This document provides an overview of abrasives and polishing techniques used in dentistry. It defines abrasion and discusses different types of abrasives including natural abrasives like Arkansas stone and manufactured abrasives like silicon carbide. It also covers abrasive tools, polishing protocols for different dental materials like amalgam, composites and ceramics, and factors that influence abrasion and polishing effectiveness. The conclusion is that an ideal abrasive satisfying all dental material polishing needs has yet to be developed.

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2. • INTRODUCTION
• DEFINITION.
• CONSIDERATION OF ABRASTION AND EROSION
• DESIGN OF ABRASIVE INSTRUMENTS
• TYPES OF ABRASIVES
• POLISHING
• FINISHING AND POLISHING OF COMMONLY EMPLOYED
RESTORATIONS
• SUMMARY AND CONCLUSION
• REFRENCES
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3. INTRODUCTION
HISTORY
• Stones ,spear ,shield and daggers were produced by
abrading against a cylindrical stone.
• Chinese introduced first coated abrasives.
• In 1900s alumina grains , diamond particles and
silicon carbide were used .
BENEFITS
ORAL
HYGIENE
ORAL
FUNCTION
ESTHETICS
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4. • ABRASION –The wear away of substances or
structure through some unusual or abnormal
mechanical process.
• ABRASIVE AGENTS –Substances used for abrading
,smoothing or polishing.
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5. • POLISHING –The act or process of making a
denture or casting smooth , glossy and to give
lustre .
• POLISHING AGENTS-Any material used to impart
lustre to a surface.
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6. CUTTING
• It is done using bladed instrument
• It divides substrate into large separate segments or may
sustain deep notches and grooves by cutting operation
• Eg – carbide bur and diamond burs
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7. GRINDING
• Removes small particles of substances through action of
bonded or coated abrasive instruments
• Grinding instruments contains many randomly arranged
abrasive particles
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8. FINISHING AND POLISHING –
The most refined of finishing processes, remove the
finest surface particles . Each type of polishing
abrasive acts on an extremely thin region of the
substrate surface .
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9. CONSIDERATION OF ABRATION AND
EROSION
ABRASIVE WEAR
Craig has defined abrasion as :“A process of wear
where by a hard rough surface or hard irregular shaped
particle plough grooves in a softer material and cause
materials from these grooves to be removed from the
surface”.
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10. ACCORDING TO SKINNER :-
1.Wear – Is a material removal process that can occur
whenever surfaces slide against each other . In
dentistry the outermost particle or the surface
material of an abrading instrument is referred to as
Abrasive. The material being finished is termed as a
SUBSTRATE.
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11. 2. ABRASIVE WEAR
Two body wear – occurs when abrasive particles are
firmly bonded to the surface of the abrasive instrument
and no other and abrasive particles are used eg, a
diamond bur abrading a teeth.
Three body wear – when the abrasive particles are free to
translate and rotate between two surfaces Eg, dental
prophylaxis pastes (between tooth and rubber cup).
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12. EROSIVEWEAR
Erosive wear – This is caused by hard particles
impacting a substrate surface, carried by either a
stream of air or a stream of liquid.
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13. The abrasives employed could be one of the three types
which are:-
A. Abrasive Grits.
B. Bonded Abrasives.
C. Coated Abrasive Disks and Strips
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14. A. ABRASIVE GRITS
• Abrasive grits are derived from (abrasive) materials that
have been crushed and passed through series of mesh
screens to obtain different particle size ranges. The grits
are classified as – COARSE, MEDIUM COARSE, MEDIUM
FINE and SUPER FINE according to the particle size ranges
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15. B. BONDED ABRASIVE
• These consists of abrasive particles
incorporated through a binder to form grinding
tools.
• The abrasive particles are bonded by 4 general
methods :
• 1. Sintering.
• 2. Vitreous bonding
• 3. Resin bonding
• 4. Rubber bonding.
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16. 1. Sintering – Sintered abrasives are the
strongest variety since the abrasive particles are
fused together.
2. Vitreous Bonded – Are mixed with a glassy or
ceramic matrix material, cold pressed to the
instrument shape and fired to fuse with the binder.
3. Resin Bonded – are cold or hot pressed and
then heated to cure the resin.
4. Rubber Bonded – made in a manner which is
similar to resin bonded.
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17. C. COATED ABRASIVE DISK OR STRIPES
• These abrasives are supplied as disks and finishing
strips. They are fabricated by securing abrasive
particles to a flexible backing material (heavy weight
paper or Mylar)
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18. These factors are as follows:
1. The hardness of the abrasive particle .
2. The Shape of the abrasive particle .
3. Particle size of the abrasive .
4. Mechanical properties of the abrasive .
5. Rate of movement of the abrasive particles.
6. Pressure applied
7. Properties of material that is being abraded
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19. According to Craig :
A. Finishing Abrasives
These are hard, coarse abrasives used initially to
develop desired contours and remove off gross
irregularities.
B. Polishing Abrasives
These have a smaller particle size and are less
hard than abrasives used for finishing. They are used
for smoothening surfaces that are typically roughened
by finishing abrasives.
C. Cleansing Abrasives
These are soft abrasives with small particle size and
are intended to remove softer materials that adhere to
enamel or a restoration.
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20. 1. 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. Kleselguhr
Are generally preferred because
of their more predictable physical
properties.
1. Silicon carbide
2. Aluminium oxide
3. Synthetic diamond
4. Rouge
5. Tin oxide
A. Natural Abrasives B. Manufactured Abrasives
Secondly Skinner’s has grouped the abrasives
employed in dentistry as follows:
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21. • 1. Arkansas stone
• Semitranslucent, light gray, siliceous
sedimentary rock, mined in Arkansas.
• It contains microcrystalline quartz.
