Finishing and polishing materials

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FINISHING AND POLISHING AGENTS

-Presented byDr Arpita Dutta

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• INTRODUCTION• HISTORY• OBJECTIVES OF FINISHING AND POLISHING• RATIONALE• TERMINOLOGIES ASSOCIATED• FACTORS AFFECTING FINISHING AND POLISHING• PRINCIPLES• STEPS IN FINISHING AND POLISHING• SPEEDS• ABRASION

– TYPES OF ABRASION– FACTORS AFFECTING ABRASION

• CLASSIFICATION OF FINISHING AND POLISHING AGENTS• POLISHING OF RESTORATIONS

– ACRYLIC RESINS– ALLOYS– CERAMICS– STAINLESS STEEL CROWNS

• PRECAUTIONS• RECENT ADVANCES• REVIEW OF LITERATURE• CONCLUSION• REFERENCES

CONTENTS

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Well finished restorations offer-

High esthetic resultsLongevity of restorationsMaximal oral health for

patient

INTRODUCTION

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HISTORY

THE PREHISTORIC ERA-

•Over 10000 years ago- hunting and gathering instruments were sharpened by chipping and abrading one surface against another

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THE MIDDLE AGES- Stones, spears, shields

and daggers were produced by abrading against a cylindrical stone with abrasive surface

AGE OLD GRINDING STONE(Introduced about 4000 years ago)

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• THE 13TH CENTURY- The Chinese introduced the

first coated abrasives by embedding seashell fragments in natural gums that were spread on a parchment

• EARLY 1900s- Abrasive technology advanced

further through development and use of alumina grains, diamond particles and silicon carbide grit

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4. Achieving well adapted cavosurface margins5. Elimination of minute scratches 6. Establishing smooth light reflecting enamel surface

1. Removing marginal irregularities2. Defining anatomic contours3. Smoothening surface roughness

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• Rough surfaces are more likely to-

Retain plaque

Cause surface breakdown

and corrosion

Fracture

Cause wear of adjacent tooth or restoration

Produce stress conc.

points

Compromise esthetics

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ABRASION•Process of wearing away of a surface by friction

ABRASIVE•Outermost particle or surface material of an instrument that produces abrasion

SUBSTRATE•Material/surface being finished

CUTTING• Process of removing material from the substrate by use

of a bladed bur or an abrasive embedded in a binding matrix on a bur or disk.

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BULK REDUCTION: Process of removing excess material by cutting or grinding a material with rotary instruments to provide a desired anatomic form.

CONTOURING: Process of producing a desired anatomical form by cutting or grinding away excess material.

FINISHING: Process of removing surface defects or scratches created during the contouring process through the use of cutting or grinding instruments or both

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Grinding: Process of removing material from a substrate by abrasion with relatively coarse particles

Polish: Lustre or gloss produced on a finished surface.

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Speed and pressure of

application of abrasive

Difference in hardness of

substrate and abrasive

Abrasive properties(particle

size, shape, hardness)

Lubricants used

Properties of the backing/ bonding material – rigidity,

elasticity, flexibility, thickness, porosity

Structural properties of

substrates

FACTORS DETERMINING FINISHING AND

POLISHING

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PRINCIPLES

1. CUTTI

NGUse of any instrument in a

blade like fashion

Regularly arranged blades that remove

small shavings of the substrate

Unidirectional cutting pattern

2. GRINDINGRemoves small particles of a substrate through the action of bonded or coated abrasive instruments

Predominantly unidirectional

3. POLISHINGMultidirectional in its course of action

Acts on an extremely thin region of the substrate surface

fine scratches - not visible unless greatly magnified

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STEPS IN FINISHING AND POLISHING

1. BULK REMOVAL

2. CONTOURING

3. FINISHING

4. POLISHING

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1. Bulk reduction and Contouring

• Removal of excess material through

cutting and grinding

• Instruments - diamond, carbide and

steel burs, abrasive coated disks

• Desired anatomy and margins must be

achieved

BULK REDUCTION CONTOURING

CARBIDE BUR 8-12 FLUTED 12 - 16 FLUTED

ABRASIVE S >=100µm 30 - 100 µm

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3. Finishing

• Introducing finer scratches to surface of substrate

• Provides a blemish free smooth surface.

