Finishing & polishing materials in dentistry/ rotary endodontic courses by indian dental academy

Finishing and polishing
materials

INDIAN DENTAL ACADEMY
Leader in Continuing Dental Education
www.indiandentalacademy.com

introduction

Terminologies

•Principles of cutting, grinding ,finishing and polishing

Classification of materials

Benefits of finishing and polishing

Steps in finishing and polishing

Finishing and polishing procedures

Glass Direct filling
composites amalgam ceramics
Ionomer gold
cement

Summary and conclusion

introduction
Finishing, polishing of dental restorations are important
aspects of clinical restorative procedures that enhance
both aesthetics and longetivity of restored teeth.

Residual surface roughness, associated with improper
finishing and polishing of dental restorations ,can result
in number of clinical difficulties.

The problems include excessive plaque accumulation
,gingival irritation, increased surface staining, poor or
suboptimal aesthetics of the restored teeth.


Finishing and polishing refers to gross contouring of the
restoration to obtain the desired anatomy,

and the reduction and smoothing of the roughness and
scratches created by finishing instruments.

A number of methods and tools for finishing and
polishing restorations are available to clinicians
including: fluted carbide bur; diamond burs; stones;
coated abrasive discs and strips; polishing pastes; and
soft or hard rubber type cups, points, and wheels
impregnated with various abrasives grits.


Proper finishing of restorations is desirable not only for
esthetic considerations but also for oral health.

The primary goal of finishing is to obtain a restoration
which has good contour, occlusion, healthy embrasure
forms, and smoothness. Tight margins should blend
esthetically into the tooth’s natural contours.

The polish should be smooth enough to be tolerated
well by gingival tissue.

It has been proven that rough surfaced restorations can
create clinical problems such as plaque retention,
gingival irritation, staining, higher wear rates, and
recurrent caries.


Preferential retention of microorganisms occurs on the
rough surface of the restorations

Quiern et al 1995

The efficacy of finishing and polishing materials and
procedures on contemporary composites is an important
and often formidable challenge within the restorative
process.
Besategui et al 1992
Restoration finish surface roughness and surface
integrity, as well as the physicochemical properties of
material itself, can affect plaque retention periodontal
disease and recurrent decay
Weitman et al 1994

Definition

Finishing refers to gross contouring or reduction of
restorations to obtain the desired contour, while polishing
refers to the reduction of roughness and surface
scratches .
Auj.Yap et.al

Journal of Operative Dentistry. 2004


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

Polishing: the most refined of the finishing
processes, removes the finest surface particle.

Kenneth j. Anusavice


Terminologies
Abrasive: a hard substance used for finishing and
polishing a less hard substance

Buffing: process of producing a lustrous surface through
the abrading action of fine abrasives bound to non
abrasive binder medium

Bulk reduction: process of removing excess material with
rotary instruments to produce a desired anatomic form.


Contouring: process of producing a desired anatomic
form by cutting away excess material

Cutting: process of removing material from the substrate
by use of a bladed bur or an abrasive embedded in
binding matrix on a bur or disk

Finished and polished restoration: a prosthesis or a
direct restoration whose outer surface been
progressively refined to a desired state of surface finish

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


Abrasivity: property of one material to abrade another
material by means of frictional heat

Polishing agents: any material used to impart luster to a
surface

Abrasion: the wearing away of substance or structure
through or abnormal mechanical process


Glaze ceramic: specially formulated ceramic powder
when mixed with liquid and applied to ceramic surface
and heated to appropriate temperature produces a
smooth glassy surface

Grinding: process of removing material from a substance
by abrasion with coarse particles.

Polish: luster or a gloss on a material surface.

Substrate;.. The material being finished is called the
"substrate"
[According to Journal of prosthodontic terms – 1991]

Benefits of finishing and
polishing


Mainly provide

Oral health
Function
esthetics


Oral health

A well contoured and polished restorations promotes
oral health by resisting the accumulation of food debris
and pathogenic bacteria.

This is accomplished through reduction in total surface
area and reduced roughness of the restoration

Smoother surfaces have less retention areas and are
easier to maintain in a hygenic state.


ORAL FUNCTION

A highly polished restoration show a very less tarnish
and corrosion

Oral function is enhanced with a well polished restoration
because food glides more freely over occlusal and
embrasure surfaces during mastication, and minimizes
the wear rates.

Rough surfaces will develop high contact stress that can
cause the loss of functional and stabilizing contacts
between teeth.


Finishing and polishing improves the
strength of the restoration especially in the
areas that are under tension.


AESTHETICS

Finishing and polishing gives lusture to visible surface of
a restoration thus increases the optical property of
materials.

A high mirror like polish is preferred in highly visible
areas such as the labial surfaces of the maxillary anterior
teeth.
These surfaces are not subject to high contact stresses
and they are easily accessible for cleaning.

Important anatomic features and textures may be added
to these area without affecting oral health or function


Principles of cutting grinding
finishing and polishing


Even though there are distinct differences in function of
cutting grinding and polishing at times they overlap

Depending on the hardness, shape and size of the
abrasive particles used and the speed of the hand piece
each of the process is done.

Higher speed and higher pressure removes excess
material


Cutting: refers to the use of bladed instrument or the use
of any instrument in a blade fashion.

Substrate may be divided into large separate segments,
or they may sustain deep notches or grooves.

Grinding :removes small particles of the substrate
through the action of the bonded or coated abrasive
Contains randomly arranged abrasive particles

Each particle contains several sharp points that run
along the substrate surface and removes particles.

Cutting and grinding are uni directional.


Bulk reduction

Instruments used are diamond, carbide, steel burs-
coated discs,seperating discs
Diamond , abrasive coated disks cuts by grinding
action
Steel and carbide burs is by cutting action
Abrasive coated discs are popular instruments for
bulk reduction of composites


Contouring
Even though contouring can be achieved during bulk
reduction ,in some cases it requires finer cutting
instruments

Desire anatomy and margins are obtained

The smoothness depends on the instrument used and
further requires further steps to achieve smoothness

12 to 16 fluted carbide burs and abrasives ranging from
30 to 100 micro meter provide fine contouring action


FINISHING.
The term polish would remain an operative tem whereas finish would
be the preferred term used, to describe the type and character of a
final surface

Not all finishes are achieved by polishing
In some instances the finish of a material is a coating that has been
placed.

