Issuu on Google+

COMPOSITE RESIN INTRODUCTION: Although restorative dentistry is still concerned with the same treatment area as it was 20 yrs before; with the advent of some new materials and techniques it has changed the concept. Materials – properties – bond well - esthetic -

Functionally durable

-

Repairable

-

Easy to manipulate

-

Biocompatible

Composites are resin restorative materials having such physical structure as they are – -

insoluble

-

aesthetic

-

nsensitive to dehydration

-

easy to manipulate

DEFINITIONS: Skinner: A compound of two or more distinctly different materials with properties that is superior to the individual constituents. Philips and Lutz: A three dimensional combination of at least two chemically different materials with a distinct interface.

1


McCabe: A product, which consists of at least two distinct phases normally formed by blending together the components having different structures and properties.

HISTORY AND DEVELOPMENT: • 1940’s & 1950’s  Partially successful • Tooth like appearance Insolubility in oral fluids Polymerization shrinkage High coefficient of thermal expansion Clinical deficiencies and premature failure Inert filler particles were added to reduce the volume of the resinous compound

Bunocore 1955: Acid Etching Technique R.L. Bowen 1962: Development of modern composite  Experimenting on reinforcing epoxy resin with filler particles Main

innovation

Development

of

Bisphenol-A

glycidyl

methacrylate [BisGMA] Use of saline to coat filler particles that would bond chemically to the resin.

COMPOSITION AND ROLE OF ITS CONSTITUENTS: • Organic resin matrix • Inorganic filler particles 2


• A coupling agent • Activator-initiator system • Inhibitors • Colouring pigments Resin Matrix: Methacrylate – high polymerization shrinkage - higher co-efficient for thermal expansion Bowen – Bis-GMA resin matrix  Di-methacrylate  increased higher molecular water  * Extensive cross linking * Improvements in the properties of polymer Filler Particles: • Increased proportion of the matrix • Resin matrix is decreased  Polymerization shrinkage is less • H2O sorption and co-efficient of T.E. is less • Mechanical properties Types: Conventional Latest

3


Coupling Agent: Resin (flexible)

Coupling Agent Transfer stresses

Filler (stiffer)

- Improves properties e.g.

Titanates Zirconium Organosilanes

Activator – Initiator System: Methacrylate and dimethacrylate

Addition Polymerize Free radicals

Chemical 2 paste  Initiator – benzoyl peroxide  Activator – N, N dimethyl toluidine Both mixed together and addition polymerization reaction is initiated Light/heat: - First light activated system  U.V. light Replaced Visible light - Greater improved ability to polymerize increments up to 2mm - Single paste photo initiator

- Camphor quinone - Amine accelerators - Diphen amino ethyl methacrylate

- When left unexposed to light  do not react

4


Exposure to correct wavelength  Elicited photo initiation  Interaction of amines to form free radicals Inhibitors: -

Minimize/ prevent spontaneous polymerization of monomer

-

Free radical formed inhibits chain propagation

-

Butylated hydroxytoluine (0.01 wt%)

Optical Modifiers: -

Match appearance of teeth  Translucency

-

Shading  Pigments  Metal oxide

-

Opacity titanium dioxide

CLASSIFICATIONS: 1. Skinner: Traditional or conventional:

8-12 µm

Small particle filler:

1-5 µm

Microfilled:

0.04-0.9µm

Hybrid:

0.6-1µm

2. Philips & Lutz: Mean particle size of the filler Traditional:

5.30 µm; 1.5 µm]

Hybrid:

1.5µm; 0.1µm 5


Homogenous microfilled: 0.05 – 0.1 µm Heterogenous microfilled: 0.05 – 1; 1-2 µm 3. Based on Inorganic Loading: Heavy filled materials:

75%

Lightly filled materials:

66%

According to Bayne and Heyman: Megafill

Large individual filler particles (range)

Macrofill

10-100µ

Midifill

1-10µ

Minifill

0.1 – 1µ

Microfill

0.04 – 0.4µ

Nanofill

0.005 – 0.01 µ

Hybrid: Composite with a mixed range of particles sizes are called hybrid; and the largest particle size in that is used to define the hybrid type. • If composites  filler + uncured matrix (homogenous) • Pre-cured or unusual filler (heterogeneous)

