This document discusses abrasives and polishing agents used in dentistry. It defines abrasion and the factors that affect abrasion rates such as hardness, shape, size, pressure, speed and lubrication of abrasive particles and instruments. It classifies abrasives based on their hardness and describes natural abrasives like diamond, garnet, pumice and synthetic abrasives like silicon carbide and aluminum oxide. It also discusses bonded, coated and non-bonded abrasive instruments as well as the steps in finishing and polishing restorative materials.

1. Abrasives and Polishing agents

2. Abrasives and
polishing agents
Abrasion
Erosion
Classification
Factors affecting
abrasion
Abrasive
instrument design
Finishing and
polishing process
Steps in finishing
and polishing

3. Abrasive
A hard substance used for grinding, finishing, or
polishing a less hard surface.
Finishing
Is the process of removing surface defects or
scratches created during the contouring
process through the use of cutting or grinding
instruments or both.

4. Polishing
Refers to the final removal of material from a
restoration or appliance, resulting in a highly
reflective surface that does not contain any
scratches

5. Benefits of finishing and polishing
restorative materials
• To promote oral hygiene.
• Enhance oral function.
• To improve esthetics

6. Goals of finishing and polishing
 Obtain the desired anatomy, proper occlusion
 Reduction of roughness, gouges, and scratches.
 Smooth surface
 Resist bacterial adhesion and excessive plaque
accumulation.
 Plaque should be easily removable

7. Abrasion
It is defined as wearing away of a substance
through a mechanical process, such as
grinding, rubbing or scraping, which
involves friction.
Abrasive - Outermost particles of an
abrading instrument
Substrate - Material being finished

8. Abrasive action
Harder material comes into frictional contact
with the substrate
Contact generates tensile and shear stresses
Break atomic bonds
Substrate material are removed

9. Types of abrasion
1. Two-body abrasion
Abrasive bonded to instrument
Eg - diamond bur abrading a tooth.

10. Three-body abrasion
• Non bonded abrasives
• Abrasive particles are free
Eg - dental prophylaxis paste

11. 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

12. Factors affecting rate of abrasion
Hardness
 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 Friedrich Mohs
 Knoop and Vickers hardness tests

13. Material Moh’s Brinell Knoop Material Moh’s Brinell Knoop
Talc 1 Alumnium
oxide
9 1700 1900
Gypsum 2 Silicon carbide 9-10 3000 2500
Chalk 3 Boron carbide 9-10 2800
Rouge 5-6 Diamond 10 >3000 7000
Pumice 6 450 560 SUBSTRATES
Tripoli 6-7 Acrylic 2-3 25
Garnet 6.5-7 550 Pure gold 2.5-3 30
Tin oxide 6-7 Porcelain 6-7 400
Sand 7 650 800 Amalgam 4-5 90
Cuttle 7 650 800 Dentin 3-4
Tool steel 800 Enamel 5-6 270
Zirconium
silicate
7-7.5 Glass 5-6
Tungsten
carbide
9 1200 2100 Resin
composite
5-7 200

14. Shape
• Sharp, irregular particle produces deeper
abrasion than rounder particle under equal
applied force
• Numerous sharp edges - enhanced cutting
efficiency
• Abrasion rate of an abrasive decreases
during use

15. 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 µm,
3. Fine - 0 to 10 µm.

16. Pressure
Greater force during finishing
Abrasive to cut deeper into the surface
More rapid removal of material
Raise in temperature within the substrate
Distortion or physical changes within the
substrate

17. • Deeper and wider scratches are produced
by increasing the applied force from F1
and
F2

18. Speed
Faster speed
Faster cutting rates
Temperature increases
Greater danger of overcutting

19. Lubrication
Minimize the heat buildup
Facilitates removal of debris
Cooling action and removal of debris
enhances the abrasion process.
Water is the most common lubricant
 Eg. Water, glycerin or silicone
Excess lubrication – prevent abrasive
contact

20. Abrasive Instrument Design
1. Abrasive Grits.
2. Bonded Abrasives.
3. Coated abrasive disks and strips
4. Nonbonded abrasives

21. 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

22. Bonded abrasives
• Abrasive particles that are incorporated
through a binder to form grinding tool
• Particles are bonded by four general
methods:
Sintering
Vitreous bonding
Resinoid bonding
Rubber bonding
• Eg. Diamond burs, Stones, Rubber wheels.