Electro plated deposits, pit and fissure sealants covering etched
white-spot on tooth enamel and thermally processed ceramic over
glazes are examples of finishes produced by coatings.

This type of glaze called an Auto glaze or Self glaze is an example of
a finish that is not achieved by polishing or coating


The finishing process usually removes materials such that

1. Surface blemishes and imperfections are removed
2. The material is shaped to an ideal form
3. The outermost surface of the material is developed to a
desired state
Particles of the substrate material are removed by the
action of a harder material that comes into frictional
contact with the substrate.


polishing
It is the most refined of the finishing process which
removes the surface particles

Each type of polishing abrasive acts on an extremely thin
region of the substrate surface

Progress from the finest abrasive that can remove
scratches from the previous grinding process and
completed when desired level of smoothness is achieved

The final stage produces scratches so fine they are
visible when greatly magnified


The purpose of polishing is to provide an enamel
like luster

Small particles provide smoother and shiner
surfaces

Ideally abrasive particles size ranging 20micro
meter provide luster at low magnification

The surfaces must be cleaned between steps
,the debris particles on substrate causes
scratches


Examples of polishing materials
Rubber abrasive points
Fine particles discs
Polishing pastes
Soft felt points
Muslin wheels
Prophylaxis rubber cups
A non abrasive material should be used as an applicator
while using polishing pastes.


Felt leather, rubber and synthetic foam are popular
applicator materials for buffing

Porous texture allows fine abrasive particles to be
retained during the buffing procedure

Polishing is a multi directional, in its course of action.


Method to asses the effectiveness
of finishing systems and devices


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

A. Profilo meter
B. optical microscope
C. scanning electron
microscope
D. reflecto meters


Profilometer asses surface roughness of a restorative
material after finishing and polishing procedures

It’s a device that uses a diamond stylus of precise
dimensions to trace a fixed linear distance over the
surface

It produces a tracing and using digital analog hardware
and software ,also calculates the average surface
roughness (ra value) for the resultantant tracing

All the three methods ( visual, SEM, and profilometer)
are technique sensitive ,but with care and attention to
detail all three methods can yield reproducible and
highly useful information about the finishing and
polishing procedures


Relying on one single analytical method to asses may
lead to misleading results and conclusions

Visual methods are prone to errors as a result of the
influence on shading and influence composition of the
structure of the specimens under evaluation

SEM must be done carefully to provide sufficient contrast
to observe surface topography and with low angle views
to detect clearly variations in the surface smoothness


Profilo meter data must be obtained in a reproducible
manner and with prior microscopic visual evaluation of
the finished samples to ensure that then stylus tracings
run perpendicular to the pattern of surface scratches
produced on the surface of the specimen

when each method of analyses is done carefully and
with reproducible results , all three methods should
validate each other in confirming the efficacy of finishing
and polishing devices


Abrasion
Wear of a material that occurs whenever two surfaces
slide against each other

Process of finishing involves abrasive wear of the
particles

Outermost particles on the surface of an abrading
instrument is referred as abrasive

The material being finished is called as substrate


The rotational direction of the rotary instrument is an important
factor in controlling the instrument action on the substrate surface

When hand piece and bur are in same direction of translation it
produces a rougher surface and rotational bur tends to run away
from the surface.

When a hand piece and bur at the surface being abraded is
translated in the opposite direction smooth surface is achieved


Abrasion may be two body or three body

Two body abrasion occurs when abrasive particles are
bonded firmly to abrasive instrument and no other
abrasive particles used eg:diamond bur

Three body abrasives occur when abrasive particles are
free to translate and rotate between two surfaces eg non
bonded surfaces :prophylactic paste


The cutting and grinding will be improved with the use of
lubricants

Water, glycerin or silicone is used commonly

Water soluble lubricants are used most preferred.

Excess amounts of lubricants will decrease the cutting
efficiency


erosion
Is caused by hard particles impacting a substrate surface
carried by either a stream of liquid or air such as
sandblasting a surface

Dental laboratories employ erosive methods of finishing
and polishing the materials

Two types of erosive process are
A. chemical erosion
B. hard particle erosion


Classification of finishing and
polishing devices


All abrasive finishing and polishing devices fall into one three categories.

Finishing and polishing devices:

Cutting instruments tungsten carbide burs

Abrasive finishing and
polishing devices

Bonded abrasives Coated Loose abrasives
Elastic binder’s Aluminum oxide, silicon Aluminum oxide
right binders carbide ,quartz ultra fine diamonds,
white stones

Steven.R.Jefferies DCNA ,1998


Natural abrasives
Arkansas stones, chalk, corundum diamond, garnet,
pumice, quartz, sand, Tripoli, and aluminum and silicate.

Remnants of living-organisms
kieselghur and cuttle

Manufactured abrasives
synthesized materials, that are generally preferred
because of their more predictable physical properties. Eg
silicon carbide
Anusavice


According to Hardness
a) Hard abrasive - Diamond, Silicon carbide.
b) Medium abrasive - Pumice, Silicates,
Zirconates.
c) Soft (Polishing) abrasive - calcites
( Robert g Craig)


According to use
a) Finishing abrasive.
b) Polishing abrasive.
c) Cleansing abrasive.
(Craig, Obrien, Powers)


Abrasive instrument design


Abrasive grits : derived from materials that have been
crushed and passed through a series of mesh screens to
obtain different particle size

Grits classified according to particle size
A. coarse
B. medium
C. fine
D. extra fine
Coarse and medium grit size are used for cutting and
grinding where as fine and extra fine are used for


A. bonded - diamond burs
B. non bonded- prophylactic pastes
Bonded abrasives
The abrasive particles that are incorporated through a
binder to form a grinding tools such as points ,wheels
,separating discs, coated thin discs.

