new composites

8/12/2019 New Composites

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COMPOSITES


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INTRODUCTION


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The journey of dental material science is a never-

ending phenomenon. Detailed research and constant

evolution have been inherent characteristics in this

journey.


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Introduction of new materials and different

techniques to over come the draw backs of the

previous restorative modalities has led to dramatic

changes in the way we practice dentistry today


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Traditionally metallic restorations such as gold,

amalgam have been the foundation of restorative

dentistry. Their strength and proven clinical

performance has been the benchmark for

comparison with newer materials.


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However, the advent of the esthetic era and

advances in adhesive technology along with the

deemed for life like tooth colored materials saw

the emergence of resin composite materials 1962


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DEFINITION


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According to Skinners

Acompound of two or more distinctly different

materials with properties that are superior or

intermediate to those of individual constituents.


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According to DCNA 1981

A three dimensional combination of at least two

chemically different materials with distinct

interface separating the components.


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CL SSIFIC TION


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I Skinner's

a) Traditional / Conventional 8-12m

b) Small particle filled 1- 5 m

c) Micro filled particles 0.04-0.9m

d) Hybrid composites 0.6 1m


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II Based on method of curing

1. Chemical cure

2. Light cure

3. Heat cure

III Based on Area

a) Anterior

b) Posterior


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Composition:

a) Resin matrix

b) Fillers

c) Coupling agents

d) Coloring agents

e) Activator-initiator system

f) Inhibitors


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RESIN MATRIX:

BisGMA: Bisphenol A - Glycidyl methacrylate

developed by R.L BOWEN in 1960

had certain disadvantages

- High viscosity

- Blending of filler particles was difficult

so diluent monomers were added, such as

UDMAurethane dimethacrylate

TEGDMA- Triethylene glycol dimethacrylate


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Fillers:

Are added to provide

- Increased strength, rigidity and hardness

- Increase in modulus of elasticity

- Decrease in coefficient of thermal expansion

- Reduction in polymerization shrinkage

- Improved workability

- Reduction in water sorption, softening and staining


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1. QUARTZ:

difficult to grind into finer

particles

difficult to polish

Abraded the opposing

tooth structure

Ground Quartz particles (20-30m)


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II SILICA:

Pure silica

fused silica

colloidal silica

Silica Particles (0.04m


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Glasses aluminosilicates

borosilicate

Others, Tricalcium phosphate

zirconium dioxide

Recently, Fluoride containing like

Yttrium trifluoride

Ytterbium trifluoride


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Coupling agents

- To bind filler particles to the resin matrix

- Allow the more flexible polymer matrix to transfer

stresses to stiffer filler particles.

- Provide hydrolytic stability by preventing the water

from penetrating along the filler resin interface

METHACRYLOXY PROPYL TRIMETHOXY SILANCE


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COLORING AGENTS:

Aluminium oxide

Titanium dioxide

0.0010.007% wt.


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Polymerization Mechanisms:

1.Chemically activated resins

2. Light- activated resins.


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Chemically activated resins:

Chemically activated materials are supplied as two pastes.

One of which contains the benzoyl peroxide initiator and the

other a tertiary amine activator (I.e N-N dimethyl P-

toluidine).


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When the two pastes are spatulated, the amine reacts

with the benzoyl peroxide to form free radicals and

polymerization is initiated


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Light Devices:

A number of curing lights are manufactured. The

light source is usually a tungsten halogen bulb. The white

light generated passes through a filter that removes the

infrared and visible spectrum for wavelengths greater than

500 nm.


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Degree of conversion:

A significant difference exists between light activated

and chemically activated resins. Chemically activated

resins cure throughout their bulk, whereas light

activated resins cure only where a sufficient intensity

received.


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Polymerization shrinkage:

Polymerization in composite resins is accompanied by a

shrinkage of 1% to 1.7%

The polymerization shrinkage is highest in case of the

micro filled composites because of the higher resin

content.


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The polymerization shrinkage can be reduced by:

i. Inserting and polymerizing the composite resin in

layers

ii. Preparing a composite inlay and then cementing

into the tooth


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Types of Composites


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Traditional Composites

a. First to be developed in 1970

b. Also called conventional or macro filled because of

larger filler particle size

c. Filler used is quartz

d. Filler loading is 70-80% wt or 60-65% rol


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Advantages:

1. Favorable optical properties

2. Favorable physical properties

3. Radiopaque


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Disadvantages:

Lack of polishability

Surface roughness

Plaque accumulation

Staining of surfaces

Sub optimal esthetics


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Small particle filled composites:

- Developed so as to achieve the physical properties

of the traditional composites and at the same time

the surface smoothness of micro filled composites.

- Particle size range from 1-5um


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- Filler commonly used is quartz

- Glasses with heavy metals

- Colloidal silica is added in 5 wt% to adjust

the viscosity of the paste


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Advantages:

- Surface smoothness of these resins are improved by

the use of small and highly packed filler.

