaptation

DISADVANTAGE:• High curing shrinkage• Decreased mechanical properties• Cannot be used in large restorations because of decrease wear resistance

CONDENSABLE COMPOSITES

•Because of the highly plastic, paste like consistency in the precured state,

composites cannot be packed vertically into a cavity in such a way that the

material flows laterally as well as vertically to ensure intimate contact with

the cavity walls.

•This can be explained in terms of class 2 cavity

•Compared with amalgam, the technique of composite placement is far

more time consuming and demanding.

• A solution to this problem is offered by resin composites with filler

characteristics that increase the strength and stiffness of the uncured

material and that provide a consistency similar to that of lathe-cut

amalgams.

•Elongated, fibrous, filler particles of about 100 μm in length

•RoughTextured surfaces and branched geometry tend to inter lock and

resist flow.

• This causes the uncured resin to be stiff and resistant to slumping,yetmoldable under the force of amalgam Condensing instruments (“Plugger”)

PROPERTIES

1.WORKING TIME AND SETTING TIME

Chemical cured composites:

Setting time:3-5 minutes

Working time:from start of mix till temperature

begins to rise

Light cured composites:

Curing is considered on demand

Composite may appear to be fully hard and cured after curing by light source,but curing reaction continues for 24 hours.

Degree of conversion is 75 %

Premature polymerization can occur with 60-90 seconds of exposure to the ambient light.

Degree of conversion/Degree of cure /Degree of

monomer to polymer conversion

•Percentage of carbon carbon double bonds

converted to single bonds during curing to form a

polymer resin

•Higher the DC greater is the strength,wear and

other propertiesA conversion of 50 % Bis-GMA means 50 % of polymer have

been polymerized

BUT

This does not mean remaining 40-50 % monomer is left in

resin because one of the two methacrylates group of Bis-

GMA may form covalent bonds with polymer forming a

pendant group

Conversion of monomer to polymer depends on

several factors like:

1.Resin composition

2.Transmission of light through material

3.Concentration of Sensitizer,initiator and

inhibitor

4.Lamp intensity

5.Absorbtion through composite

6.Scattering through composite

2.POLYMERIZATION SHRINKAGE

The normal range of curing shrinkage is 1.5

to 4 vol % 24 hours after curing

Composites with a high filler loading shrink

less

Chemically activated have a slow curing than

light cure resins which allows the shrinkage

stresses to relax

3.POLYMERIZATION SHRINKAGE STRESS

Curing

Spacing between monomers reduced

Polymerization shrinkage

Unrelieved stresses in resin

Stresses may break interfacial bond

Microleakage

The polymerization shrinkage and stress

affected by:

1.Total vol of composite

2.Type of composite

3.polymerization speed

4.C-Factor

REDUCTION OF RESIDUAL STRESSES

The internal pores in chemically cured resins

act to relax residual stresses that build up

during polymerization.

The slower curing rate of chemical activation

allows a portion of the shrinkage to be

compensated by internal flow among

developing polymer chains before formation of

extensive crosslinking

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 interfaces.

Approaches to overcome the problem of

stress concentration:

1)reduction in volume contracton by altering the chemistry and or composition of the resin system

2) clinical techniques designed to offset the effects of polymerization shrinkage

1.Incremental build up and cavity configuration

CONFIGURATION FACTOR (C-Factor)

• Is the ratio between the bonded surface areas of a resin based composite restoration to the non-bonded or free surface area

• Bonded surface/non bonded surface = C factor

• Residual polymerization stresses increases directly with this ratio.

• During curing, shrinkage leaves the bonded cavity surfaces in a state of stresses

• The non bonded ,free surfaces release some of the stresses by contracting inwards towards the bulk of material

• A layering technique in which the restoration,is build up in increments ,curing one layer at a time efficiently reduces polymerization stresses by minimizing the c factor

• The thinner layer lower the bonded surface and maximize the non bonded surface area.