Particles are bonded by four general mechanisms
A. Sintering
B. vitreous bonding eg glass and ceramic
C. resinoid bonding
D. rubber bonding

Sintered abrasives are strongest of abrasives where the
particles are fused together

Vitreous abrasives mixed with a glass or ceramic matrix
material, cold pressed or hot pressed in instrument
shape and fired to fuse the binder

Resin bonded cold pressed or hot pressed and then
heated to cure the resin

Rubber bonded are cured same as the resin bonded


Ideal binder holds the abrasive particles in the tool
sufficiently long enough to cut, grind, or polish the
substrate

Bonded abrasives should be trued and dressed before
its use.

Truing is a procedure through which abrasive instrument
is run against harder abrasive block until it runs out.

it indicates the efficiency of instruments, before clinical
use.


Abrasive discs

Gross reduction

Contouring and finishing and
polishing of restoration
surfaces

Most discs are coated with
aluminum dioxide


Abrasive strips
Bonded with either plastic or metal backing.

used to smooth and polish the proximal surfaces of all
direct and indirect bonded restorations

Metal strips are usually limited when tight inter proximal
contacts are seen especially in ceramic restorations

Plastic strips primarily used for composites,compomers,
hybridonomers and resin cements


Coated abrasives
Coated abrasive is finishing devices usually in the form
of a paper, nylon or polymeric backing on symmetric
matrix.

Most common example of coated abrasive include
circular coated abrasives discs.


Sof-lex contouring and polishing discs are
coated abrasives

Aluminum oxide particles constitute the
most commonly used abrasive compound
on coated abrasive discs

Rotary diamond burs are also considered
as coated abrasives.


BONDED ABRASIVES
Are devices in which the
abrasive particles and media
are uniformly dispersed
throughout the matrix

Matrix is usually elastomeric
material ,silicone rubber

rigid and non elastic in nature,
bullet shaped or pointed white
stone used in low or high
speed rotary hand piece for
reduction of composite
restorations.


LOOSE ABARSIVES
Loose abrasives are polishing pastes contain a fine particle size
distribution of either aluminum oxide or diamond particles dispersed
in water soluble vehicle, such as glycerin,

Aluminum oxide particles pastes are designed for final polishing of
composite resin materials

Particles size ranging from 0.3m to 1m

Diamond polishing pastes contain loose abrasive diamond particles
in size range less than 10m.

Effective particles size distributions of diamonds polishing pastes
size range0.3m to and 1m.


Indicated for final polishing of adjusted porcelain and
ceramic materials.

Binders for diamond abrasives are manufactured
specially to resist abrasive particles loss

diamond is his hardest particle and bonded to metal
wheels and been blanks with special heat resistant
resins such as polyamides.

Super coarse and fine grades are then plated with nickel


Nickel plating provides improved properties and acts as
a heat absorber.

Titanium coatings are given to extend the longitivity.

Finishing diamonds for composites contain particles
40um or less in diameter.

Diamond burs should be used with copious amounts of
water spray and rotational speed less than 50.000 rpm.


COATED
Abrasive disks and strips: Are fabricated by securing
abrasive particles to flexible backing material (heavy
weight paper, metal or nylon) with a suitable adhesive
material.

Supplied as disks and finishing strips

Moisture resistant


ABRASIVE MOTION:
The motion of abrasive instruments is classified
as
rotary, planar, reciprocal.
Burs- rotary
Disks – planar
Reciprocating hand pieces cyclic motion
Provide benefit of accessing interproximal and
sub gingival areas to remove overhangs to finish
sub gingival margins without creating ditches
and to create embrasures.

Hardness of abrasive
The strength of an abrasive is often measured by the
hardness of the particles of surface material

The hardness is a surface measurement of the
resistance of one material to plastic deformation of
another material when the force is applied.

The first hardness ranking was published by Fredric
Mohs a German mineralogist in 1820

He ranked 10 minerals by their relative scratch
resistance to one another

The least scratch resistant mineral talc received a score
of 1 and the most scratch resistant mineral diamond

TYPES OF ABRASIVES


Natural abrasives
Arkansas stones, chalk, corundum diamond
garnet, pumice, quartz, sand Tripoli, and
silicates.
Remnants of living-organisms
kieselghur and cuttle
Manufactured abrasives
synthesized materials that are generally
preferred because of their more predictable
physical properties. Eg silicon carbide

Diamonds

Transparent, colorless mineral
composed of carbon

it’s the hardest substance known

It has the super abrasive ability to
abrade any substance

Bonded abrasive available in
rotary instruments

non bonded will come in diamond
abrasive polishing pastes

Finishing diamonds are used to
contour, adjust, and smooth
composites, or porcelain


These burs have bits of industrial diamond incorporated
into their working surfaces.

They are manufactured in a variety of shapes and sizes
and come in different grits, ranging from 8µ to 50µ.

In most cases, they are applied in sequence, starting with
a coarser grit and progressing to a finer grit.

Diamond burs should always be utilized with water spray
and at speeds less than 50,000 rpm.


Other polishing instruments, such as rubber
polishing instruments or pastes, will
usually follow the use of diamonds.


Synthetic diamond abrasive
They are primarily used on tooth structure, ceramic materials and
composites

Advantage over natural diamonds include they are contourable
,consistent in many sizes and shapes

Shape determines the binder needed to use binder can be either
resin or metal

Used exclusively as abrasive

Polishing pastes contain the particle size ranging from 1to 5 microns


ARKANSAS STONE
Is a semi translucent light grey
silica

Sediment of rock mined in
Arkansas.

It contains microcrystalline
quartz and is dense hard and
uniformity textured.

Small pieces of this mineral
are attached to metal shanks

For fine grinding of tooth
enamel and metal


CHALK:

One of the mineral form of
calcite is chalk,

white abrasive component of
calcium carbonate.

Used as mild abrasives paste
to polish tooth enamel gold foil
and amalgam restorative
materials


Emery
Grayish black corundum in the fine grain form.
Predominantly as coated abrasive disk.
Finishing metal and acrylic resin.