• 18 - 30 fluted carbide burs , fine and super fine diamond

burs, or abrasives upto 20 µm in size.

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4. Polishing

• Provides lustre.

• Smaller particles provide smoother and shinier surfaces

• Abrasives of 8-20 µm

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Adsorbed gases & water vapor(1nm) Oxide (10-100nm)

BEILBY LAYER (1-100nm)

Worked layer(1-100nm)

Bulk material

THE BEILBY LAYER

An amorpho

us disorganiz

ed molecular surfa

ce layer

of highl

y polished metal

which is

a result of melting and

surface

flow during

machining of the

molecular layer

s such

as using a

series of abrasives

of decreasing

coarsene

ss during the

polishing processe

s

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Importance of polishing dental restorations and teeth

Less bacterial colonization

Metallic restoration - prevention

of tarnish and corrosion

Comfortable for the patient

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SPEEDS USED FOR FINISHING AND POLISHING

LOW SPEED-

• <12000rpm• Better tactile sensation• Lesser heat generation• Cleaning, caries excavation, polishing

MEDIUM SPEED/ INTERMEDIATE SPEED

• 12000-2,00,000rpm• Contouring

HIGH SPEED/ ULTRAHIGH SPEED

• >2,00,000 rpm• Faster, need lesser pressure, vibration• Cutting teeth, removing old restorations, gross

finishing and contouring

The standard Micomotor handpiece- 35000rpm

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ABRASION AND ABRASIVES

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ABRASIVE ACTION- PRINCIPLE

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TYPES OF ABRASION

1. TWO BODY WEAR-• Abrasive bound to instrument and used to polish

specimen• E.g.- Trimmers, abrading burs, bonded abrasives,

coated abrasives

Abrasive Substrate

Two body wear

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2. THREE BODY WEAR• Abrasive is a loose slurry between polishing

substrate and surface of the specimen to be polished• Use of lubricant( water, glycerin or silicone)• E.g.- Polishing pastes containing Aluminium oxide,

diamond particles

Rubber cup

Abrasive paste Substrate

Three body wear

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EROSION

• Wear caused by hard particles impacting a substrate surface, carried by a stream of liquid or stream of air. Eg. Sand blasting a surface

• Chemical erosion Acid etching

Enhance bonding

Not a method of finishing/polishing

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Factors affecting abrasionHardness

Shape

Size

Pressure

Speed

Lubricants

Factors affecting rate of abrasion

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Relates to durability of an abrasive

Measure of a material’s ability to resist indentation

Abrasive particle must be harder than the surface to be abraded

First ranking of hardness was published in 1820 by Carl Friedrich Mohs

Knoop and Vickers hardness tests

HARDNESS

FRIEDRICH MOHS

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Material Moh’s Material Moh’s

Talc 1 Aluminium oxide 9

Gypsum 2 Silicon carbide 9-10

Chalk 3 Boron carbide 9-10

Rouge 5-6 Diamond 10

Pumice 6 SUBSTRATES

Tripoli 6-7 Acrylic 2-3

Garnet 6.5-7 Pure gold 2.5-3

Tin oxide 6-7 Porcelain 6-7

Sand 7 Amalgam 4-5

Cuttle 7 Dentin 3-4

Tool steel Enamel 5-6

Zirconium silicate 7-7.5 Glass 5-6

Tungsten carbide 9 Resin composite 5-7

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Diamond is the hardest naturally occurring substance

However….

Harder substances are • Synthetic- Wurtzite form of boron

nitride (w-BN)

• From outer space- Lonsdaleite (from meteorites)

BUSTING THE MYTH

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SHAPESharp, irregular particle produces deeper abrasion than rounder particle under equal applied force

Numerous sharp edges - enhanced cutting efficiency

Abrasion rate of an abrasive decreases with use

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SIZE

Larger particles size, abrade a surface more rapidly

Particles based on their size: 1. Coarse -100 µm to 500 µm, 2. Medium -10 µm to 100 µm3. Fine - 0 to 10 µm

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PRESSURE

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Deeper and wider scratches are produced by increasing the applied force from F1and F2

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SPEED

Faster speed

Faster cutting rates

Temperature increases

Greater danger of overcutting

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LUBRICATION

Minimize the heat buildup

Facilitates removal of debris

Cooling action and removal of debris enhances the abrasion process.