ADVANTAGE

• This technique overcomes the limited depth cure and residual stress concentrations

DISADVANTAGE

• Adds to time and difficulty in placing restoration

2.Soft start,ramp curing and delayed curing

Photo-polymerization stress buildup

inspired by chemical initiation by

providing an initial low rate of

polymerization thereby extending the

available time for stress relaxation before

reaching gel point .

In this technique curing begins with a low

intensity and finishes with high intensity

SOFT START

SLOW POLYMERIZATION

INITIALLY

INCREASED STRESS

RELAXATION

GELATION POINT REACHED

INCREASE INTENSITY TO

MAXIMUM

Ramped curing and delayed curing

Variations of soft start

RAMPING CURING:

The intensity is gradually increased or ramped up during exposure.

Consist of either stepwise, linear or exponential modes

Delayed curing:

LOW INTENSITY

INCOMPLETE CURING

CONTOUR AND

SCULPTING RESIN

SECOND EXPOSURE FOR FINAL

CURE

Delay allows substantial stress relaxation to take place.

The longer the time period available for relaxation the lower the residual stresses.

Delayed and exponential ramp curing appear to provide the greater reduction in curing stress.

Intensity of the curing lamps must be considered in such situations as exposure time and curing are related to the intensity of the lamps.

4.COEFFICIENT OF THERMAL EXPANSION

Linear coefficient of thermal expansion of composite ranges between 25-30 x 10-6 /℃ and 55-68 x 10-6 /℃

Large differences between CTE of tooth and composite causes expansion and contraction resulting in stress

Filler loading is the only way to reduce the CTE.

5.WATER SORPTION

Water sorption may occur when:

1.Material may have a high solublity rate.

2.Resin may contain voids

3.Hydrolytic breakdown of the bonds between fillers and resin

Water sorption can decrement the longetivity of the restorations.

6.SOLUBLITY

Inadequate light intensity and duration especially in deeper areas causes incomplete polymerization and increased solublity.

ADA specifies solublity should be less than or equal to 7.5 µg/mm

Higher values lead to reduce wear and abrasion resistance.

7.RADIO OPACITY

Radio opacity is to check the integrity of resin

Radio opacity can be provided by glass

ceramics with heavy metals like Ba,Sr and Zr

Not chemically inert

8.COLOUR STABILITY

Esthetics is the major factor for use of

composites

Discolouration can be;

1.Marginal

2.Surface

3.Bulk

1. Marginal discolouration

May occur due to:

1.Improper adaptation of material to cavity

margin

2.Breakage of interfacial bonds between resin

and cavity

Marginal discolouration

Improper adaptation

Broken interfacial

bonds

Marginal staining

Accumulation of debris

Marginal gap

2.SURFACE DISCOLORATION

Related to surface roughness of the composite.

Seen in composites with larger filler sizes.

Debris gets entrapped between the spaces and

cannot be removed by routine brushing.

Dark pitted discolouration may be seen due to

exposure of air void when composite wears away.

3. Bulk discolouration

Seen in chemically activated resin mainly

Chemical degradation of components and

absorbtion of fluids from oral enviroment

Composites show loss of surface contour of composite

restorations in the mouth

Abrasive wear from chewing and tooth brushing

Erosive wear from degradation of the composite in the oral

environment

Wear of posterior composite restorations is observed at the

contact area,where stresses are the highest.

Interproximal wear has also been observed.

9.WEAR RATES

Ditching at the margins within the composite is observed for

posterior composites,resulting from inadequate bonding and

polymerization stresses.

Packable composites have better wear resistance than micro

filled or flowable composites

Two types of wear seen in composites:

2 body wear

3 body wear

Factors causing wear:

1.Fillers

2.Degree of polymerization

3.Tooth position

Picture from phillips pg

284

BIOCOMPATIBLITY

BIOCOMPATIBLITY

It is usually related to the effects on pulp from two aspects:

1. Inherent chemical toxicity of material

2. The marginal leakage of the fluids

•Pulp can be affected if chemicals leach out from the composites.