Indications: -

Restoration of cavities

-

Core build-ups

-

Pit and fissure sealant

-

Esthetic enhancement procedure’s 6


-

Periodontal splitting

-

Orthodontic bonding

Contraindication: -

Operating site cannot be isolated

-

High caries index

-

If all of the occlusion is on the restoration

-

Deep subgingival areas

-

Parafunctional habit

Traditional Composites: -

Rough surface

-

Finishing

-

Discoloration

-

Poor resistance to occlusal wear

Microfilled Composites: -

Colloidal silica particles

-

0.04 µm; 2-3 hundred times smaller

-

To increase filler loading  Colloidal silica sintered  Particles several tenth of micron obtained

Properties: -

Low tensile strength

-

Smoother and esthetic surface

7


-

Silica filler is removed along with embedded resin during finishing

Clinical Considerations: -

Stress bearing situations and sites potential chipping

-

Resin of choice of anterior teeth

Small Particle Filled Composite: Developed to achieve smooth surface  Improve properties  Inorganic filler are grounded to a size smaller than used for traditional composites Average filer: 1-5µm Used quartz: Glasses that contain heavy metals Properties: -

Tensile strength is double than traditional

-

Co-efficient of thermal expansion is less

-

Surface smoothness is improved

-

Polymerization shrinkage is less

Clinical Consideration: -

Improved strength  large stress and abrasion

-

Smooth surface for anterior application

8


Hybrid Composites: -

Developed to obtain smoother surface

-

Consist of colloidal silica ground particles of glass with metals 75-80% - filler content

-

Average particle size 0.6 – 1.0µm

-

Physical and mechanical properties range between traditional and small particle; generally superior to microfill.

Clinical Consideration: Surface smoothness + Reasonably good strength – Widely used Posterior Composites: [Packable] -

Recent years widespread demand

-

Number of advantages associated with them Thermally non conductive Mercury free Bondable to the calcified tissue

Requirement: -

Aesthetics

-

Hardness value of the filler particles must not be higher than 3.39 Gpa

-

Young’s modulus ____ dentine

-

R.I. ___ enamel

-

Compressive strength more  Enamel 348 MPa  Dentine 297 MPa

-

Radiopacity should be higher than enamel 198% 9


Most common problem  Occlusal wear & poor fracture resistance  Occlusal loading and polymerization shrinkage Two mechanisms have been proposed: 1. Direct contact of the restoration with opposing cusp  High stresses are developed in small area of contact 2. Loss of material in non-contact area  Contact with a food bolus as forced across the occlusal surface Chewing habits Force levels

Patient variation

Oral environment Advantages: -

High free

-

Thermally non conductive

-

Bonding to tooth structure

Disadvantages: -

Technique sensitive

-

Contouring and wedging

-

Gap formation at interface

10


Indications: -

Patient allergic or sensitive to Hg

-

Patient afraid of Hg toxicity

-

Demand esthetics

Contraindications: -

Moisture control

-

Lack of time

-

Cost

Glass ionomer base under posterior composite: Concluded that, a flexible lining under posterior composite is required; because the interface between the restoration and the cavity wall is being stressed from the outset; due to polymerization contraction and later by mismatch of strain during functional loading. Flowable Composite: • Modulus of elasticity  composite increased Do not behave well under stress Ability to deform before breaking is reduced  Brittle • Polymerization shrinkage  flowable composites Modulus of elasticity  1/3rd of hybrid

11


• Used 1st increment of restoration as layer between dentine and restorative material  Absorbs some energy from the shrinkage of the restorative material Acts as a cushioning effect • Blocking out cavity undercuts during inlay; onlay and crown preparation Polymerization shrinkage and elasticity of flowable composite and filled adhesives: Studied polymerization shrinkage and elasticity of flowable composites. shrinkage

They than

found

that

traditional

flow

composites

composites;

while

show densely

higher filled

adhesives showed lower shrinkage. More densely filled adhesives were more rigid. Fibre Reinforced Composites: Structural material  Two distinct constituents  Reinforcing  Strength & Stiffness Surrounding – supports the reinforcement and provides workability -

Glass/ polyethelene and carbon fibres

12


-

Desirable properties – esthetics, adaptability, ease of use, potential for direct bond

Indirect Posterior Composites: Composite inlay system  Polymerized outside the mouth  Cemented to tooth with a compatible resin material Direct Indirect Light

Combination  Resin inlay construction

Heat Pressure

Direct:-

Apply separating medium to tooth  Restoration formed; light cured; removed  Subjected to additional light or heat 100° for min  Preparation is etched  Inlay is cemented to place with dual cure  Polished