Corundum
Mineral form of aluminum oxide is usually white
Physical properties are inferior to those of manufactured aluminum
oxide
Used for grinding metal alloys, available as bonded abrasive in
several shapes
It is most commonly used in the instrument white stone


GARNET
Number of different minerals that possess similar
physical properties and crystalline forms.

These minerals are silicates of aluminum cobalt, iron
magnesium, and manganese.

Garnet is dark red.
forms chisel shaped plates which make it highly
effective.
Used in grinding metal alloys and acrylic resin materials.


PUMICE:
Volcanic activity produces this light
grey highly siliceous material.

Used mainly in the grit form but
can be found in some rubber
bonded abrasives.

Flour of pumice is fine grained
volcanic rock derivative from Italy

polishing of tooth enamel gold foil,
dental amalgam, acrylic resins


QUARTZ:
Most commonly used form of
quartz is very hard, colorless
and transparent.

Most abundant and
widespread of minerals.

Quartz crystalline particles are
pulverized to form sharp
angular particles used for
coated abrasive disks.

Finish metal alloys, grind
dental enamel.


SAND:
Mixture of small mineral particles
predominantly composed of silicate
particles, represent a mixture of colors
making abrasive distinct in appearance.

Particles are rounded to angular shape.

Applied under air pressure to remove
refracting investment materials from base
metal alloy castings.

Coated on to paper.


TRIPOLI:
Tripoli named after the place Tripoli in Africa
where the sediment rocks are obtained.

This abrasive is derived from a light weight
friable silicones sedimentary rock ,can be white
gray ,pink, red or yellow.

The gray and red type is most frequently used
in dentistry.

The rock is in ground into very fine particles
and formed with soft binders.

Used in the bar form

Used for polishing metal alloys and some
acrylic resin materials.


ZIROCONIUM
SILICATE
The material is ground to
various particle sizes and
is used to make coated
abrasive disks and strips.

Component of dental
prophylaxis paste.


CUTTLE :
Referred as cuttlefish ,cuttlebone, or cuttle white

calcareous powder from the pulverized internal shell of a
Mediterranean marine mollusk

coated abrasive

And is useful for delicate abrasive operations such s
polishing of metal margins and dental amalgam
restorations.


Kieslghur

composed of silicones remains
of minute aquatic plants known
as diatoms.

Mild abrasive

chronic exposure will cause
respiratory silicosis.


SILICON CARBIDE
Extremely hard abrasive was first synthetic
abrasives to be produced.

Green and black types of silicon carbide
are produced.
Green form is most preferred because
substrate is more visible against green
carbide

Silicon carbide extremely hard and brittle.
particles are sharp this leads to high
cutting efficiency.
Metal alloys, ceramics, acrylic resin
materials
silicon carbide available as an abrasive as
coated disk.

ALUMINIUM OXIDE

Second synthetic abrasive developed
much harder than corundum because of its
purity

bonded abrasive and coated abrasive.

Sintered aluminum oxide is used to
make white stones

Finishing metal alloys resin based composite
and ceramic materials.

Pink and ruby variations are made by adding
chromium oxide available in mounted stones
for the preparation of metal ceramic alloys to
receive porcelain.


Rouge

Iron oxide is the fine red abrasive
Contraindicated in polishing of
chromium containing alloys as it
contaminates the surface and
leads to corrosion

Use to polish high noble metal
alloys.


TIN OXIDE
Extremely fine abrasive
used extensively as a
polishing agent for
polishing teeth and
metallic restorations

Mixed with alcohol, water
or glycerin


Abrasive pastes
Most commonly contains
abrasive such as
aluminum oxide or
diamond particles.
Abrasive pastes are used
in dry conditions.
The instruments used to
apply paste are ribbed
prophy cups, brushes, felt
wheels


DISADVANTAGES

Relatively thick and cannot gain access
into embrasures

Paste tends to spatter the instruments

Heat is generated when insufficient
coolant is used.

Material f/ p Chem. Forms available uses
Comp
Pumice Polishing Silica Grit form, Rubber Acrylic, tooth
bonded abrasive enamel, gold
foil, amalgam
Quartz Finishing Silica Coated Abrasive Metal alloys
disks

Sand Finishing Silica Sand paper & Metal alloys,
powder form for Acrylic resin
sand blasting

Tripoli Polishing Silica Bar form Metal alloys

Zirconium Polishing Silica Coated abrasive Metal margins,
Silicate disks, strips tooth enamel

Cuttle Polishing Silica (white Coated abrasive Metal margins,
Calcereous Amalgam
powder) restorations

Kieslghur Polishing Silica Coated abrasive Amalgam
restorations

Tin Oxide Polishing Tin Oxide Paste Form High noble
metal alloys

Material f/ p Chem. Comp Forms available uses
Arkansas stone Finishing Microcrystall Attached to metal Fine grinding of
ine quartz shanks tooth enamel
Chalk Polishing Calcium Paste form tooth enamel,
carbonate gold foil,
amalgam.
Corundum Grinding. Alpha bonded abrasive Grinding metal
aluminium alloys
oxide
Diamond Finishing and Mineral of Bonded abrasive, Finishing and
polishing carbon rotary instruments polishing of
, abrasive strips porcelain and
and polishing ceramics
pastes

Emery Finishing Grayish Coated abrasive Finishing metal
black disks alloys and acrylic
corundum resin
Silicon Carbide Cutting Silica Coated discs Metal

Aluminium Oxide Finishing & Al203 Bonded abrasive Composites &
polishing Porcelain
Rouge Polishing Iron oxide Cake Form High noble alloys

FACTORS AFFECTING THE
EFFICIENCY OF ABRASIVE


SHAPE AND HARDNESS OF A PARTICLE
SIZE OF PARTICLE
SUBSTRATE PROPERTY.
SPEED
PRESSURE
HEAT PRODUCTION


1. SHAPE AND HARDNESS OF A PARTICLE:

Abrasive must be harder than the material which it abrades.

Abrasive must be strong and should show no permanent
deformation under load.