23. Type of bonding and grinding behaviour
1. Abrasives that tend to disintegrate rapidly
Abrasive bond too weak
Reduced instrument life
2. Abrasives that tend to degrade too slowly clog
with grinding debris
Loss of abrasive efficiency, increased heat
generation, and increased finishing time

24. 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 runout when
placed on a substrate.
• Dressing : Same as truing but serves two purposes:
1)Reduces instrument to correct working size, shape
2)Removes clogged debris (abrasive blinding) -
Restores grinding efficiency

25. Coated Abrasive Disks and Strips
Abrasives are supplied as disks and
finishing strips.
Fabricated by securing abrasive particles
to a flexible backing material
The disks are available in different
diameters with thin and very thin backings.
 Moisture – resistant backings are
advantageous

26. • 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 all direct and
indirect bonded restorations.

27. Nonbonded abrasives
Polishing pastes - final polishing.
Applied to substrate with a nonabrasive
device - synthetic foam , rubber, felt, or
chamois cloth.
Dispersed in water soluble medium such as
glycerin for dental appliances.
Aluminium oxide and diamond

28. Classification of finishing and polishing
devices
• Based on surface removal
1. Cutting Instruments : Tungsten carbide
2. Bonded abrasive
Diamonds
Silicon carbide
White stone
Tripoli
Rouge

29. 3. Impregnated abrasives-
• Aluminium oxide
• Emery
• Quartz
• Silicon carbide
• Garnet
• Zirconium silicate
• Cuttle
4. Loose abrasives
• Aluminum oxide
• Ultra fine diamond particles
• Tin oxide
• Pumice

30. According to Hardness
• Diamond - 7500 KHN
• Silicon carbide - 2500 KHN
• Aluminum oxide - 2100 KHN
• Emery - 2000 KHN
• Corundum - 2000 KHN
• Tungsten carbide - 1900 KHN
• Garnet - 1350 KHN
• Quartz - 800 KHN
• Sand - 560 KHN
• Pumice - 560 KHN
• Chalk - 135 KHN

31. Natural Abrasives
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. Kieselguhr

32. 1.Silicon carbide
2.Aluminium oxide
3.Synthetic diamond
4.Rouge
5.Tin oxide
Synthetic
Abrasives

33. 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

34. 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.

35. 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

36. 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

37. Diamond burs color coding and grit size
Bur 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

38. Emery
• Natural form of an oxide
of aluminium
• Grayish- black corundum
• Coated abrasive disks
• Greater the content of
alumina - finer the grade
of emery.
• Finishing metal alloys or
acrylic resin materials.

39. 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.

40. Pumice
• Highly siliceous material
of volcanic origin Used
either as abrasive /
polishing agent
• Powder-crushing pumice
stone
• Abrasive action is not
very high.
• Polishing tooth enamel,
gold foil, dental amalgam
and acrylic resins.

41. 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.

42. Sand
• Predominantly composed
of silica.
• Particles represent a
mixture of color.
• Rounded to angular
shape.
• Applied under air pressure
to remove refractory
investment materials
• Coated on to paper disks

43. Tripoli
• Derived from light weight,
friable siliceous
sedimentary rock.
• Color-
white/grey/pink/red/yellow.
Grey and red types -most
frequently used.
• Polishing for metal alloys
and some acrylic resins.

