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1. INDIAN DENTAL ACADEMY
Leader in continuing Dental Education

2. Contents
• Introduction
• Definition
• Factors affecting the rate of abrasion
• Factors affecting the efficiency of abrasion
• Design of the abrasive instrument
• Types of abrasives
• Polishing

3. Finishing and polishing :Denture base resins
RPD frameworks
Gold castings
Restorative resins
Posterior tooth colored
Restorations
Porcelain
Ceramic restorations and
Review of literature
Summary
Conclusion
References

4. INTRODUCTION

5. DEFINITIONS
Abrasion
Craig , has defined abrasion as :
“A process of wear whereby a hard rough surface
( like a sand paper disk ) or hard irregular shaped
particles ( like those in a slurry ) plough grooves in
a softer material and cause materials from these
grooves to be removed from the surface”.
Skinner has stated abrasion to be either a two body
process or a three body process.

6. Finishing :
The term finishing denotes to cut or remove the
excess . It is usually performed with coarser
abrasives when compared to polishing .
Polishing :
The use of progressively finer abrasives to remove
scratches and give a high shine or luster to the
material .
To understand this more specifically , the terms
such as abrasive wear and erosive wear need more
specific understanding .

7. Wear :
It 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 abraded is
called as Substrate .

8. Abrasive wear : Two types –
Two Body Wear :
Occurs when abrasive particles are firmly bonded to
the surface of the abrasive instrument and no other
abrasive particles are used eg. A diamond bur
abrading a tooth .
Three body wear :
occurs when the abrasive particles are free to
translate and rotate between two surfaces eg. action of
prophylaxis paste as they are applied to tooth enamel
by a rubber cup .

10. Erosive wear :
This is caused by hard particles impacting a
substrate surface, carried either by a stream of air
or a stream of liquid .Erosive wear should be
differentiated from chemical erosion more
commonly know as acid etching which involves
acids and alkalis instead of hard particles to
remove the substrate material .

11. Factors affecting the rate of abrasion :
1. Concentration of the abrasive particles
2. Size of the particles : expressed in millimeters
classified as –fine, medium and coarse.
3. Speed :
The faster the speed , faster will be the rate of abrasion.
4. Pressure of the abrasive particles against the surface
being abraded :
Heavy pressure will lead to formation of deeper
scratches and faster removal of the substrate .

12. Factors influencing the efficiency of the abrasives :
1. Hardness of the abrasive particle .
2. Rate of movement of the abrasive particles
3. Properties of the material being removed:
A brittle material can be abraded rapidly whereas a
malleable and ductile material eg. Gold will flow
instead of being removed by the abrasive .

13. a Cutting operation ,
a Grinding operation
and
a Polishing operation
Difference Between

15. Design of Abrasive Instrument
Finishing and polishing devices
Abrasive and polishing devicesCutting instruments
Loose abrasives Bonded abrasives Coated abrasives

16. Loose abrasives or grits :
They are derived from abrasive materials that
have been crushed and passed through series of
mesh screens to obtain different particle sizes-
Coarse, medium coarse, medium fine and super
fine.
Loose abrasive polishing pastes contain a fine
particle size distribution of either aluminium
oxide or diamond particles dispersed in a water
soluble vehicle , such as glycerine.

17. Bonded abrasives
These consists of abrasive particles incorporated
through a binder used for grinding tools.
The matrix is usually an elastomeric material such
as rubber or silicone compound, but can also be
rigid and non elastic in nature.
Eg. Bullet or Pointed white stone used at low speed
.

18. The abrasives are bonded by four methods:
1. Sintering.
2. Vitreous bonding.
3. Resinous bonding.
4. Rubber bonding.

20. Coated Abrasives
They are usually in the form of a mylar, paper or some
other polymeric backing, wherein the abrasive particles
are distributed on the surface of the backing or some other
symmetric matrix design.
The abrasive particles are retained on the surface of the
disc or matrix by an adhesive polymeric surface coating or
layer.
-Aluminium oxide.
-silicon carbide.
Moisture resistant backings are advantageous as the
abrasive stiffness is not reduced by water degradation.