In other words the elastic limit should be equal to its maximum
strength.

Hardness is a surface measurement of the resistance of one
material to plastic deformation by another material.

Shape also plays an important role. Sharp edges will abrasive more
than the dull particle and particle with acute angle will cut more than
a particle with obtuse angle.


2. SIZE OF PARTICLE:

Large abrasive particles present inside the cutting edge and will cut
large and deep grooves.
Fine abrasive will remove small shavings.

Therefore coarse abrasive instruments followed by finer one before
the surface is polished.

Taking a large and deep cut, the coarse abrasive is subjected to
large force resisting its progress across material.

Therefore such an abrasive is moved slowly over a surface,
frequently fracture of grain of abrasive would be expected in this
case if it is moved fastly.


SUBSTRATE PROPERTY

Brittle surface abrade more than malleable and ductile
material.


SPEED
Slower the speed more deep are the scratches and more
force is required to dislodge the abrasive from the
binder.

Faster the speed, the action become vice-versa.

But since more particles will be followed in rapid
succession, the total amount of material removed will
remain approximately same

Therefore for the given abrasive particle size the high
rotation speed does not alter the amount of material
removed, but reduces the amount of wear of abrasive.

Sequential use of abrasives


1)gross reduction ,contouring and
margination

This step involves use of abrasive elements of
the coated or bonded variety with abrasive
particles in the order of 100 microns or larger to
permit the efficient removal of the restorative
materials , usually minimal removal of the tooth
structure .
Tungsten carbide burs are used.


Instruments used for gross
reduction and contouring

A) Diamonds
The primary intended purpose for finishing
diamonds is to contour , adjust porcelain and
composites especially microfilled composites
,which are prone for surface micro cracks when
finished with finishing fluted carbide burs

They come in various grit size ranging from 5 to
60 microns


B) fluted finishing burs

They are available in 8,12 , 16, 20 and 30 fluted bur
designs

The fewer the flutes , the more aggressive is the cutting

They are used for finishing composites

30 fluted burs can be used to smooth, abrade porcelain
surfaces before application of diamond polishing pastes

Several specific group of fluted finishing burs have been
developed for finishing of composites known as esthetic
trimming burs


Abrasive finishing discs
Coated abrasive discs are used

In the coarse and medium grit size can be used for bulk
reduction or gross reduction

The coarse abrasive disc of so flex finishing and
polishing disc is coated with 100 microns aluminum
oxide particles

The medium grit is coated with 40 microns to 100
microns

The greatest ability to reduce composites , porcelain ,
can be obtained with the coarse disc ,whereas medium
disc can also be used to reduce the bulk of the material

Advantage is it can access incisal edges , embrasures ,
and line angles which is not possible with rotary or
bonded abrasives


The sof-lex extra fine contouring and polishing well
suited to access the embrasure areas

Disadvantage of abrasive discs is they have tendency to
flatten surface features and restoration contours,
creating a less anatomic details


Instruments for inter mediate

Coated abrasive disc
Available as finer grit discs and medium
Bonded abrasive discs
Fine diamond and multi fluted finishing burs


Materials for final finishing
Extra fine coated abrasives

Loose abrasive polishing pastes


FINISHING AND POLISHING
TECHNIQUES


The larger the abrasive particles, the deeper the scratch
will be and conversely, the smaller the abrasive particle,
the finer the scratch will be.

If the particle size of the abrasive is decreased
sufficiently, the scratches finally become very fine and
with extremely fine abrasives, they may disappear
entirely.

The surface then acquires a smooth shiny layer known
as a polish.

The most recent theory is that polishing agents actually
removes material from the surface, molecule by
molecule and thus produces very smooth surfaces.

In the process fine scratches and irregularities
are filled in by the fine particles being removed
from the surface.

This microcrystalline layer is referred to as the
POLISH Layer or BEILBY layer.

There evidence that a Beilby layer may be
obtained on enamel surfaces as well as on metal
surfaces.


Advantages of highly polished surface

- more resistant to cariogenic action than a surface which is
not polished. For example it has been shown that a
polished tooth surface is approximately 15% less soluble
in acid than one with a rough surface.


Finishing and polishing of
composites


Once a composite has been cured, it must be finished
and polished to produce the final surface.

This step removes the air-inhibited layer.

It also removes the outer surface of the composite that is
resin rich and actually is already a smooth surface.

However, this cannot be avoided. The anatomic
contours of composites cannot be so well established
before curing to avoid reshaping.


The trick to finishing and polishing is to gradually move
from larger-to-smaller abrasive containing agents.

This will produce finer-and-finer scratches in the surface
as shown above.

As a smooth surface is approached, there is more of a
chance to smear remaining polymer into the dips or
grooves remaining on the surface.


This generates a highly polished surface.

However, some of this smoothness may be lost over
time and require re polishing.

Composites with very small particle sizes (mini-hybrids
like Kerr Point 4 and nano -composites) allow a highly
polished surface to be generated with impressive gloss
and good wear resistance.


The finishing procedure for composite restorations will
usually consist of three to four steps involving a number
of instruments.

Gross reduction where excess restorative material is
removed.


Contouring- includes the reproduction of the size,
shape, grooves and other details of the tooth form.
Re-establishing contact with adjacent teeth to a
normal and functional form.

Finishing and polishing establishes an even, well-
adapted junction between the tooth surface and the
restoration and removes scratches to produce a
visually smooth and shiny surface.


Chemical cured materials must be accurately
timed to complete polymerization.

It has been suggested that before finishing the
restoration it should be left undisturbed for a
minimum of 10 minutes to allow the resin to
completely polymerize.

This may aid in reducing surface trauma from
the finishing process.


Sof-Lex Finishing and Polishing
Discs


The original Sof-Lex finishing and polishing discs are made from a
urethane coated paper that gives the discs their flexibility.

The system is comprised of four individual aluminum oxide grits
ranging from coarse to superfine.

The discs are available in three sizes; 13mm (1/2 inch), 9mm (3/8
inch), and a 16mm (5/8 inch) size with a square brass eyelet.


