FINISHING & POLISHING MATERIALS
By
Dr K.R.Hassan
Head Science of Dental Materials Department
R.I.H.S
Islamabad
• FINISHING: Process of removing surface
defects/scratches.
• POLISHING: Polishing is the process of
providing luster or gloss on a material surface.
• FINISHED & POLISHED RESTORATION:
A prosthesis or a direct restoration
whose outer surface has been refined to a
desired state of finish.
GOALS
The goals of
finishing & polishing
procedures are to obtain
the desired anatomy,
proper occlusion &
the reduction of
roughness, gouges
& scratches that are
produced during the
making of the prosthesis.
BENEFITS OF FINISHING &
POLISHING
Finished & polished restorations provide 3
major benefits of dental care:
 Oral health:
A well contoured & polished restoration
resists the accumulation of food debris &
pathogens.
Tarnish & corrosion activity of the
restorations is reduced.
Polished restoration surfaces minimizes
the wear rates of opposing & adjacent teeth.
 Function:
Rough surfaces causes development of
high-contact stresses which hinder functions &
stabilizing contacts b/w the teeth.
 Aesthetics:
Finally, to achieve the goal of patients’
demands of a polished restoration, as aesthetics
play a major role in dentistry.
Most finishing & polishing in dentistry
are performed by ABRASION.
ABRASION:
Is the process of wear of a material by
another material through scratching, chiseling or
other mechanical means.
ABRASIVE
Is a hard substance used for grinding,
finishing or polishing of a less hard surface, or
the material that causes wear is called abrasive.
SUBSTRATE
The material being abraded is called a
substrate.
P.S ABRASIVE IS HARDER THAN THE
SUBATRATE.
EROSION
Is caused by hard particles impacting a
substrate surface, carried by a stream of either
liquid or air e.g. sandblasting.
BULK REDUCTION
Is the process of removing excess material
by cutting or grinding by a rotary instrument.
GRINDING
Is the process of
removing material by
abrasion with
relatively coarse
particles.
CONTOURING
Is the process of
producing a desired
anatomical form by
cutting or grinding.
FACTORS AFFECTING RATE OF
ABRASION
The following factors causes changes in the
rate of abrasion of an abrasive:
 HARDNESS
Hardness of an abrasive is directly
proportional to the rate of its abrasion i.e. the
harder the abrasive than the substrate the more
abrasion will be produced.
 PARTICLE SIZE
The particle size of a material is
Expressed in MICROMETRES.
By convention, particles are classified as
 FINE
0 - 10µm
 MEDIUM
10 - 100µm
 COARSE
100 - 1000µm
Larger, coarse abrasive particles will abrade a
surface more readily than smaller particles , but
they tend to leave more coarser scratches in the
substrate.

PARTICLE SHAPE
Sharp, irregular shaped particles will abrade a
surface more rapidly than will rounded particles having
dull cutting angles. However the former will produce
deeper scratches than later.
 SPEED & PRESSURE
Both speed & pressure are directly
proportional to the rate of abrasion.
At higher speed greater friction is produced, which tends to
produce higher temperatures. Similarly, greater pressure
causes higher temperatures & possibly patient
discomfort.
 LUBRICATION
Lubricants are used during abrasion
for two purposes:
 to reduce heat buildup
 to wash away debris to prevent clogging
but too much lubrication can reduce the abrasion
rate by preventing the abrasive from coming in
contact with the substrate.
CLASSIFICATION OF
ABRASIVES
Abrasives used in dentistry can be classified
into the following three types:
 FINISHING ABRASIVES
are generally hard, coarse & used
primarily to produce the desired contours of a
restoration or tooth preparation.
 POLISHING ABRASIVES
have finer particle sizes & are less
hard than the finishing abrasives, they are used
to smooth surfaces roughened by finishing
abrasives.
 CLEANSING ABRASIVES
are generally soft materials with small
particle sizes & are intended to remove softer
materials that adhere to the enamel or
restorations.