44. Zirconium silicate / Zircon
• Off -white mineral.
• Ground to various particle sizes - coated
abrasive disks and strips.
• Component of dental prophylaxis pastes

45. Cuttle
• Referred to as cuttle fish,
cuttle bone, or cuttle.
• White calcareous powder -
pulverized internal shell
of marine mollusk
• Available as a coated
abrasive
• Polishing of metal margins
and amalgam restorations.

46. Kieselguhr
• Siliceous remains of minute aquatic plants
- diatoms.
• Coarser form - diatomaceous earth
• Excellent mild abrasive
• Risk for respiratory silicosis caused by
chronic exposure

47. Synthetic
Silicon carbide:
• Extremely hard abrasive and 1st
synthetic abrasives
• Green and blue black types of
silicon carbide are produced
• Highly effective cutting of metal
alloys, ceramics and acrylic resin
materials.
• Abrasive in coated disks and as
vitreous - bonded and rubber
instruments.

48. Aluminum oxide:
• Second synthetic abrasive to be
developed.
• White powder
• Widely used for making bonded
abrasives, coated abrasives and
air propelled abrasives.
• Finishing metal alloys, resin
based composites and ceramic
materials.
• Pink and ruby variations- adding
chromium compounds

49. Rouge
• Consists of iron oxide, which
is the fine red abrasive
component.
• Adheres well to the skin
• Blended in to various soft
binders in to a cake form.
• Used to polish high noble
metal alloys.

50. 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.

51. Synthetic Diamond
• Controllable, consistent size and shape as well
as their lower cost.
• Resin bonded diamonds have sharp edges,
• Metal bonded diamonds are regular and more
consistent in size.
• Larger synthetic diamond particles – greenish
• Blocks with embedded diamond particles –
truing other bonded abrasives
• Used primarily on tooth structure, ceramics and
resin based composites.

52. Steps in finishing and polishing
Bulk reduction
• Removal of excess material
• Instruments - diamond, carbide and steel
burs, abrasive coated disks, or separating
disks.
• 8 - 12 fluted carbide burs or abrasives with
particle size of 100µm or larger

53. Contouring
• Achieved during bulk reduction
• Finer instruments may be used
• Desired anatomy and margins must be
achieved.
• 12 - 16 fluted carbides or 30 - 100 µm
sized abrasive particles used

54. Finishing
• Introducing finer scratches to surface of
substrate
• Provides a blemish free smooth surface.
• 18 - 30 flute carbide burs , fine and super fine
diamond burs, or abrasives between 8 and 20
µm in size.

55. Polishing
• “Smooth mirror like surface without much loss of
any external form”.
• Provide enamel like luster.
• Smaller particles provide smoother and shinier
surfaces
• Abrasives of 20 µm provide luster
Importance of polishing dental restorations and
teeth
Less receptive to bacterial colonization
Metallic restoration - prevention of
tarnish and corrosion
Comfortable for the patient

57. Principles of cutting, grinding, and
polishing
Cutting operation
• Use of any instrument in a bladelike
fashion
• Regularly arranged blades that remove
small shavings of the substrate
• Separating wheel - used in a bladelike
fashion
• Unidirectional cutting pattern

58. Grinding procedure
Removes small particles of a substrate
through the action of bonded or coated
abrasive instruments.
Predominantly unidirectional
Innumerable unidirectional scratches
Eg: a diamond coated rotary instrument

59. Polishing
Most refined of the finishing processes
Multidirectional in its course of action
Acts on an extremely thin region of the
substrate surface
Use of progressively fine polishing media
Final stage produces fine scratches - not
visible unless greatly magnified

60. Polishing instruments
• Rubber abrasive points.
• Fine particle disks and strips.
• Fine particle polishing pastes – applied
with soft felt points, muslin wheels, prophy
cups or buffing wheels.

