• Abrasive action • Types of abrasion • Principles of Cutting Grinding Finishing & Polishing • Desirable Characteristics Of An Abrasive • Factors affecting rate of abrasion • Abrasive instrument design • Classification of abrasive agents • Biological hazards of abrasive agents • Recent Advances • Conclusion

1. Dr aSHITHA DOMINIC
I year pg
prosthodontics and implantology

2. ▪• Abrasive action
▪• Types of abrasion
▪• Principles of Cutting Grinding Finishing & Polishing
▪• Desirable Characteristics Of An Abrasive
▪• Factors affecting rate of abrasion
▪• Abrasive instrument design
▪• Classification of abrasive agents
▪• Biological hazards of abrasive agents
▪• Recent Advances
▪• Conclusion
2

3. Craig has defined abrasion as:
A process of wear whereby a hard rough
surface (like a sand paper disk) or hard irregular shaped
practicles (like those in an abrasive slurry) plough
grooves in a softer material and cause materials from
these grooves to be removed from the surface.
3
.
Definition

4. Abrasive action
Harder material comes into frictional contact with the substrate
Contact generates tensile and shear stresses
Break atomic bonds
Substrate particles are removed
4

5. Types of Abrasion
▪ Two body abrasion ▪ Three body abrasion
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6. Abrasive particles are bonded to instrument
The hard surface abrade the soft surface
Eg - diamond bur
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Two-body
abrasion

7. Abrasive particles are free to translate and rotate
between 2 surfaces
Eg – dental prophylaxis paste
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Three body
abrasion

8. ▪ Erosion
▪ Wear caused by hard particles impacting a substrate
surface, carried by stream of liquid or stream of air.
▪ Eg. sand blasting
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9. ▪ CUTTING
▪ GRINDING
▪ FINISHING
▪ POLISHING
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10. CUTTING
• Use of any instrument in a bladelike fashion
• Regularly arranged blades that remove small shavings of
the substrate
• Unidirectional cutting pattern
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11. ▪ GRINDING
▪ • 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
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12. ▪ FINISHING
▪ The term denotes to cut or remove the excess
▪ It is done with coarser abrasives than polishing .
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13. POLISHING
• Most refined of the finishing processes which removes the fine
surface particles.
• Multidirectional in its course of action
• Acts on an extremely thin region of the substrate surface
• Final stage produces fine scratches - not visible unless greatly
magnified
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14. Factors affecting abrasion
• Hardness
• Shape
• Size
• Pressure
• Speed
• Lubricants
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15. HARDNESS :- hardness of an abrasive is directly
proportional to the rate of its abrasion i.e. harder the
abrasive than the substrate the more abrasion will be
produced.
PARTICLE SIZE :- the particle size of the material is
expressed in micrometers. By convention ,particles are
classified as
▪ Fine
▪ Medium
▪ Coarse
larger, coarse abrasive particles will abrade a surface more
readily than smaller particles, but they tend to leave more
coarser scratches in the substrate.
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16. ▪ SHAPE :- sharp irregular shaped particles abrade a surface
more rapidly than rounded particles having dull cutting
angles.
▪ .numerous sharp edges- enhance cutting efficiency
▪ SPEED & PRESSURE :- both are directly proportional to
the rate of abrasion.
▪ At higher speed= greater friction = higher temperature.
Similarly greater pressure =higher temperature & possibly
patient discomfort.
▪ .16