21. Air Abrasive Technology
As an alternative to the use of rotary cutting, air
abrasive systems can deliver a fine, precisely
controlled high-pressure stream of 25 to 30um
aluminium oxide particles to remove enamel,
dentin, and restorative materials.
Because air abrasion generates minimal heat or
vibration, the potential for tooth chipping or
micro fracturing is minimized.

22. A controlled delivery of air , water and
sodium bicarbonate slurry to remove
plaque and stains from tooth surfaces is
also employed for Dental Hygiene
procedures.

23. Skinners has grouped abrasives as
Natural abrasives :
Arkansas stone Sand
Chalk corundum Tripoli
Diamond Cuttle
Emery Quartz
Garnet Kieselguhr
Pumice
Zirconium silicate
Manufactured abrasives : Silicon carbide
Aluminum oxide
Synthetic diamond
Rouge
Tin oxide

24. 1. Arkansas Stone :
Semi-translucent , light grey , siliceous sedimentary
rock mended in Arkansas
Contains mico-crystalline quartz .
Small pieces are attached to metal shanks and trued
to various shapes for fine grinding of tooth enamel.
2. Chalk :
mineral form of calcite
contains calcium carbonate
used as a mild abrasive paste to polish teeth enamel ,
gold fillings ,…

25. Corundum :
Largely replaced by alpha aluminium oxide due to its
various superior physical properties .
Available as bonded abrasive and is used primarily to
grind metals .
Diamond :
Transparent colorless mineral composed of carbon
called SUPER-ABRASIVE because of its ability to
abrade any known substance .
Hardest substance known .
Used on ceramic and resin based composite materials.
Supplied as – bonded abrasive , diamond abrasive
pastes , abrasive strips .

27. Emery :
Consists primarily of a natural oxide of aluminium
called corundum .There are various impurities
present , such as iron oxide which also act as
abrasives .Usually bound to paper discs and can be
used on gold or porcelain .
Garnet :
Includes several minerals , which posses similar
physical properties and crystalline form like silicates
of Al,Co,Mg, Mn. Is dark red , extremely hard and
when fractured during abrasive activity forms sharp
chisel shaped plates-thus making garnet an effective
abrasive.Usually coated on paper or cloth with a
binder. Cuts both metal and porcelain.
Denture abrasive discs
.

28. Pumice :
Highly siliceous material of volcanic origin .
Suitable for use as an abrasive or a polishing agent
according to its particle size .Can be used for many
operations from smoothening of denture bases to the
polishing of teeth in the mouth .
Quartz :
The particles are pulverized to form sharp angular
particles , which are useful in making coated discs .
Used to finish metal alloys and may be used to grind
dental enamel .

29. Sand :
Is an abrasive agent along with other forms of quartz
Eg. Sandpaper is coated with a dense crystalline
form of quartz called Flint.
Flint is a naturally occurring mineral that chips to
form sharp cutting edges . It is not as durable or
strong as other abrasives , but it is a useful abrasive in
the finishing cast gold .Also available a powder in
sandblasting equipment .

30. Tripoli :
Mild abrasive and polishing agent
True Tripoli originates from certain porous rocks,
first found in Northern Africa near Tripoli , for
which it was named .
Used for polishing metal alloys and some plastic
metals .

31. Zirconium silicate :
Occurs in nature as Zircon .
Is ground to various particle sizes and used as a
polishing agent .
It is used as a constituent of dental prophylactic
pastes and in abrasive impregnated polishing strips
and discs .
Cuttle :
A fine , relatively soft polishing agent made from
calcified internal shell of cuttle fish .
It is used on paper discs and for delicate operations
like polishing of metal margins .