Water, glycerin or silicone ; Water most common

Excess lubrication – prevent abrasive contact

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ABRASIVE INSTRUMENT DESIGNREQUIREMENTS OF

AN ABRADING INSTRUMENT-

Right particle size

Not produce deep scratchesSharp edges that

break down to expose new edge

particlesNot gouge the substrate

Not permanently deform under load

or high temp

Abrasive motion

• Abrasive motion can be classified as 1. Rotary- burs2. Planar- disk3. reciprocal motion.

• ROTARY• In rotary motion, the bur in a high speed hand piece

rotates in a clockwise direction.

• Planar motion• disks • removes material along a plane. • preferably be done in one direction to

obtain a smoother surface.

• Reciprocal motion• two different motions at the same time:

part cyclic and part up and down motions. • This is useful to access interproximal areas

to remove overhangs, to finish sub-gingival margins without creating ditches, and to create embrasures.

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Abrasive grits

• Derived from materials that have been crushed and passed through a series of mesh screens

• Dental abrasive grits based on particle size are

• Coarse• Medium coarse• Medium • Fine• Superfine

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MAINTENANCE OF THE EFFICIENCY OF

ABRASIVE

• Truing :

Abrasive instrument is run against a harder

abrasive block until the abrasive instrument

rotates in the hand piece without eccentricity or

run out when placed on a substrate.

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• Dressing :

1)Reduces instrument to correct working size,

shape

2)Removes clogged debris (abrasive blinding) -

Restores grinding efficiency

Truing Dressing

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1

2

Classification of abrasives.

ABRASIVE

VITREOUS BONDING

RUBBER BONDING

RESINOID BONDING

BONDED NON BONDED

SINTERED BONDING

DISPERSED IN WATER SOLUBLE

MEDIUM

POLISHING PASTES

COATED

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Bonded abrasives-Abrasive particles are incorporated through a binder to form a grinding tool

• Particles are bonded by four general methods:

1. Sintering- Strongest, produced by fusing particles together

2. Vitreous bonding-Abrasive+ glassy ceramic matrix, cold pressed to shape and fired

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Sintered Diamond points Vitreous bonded abrasives

Resinoid bonded abrasives

Silicone bonded abrasives

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Non bonded abrasives- not bonded to a substrate ( 3 body wear)• Dispersed in gel or paste form

• Polishing pastes Fine or ultrafine

Al2O3(<1μm)or diamond particles(1-

10μm)

• Applied to substrate with a

nonabrasive device - synthetic foam,

rubber, felt, chamois cloth, wheel.

• Dispersed in water soluble medium

such as glycerin

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Coated abrasive disks and strips• Supplied as disks and finishing strips.

• Fabricated by securing abrasive particles to a flexible

backing material

• Available in different diameters with thin and very thin

backings.

• Moisture – resistant backings are advantageous

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Abrasive discs : • Gross reduction, contouring, finishing, and polishing of

restoration surfaces

• Coated with aluminum oxide abrasive

Abrasive strips : • With plastic or metal backing are available for

smoothening and polishing the interproximal surfaces of

direct and indirect bonded restorations

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OTHER CLASSIFICATIONS OF FINISHING AND POLISHING AGENTS

1. Cutting Instruments : • Tungsten carbide

2. Bonded abrasive • Diamonds • Silicon carbide • White stone • Tripoli • Rouge

3. Impregnated abrasives-Aluminium oxideEmeryQuartzSilicon carbideGarnetZirconium silicateCuttle

4. Loose abrasivesAluminum oxideUltra fine diamond particlesTin oxidePumice

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According to Hardness According to Hardness a) Hard abrasive - Diamond, Silicon carbide.

b) Medium abrasive - Pumice, Silicates, Zirconates.

c) Soft (Polishing) abrasive - calcites ( Robert Craig)

Natural abrasives1. Arkansas Stone

2. Chalk

3. Corundum

4. Diamond

5. Emery

6. Garnet

7. Pumice

8. Quartz

9. Sand

10. Tripoli

11. Zirconium silicate

12. Cuttle

13. Kieselguhr

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Synthetic Abrasives1.Silicon carbide2. Aluminum oxide3.Synthetic diamond4.Rouge (Iron oxide)5.Tin oxide

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Arkansas stone

• Semi translucent , light gray, siliceous sedimentary rock.