Indirect:-

Impression

13


 In addition to conventional light and heat curing; lab processing  140° pressure 6 MPa for 10 min  Polymerization under heat and pressure  Homogenous microfilled resin  Higher filler content Less porosity Greater colour stability Advantages: -

Improved physical properties; resistance to wear

-

Polymerization shrinkage does not occur in tooth  Induced stresses / bond failure/ leakage

-

Resins reparable in the mouth

-

Do not abrade the opposite tooth

Smart Composites: -

Flouride releasing composites

-

When there is a drop of pH on any particular surface; these composites then release fluoride from its surfaces and helps prevent demineralization of the tooth structure

Compomer: 14


Poly acid modified composite Introduced in 1993 ďƒ  Composite ďƒ  G.I chemistry 2 parts: Restorative material:

Primer/ adhesive:

- Resins

- TGDMA

- Activator/ initiator

- Elastomeric resin

- Glass

- Acetone

Advantages: Over G.I.:

Composite:

1. Easy to handle

1. Bonding quicker/ simpler

2. Better colour

2. No acid etching

3. More strength

3. Flouide release

4. No mixing 5. Instant finishing 6. Resistant to abrasion -

Chemically almost similar to composite

-

H2O sorption almost equal to composite

-

Bond strength increase dentine than enamel

Widespread

- Simplicity in application - Less technique sensitive - Preventing technical errors during bonding

Nilaido et al (1997) demonstrated one recent area of concern to the use of compomer is that; one layer of primer adhesive does not

15


guarantee

a

reliable

bond.

They

found

that

double

bond

significantly improved the bond strength.

Hardness of resin modified glass ionomer and compomers: Evaluated the bond strength of a compomer to dental enamel; dentine and cementum. They concluded that acid etching of enamel is recommended before the use of a bonding agent because it promotes higher bond strength of compomer to enamel; however similar treatment is not needed in case of dentine and cementum. Technical Considerations: 1) Local anaesthesia 2) Preparation of operating site: Clean ďƒ  Plaque; pellicle; stains Calculus ďƒœ Site more receptive to bonding 3) Shade selection o Before subject the tooth to drying o Good natural light is advocated 4) Isolation: Rubber dam Cotton rolls Retraction cord

16


Acid Etching Technique: 1955 Bunocore  Uses phosphoric acid  Composite applied  Bonds well  Retentive system Technique: Clean tooth surface with pumice  Rinse – water spray  Carefully dry the tooth  Apply a base layer  With small applicator; bath the surface with etchant  Rinse the tooth from all aspects with water  Air dry  Frosty white appearance – successful etch 17


ďƒœ Restorative material placed

18


Dentine Bonding Agents: React – Mechanically Chemically Depends – Penetration of adhesive monomers into the collagen fibres left exposed by acid etching. First Generation: Development of surface active agent  Chelates with calcium on the tooth surface to generate water resistance chemical bond of resin to dentinal calcium. Second Generation: Phosphate ester material Negatively charged phosphate groups in the resin reacted with calcium in the smear layer. Third Generation: -

Acid etching followed by dentine bonding

-

Modified the smear layer to allow penetration of acidic monomer

Technique for Insertion of Composites: Chemically activated composites: 1. Equal amounts 2. Cross contamination avoided 3. Homogenous mixing 4. Inserted immediately after spatulation 5. Avoid air incorporation

19


6. Use of matrix band; without retainer Light Activated Composites: 1. Single component 2. Depth of cure limited 3. Not exposed to operatory light 4. High intensity curing unit should be used. 5. Curing  Proximal surface 6. Avoid looking on visible light

Curing of Composite Resins: 1. Chemically activated 2. Light curing -

Visible light – tungsten

-

Plasma arc light

-

Argon laser light

-

Led

3. Dual cure Chemical Curing: 2 paste  Initiator

Free Radical  Initiate

 Activator

polymerization

Disadvantages: 1. Oxygen incorporation 2. No control of working time

20


Light Curing: -

Single paste

-

Adequate working time

-

Allow insertion and contouring before curing is initiated

-

Not as sensitive to oxygen

Curing Lamps: -

Hand held devices

-

Few power unit connected to the hand piece by a long flexible liquid-filled light guide

-

Quartz

bulb

with

a

tungsten

filament

environment Light Emitting Diode: -

Emit light only in blue part of spectrum

-

440-480 nm

-

Do not require fillers – no heat

-

Cooling fan not needed

-

Require low wattage  battery powered

-

Low intensity radiation

Quartz Tungsten Halogen: 