TYPES OF ABRASIVES
A variety of abrasives are available but the
types listed below are widely used in dentistry.
 NATURAL abrasives include
 ARKANSAS STONE
is a semi translucent, light gray
sedimentary rock mined in Arkansas. It is dense,
hard & contains uniformly textured
microcrystalline quartz. It is used for fine
grinding of tooth enamel & metal alloys.
 CHALK
Is a white
abrasive composed of
CaCO3. Chalk is used
as a mild abrasive
paste to polish tooth
enamel, gold foil,
amalgam & plastic
materials.
 CORUNDUM
is a white mineral form of Al2O3. It
is largely replaced by synthetic Al2O3 in dental
applications due to its inferior physical properties.
It is used primarily for grinding metal alloys.
 DIAMOND
is a transparent, colorless mineral
composed of carbon. It is the hardest
known substance & is called a super
abrasive because of its ability to abrade
any other known substance.
Synthetic diamond
abrasives are used far
more commonly than
natural diamond due to its
consistent shape & size &
low cost.
Diamonds are mostly used
on tooth structure,
ceramics & resin-based
composite materials.
EMERY
is a fine-grain
grayish black
corundum, used for
finishing metal alloys
& acrylic resin
materials.
 GARNET
consists of a group of different minerals
that have the same physical properties &
crystalline forms. Minerals included in this group
are silicates of Al, Co, Fe, Mg & Mn. The type of
garnet used in dentistry is usually dark red. It is
used in grinding metal alloys & acrylic resin
materials.
 PUMICE
is a light gray
volcanic rock
derivative, used in
polishing tooth
enamel, gold foil,
dental amalgam &
acrylic resins.
 QUARTZ
is a hard, colorless,
transparent & most
abundant mineral. It is
used mainly to finish
metal alloys but can be
used to grind dental
enamel.
 SAND
is a mixture of
mineral particles,
predominantly composed
of silica. The particles
represent a mixture of
colors, making it distinct
in appearance. They are
coated onto paper disks
for grinding of metal
alloys & acrylic resin
materials.
 TRIPOLI
is derived from a
light-weight, friable
siliceous sedimentary
rock. Tripoli can be white,
gray, pink, red or yellow.
The gray & red types are
mostly used in dentistry.
It is used for polishing
metal alloys & some
acrylic resin materials.
ZIRCONIUM
SILICATE
or zircon is an offwhite mineral. It is
frequently used as a
component of dental
prophylactic pastes.

CUTTLE
commonly referred
to as cuttlefish or cuttle
bone, is a white
calcareous powder made
from the internal shell of a
Mediterranean marine
mollusk. It is available as
coated abrasive & used
for polishing metal
margins & dental
amalgam restorations.
 KIESELGUHR
is composed of the
remains of minute aquatic
plants known as diatoms.
Its coarser form is called
diatomaceous earth & is
used as a filler in many
dental materials, such as
hydrocolloid impression
materials.
 SYNTHETIC abrasives include
 SILICON CARBIDE
It was the first of the synthetic abrasives to
be produced. It is available in green & blue-black
types, having equivalent physical properties.
Silicon carbide is extremely hard & brittle &
results in highly efficient cutting of materials,
including metal alloys, ceramics & acrylic resins.
It is available as an abrasive
in coated discs, & bonded
instruments.
 ALUMINUM OXIDE
Fused aluminum oxide was the second
synthetic abrasive to be developed. Aluminum
oxide (alumina) is much harder than corundum
(natural alumina) due to its purity. Several grain
sizes are available & has largely replaced emery
for several abrasive uses. Alumina is largely
used in dentistry to make bonded, coated & air
propelled grit abrasives. It is popular for
adjusting dental enamel & for finishing metal
alloys, resin-based composites & ceramic
materials.
 ROUGE
Fe2O3 is the fine,
red abrasive
component of rouge.