•Inadequately cured composites at floor of cavity act as a

reservoir of diffusable components that can induce long term

pulpal inflammation.

•This is for concern in case of light cure.

•If clinician attempts to cure a thick segment or inadequate

exposure the uncured material can leach out constituents

adjacent to the pulp.

•Adequately polymerized resins leach out in very small amounts

which cannot cause toxicity.

Inherent chemical toxicity of material

• The shrinkage of composite during polymerization and the subsequent marginal leakage is a well known phenomenon

• The marginal leakage might allow bacterial growth and the microorganisms may cause secondary caries or pulpalreaction.

• Therefore ,the restorative procedure must be designed to minimize polymerization shrinkage and marginal leakage

The marginal leakage of the fluids

• Bisphenol A (BPA), a precursor of BiSGMA has been

shown to be a xenoestrogen ,or a compound found

in environment that mimics the effects of estrogen

by having affinity for estrogen receptors

• BPA has been shown to cause reproductive

anomalies especially in development stages of fetal

wildlife

• Controversy surrounds this issue because it is unclear

how much BPA or BPA-DM is released to the oral cavity

and what dosage is enough to affect human health.

•Gic liners are applied as pulp protection in deep cavities

•Zincoxide eugenol is contraindiated as it interferes with

polymerization

Technique

1.Preparation of operating site

2.Shade selection

3.Cavity preparation

4.Isolation

5.Pulp protection

6.Adhesion

7.Matrix placement

8.Insertion,prepolymerization contouring and

curing

9.Finishing

10.Polishing

1.Calculus removal with proper instruments

2.Cleaning operting site with pumice slurry

Create a site more receptive for bonding

Prophy paste containing flavouring agent,glycerine

or flouride act as contaminants and conflict with

acid etch technique.

Shade of the tooth should be selected before isolation

Shade should be selected without prolonged drying the tooth

Composite materials are available in:

Enamel shadesDentin shadesTranslucent shadesOpaque shades

Good lighting should be present for proper color selection

1.Operator should hold shade tab near the tooth to determine natural colour.

2.Shade tab should be partially covered with operators thumb or patients lip – natural effect of shadows

3.The selection of shade should be done in natural light

4.The selection should be made rapidly

5.Final shade can be verified by patient with a mirror

6.Bleaching if done should be done before any restoration placement

The shade selected should be placed directly on the

tooth close to area to be restored and cured

PROCEDURE

Objectives in tooth preparation:

Extent is determined by size, shape, and location of defect

Remove all Caries, any fault, defective, old friable tooth structure.

Removal of discolored tooth structure as required for esthetics.

Create prepared enamel margin of 90° or greater by giving bevel wherever required.

Create 90° cavosurface on root surfaces

Outline form

Extend from periphery to sound tooth structure

Preparation should be done in most conservative way as possible

Retention form

Micromechanical retention by etching of enamel and dentin.

Dentinal retention groove

Enamel beveling

Beveling provides increased surface area of etching

Increased retentionDecreased microleakage

Gradual transition between composite and tooth

Bevels of 45 degrees should be given:1-2mm wide facially0.5mm other areas

Bevels should be prepared with medium grit diamond burs

Bevels should be avoided in:Class 1 restorationsClass 2 restorationsCervical margins with thin enamel

Resistance form

Primarily by micromechanical bonding

May be improved by:

• Flat preparation floors

• Floors perpendicular to occlusal forces

• Boxlike forms

Cavity designs for composite cavity preparation

• Conventional

• Beveled conventional

• Modified

• Box shape

• Facial/lingual slot

CONVENTIONAL

Similar to that of cavity preparation for amalgam restoration.