Sof-Lex XT Finishing and Polishing
Discs


The Sof-Lex XT (extra thin) finishing and polishing discs
are made with a polyester film which is one third the
thickness of the original paper discs.

The thinner discs are slightly stiffer and allow more
precise refinement of embrasures.

These discs also have four individual aluminum oxide
grits, ranging from coarse to superfine.

They are available in two sizes, 13mm (1/2 inch), or
9mm (3/8 inch).


Sof-Lex Finishing Brush


The Sof-Lex finishing brush is made from a
thermoplastic polyester elastomer that contains
aluminum oxide abrasive particles molded into a shape
similar to a prophy brush.

The brush itself is detachable from a stainless steel
mandrel. The Sof-Lex Finishing Brush is an easy to use,
one-step, reusable brush developed for polishing the
concave and convex anatomy found on posterior
composite restorations.

The soft bristles will conform to the restoration as it
travels across the surface resulting in a smooth polished
finish.


Sof-Lex Finishing and Polishing
Strips


The design of the Sof-Lex strips allows for easy
interproximal finishing.

The strips are made of plastic and are coated with an
aluminum oxide abrasive.

Sof-Lex strips are free of any abrasive coating at their
centers for easy interproximal insertion.

Each strip contains two different grits; a coarse/medium,
or a fine/superfine.

They are also color coded similar to the discs. The
coarser grit on each strip is a darker color than its
opposing side.

Directions for Use

Place the disc on the mandrel by firmly pushing the
eyelet portion onto the mandrel until the disc is secure
and does not wobble.

The polishing motion should be constant and move from
the bulk of the restoration toward the margins.

A back and forth movement over the composite/enamel
margin is not recommended, as a white line may form.


Use light pressure when polishing; let the discs do the
work. To produce a smoother, more uniform finish, keep
the tooth, restoration, and disc dry while polishing.

Avoid touching the composite with the mandrel or disc
eyelet because discoloration may occur.

This discoloration can be removed by repetition of the
finishing steps


Skipping a grit size in the finishing sequence may
compromise the quality of the restoration’s polish.

Remove discs from the mandrel either by positioning a
thumbnail under the disc eyelet portion and pushing the
disc away from the hand piece, or by grasping the disc
and eyelet and peeling the disc upward and away from
the hand piece.

It is important to maintain a dry field when using this
system. After rinsing, and before proceeding to the next
grit sequence, dry the area.

The following procedure produces a
quality polish regardless of the Sof-Lex
disc system used.


1. Remove excess composite and contour to desired
shape using a fine diamond or a 12-fluted carbide bur.

2. For gross reduction, use the Sof-Lex coarse-grit disc at
medium speed (10,000 rpm). Rinse and dry.

3. For final contouring, use the Sof-Lex medium-grit disc
at medium speed (10,000 rpm) for 15 to 20 seconds.
Rinse and dry.


4.To finish, use the Sof-Lex fine-grit disc at high speed
(30,000 rpm) for 15 to 20 seconds. Rinse and dry.

5. Polish using the Sof-Lex superfine-grit at high speed
(30,000 rpm) for 15 to 20 seconds.

6. Wash away powder or debris from restorative surface


7. Discard each disc after single use.

8. For interproximal areas insert the abrasive free center
of a Sof-Lex coarse/medium grit finishing strip
(beige/white) between contact points.

9. Position the beige portion of the strip over the
composite surface to be finished, firmly grasp both
ends of the strip and draw the abrasive over the
composite in a vigorous, back and forth motion.

Repeat the procedure using the white portion of the
strip. Discard the strip after single use.

10. Repeat steps 8 and 9 with the Sof-Lex fine and
superfine strip (gray/blue) using first the gray and then
the blue side.

Start with coarse discs to remove excess restorative material and
establish preliminary anatomy. Rinse and dry surface before moving onto
medium disc.


Use medium discs for advanced contouring,
establishing marginal ridges and adjusting incisal edges.
Rinse and dry before using the fine disc.


Follow with fine disc to further improve finish quality
and prepare surface for final polishing.


Conclude polishing with superfine discs for the most
durable, smoothest, high gloss finish.


After contouring posterior composite, polish surface
with Sof-Lex finishing brush at low speeds.


Use Sof-Lex strips for finishing proximal areas by
gently inserting the center gapped area between teeth.
Operating sequence of strips (coarse/medium,
fine/superfine) is the same as discs.


Finishing and polishing of amalgam


AMALGAM RESTORATIONS

a) OBJECTIVES

Finishing and polishing should be considered as important as
condensation and it does continue the objectives of carving through
this process amalgam flash that was left behind after carving is
removed.

Major overhangs are removed and minor enamel under hangs are
corrected thus assuring the continuity between tooth surface and
amalgam surface

Conversion of the superficial amalgam into a relatively inert layer
galvanically (This minimizes electrolytic corrosion).

The most important objectives of finishing & polishing is the removal
flash and overhangs and corrects minimal enamel under hangs.
polishing is the process, which creates a corrosion resistant layer by
removing scratches and irregularities from the surface.


superficial scratches and irregularities.
It will minimize fatigue failure of the amalgam under the cyclic loading of
mastication.

This failure occurs in the form of surface cracks which propagate
inwards.

If such cracks join together or subsequently connect with internal voids
or flaws, they can precipitate gross fracture and increase corrosion and
micro leakage.

The scratch and irregular free surface layer created by the polishing
procedure minimizes the concentration cell corrosion and presents the
adherence of plaque


b) PRINCIPLES

Finishing and polishing procedures are necessary
1. To complete the carving.
2. Refine the anatomy contour and marginal integrity.
Enhance the surface texture of the restoration.
Finishing and polishing procedures for amalgam
restorations are not
attempted within 24 hours of insertion, since
crystallization is not complete.


Polishing of high-copper amalgams is less important than
with
conventional amalgams because high copper amalgams are
less susceptible to tarnish and marginal breakdown.

Many operators prefer to polish all amalgam restorations to
minimize their clinical performance.

