A comprehensive lecture on finishing and polishing materials by Dr Rashid Hassan covering all the aspects of the topic from basic concepts to the applications in dentistry. For more lectures on different topics of Dental Materials by Dr Rashid visit and follow Dr Rashid lectures on Dental Materials on Facebook (dmbydrrashid)

1. By
Dr. RASHID HASSAN
BDS(de’ Mont) MSc (QMUL.UK)
Hod Science of Dental Materials

2. Abrasion
• Smoothening of rough surface
before polishing.
• The wearing away of a
substance or structure through
a mechanical process, such as
grinding, rubbing or scraping.
• Each point/edge of an abrasive
acts as an individual cutting
blade.
• Hardness, strength, ductility &
thermal conductivity affect the
process of abrasion.
• Types of Abrasion:
A two body process.
A three body process.

3. Desirable Characteristics of an
Abrasive
 It should be irregular in shape.
 Abrasive should be harder than the worked it
abrades.
 They should have a high impact strength.
 Should have attrition resistance, so that it does not
wear.

4. Abrasion Vs. Cutting
Cutting:
– Blades or cutting edges are
regularly arranged.
– Removal of the material is
corresponding to this
regular arrangement.
Abrasion:
– They have many abrasive
points, which are not
arranged in an ordered
pattern.
– Innumerable random
scratches are produced.

5. Rate of Abrasion
1. Size of the abrasive particle.
• Large particles  deeper scratches & Work fast.
• Course abrasive are used on highly rough surface.
fallowed by finer course surface.
2. The pressure of the abrasive agent.
• Heavy pressure
• Deeper scratches and fast work.
• Less control over abrasion process.
3. Speed at which the abrasive particle moves across
the surface being abraded.
• Higher the speed  inc rate of abrasion.

6. Classification on The Basis of Use
1. Finishing Abrasives.
• Are hard, coarse abrasives.
• Used for initially to develop
contour and remove gross
irregularities.
• e.g. coarse stones.
2. Polishing Abrasives.
• Have finer particle size and
are less hard than finishing
ones.
• Used for smoothening
surfaces after finishing
abrasive.
• e.g. polishing cakes,
pumice.
3. Cleansing Abrasives.
• Are soft materials with
small particle size
• Used to remove deposits
that adhere to enamel or
restorative material.

7. Types of Abrasives
1) Emery.
2) Aluminium oxide.
3) Garnet.
4) Pumice.
5) Kieselgurh.
6) Tripoli.
7) Rouge.
8) Tin oxide.
9) Chalk.
10)Chromic oxide.
11)Sand.
12)Carbides.
13)Diamond.
14)Zirconium silicate.
15)Zinc oxide.(mixed with
alcohol to polish dental amalgam)

8. Types of Abrasives
1. EMERY
• Consists of natural oxide of
aluminium called corundum.
• Impurities present (iron oxide)
act as an abrasive too.
• Greater the alumina = finer
the grade of emery.
2. ALUMINIUM OXIDE
• Prepared from bauxite
(impure aluminium oxide)
• Have very fine grain size.

9. Types of Abrasives
3. GARNET
• Composed of minerals having
similar physical properties &
crystalline form.
• Silicates of aliminium, cobalt,
iron, magnesium & maganese
form the mineral.
• Garnet is coated on paper or
cloth with glue.
4. PUMICE
• Highly siliceous material of
volcanic origin.
• Depending on particle size can
be used as both abrasive &
polishing agent.
• Use ranges from smoothening
dentures to polishing teeth in
oral cavity.

10. Types of Abrasives
5. KIESELGURH
• Siliceous remains of minute
aquatic plant (diatoms)
• Coarser form is
diatomaceous earth.
• Excellent as mild abrasive &
polishing agent.
6. TRIPOLI
• Originates from certain porous
rocks first found in North
Africa near Tripoli.
• Substitute for kieselgurh.
• Mild abrasive & polishing
agent.

11. Types of Abrasives
7. ROUGE
• Used in cake form.
• Fine red powder composed of
iron oxide.
• Impregnated on paper or cloth
(crocus cloth)
• Excellent polishing agent for
gold & noble metal alloys.
• Dirty to handle.
8. TIN OXIDE
• Putty powder used as a
polishing agent for teeth &
metallic restorations in
mouth.
• Mixed with water, alcohol &
glycerin & used as a paste.

12. Types of Abrasives
9. CHALK
• Calcium carbonate prepared
by precipitation method.
• Various physical forms
available for various
techniques.
• Used in dentifrices as polishing
agent.
10. CHROMIC OXIDE
• Relatively hard abrasive.
• Used as a polishing agent
for stainless steel.

13. Types of Abrasives
11. SAND
• Sand & other forms of quartz
are used as abrasive agent.
• In powder form used in
sandblasting.
• Use as sand paper is a
common example.
12. CARBIDES
• Silicone carbide & boron
carbide are used as effective
abrasive agents.
• Both silicone & boron are
heated at a high temperature
for fusion with carbon.
• Most of the stone burs used
for cutting tooth structure are
made of silicon carbide.

14. Types of Abrasives
13. DIAMOND
• Hardest & most effective
abrasive material.
• Diamond burs & discs are
the most popular among
dental profession.
14. ZIRCONIUM SILICATE
• Occurring in nature as zircon.
• Used as a polishing agent in
grounded form.
• Used as a constituent in
prophylactic pastes.
• Also used as abrasive
impregnated polishing strips &
discs.

15. Polishing
Production of a smooth
mirror like surface
without much loss of
any external form.
Polishing agents remove
material from the
surface molecules by
molecules.
In the process scratches
and irregularities are
filled in by powder
particles.

16. Non-Abrasive Polishing
1. Composite Glazing:
• A layer of clear transparent
liquid (unfilled resin) is applied
over the restoration and cured.
2. Glazing ceramic:
• Finished restoration is placed
at high temp. surface layer
melts and produce a smooth
glass-like surface.

17. Non-Abrasive Polishing Contd..
3. Electrolytic polishing:
• Reverse of electroplating.
• Alloy to be polished is
made as anode of an
electrolytic cell.
• When current passed
surface layer of anode is
dissolved away  bright
surface.
Anode

18. Dr. RASHID HASSAN
BDS(de’ Mont) MSc (QMUL.UK)
Hod Science of Dental Materials

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