A uniform depth of the cavity

90° cavosurface margin is required

INDICATIONS

1. Moderate to large class I and class II restorations

2. Preparation is located on root surfaces.

3. Old amalgam restoration being replaced

BEVELED CONVENTIONAL

• Similar to conventional cavity design

• Have some beveled enamel margins.

INDICATIONS

1. Composite is used to replace existing restoration.

(class III, IV, V)

2. Restore large area

Rarely used for posterior composite restorations

MODIFIED

• All parameters determined by extent of caries.

• Conserve tooth and obtain retention (MICRO MECHANICAL).

• No specified wall configuration.

• No Specified pulpal or axial depth.

• Scooped out appearance

INDICATIONS

• small,cavitated,carious lesion surrounded by enamel

• correcting enamel defects.

BOX ONLY

•When only Proximal surface is faulty and no lesion on occlusal surface

•Extent is determined by caries

FACIAL OR LINGUAL SLOT

1. Lesion is proximal but access is made through

facial or lingual surface

2. Cavosurface is 90 or greater.

3. Direct access for removal of caries.

Isolation can be accomplished by rubber dams,cotton rolls

Retraction cords can be used for subgingival extensions

Contamination with saliva leads to decreased bond strength

Calcium hydroxide

Glass ionomer cement

Resin Modified Glass Ionomer

Zinc oxide eugenol is contraindicated

Acid

etchingBonding

agents

Acid may be grouped as:

Minerals (phosphoric acid,nitric acid)Organic (maleic acid,citric acid)Polymeric(e.g polyacrylic acid)

Most frequently used acid is 37% phosphoric acid

Available as: Gel or liquid form

Applied by brush or directly through syringe

15-20 seconds etching time

Primary teeth or young teeth with mind flourosis require longer etching time

Freshly cut enamel etches faster

Clinically the most important parameter of proper etched

tooth is presence of a frosty white appearance on tooth

Acid etch

Smear

layer

+

Enamel

removed

from

surface

1.Selective

dissolutio

n of

enamel

rods

2.Increase

d surface

area

Increased

surface

energy

Resin

penetrates

to

microporo

sites

Resin tags

Removes

hydroxy

appetite

layer

Microporous

collagen

network in

H20

Partially

open

dentinal

tubules

Clean tooth and isolate

Place mylar strip to

protect adjacent tooth

Place etchant liquid/gel

15-20 seconds

Wash for 10 sec

longer if gel used

Dry surface

Chalky white

appearance

Over drying must be avoided if dentin invloved as it may

result in collapse of collagen mesh which results in

forming a dense film and prevents bonding agent to

penetrate.

A thin layer of resin between conditioned dentin and resin matrix of resin composite restorative material.

Restorative resin are hydrophobic and tooth is are hydrophillicso bonding agent should have both parts.

The hydrophillic part bonds with calcium in hydroxyappatitecrystals or collagen and hydrophobic component bonds with restorative resin.

ETCHANT/CONDITIONER:selectively dissolves tooth structure to provide retention for restoration

PRIMERS:Bridge to connect tooth to adhesive

hydrophillic monomers in a solvent like alcohol,ethanol or water

Penetrate moist tooth structure especially dentin and collagen mesh and improve bond

EG:HEMA(2-hydroxylethyl methacrylate,4-MET(methacryloxyethyl trimelleticacid)

ADHESIVE:Hydrophobic monomers + small amount hydrophillic monomer

Used in combination with primers to form effective bond to tooth structure.

Adhesive bonds resin to primer

Primerpenetrates tooth and completes binding sequence

Eg: hydrophobic dimethacrylates like Bis-GMA with small amount of hydrophillic monomers like HEMA

Remove all debris and remove

excess water

Isolate tooth from saliva

contamintation

Saturate microbrush with

bonding agent

Apply with gentle rubbing

motion

Use gentle air pressure to

remove excess acetone and

water solvent

Cure for 20 seconds

Finishing

Good contour Occlusion smoothness

Appropriate

embrasure

form

Finishing—Process of removing surface defects or scratches created during the contouring process through the use of cutting or grinding instruments or both.