32. Kieselguhr :
It is composed of siliceous remains of minute
aquatic plants know as diatoms .
The coarser form is called diatomaceous earth ,
which is used as a filler in many dental materials .
It is an excellent mild abrasive and polishing agent .
Precaution should be taken – respiratory silicosis
due to long term exposure .

33. Manufactured abrasives
Silicon carbide :
First of the synthetic abrasives to be developed .
It is the basic material of corundum
Two types are manufactured –green form and blue
black form .
Cutting efficiency of silicone carbide abrasives is
higher as the particles are sharp and break to form
new sharp particles .
Supplied as an abrasive in coated discs, vitreous and
rubber alloys , ceramic and plastic materials .
Most of the steel burs employed for the tooth cutting
are made of silicon carbide .

34. Aluminium Oxide :
This is the second synthetic abrasive to be manufactured
.
Pure aluminium oxide is manufactured from bauxite , an
impure aluminium oxide.
Extremely fine particles of aluminium can be obtained
by a water floation process. In this form it is know as
levigated alumina and it is used extensively for
polishing metallographic specimens .
The forms usually prepared are :
Coarse grit aluminium oxide is the abrasive in brown ,
pink , or coral stones used for finishing metal and
ceramic copings .
A very fine grit (400) is used for the manufacture white
polishing stones, sometimes called Poly stones

35. Synthetic diamond :
The synthetic or manufactured form of diamond
saws, wheels and burs , diamond blocks-used for
truing of bonded abrasives .
They are used primarily on teeth , ceramic
materials ..
Rouge:
It is a fine red powder composed of iron oxide.
Usually employed in cake form
It is impregnated on paper or cloth, known as Crocus
cloth
Excellent polishing agent for gold and noble metal
alloys.

36. Tin oxide :
Also called as Putty powder ,it is used as a polishing
agent for teeth and metallic restorations in the mouth
It is mixed with water , alcohol or glycerin and used as
a paste.

37. Polishing
Is the production of a smooth mirror like surface
without use of any external form.
If the size of the abrasive is reduced sufficiently, the
scratches finally become extremely fine and may
disappear entirely.
The surface then acquires a smooth shiny layer
referred by Skinner as a POLISH.

38. The polished layer is thought of one made up of minute
crystals, thus know as the “Micro crystalline layer
or Beilby layer”
which is easily kept clean and has high corrosion
resistance.

39. Finishing and polishing of the denture base resin
1.Remove the stone from the denture in small sections.
Use a bur or a saw judiciously in removing the stone
in sections without damaging the denture .
Edentulous casts may have undercut areas and also
cast is stronger than the plastic denture . Injudicious
prying will result in a broken denture
2.A shell blaster is also helpful in removing stone from
the interior of the denture . A pneumatic chisel also
aids in removing stone from the denture .
3. After separating the denture the cast , it is ready for
finishing and polishing .

43. Finishing and polishing the partial
denture framework :

51. The technique consists of the following steps
1. Contour with carbide burs, green stones (Silicon Carbide
or heatless stones.
2.Finish with pink stones ( Aluminium oxide) or Medium
grade abrasive impregnated rubber wheels and points
(Brown and Green)
3.Apply fine abrasive impregnated rubber wheels, cups and
points ; and if necessary
4.Apply Tripoli or Rouge with rag or leather wheels.
Finishing and Polishing of Gold Alloys

52. Finishing and polishing of Porcelain
Usually two types of kits are available to polish
porcelain-
1 Extra oral kits
2. Intra oral kit
Examples of extraoral kits : komet/brasseler Dialite
Porcelain polishing kit ; Revitalizer (Cosmedent ),
Ceramiste Silicon Points (Shofu ).

53. These are bonded abrasives and rubber polishing
devices that fit straight laboratory handpieces and can
operate at higher RPM. The use of diamond polishing
paste along with these kits help to produce a polished
porcelain surface that is highly smooth and with a
surface gloss equivalent to that produced by glazed
porcelain.