Bulb

Filament

-

Both U.V. and white light – filtered

-

400 – 500 nm

-

Bulb intensity diminishes  21

in

a

halogen


Calibration meter to measure output intensity Plasma Arc Curing: -

Use a xenon gas  Ionized to produce a plasma

-

High intensity white light is filtered

-

Polymerization initiated  When free radical formed

-

For maximum curing  Which is 50-60% monomer conversion  16 joules/ cm2 for 2mm thick  Can be obtained by 40 sec exposure to a light emitting 400mW/sec2 Or 20 sec exposure / 800mW/sec2 or 13 sec / 1200 mW/sec2

Thus increased power density of lamp Increased rate of degree of cure Disadvantages: -

Placed incrementally 22


-

Shrink towards the light source

-

Technique sensitive

Dual Cure Resin:  Light + chemical 2 paste system: Benzoyl peroxide

Aromatic ter. amine

Mixed / Exposed  Polymerization is promoted Used: Situations that do not allow sufficient light penetration  Monomer conversion Recent Advances: Argon laser  initiate polymerization  Physical property superior  visible light Advantage: Rapid 10 sec application Xenon Plasma Arc Light: More intense than halogen  This neon laser produces increased heat  3 seconds 23


Diode Laser Light: -

True laser light

-

Ultra fast; 3-5 sec

-

Produces no heat

Curing Efficiency  Effectiveness of light energy  Visible light cure  410 – 500 nm

Precaution: Hardness

evaluation

of

dental

composites

polymerized

with

experimental LED base device. (J. Dent. Mat 201; 17(4):309-315) Evaluated hardness of composite resin cured by different LED; compared with conventional curing units. Hardness test. The LED  inferior hardness value when compared at 40 sec The light curing (device of 6 LED’s) was more efficient; it obtained 79 mw/cm2; whereas halogen irradiation was 475 mV/cm2.

A light curing method for improving marginal sealing and cavity wall adaptation of resin composite. (J. Dent. Mat 2001; 4:359-366) They studied to evaluate influence of light on – -

Marginal sealing and resin composite adaptation

-

Polymerization shrinkage rate

24


-

Hardness at top and bottom of surface. This study signifies that the use of a low initial light intensity

270 mw/cm2 for 10 seconds followed by 600 mW/cm2 for 50 seconds provides the best adaptation to the cavity walls and possibly the least polymerization shrinkage contraction stress. Finishing Process

of

adapting

Polishing the Removing

irregularities

to

restorative material to the tooth achieving the smoothest possible e.g. remove over hang margins, surface. shaping occlusal surfaces Optimum finishing + polishing impression ďƒœ Residual surface roughness ďƒœ Encourage bacterial growth Steps: Contour the restoration with a bur -

Carbide

-

Diamond

-

Coarse-abrasive coated disc

Finish the restoration with -

Fine; extra fine diamond burs

-

White stones

-

Medium / fine abrasive coated discs ďƒœ

25


Polish with fine and extrafine paste rubber polishing discs

*Surface sealant application: (Low viscosity resin) -

Surface porosity

-

Microcracks

-

Never over heat

-

Well polished composite lasts longer

Class of composite Traditional (large particle) Hybrid (large particle) Hybrid (midifiller) Hybrid (minifiller/ SPF) Packable hybrid Flowable hybrid Homogeneous microfill Heterogeneous microfill

Particle size

Clinical use

1-50 µm glass

High-stress areas

1. 1-20 µm glass 2. 0.04 µm silica 1. 0.1-10 µm glass 2. 0.04 µm silica 1. 0.1-2 µm glass 2. 0.04 µm silica Midifiller/ minifiller hybrid, but with lower filler fraction Midfiller hybrid, but with finer particle size distribution 0.04 µm silica

High-stress areas requiring improved polishability (Classes I, II, III, IV) High stress areas requiring improved polishabiity (Class III, IV) Moderate stress areas requiring optimal polishability (Classes III, IV) Situations in which improved condensability is needed (Classes I, II) Situations in which improved flow is needed and/or where access is difficult (Class II) Low-stress and subgingival areas that require a high luster an polish Low-stress and subgingival areas where reduced shrinkage is essential

1. 0.04 µm silica 2. Prepolymerized resin particles containing 0.04 µm silica

26


Composite resin/ dental implant courses by Indian dental academy