Some of the fast setting high copper amalgams can be
polished about 8 to 12 minutes after placement because of
their rapid development of strength.


c) RESULTS OF FINISHING AND POLISHING.
The following conditions results from proper [finishing and
polishing]:

1. Smooth and flush cavosurface margins.
2. Recreation of defined anatomy.
3. Decreased plaque retention.
4. Healthier surrounding tissue.
5. Higher resistance to tarnish and corrosion.
6. Increased longevity of the restoration.
7. Improved esthetics.


d) Determining factors for finishing and
polishing versus replacement
Finish and Polish Replace Restoration

A. Overhangs A. Open contact
B. Lack of functional B. Excessive corrosion
anatomy
c. Tarnish C. Amalgam fracture
D. Overextension D. Open margin
E. Premature occlusal E. Recurrent decay
contact
Oleinisky JC, Baratieri LN. et. al
www.indiandentalacademy.comDec
Quintessence Int. 1996

A. Evaluate Restoration.
1. Surfaces

Always examine the amalgam surfaces for functional
anatomy and defects.

2. Margins
Using the explorer (or a periodontal probe with a small
tip) in a zigzag
motion, determine if the cavosurface margins have any
excessive discrepancies.

The cavosurface margin is the area formed by the cavity
wall and external tooth surface. Remember that a rough
margin is a poor predictor of recurrent decay. The
patient's risk for caries must also be considered

3. Occlusion

Evaluate the patients occlusion.
a) Articulating paper
Insert articulating paper along the occlusal surface and
have the patient tap his teeth together.

b) Determine intensity
Observe all markings to determine if they have the same
intensity.

c) Reduce the amalgam if it exhibits
Premature contacts or "high spots".


Premature contacts are areas where the amalgam has
been under carved and these will register a darker areas
when checked with articulating paper.

Occlusal contacts registered by using articulating paper
areas when checked with articulating paper.

d) Even intensity
Check these areas throughout the finishing procedure to
ensure that occlusal markings of equal intensity are
achieved.

4. Proximal contacts
Check proximal contacts with dental floss.


1. Hand instruments
a) Use a finishing knife and or dental file at the gingival and
proximal margins to remove overhangs.

b) Use short, overlapping shaving strokes to prevent the amalgam
from fracturing.

2. Finishing bur
a) A flame-shaped bur is recommended when the area is
easily accessible.

3. Finishing discs
Discs come in varying sizes and grits. Select a size easily adaptable to the
proximal surface.


b) Technique
Use short, overlapping strokes and move diagonally across the
cavosurface margins.

c) Sequence

Discs are used in a sequence of more abrasive to less abrasive
grits.

d) Embrasures
When using discs in embrasure areas, care must be taken not to
damage the contact area or papilla.


4. Finishing strips.

a) Use fine or medium [finishing strips after using discs,
burs, knives or files].

b) Position the strip so that it is on both the tooth and the
amalgam, and move in a back-and-forth motion.

c) Avoid the contact area when using finishing strips, and
use caution in areas of the inter dental papilla and
surrounding tissue.

Wider strips may be cut in half lengthwise to make narrow
strips.


F. Remove occlusal excess and eliminate flash

1. With burs or stones
Use a round finishing bur or a green stone to remove
excess material and irregularities from the occlusal
surface, grooves and the cavosurface margin.

2. Sequence
Begin with the largest finishing bur that will adapt to the
surface and progress to smaller and less abrasive
finishing burs.


3. Technique
Adapt the side of the bur or stone along the margin,
contacting both tooth and amalgam.

4. Direction of stroke
Rotate the bur or stone from the amalgam to the tooth
to
avoid fracturing the amalgam margins.

5. Direction of work
Always begin at the centre of the restoration and work
toward the cavosurface margin.

procedures for two method of amalgam polishing.
a) Pumice and tin oxide slurries.
This method is accomplished using a rubber cup,
brush, and wheel brush.

Prepare a slurry mix of pumice, and water in a dappen
dish.

Polish all surfaces of the restoration with a brush or cup and
plentiful pumice.

Remember, the pumice does the polishing, the cup only moves the
pumice a smooth satin finish is accomplished

The satin finish produced will exhibit a dull appearance.
Polish the proximal surface with medium and fine polishing strips.
Rinse and dry the mouth.

Prepare the wet mixture of tin oxide and alcohol in a dappen dish.
Water or mouth wash is an acceptable substitute for alcohol.

Polish all surfaces of the restoration with a new, clean cup
or brush and the tin oxide slurry.

An optimal final step may include using a soft wheel brush
in a straight hand piece with tin oxide.

Continue to polish the amalgam until the tin oxide begins to
dry and a high luster is achieved.
Rinse and dry the tooth.
Examine with mouth mirror and explorer.
OR
b) Rubber cups and points impregnated with Abrasive
particles


Colors.
Abrasive-impregnated rubber cups and points are
supplied in three colors: brown, green and yellow-
banded green. Each color denotes different degree of
abrasiveness.
In some instances they are referred to as "brownies",
"greenie" and "super greenies".

use.
The cups are designed for use on the proximal surfaces,
and the points are used on the occlusal surface.
Often, they are used interchangeably.
They should be operated at a relatively low speed, using
light, intermittent strokes under wet conditions.


Advantages.
The cups and point will polish restorations quickly and tend
to be less messy than using two slurries of different
abrasives.

Disadvantages.
The cups and points wear quickly from use and
autoclaving.
Eventually a metal surface is exposed that will scratch the
amalgam surface.

The greatest disadvantage, however, is heat production.

The amalgam surface MUST NOT be heated above 140'F
by the
polishing procedure. Heat is generated rapidly with the
use of
abrasive impregnated rubber cups and points.

Procedure for use.

Brown abrasive cups and points are used first to produce
an initial smooth satin finish.

Polish the occlusal the proximal, and then finally the facial
and lingual surfaces.

Polishing is performed with fine pumice followed by tin
oxide or white rouge applied with a soft webless rubber
cup.