- Wear resistance is improved.

- Polymerization shrinkage is less.


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Clinical considerations

- Because of high strength and higher filler loading they

are indicated in regions having large stresses.

- Because of small particle size, it is easier to achieve

smooth surface for anterior restorations.


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Micro filled composites.

Inorder to over come the problems of surface roughness

associated with traditional composite, micro filled was

developed

- Particle size0.040.4 um (200-300 times smaller

than traditional

- Fillercolloidal silica

To increase the filler loading

polymerized composite that is highly loaded with colloidal

silica is used.


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Advantages:

1. Decrease polymerization shrinkage good polishability

permanent surface smoothness excellent esthetics Good

wear resistance

Disadvantages:

1. Technical sensitive

Radiolucent

Short clinical usage

Alteration in physical properties


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Clinical Considerations:

The bond between the composite particles and the usable

matrix is weak resulting in chipping of such restoration

- Unsuitable for stress bearing areas


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HYBRID COMPOSITES

These composites were developed so as to maintain better

surface smoothness than small particle composites while

maintaining the superior properties of the same.


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As the name implied, there are two kinds of filler

particles It is a combination of colloidal silica (0.04um)

about 10-20wt% +Glasses with heavy metals 70-80%

wt (0.6- 1um)


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Advantages:

1. Favorable optical properties

2. Favorable Physical properties

3. Improved wear resistance

4. Superior surface morphology

5. Radiopaque

6. Acceptable esthetics

Di d t


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Disadvantages:

Increase surface roughness with time

Clinical considerations:

Because of their surface smoothness are widely used

in anterior and posterior restoration


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Indications:

- Used in Cl IIV except high stress bearing areas

like extensive Cl III

- Enamel hypoplasia

- Non carious lesions like abrasion and erosion

- Veneering

- Restoration of fractured incisal edges


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- Core build up

- Veneering of metallic restoration

- Splinting of fractured and luxated teeth

- Diastema closure

- Composite inlays

- Repair of old defective composite restoration.

C t i di ti


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Contra indications:

- In high stress bearing areas like cusp tips, ridges and

extensive class II

- Pts with abnormal habits like bruxism

- With high caries incidence

- Caries extending into sub gingival areas

- Repeated fracture of old composite restoration where

most of tooth str is involved


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Advantages:

- Good esthetics

- Less tooth structure reduction

- Low thermal conductivity

- Sufficient working time


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- Less time consuming (Single visit) Easy repair

- No health hazards like hg poisoning no varnish

2 corrosion

- No varnish 2 corrosion

- Micro mechanical bonding to enamel

CHEMICAL CURED LIGHT CURED


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CHEMICAL CURED LIGHT CURED

Polymerization is central Peripheral

Curing is in one phase is in increments

Sets within 45 seconds sets only after light

activation

No time for manipulation plenty of time for

manipulation


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Shrinkage is towards Shrinkage is towards

light source center of bulk

Less chance of air entrapment Air may get

incorporated during manipulation incorporated

more homogeneous mix

More wastage Less wastage

Not properly finished better finish


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UV LIGHT VISIBLE LIGHT

360-400 nm 400-480nm

Intensity falls with time remains the same

Injurious to operator and Not Injurious

patient eyes

Greater depth cannot Greater depth can be cured

be cured


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Indications

1. Classes I,II,III,IV and VI restorations

2. Foundations or core buildups

3. Sealants and conservative composite restorations

(preventive resin restorations)


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4. Esthetic enhancement procedures

- Partial veneers

- Full veneers

- Tooth contour modifications

- Diastema closures

5. Cements (for indirect restorations)

6. Temporary restorations

7. Periodontal splinting

Ad t


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Advantages:

1. Esthetic

2. Conservative of tooth structure removal (less

extension; uniform depth not necessary;

mechanical retention usually not necessary)

3. Less complex when preparing the tooth

4. Insulative, having low thermal conductivity


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5. Used almost universally

6. Bonded to tooth structure, resulting in good retention,

low microleakage, minimal interfacial staining and

increased strength of remaining tooth structure

7. Repairable


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2. Are more difficult, timeconsuming, and costly

(compared to amalgam restorations) because:

- Tooth treatment usually requires multiple steps.

- Insertion is more difficult

- Establishing proximal contacts may be more difficult

- Finishing and polishing procedures are more difficult


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Class I Restorations: All pit- and fissure restorations

are class I,


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Restorations on Occlusal Surface of Premolars and

Molars.

Restorations on Occlusal Two Thirds of the Facial

and Lingual Surface of Molars.

Restorations on Lingual Surface of Maxillary

Incisors.


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Class II Restorations: Restorations on the proximal

surface of posterior teeth are class II


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Class IV Restorations: Restorations on the proximalsurfaces of Anterior teeth that do not involve the

incisal edge are class IV.


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