USES- fine grinding of tooth enamel
and metal alloys.
2. Chalk
Mineral form of calcite.
Contains calcium carbonate.
USES -as mild abrasive paste
to polish teeth enamel, gold foil,
amalgam and plastic materials.
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22. Corundum
• Is largely replaced by – Aluminium
oxide due to its superior physical
properties.
USES for grinding metal alloys.
DIAMOND
• Is a transparent mineral composed of carbon called
super abrasive because of its ability to abrade any
other known substance.
• It is the hardest substance known.
USES - ceramic and resin based
composite materials.
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23. EMERY
• This abrasive is a grayish black
corundum that is prepared in a
fine grain form.
USES for finishing metal alloys or plastic
materials
GARNET
• The term garnet includes several minerals which possess
similar physical properties like Silicates of Al, Co, Fe, Mg and
Mn.
• Garnet is dark red, extremely hard
and when fractured during abrasive
activity forms sharp chisel shaped
plates .
USES in grinding metal alloys and
acrylic resin materials.
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24. • Pumice
• Volcanic activity produces light gray
Siliceous material.
• Flour of pumice is an extremely fine
grinded volcanic rock derivative from
Italy.
• USES in polishing teeth enamel, gold foil, dental amalgam
and acrylic resins.
Quartz
• The particles are pulverized to form sharp angular particles
which are useful in making
coated abrasive disk.
• USES to finish metal alloys and
may be used to grind dental
enamel.
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25. SANDS
Is a mixture of small mineral particles
predominantly silica.
• Particles have rounded to
angular shape.
• USES- to remove refractory investment
material from base metal castings and is also used for
grinding of metal alloys and dentures.
TRIPOLI
• Derived from a lightweight, siliceous
sedimentary rock
• Could be white, gray, pink, red , yellow
USES- for polishing metal alloys
And dentures
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26. Zirconium silicate
• Off white mineral, ground to various
sizes used to make coated disks and
strips.
• USES as a component of dental
prophylaxis pastes.
Cuttle
• Made from the pulverized internal shell of a
Mediterranean marine mollusk, this abrasive is
obtained as a white calcareous
powder.
USES for delicate operations like
polishing of metal margins and
dental amalgam restorations.
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27. Kleselguhr
This abrasive is obtained from the silaceous remains of
minute aquatic plants known as diatoms.
• The coarser variety is known as DIATOMACEOUS
EARTH
• May cause respiratory silicosis .
• USES as a filler for dental materials such as agar.
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28. 1.Smoothen the work with a coarse abrasive to produce
large scratches.
2.Remove large scratches with a finer abrasive
3.Continue using the fine abrasive until scratches are no
longer visible
4.Primary polishing with pumice flour with a canvas buff
wheel
5.Then the work is cleaned to remove all abrasive particles
and then pumice and water paste of a muddy consistency is
applied and buffing done till a bright and well polished
surface is obtained.
6.Clean the work with soap water and change to a buff
wheel. Polishing cake with grease is held against buff wheel
to impregnate with the agent.
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29. • FINISHING AND POLISHING OF COMMONLY
EMPLOYED RESTORATIVES
• Amalgam
• After initial carving, restoration is left undistributed for
an appropriate period .
• Polishing is done through the sequential use of
finishing fine stone and disks or strips.
• Final polish is done by the application of extra fine
silen; followed by a thin slurry of tin oxide with a
rotating soft brush.
• During final polishing restoration should be kept moist.
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30. • Composites:
• The smoothest surface on a freshly inserted composite
can be obtained by allowing polymerization to occur
against an inserted Mylar matrix.
• Use of green/carbide stones 12 - blade carbide burs is
also accepted for removal of excess near enamel
margins of macro filled resins.
• This is followed by use of:
• Aluminium oxide disks – for accessible areas finishing.
• White source stones of suitable shapes – inaccessible
areas.
• Fine and micro fine diamonds – finishing of micro filled
resins.
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31. • A zirconia based ceramics crowns are difficult to
polish due to its brittleness, polishing pressure, pad
wear, subsurface damage, and microcracks arising
during conventional polishing processes.
• A new polishing technology using magnetorheological
(MR) fluids was intoduced
• MR fluids are suspensions of very small magnetic
additives, such as carbonyl iron , and nonmagnetic
fluids such as mineral oils or water.
Hong, K.-P., (2012). Magnetorheological (MR) Polishing of Zirconia Ceramics Using
Diamond Abrasives for Dental Application. Materials and Manufacturing Processes, 27(10),
1135–11
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32. RESULT
• A very fine surface roughness of 1.960 nm was
obtained when the electric current was 0.5 A
and the wheel rotational speed was 300 rpm
after 60 minutes of MR polishing. From the
results of this study it can be seen that the
applied MR polishing method provides a suitable
polishing technique to obtain ultraprecision
surface qualities of ceramics.
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33. Though a varied range of abrasive and polishing
agents have been described with relation to
individual dental materials, an ideal abrasive or a
polishing agent which would satisfy all polishing
needs of the dental materials, one would say is
yet to be developed.
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34. • REFERENCES
1.Kenneth J. Anusavice “Philips Science of Dental
Materials”. 10th edition, 1998 ; W.B. Saunders
Publications.
2.Ralph W. Phiips “Skinner’s Science of Dental
Materials”. 9th edition, 1992 ; W.B. Saunders
Publications.
3.Combe E.C. “Notes on Dental Materials”. 6th edition,
Churchill, Livingstone Publications.
4.Subbarao V. “Notes on Dental Materials”. 3rd edition,
1997 ; V.K.S. Publications.
5.Robert G. Craig, William O’Brien and John M. Powers
“Dental Materials – Properties and Manipulation”. 5th
edition, 1992; Mosby Publications.
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