54. Sequence for Extraoral Finishing and Polishing
1. Finishing diamonds, eg. Esthetic Trimming
diamonds (Komet/Brasseler), Two Stripper MFS
(premier),and T&F and Hybrid points (Shofu) are
used dry to adjust and provide gross finishing.
2. Finishing discs or bonded abrasive wheels can also
be used , desired for gross adjustment.
3. Rubber porcelain polishing devices are used to pre
polish and provide initial polish to the adjusted
area.

55. 4. Loose abrasive diamond porcelain polishing paste is
applied .For example, Porcelize (Cosmedent ),
Truluster polishing system (Komet ) ,Two Stripper
Mfs Diamond Polishing System (Premier) and
Diamond Polish (Ultradent ), using felt wheels and
points or a soft using felt wheels and points or a soft
Robinson brush on occlusal areas.

56. Intra-Oral Polishing
Follows similar procedural steps as extra oral
polishing. The rationale for the necessity of intraoral
porcelain polishing follows from clinical observation
that unpolished porcelain can accelerate wear of
opposing natural tooth structure and unpolished
margins of bonded restorations are more susceptible
to inflammation and poor esthetics.

57. The Sequence
1.Finishing diamonds.
2.Finishing discs or Enhance disc or Rubber polishing
instruments .
3.Diamond polishing paste.
-Is also applicable intraorally with some modifications.
Diamonds should be used wet to avoid excessive heat.
Preferred devices to apply diamond -polishing paste
intraorally include enhance polishing cups (Densply) or
Robinson brushes.

58. Finishing Of All Ceramic Restorations :
1. Broad, relatively flat surfaces are best reduced
extra orally with large, smooth-cutting Busch silent-
stone, while grooves and ridges are reshaped with
smaller pointed diamond stones and green stones.
2. Instruments that have been used on metals should
not be used on porcelain. Metal particles become
embedded in pores in the porcelain and cause
discoloration.
3. When working near an acute edge of porcelain.
apply the stone so that it is moving from the edge
towards the greater bulk to prevent chipping the
fragile edge. This is opposite of the technique used
in finishing metal margins.

59. 4. Roughened ceramic surfaces are smoothened with
clean white stones and polished with rubber wheels
of progressively finer grit such as those found in the
ceramsite kit is indicated by stripes around the
shank of the instrument. No stripe is coarse, one
yellow stripe is medium and either two yellow
stripes or one white stripe is fine.
5. Pastes containing diamond dusts are available for use
on cups and brushes. Porcelain may also be
reglazed after it is polished.
6. Final finishing procedures can be accomplished with
porcelain polishing agents, including rubberized
abrasives and diamond polishing paste. The
proximal areas can be finished with finishing strips.

60. 5. Pastes containing diamond dusts are available for use
on cups and brushes. Porcelain may also be reglazed
after it is polished.
6. Final finishing procedures can be accomplished with
porcelain polishing agents, including rubberized
abrasives and diamond polishing paste. The proximal
areas can be finished with finishing strips

61. Polishing of teeth :
Acrylic resin teeth are polished by the same method as
the denture base material.
Polishing of porcelain teeth :
Since it is more difficult to polish ground porcelain
teeth than acrylic teeth, restoring a satisfactory
surface requires more effort.
1. Smoothen the surface of ground porcelain teeth
with a medium polishing wheel.
2. Smoothen the surface again with a fine polishing
wheel .

62. 3. Polishing in two directions with a lathe-mounted
rag wheel and slurry of flour of pumice.
4. The final polishing is done with a clean lathe-
mounted rag wheel and slurry of porcelain
finishing polish.