61. Non-abrasive polishing
• Composite glazing
• Ceramic glazing
• Electrolytic polishing

62. Composite glazing
Layer of glaze – unfilled resin
Smooth highly glossy surface

63. Glazing ceramics
Subjected to high temperature
Glass like surface

64. Electrolytic polishing
Electrochemical process
Reverse of electroplating
Excellent method for Co-Cr alloys

65. Finishing and polishing procedures
Resin based composite restorations
• Most difficult to polish and finish
• Depends on fillers, preparation design,
curing effectiveness and the post curing
time.
• Finishing & Polishing - in one direction
only
• Should continue in a direction
perpendicular to the previous one.

66. Gold alloys
• Slow speed hand piece should be used
Steps:
• Contour with carbide burs, green stones, or
heatless stones.
• Finish with pink stones ( aluminum oxide) , or
medium grade abrasive impregnated rubber
wheels and points( brown and green)
• Apply fine abrasive- impregnated rubber wheels,
cups and points .
• Apply Tripoli or rouge with rag or leather wheels

67. Ceramometal restorations
• Critical area while polishing is the porcelain
metal junction
• Using an air water spray and
maintaining intermittent contact
• Several kits-Axis dental corp, Universal ceramic
polishers, Dialite
• Recommended polishing speed -10,000 rpm
• Polishing at 20,000 rpm reduces flexural
strength of ceramics

68. General technique
• 1. Contour with flexible diamond disks, diamond
burs, or green stones (silicone carbide)
• 2. Finish with white stones or abrasive
impregnated rubber disks, cups and points.
• 3. Polish with fine abrasive impregnated rubber
disks, cups and points or if necessary, use a
diamond paste applied with a brush or felt
wheel.

69. Acrylic resins for Denture Bases and
Veneers
• 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.

70. 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.

71. 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

72. Biological hazards of the finishing
procedure
• Aerosols – silica based materials (smaller than
5µm)
• Silicosis or grinders disease
• Precautions -adequate water spray, suction
-eyeware ,facemasks
-proper ventilation

73. Dentifrices
• Available as toothpaste, gels and powders.
• Function :
• 1)Abrasive and detergent action
• 2)Polish teeth
• 3)Act as vehicles for delivery of therapeutic
agents like fluorides, tartar control agents,
desensitizing agents, remineralising agents.
• The abrasive concentrations in paste and gel
dentrifices are 50% to 75% lower than those of
powder dentrifices

74. Prophylaxis pastes
• Used for removal of exogenous stains, pellicle,
material alba, and oral debris.
• Usually contain only moderately abrasive
materials, such as pumice.
• Silcon dioxide and zirconium silicate are also
used
• Applied to teeth through rubber cup on a slow
speed handpiece.

75. 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.
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

76. Guler A U et al, Effects of various finishing procedures on the staining
of provisional restorative materials, J Prosthet Dent 2005;93:453-8
• The purpose of this study was to investigate the
effect of different polishing methods such as with
pumice, diamond polishing paste , polishing disc
and their combinations on color stability of
autopolymerized bis-acrylic composites, a light
polymerized composite, and a methyl methacrylate–
based PR material upon exposure to a staining
agent.

77. References
• O’Brien W.J.,Dental materials and their
selection,2nd edition,1997, Quintessence
publications Canada, Pp 115-122
• J.L. Ferracane, Materials in Dentistry, 2nd edition,
2001, Susan Katz publishers, USA, Pp 293-308
• Anusavice, Phillips Science of Dental Materials,
11th edition, 2003, Elsevier publications, Florida,
Pp 351-377

78. • Craig . Powers and Wataha, Dental Materials,
Properties and manipulation, 8th edition,2005,
Elsevier publications, India , Pp 110-28
• 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
• Guler A U et al, Effects of various finishing
procedures on the staining of provisional
restorative materials, J Prosthet Dent
2005;93:453-8

79. • Jefferies S R, Abrasive Finishing and Polishing
in Restorative Dentistry: A State-of-the-Art
Review, Dent Clin N Am 51 (2007) 379–397
• Dental materials ppt