The green cups and points are used in the same manner
as the brown.
After use, examine to determine if a smooth shiny finish
has been achieved

A yellow banded green cup or point is used as the final
step.

These are used in the same manner as the brown and
green cups and points.

Examine to determine if a smooth lustrous polished finish
has been achieved.

Rinse and evacuate debris.

Evaluate the polished amalgam using a mouth mirror and
explorer.
The amalgam should appear smooth and highly polished,
and should have a lustrous shine

There should be no damage to the adjacent


Evaluation criteria for amalgam polishing.

Amalgam is void of scratches and appears smooth.

Amalgam has a high polish and lustrous shine.

There is no damage to adjacent tooth structure.


Finishing and Polishing of
Ceramics


Ideal surface for ceramic restoration is a polished and
glazed surface

The production of a glazed layer through natural glaze or
over glaze processes will not necessarily yield a smooth
surface if initial ceramic surface has significant
roughness

Polishing can improve strength within surface region of a
ceramic prosthesis because it removes pores and micro
cracks


Adequate cooling is important in vivo when finishing and
polishing ceramic restoration

Using an air water spray and maintaining intermittent
contact between restoration and rotary instruments are
critical during operation

Continuous contact between restoration and rotary
instruments should be avoided

Heat less stone like silicon carbide provide heat
reduction and can be used as an alternative


Techniques
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


Glass Ionomer Cement


Conventional versions of glass ionomer ideally require a
polymerization period of 24 hours before final contouring and
polishing

After removing the matrix the restoration gross excess is shaved
away with either no-12 surgical blade in bald parker handle or sharp
knives of scalers

Major part of finishing and polishing should be accomplished by
hand instruments to preserve the smooth surface

if rotary instruments are used care must be taken not to dehydrate
the surface


Fine disks are used for final finishing

Micron finishing diamonds are used to contour

A fine grit aluminum oxide polishing paste applied
with a prophy cup to smoothen the surface


FINISHING OF DIRECT FILLING
GOLD


Once the final contour is been obtained

Cuttle discs are used in decreasing abrasiveness to ready the
surface for final polishing

polishing is performed with fine pumice followed by tin oxide
or white rouge applied with a soft rubber cup

the abrasives are therefore used dry so that the field kept may
be clean and exact position of the rubber cup seen at all the
times


sharp gold foil knife is used to remove of the excess
in the region of contact

permitting a fine finishing strip or a steel matrix strip
to pass through the contact area
a pull cut shoosan or a gold knife may facilitate
removal of excess gold facially

finishing is performed with the extra –narrow extra
fine cuttle strip

final polishing is accomplished with a worn out
cuttle


Finishing and polishing techniques are important in preparing
clinically successful restorations .

The process of abrasion is affected by properties of the abrasive
and the material being abraded

Finishing and polishing begin with coarse abrasives and end with
fine abrasives

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.

A definite sequence should be adopted in finishing and polishing of
each restoration.

References
Kenneth J. Anusavice - text book on dental
materials.
Robert G Craig –dental materials
Edward c. coombe - dental materials
Clliford m. Studavent- text book of operative
dentistry
Gerald T. Charbenau –principles and practice of
operative dentistry
Baum, Philip and Lund –text book on operative
dentistry


Auj.Yap et.al Journal of Operative Dentistry. 2004

Journal of prosthodontic terms – 1991

Bower CF, Reinhardt RA .et. al Journal of Prosthodontics-
1986 Sep
Briseno B, Ernst et al 1995 May;26(5):361-5. 1996 Dec
Quintessence Int.

van Amerongen JP, Penning C .et al Journal of
Prosthodontics- 1990 Oct
Steegmayer G, Lenz P et .al Dutch Dental Journal- 1989 Aug

Steven.R.Jefferies- DCNA ,1998


A maximal speed of 4,000 rpm should be applied when polishing is carried out
continuously without water coolant. When water cooling is used, flexible disks can safely
be used at a speed of 10,000 rpm and with continuous pressure.


Procedures carried out with low pressure showed a decrease in the pulpal
temperature of approximately 9 degrees C. High pressure decreased the
temperature of the pulp by only 4 degrees C. Therefore a water coolant is always
advised when amalgam restorations are being finished and polished.

van Amerongen JP,
Penning C .et al
J Prosthet Dent. 1990 Oct;


The life of a diamond instrument is limited by the wear of
its tip. Here the diamond layer wears off faster than on
the rest of the instrument. This calls for early
replacement of the instrument in clinical use even if the
shaft still might be functionable.

Steegmayer G, Lenz P et .al
Dutch Dental Journal 1989 Aug;44(8


Bower CF, Reinhardt RA .et. al
J Prosthet
Dent. 1986 Sep;
indicated that surfaces finished using the
carve, floss, and finishing strip polish
consistently produced a measurably
smoother surface
The use of finishing strips on the gingival
margin of Class II silver amalgam
restorations shows promise of improving
interproximal surface smoothness.


The finishing and polishing procedures of
dental restorative uses three basic
procedures steps based on the sequential
application of progressively finer grit of
abrasive medium in various types of
devices
Steven. R.
Jeffery's
Dental Clinics of
North America 1998


Ottl P, Lauer HC et al .J Prosthet Dent. 1998
Jul;80(1):12-9.

That coarse diamond burs resulted in more
pronounced temperature increases within the
pulpal chamber during tooth preparation. In
addition, the benefit of short intervals between
grinding steps and a cooling water temperature
between 30 degrees C and 32 degrees C was
confirmed.


G. Evaluate the finishing procedure

A. Excessive amalgam has been removed from cavosurface margins.

B. Amalgam appears to be smooth.

C. Occlusion registers properly with articulating paper.

D. Occlusal and marginal anatomy is better defined.

E. Porosity and pits are removed

F. Contour of the restoration approximates the original contour of the tooth.

G. Adjacent tooth structure is left undamaged.

When over heated, the surface of the amalgam will appear cloudy even
though it may have a high polish.•
This cloudy appearance indicates that mercury has been brought to the
surface, which results in corrosion of the amalgam and loss of strength.

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