• Contains microcrystalline quartz.

• Attached to metal shanks and trued to various shapes

• Fine grinding of tooth enamel and metal alloys

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Chalk

• Mineral forms of calcite.

• White abrasive composed of

calcium carbonate.

• Used as a mild abrasive paste to

polish tooth enamel, gold foil,

amalgam and plastic materials. 

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Corundum • Mineral form of aluminum oxide

• Physical properties are inferior

to those of alpha aluminum

oxide.

• Grinding metal alloys

• A bonded abrasive in several

shapes.

• Used in instrument – White

stone

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Natural Diamond• Transparent colorless mineral

composed of carbon• Superabrasive

• Supplied in several forms• Bonded abrasive

rotary instruments• Flexible metal backed

abrasive strips• Diamond polishing

pastes.

• Used on ceramic and resin based composite materials

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Diamond burs color coding and grit sizeBur type Color Grit size ISO no

Supercoarse Black ring 181μm 544

Coarse Green ring 151μm 534

Medium No ring 107-126μm 524

Fine Red ring 40μm 514

Superfine Yellow ring 20μm 504

Ultrafine White ring 15μm 494

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Emery

• Natural form of an oxide of aluminium

• Grayish- black corundum

• Coated abrasive disks, Arbor bands

• Greater the content of alumina - finer the grade of

emery.

• Finishing metal alloys or acrylic resin materials.

Garnet

• Dark red, very hard .

• Comprise - silicates of Al, Co, Mg, Fe, Mn

• Garnet is coated on paper or cloth with glue.

• Fractured during grinding sharp, chisel-shaped plates

• Grinding metal alloys or acrylic resin materials.

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Pumice

• Highly siliceous material of volcanic origin

• Powder-crushing pumice stone

• Abrasive action is not very high

• Polishing tooth enamel, gold foil, dental amalgam

and acrylic resins

• Quartz

• Very hard, colorless, and transparent.

• Crystalline particles are pulverized to form sharp,

angular particles - coated abrasive discs.

• Grinding tooth enamel and finishing metal alloys.

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Sand

• Predominantly composed of silica.

• Rounded to angular in shape.

• Applied under air pressure to remove refractory

investment materials- sandblasting

• Coated on to paper disks

• Tripoli

• Derived from light weight, friable siliceous sedimentary rock.

• Rock is ground and made into bars with soft binders

• Color- white/grey/pink/red/yellow.

• Polishing for metal alloys and some acrylic resins.

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Zirconium silicate / Zircon

• Off -white mineral.

• Ground to various particle sizes - coated

abrasive disks and strips.

• Component of dental prophylaxis pastes

Cuttle

• Referred to as cuttle fish, cuttle bone, or cuttle.

• White calcareous powder

• Available as a coated abrasive

• Polishing of metal margins and amalgam

restorations.

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Kieselguhr

• Siliceous remains of minute aquatic plants - diatoms.

• Coarser form - diatomaceous earth

• Excellent mild abrasive

• Risk for respiratory silicosis caused by chronic exposure 

Synthetic Silicon Carbide

• Extremely hard abrasive and 1st synthetic abrasive

• Highly effective cutting of metal alloys, ceramics

and acrylic resin materials.

• Abrasive in coated disks and as vitreous - bonded

and rubber instruments.

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Aluminum oxide

• White powder

• used as bonded abrasives, coated abrasives and air

propelled abrasives.

• Finishing metal alloys, resin based composites and ceramic

materials.

• Pink and ruby variations- adding chromium compounds

Rouge

• Consists of iron oxide, which is the fine red

abrasive component.

• Blended in to various soft binders in to a cake form.

• Used to polish high noble metal alloys.

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Tin Oxide

• Extremely fine abrasive.

• Less abrasive than quartz.

• Polishing teeth and metallic restorations in the mouth.

• Produces excellent polish of enamel.