63. Finishing and polishing of Restorative Resins :
Although one may think that different finishing
techniques would be appropriate for posterior and
anterior composites, Prattern and Johnson pointed out
that no statistically significant difference exists
between posterior and anterior materials. Thus,
primary considerations for finishing any restoration
are based on certain criteria :

64. 1. Instrument shape :
Anterior finishing : The correct shape for finishing
anterior restorations is dependent on the surface
being finished. For the labial surface, a long tapered
straight edge instrument is preferred, which allows
the basic straight shape of the labial surface to be
easily contoured.
For cervical finishing, a much smaller, but also
tapered finishing instrument conforms to the desired
straight emergence profile as tooth emerges from the
gingival sulcus.
For lingual finishing, the rounded, Football shaped
instrument can best supply the appropriate curve.

65. Posterior finishing :
For posterior finishing, 4 instruments can generally
finish most composite restorations. The first instrument
should be small and thin enough to remove any
overhang or excess marginal build up.
For this purpose, a 4mm tapered point instrument is
best.
The basic occlusal anatomy is then placed with the
rounded football shaped instrument. Grooves and
fissures are next placed using the round end tapered
series of diamond or carbide instruments.

66. Polishing the posterior composite is easily done using
a series of impregnated points (shofu polishing kit) .
They must be used in sequence with no band first,
followed by yellow and white-banded instruments.
Polish and paste can be used in combination with the
points or cups.

67. Surface of Finishing Instrument
Bognosian, Randolph and Jekkals, point out that
carbides should not be used at higher speeds when
trimming and finishing micro filled composite resins
as they tend to disrupt the surface.
However high speed finishing with carbide burs on
small particle composite resins produces a non
disrupted surface that was free from striations and
grooves left by diamond.

68. Finishing and polishing of Titanium
Operations Finishing materials Remarks
Removal of
Sprue runners
ST cutting disk (large)
TX cutting disk (thin)
Thin Sprue runners (quick cutter) or STM
(handtool)
Avoid tilting , cool work pieces with water
Finishing
(Rough)
Hard-alloy cutting, mini
Hard-alloy cutting, midi
Hard-alloy cutting, maxi
Hard-alloy cutting, maxi plus
Max rotation speed 10,000 per min
Low pressure
Finishing
(fine)
Aloxin grinder blue, small, B
Aloxin grinder blue, large, C
Circular grind on work piece ;
Not suitable for surfaces to be coated with
ceramics
Grinding
(fine)
Emery cloth - 500 Recommended before rubber polishing
Rubber
polishing
Rubber disks (grey)
Rubber disks (red)
Rubber disks (red)
Rubber disks (red)
Use sparingly and without pressure
Low rotation speed (danger of
overheating)
Grey – rough polish
Red fine – polish
Polishing Large polishing brush
Black polishing brushes
Small brushes
Tiger brilliant, Polishing paste
Change direction of polishing frequently
Add no more polishing paste for high
lusture

69. Review of Literature
G. Theuniers and M.De Clercq in 1987 made a
comparative study of the smoothness of preparation on
margins obtained by different finishing procedures .The
study compared the finish obtained with a diamond bevel
bur, a finishing stone (Dura White), a tungsten-cobalt
finishing bur and a tungsten-vanadium finishing bur.
The authors concluded
1.A diamond bevel bur creates a relatively rough tooth
surface. The best result could be obtained with carbide
finishing burs. An intermediate result was obtained with a
finishing stone (dura white)
2.The roughness of the surface prepared with diamond
burs was directly proportional to the diamond grain size

70. 3. Pretreatment with a fine grained diamond bur was
necessary. Polishing of the margins was necessary
and it could be achieved with a stone (Dura White) or
better with finishing burs.
4. Polishing capacity of a bur was enhanced by
reduction of rotation speed

71. D.A. Felton,et al in 1991 conducted a scanning
microscopic analysis on the effect of air abrasives on
marginal configurations of PFM alloys.
Their investigation qualitatively and quantitatively
evaluated the effects of commercially available air
abrasives (AL2O3 and glass beads) used for
sandblasting on various marginal configurations of 5
metal ceramic alloys.