Like tripoli, rouge is
blended with various
soft binders into a
cake form. It is used
to polish high noble
metal alloys.
 TIN OXIDE
SnO is an extremely
fine abrasive used
extensively as a polishing
agent for polishing teeth
& metallic restorations. It
is mixed with water,
alcohol or glycerin to form
a mildly abrasive pastes.
 ABRASIVE PASTES
The most commonly
used abrasive pastes
contain either alumina or
diamond particles.
Alumina pastes should be
used with a rotary
instrument & increasing
amounts of water.
Diamond abrasive pastes
are used in dry
conditions.
Abrasive pastes have several disadvantages like
> they are relatively thick & so don’t readily gain
access to embrasures.
> they tend to splatter off of the instruments.
> heat is generated when insufficient coolant is
used or when an intermittent polishing technique
is not used.
DENTIFRICES
Dentifrices are
available as
toothpastes, gels &
powder.
They are used for three important functions :
 their abrasive actions provide more efficient
removal of debris, plaque & stained pellicle
compared with toothbrush alone.
 they polish teeth to provide increased light
reflectance & superior aesthetic appearance.
the high polish enables teeth to
resist accumulation of microorganism & stains
more than rough
surfaces.
 finally, dentifrices act
as vehicles for
delivery of therapeutic
agents e.g. fluorides,
tartar controlling
agent, desensitizing
agent etc.
The products advertised as whitening tooth
pastes may contain an abrasive agent alone or
along with a chemical agent.
The former additive acts through a surface
stain removal mechanism, whereas the latter
acts through a combined action of abrasion &
bleaching.
COMPOSITION
A typical dentifrice comprises of the following
components:
Abrasive e.g. CaCo3, hydrated alumina/ silica
soda bicarb or a mixture of these.
purpose removal of plaque/stain & polish
Detergent e.g. Sodium lauryl sulfate
purpose aids in debris removal
Colorants e.g. Food colors
purpose
appearance
Flavoring e.g. Oils of spearmint, peppermint or
cinnamon
purpose
flavor
Humectant e.g. Sorbitol, glycerin
purpose
maintains moisture content
Water e.g. Deionized water
purpose
suspension agent
Binder e.g. Carrageenan
purpose
thickener, prevents liquid-solid
separation
Fluoride e.g. Sodium monofluorophosphate
purpose
prevents dental caries
Tartar control e.g. Disodium pyrophosphate
purpose
inhibits formation of calculus
above gingival margin
Desensitizing e.g. Potassium nitrate
purpose
promotes occlusion of dentinal
tubules.
The abrasive concentrations in paste & gel
dentifrices are 50 – 75% lower than those of
powder dentifrices. So powders should be
used more sparingly & with greater caution to
avoid excessive dentinal abrasion & pulpal
sensitivity.
TOOTHBBRUSHES
Toothbrush bristle stiffness alone have no effect
on abrasion of hard dental tissues. However,
with the use of a dentifrice, there is evidence
that brush bristles bend more readily & bring
more abrasive particles into contact with the
tooth structure. This interaction produces more
effective abrasion & cleaning action.
Factors Affecting Dentifrice Abrasiveness:
EXTRAORAL FACTORS
≈ Abrasive particle type, size, & quantity in the
dentifrice.
≈ Amount of dentifrice used.
≈ Toothbrush type.
≈ Toothbrush method & force applied during
brushing.
≈ Toothbrushing frequency & duration.
≈ Patient’s coordination & mental status.
INTRAORAL FACTORS
≈ Saliva consistency & quantity.
≈ Xerostomia induced by drugs, gland pathology
or radiation therapy.
≈ Dental deposits e.g.
pellicle, plaque, calculus
their presence, quantity
& quality.
≈ Exposure of dental root
surfaces.
≈ Presence of restorative
materials, dental
prostheses, &
orthodontic appliances.
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