• Mixed with water or glycerin - abrasive paste.

Synthetic Diamond

•Controllable, consistent size and shape.

•Resin bonded diamonds have sharp edges

•Larger synthetic diamond particles – greenish

•Blocks with embedded diamond particles – truing other bonded abrasives

•Used primarily on tooth structure, ceramics and resin based composites.

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Polishing instruments

Rubber abrasive points.

Fine particle disks and strips.

Fine particle polishing pastes

Electrolytic Polishing

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POLISHING DISCS

POLISHING STRIPS

POLISHINGPASTES

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Electrolytic polishing

• Electrochemical process

• Excellent method for Co-Cr alloys

ELECTROLYTES-

CONC ACIDS-•SULPHURIC ACID+ HCl•PERCHOLATES•ACETIC ANHYDRIDE

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FINISHING OF INDIVIDUAL

RESTORATIONS

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• Contour with tungsten carbide burs and sand

paper. Use a rubber point to remove the scratches.

• Apply pumice with a rag wheel, felt wheel, bristle

brush or prophy cup.

• Apply Tripoli or a mixture of chalk and alcohol with

a rag wheel.

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FLEXIBLE DENTURES

FINISHING-• Use of rubber wheels- pink and brown• TC bur

POLISHING-• Use of synthetic pumice• Polishing with brown tripoli• Use of Black B20 bristle brush without any compound• Mirror shine compound

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• 2 types of kits-• 1 Extra oral kits • 2. Intra oral kit

Extraoral Finishing and Polishing 1. Finishing diamonds2. Finishing discs or bonded abrasive wheels3. Loose polishing paste used on Robinson’s brush

FINISHING AND POLISHING OF CERAMICS

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Intraoral polishing of ceramics1.Finishing diamonds. 2.Finishing discs or Rubber polishing

instruments . 3.Diamond polishing paste

Diamonds should be used wet to avoid excessive heat. Preferred devices to apply diamond -polishing paste intraorally include enhance polishing Prophy cups or Robinson brushes.

FINISHING AND POLISHING OF ALL CERAMICS

• Contour with flexible diamond disc diamond burs, heatless or polymer stones or greenstones

Finish with white stones or abrasives

impregnated rubber disc, cups and points

• Apply over glaze or natural glaze on ceramic if necessary

ALLOYS

• Alloys used for PFMs or denture frameworks can be finished with combination of stones, disks and wheels.

• After casting cleaned of investment debris with water and a tooth brush

• Soaked or pickled, in warm HCL acid to remove the surface oxide layer.

• Small nodules of metal Carborundum stone.

• The surface of casting rubber wheel impregnated in abrasive particles (e.g Al2O3 or SiO2) reduces surface roughness to level 0.10 to 0.15 µm.

• Final polish Tripoli and rouge on rag wheel. The final surface roughness -0.05 µm.

FINISHING OF STAINLESS STEEL CROWNS

• Smoothened and polished with a cloth or chamois wheel on the dental lathe, using Tripoli polishing agent and jeweler’s rouge (iron oxide) .

• Debris from the finishing process, accumulated inside the crown, can be removed with a wet cotton swab.

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RECENT ADVANCES

AIR ABRASION

NANOPARTICLE INCORPORATION

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AIR ABRASIVE TECHNOLOGY

• Alternative to rotary instrument

cutting.

• High pressure stream of 25-30µm

Al2O3.

• ‘Air polishing’- controlled delivery of

air, water and Sodium bicarbonate

slurry.

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Uses 

• Cavity preparation

• Removal of defective restorations

• Endodontic access through porcelain crowns

• Minimal preparation to repair crown margins

• Superficial removal of stains

• Roughening of internal surfaces of indirect

porcelains or composite restorations

Application Of Nanotechnology In Abrasives

• Nano silica abrasives

• Particle size of nano silica ranges from 10-90nm and is spherical in shape.

• It has been reported that polishing with nano-silica provides high polishing and low surface roughness . Also polishing of teeth with nano silica helps in prevention of damage caused by cariogenic bacteria.

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Biological hazards of the finishing procedure

• Aerosols – silica based

materials (smaller than 5µm)

• Silicosis or grinders disease

• Precautions -adequate water

spray, suction, eye gear,

facemasks, proper ventilation

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Precautions• Heat generation during cutting and contouring ,

finishing and polishing procedures is a major

concern.