72. The Authors concluded
1.The smaller the margin angle, the greater was the
loss of alloy after air abrasion.
2.The abrasion resistance of the alloys investigated
generally increased with greater alloy hardness and
percent of elongation.

73. M.Kern and V.P. Thompson 1994 studied the effect
of sandblasting and silica procedures on pure
titanium. The study evaluated the effects of
sandblasting and costing techniques on volume loss,
surface morphology and composition changes in
pure titanium.
They concluded :
1. Sandblasting plays a critical rolw in bonging of
resin to metal by creating a roughened surface that
is also changed in composition partially, by the
embedding of aluminium particles.
2. Clinical or lab. Sandblasting does not remove a
suffucuent volume of surface material as to affect
the clinical fit of titanium restorations.

74. Jacobi and Shillinburg 1991 compared the
abrasiveness of 6 ceramic surfaces and gold .The
authors attached a type III gold alloy and 6 different
ceramic surfaces in an abrasion machine opposing
extracted teeth to determine their relative
abrasiveness and resistance to wear
Authors found
1. Type III gold was least abrasive.
2. Glazed porcelain was more abrasive than polished
porcelain.
3. Dicor shading porcelain had approximately the
same abrasiveness as VMK 68 porcelain when
glazed.

75. 4. Dicor cast ceramic material without shading was the
least abrasive ceramic material but the most subjected
to wear .
5. The cerammed skin of Dicor cast ceramic material
was the most abrasive and wear resistant of the
ceramic surfaces.

76. Robert C.S. Chen, Daniel C.N. Chan et al 1998
conducted a study of finishing and polishing
technique for a composite.
The study evaluated and compared 6 finishing and
polishing techniques with commonly used materials
and methods to identify an effective finishing and
polishing technique for microfilled composite
restorations.
They concluded
1. Soflex disk produced the smoothest polished surface.
2. Finishing and polishing by diamond burs followed
with a vivadent polishing point produced the second
smoothest polished surface

77. 3. A carbide bur followed by a vivadent polishing point
and finishing and polishing diamond burs alone, or
followed with Den Mat polishing paste produced a
relatively smooth surface.
4. Carbide burs followed with Den Mat polishing paste
produced the least desirable surface.

78. In a study conducted by Dr. Ponnanna A.A. 1999
under the able guidance of Dr. N.P.Patil to evaluate
the polished surface characteristics of Co-Cr castings
subsequent to finishing and polishing techniques
A total no. of 30 disc shaped test specimens of cast
Co-Cr alloy were fabricated for the evaluation of
surface characteristics
They concluded
1. Various finishing and polishing techniques employed
for the surface Rx of cast Co-Cr alloys revealed
improved surface characteristics using the sequence
of sandblasting, coarse grit abrasive, medium grit and
the fine grit abrasive.

79. 2. Perthometric evaluation of the surface characteristics
seems to be a better method of evaluation of finished
and polished surface.
3. Loss of weight of metal affecting the physical quality
of the alloy can be carefully avoided by judicious
sandblasting and application of proper grit of abrasive
agents.

80. Summary&Conclusion
A lot of materials are available commercially to
perform finishing and polishing. Discretion on the
part of the dentist is necessary to select the right
material for that technique.
Since each manufacturer advocates his own
method, standardization of technique becomes
very difficult.
Every technique follows the use of abrasive grits in
a sequence of coarse to fine to achieve optimal
results.

81. An optimal application of specific devices for
certain restorative materials and specific clinical
situations should be considered in order to
enhance both longevity and esthetics of the
restored teeth.
Also due to rapid development in technology, these
materials and equipment undergo changes. But
one should follow the basic principles of finishing
irrespective of the system or product chosen.

82. References
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84. • Jeffries S.R. “The art and science of abrasive and
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