Remove all unattatched bonding agent with bard parker blade no 12,composite resin knife or gold foil finishing instrument.

Finishing burs,diamonds,,micron diamonds,burs,rubber point and disks are used to create surface texture,lobes and ridges

Polishing cups and polishing paste are used for lusture

Metal or plastic finishing strips interproximally

Polishing—Process of providing luster or gloss on a material surface.

Removal of surface irregularites and achieving smoothest possible surface

Polishing can be DRY:superfine disksWET:Coarse disks

Aggressive use of disks may be avoided

Polishing paste can be used for 15-30 seconds using rubber cup moistened with water

Microfilled composites can be polished with disks

Small particle hybrids can be polished with fine diamonds,flexibledisks and very fine polishing paste

Dry polishing:should be resrved only for microfilledcomposites.The heat from the disks produces highly durable,smear layer of resin over microfill

Recent advancements

“Alert”

Polyester using carbonate (-O-CO-O-)

Connects methacrylate ends to the central section of monomer.

PROPERTIES:packable like amalgam

photocurable in bulk

Segments

curable without generating high residual shrinkage stress.

Kalore

High molecular weight

Long rigid central section

Flexible methacrylate end groups

PROPERTIES:Reduced curing shrinkage

Enhanced monomer to polymer conversion

“Venus Diamond

4,8-di(methacryloxy methylene)-tricyclodecane(TCDDMA)

Bulky space-filling dimethacrylate monomer

Bulky three-ring central group provides steric hindrance

Which holds the monomers apart

PROPERTIESslows the rate of polymerization

Steric

hinderence

Dimethacrylate with a Bulky, Space-Filling Central Group

Durance

Dimer dicarbamate dimethacrylate (DDCDMA)

Bulky central group:

6-carbon aliphatic ring

two long hydrocarbon side chains

Center section is connected to two methacrylate end groups via urethane

groups

PROPERTIES

Greater stress relaxation

reduced shrinkage.

reduced water absorption

High-Molecular-Weight Phase-Separating Dicarbamate

with Hydrophobic Side Chains

“Filtek LS”

chemistry based on epoxy, rather than acrylic functionality.

tetra-functional “silorane” monomers

ring-opening polymerization.

STRUCTURE:

Silorane chemistry utilizes a combination of epoxy functionality

three-unit ring with two carbons and an oxygen

combined with siloxane units

PROPERTIES:

Reduced polymerization shrinkage

Silorane” Ring-Opening Tetrafunctional Epoxy Siloxane

Organically Modified Ceramic Oligomers

Ormocer is an acronym for organically modified ceramics.

molecule-sized hybrid structures

inorganic-organic copolymers.

ORGANIC MONOMER

+

CENRAL CYCLIC POLYSILOXANE

High-mol-wt flexible

relatively low-viscosity

cross-linkable mol

PROPERTIES:

Reduced polymerization shrinkage,

abrasion resistance

low water sorption

very high biocompatibility

excellent esthetics.

Polyhedral Oligomeric Silsesquioxane (POSS)

12-sided silicate cages

silane and functionalized to copolymerize with other monomers.

molecule-sized hybrid organic-inorganic oligomeric compound

“Artiste Nano-Hybrid Composite” (Pentron Clinical, Wallingford, CT).

PROPERTIES:Highly polishable

Excellent polish retention,

Good mechanical properties

Good wear resistance.

Patient's demands for aesthetics, phenomenal developments in the resin and filler

technologies, advance in nanotechnology and clinical training in their use has made

composite resins a material of choice for direct restorative purposes. The wide range of

colours,shades,translucencies,opacities,flouroscence,tones,viscosity etc available with

present generations of composite resins have enabled clinicians to provide a restoration

that mimics natural tooth structure and optimizes function as well.

Further research is always an ongoing process to reduce or eliminate drawbacks of

composite resins