• To avoid adverse effects to the pulp, cool the

surface using air water spray and intermittent

contact.

Methods to assess the effectiveness of finishing systems and devices

The most common to asses the effectiveness of finishing and polishing system and devices on dental restorative materials include aided and unaided visual evaluation

a. Profilometerb. Optical microscopec. SEM ( scanning electron microscope )d. Reflectometer

Review of literature

• The objective of this study was to compare both qualitatively and quantitatively the effects of 4 chairside polishing kits (Exa Technique, Acrylic Polisher HP blue, AcryPoint, Becht Polishing Cream) and conventional laboratory polishing (Universal Polishing Paste for Resins and Metals, Lesk Polishing Liquid) on 3 different types of acrylic resins: autopolymerizing, heat-polymerizing, and injected heat-polymerizing resin materials.

• Conventional laboratory polishing was found to produce the smoothest surface of denture base acrylic resin.

• Chairside silicone polishing kits produced a significantly smoother surface of acrylic resin than specimens polished with a tungsten carbide bur.

Kuhar M et al, Effects of polishing techniques on the surface roughness of acrylic denture base resins, J Prosthet Dent, 2005;93(1):76-85

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Methods Of Polishing Adjusted Porcelain Advocated By Various Authors• Sulik and Plekavich 1981- Hard rubber wheelwet pumicewet tin oxide• Klausner et al 1982- Diamond paste and the pumice/whiting.• Zalkind et al 1986- Sandblasting with aluminum oxide before refiring.• Haywood et al 1988, 1989- Instruments which progressively decrease in particle size

(series of finishing grit diamonds) 30 fluted carbide bur and diamond polishing paste. • Goldstein 1989- Cups and points made by Shofu• Haimondo et al 1990- Shofu kit diamond paste.• Jagger and Harrison 1994- Series of sandpaper disks of increasing fineness (Soflex)

and rubber points (Shofu).

• Author suggests- hybrid points with fine grade 15 micron diamond grit• Dura-white stones; • Silicone rubber points; • Silicon rubber cups used in conjunction with a fine grade 2 mm diamond polishing paste

Glazing and Finishing Dental Porcelain: A Literature Review Ahed Al-Wahadni

• To find out the correlation between the roughness of diamonds and roughness created on dentin after tooth preparation & to measure the surface roughness of dentin after tooth preparation with different grit sizes of diamond rotary instruments

• There is positive correlation (r = 0.93) between the roughness of diamonds and roughness created on the dentin

• Selection of correct grit size and their correct sequence for tooth preparation has an influence on the surface characteristics

• So completion of the tooth preparation with a finishing bur appeared to be the method of choice if a smooth tooth preparation surface is preferred

The effect of grit size of diamonds on the dentinal surface : Dr. Shivangi Sinha

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Finishing and polishing

techniques are important in

preparing clinically

successful restorations .

A definite sequence should

be adopted in finishing and

polishing of each restoration

Finishing and polishing begin

with coarse abrasives and end with fine

abrasives

The process of abrasion is affected by

properties of the abrasive and the material being

abraded.

Clinically it is easier to control

the rate of abrasion by

speed rather than the

pressure. Care must be taken to

avoid over finishing margins and contours of restorations and

to avoid over heating.

CONCLUSION

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REFERENCES

Anusavice, Phillips Science of Dental Materials, 12th edition, 2012, Elsevier publications, Florida, Pp 231-254

Hatrick Eakle Bird Dental Materials 2nd Edition p 143-156 Craig . Powers and Wataha, Dental Materials, Properties and

manipulation, 8th edition,2005, Elsevier publications, India , Pp 110-28

Mahalaxmi Textbook of Dental Materials

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REFERENCES

Kuhar M et al, Effects of polishing techniques on the surface roughness of acrylic denture base resins, J Prosthet Dent, 2005;93(1):76-85 The effect of grit size of diamonds on the dentinal surface : Dr. Shivangi SinhaGlazing and Finishing Dental Porcelain: A Literature Review Ahed Al-Wahadni

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THANK YOU