17. ▪ LUBRICATION :- reduces the heat buildup & washes the
debris.
▪ Too much lubrication can reduce the abrasion rate
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18. Desirable Characteristics Of An
Abrasive
▪ • It should be irregular in shape so that it presents a
sharp edge.
▪ • It should be harder than the surface it abrades.
▪ • Abrasive point should always fracture rather than dull
out so that always a sharp point or edge is available.
▪ • Abrasive should possess attrition resistance so that it
does not wear.
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19. Abrasive Instrument Design
• Abrasive Grits.
• Bonded Abrasives.
• Coated abrasive disks and strips
• Non bonded abrasives
• Abrasive motion
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20. Abrasive grits
• Derived from materials that have been crushed and passed
through a series of mesh screens
• Classified based on particle size are
▫ Coarse
▫ Medium coarse
▫ Medium
▫ Fine
▫ Superfine
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21. Bonded abrasives
▪ • Abrasive particles are incorporated through a binder to form
grinding tools like points, wheels, separating disks, etc.
▪ • Particles are bonded by four general methods:
• Sintering
• Vitreous bonding
• Resinoid bonding
• Rubber bonding
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22. Coated Abrasive Disks and Strips
• Supplied as disks and finishing strips.
• Fabricated by securing abrasive particles to a flexible
backing material with a adhesive material
• Available in different diameters with thin and very
thin backing thicknesses.
• Moisture – resistant backings are advantageous
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23. • Polishing pastes - final polishing.
• Applied to substrate with nonabrasive devices - synthetic
foam , rubber, etc.
• Dispersed in water soluble medium such as glycerin for
dental applications.
• Alumnium oxide and diamond
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24. Abrasive Motion
▪ Rotary - burs
▪ Planar - disks
▪ Reciprocal - handpieces which provide the benefit of
accessing interproximal & subgingival areas to remove
overhangs
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25. NATURAL ABRASIVES
▪ Arkansas stone Tripoli
▪ Chalk
▪ Corundum
▪ Diamond
▪ Emery
▪ Garnet
▪ Pumice
▪ Quartz
▪ Sand
▪ Zirconium silicate
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26. MANUFACTURED or SYNTHETIC
ABRASIVES
▪ Silicon carbide
▪ Aluminium oxide
▪ Synthetic diamond
▪ Rouge
▪ Tin oxide
26

27. Arkansas stone
• Semi translucent , light gray, siliceous
sedimentary rock.
• Contains microcrystalline quartz.
• Attached to metal shanks
• Fine grinding of tooth enamel and metal
alloys
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28. 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
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29. • Transparent, colorless mineral composed of carbon
• Superabrasive
• Bonded abrasive rotary instruments
• Used on tooth structure; ceramic and resin based
composite materials
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30. • Physical properties are inferior to those of alpha aluminum
oxide.
• Used for grinding metal alloys
• Used in an instrument – White stone
30

31. • Grayish- black corundum
• eg.Coated abrasive disks
•use : Finishing metal alloys or acrylic resin
materials
31

32. • Dark red, very hard .
• Comprise - silicates of Al, Co, Mg, Fe, Mn
• Garnet is available on coated disks & arbor
bands
• used :Grinding metal alloys or acrylic resin
materials.
32

33. • Highly siliceous material of volcanic origin
• Powder- by crushing pumice stone
• Abrasive action is not very high
• Polishing tooth enamel, gold foil, dental amalgam and
acrylic resins
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34. • Very hard, colorless, and transparent.
• Crystalline particles are pulverized to form sharp, angular
particles - coated abrasive discs.
• Grinding tooth enamel and finishing metal alloys
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35. • Predominantly composed of silica.
• Particles represent a mixture of color. Making it distinct in
appearance.
• grounded to angular shape.
• Applied under air pressure to remove refractory investment
materials
• Coated on to paper disks
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36. • Off -white mineral.
• Ground to various particle sizes - coated abrasive disks
and strips.
• Component of dental prophylaxis pastes
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37. SILICON CARBIDE
• Extremely hard abrasive and 1st synthetic abrasive
• Highly effective cutting of metal alloys, ceramics and
acrylic resin materials.
• Abrasive in coated disks and as vitreous - bonded and
rubber instruments
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38. ALUMINUM OXIDE
• White powder
• used as bonded abrasives, coated abrasives and air
propelled abrasives.
• Finishing metal alloys, resin based composites and ceramic
materials.
• Pink and ruby variations- adding chromium compounds
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39. ROUGE
• Consists of iron oxide, which is the fine red abrasive
component.
• Blended in to various soft binders in to a cake form.
• Used to polish high noble metal alloys
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40. 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.
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41. SYNTHETIC DIAMOND
• Controllable, consistent size and shape.
• Resin bonded diamonds have sharp edges
• Larger synthetic diamond particles – greenish
• Blocks with embedded diamond particles – truing other
bonded abrasives
• Used primarily on tooth structure, ceramics and resin
based composites
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42. DENTIFRICES
Available as toothpaste, gels and powders.
The abrasive concentrations in paste and gel
dentrifices are 50% to 75% lower than those
of powder dentrifices
Function :
Abrasive and detergent action
Polish teeth
Act as vehicles
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43. PROPHYLAXIS PASTE
▪
Removal of exogenous stains, pellicle, material alba,
and oral debris.
▪ contain moderately abrasive materials : pumice
▪ Silicon dioxide and zirconium silicate are used
▪ Applied to teeth through rubber cup on a slow speed
handpiece
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44. BIOLOGICAL HAZARDS
• Aerosols – silica based materials (smaller than 5µm)
• Silicosis or grinders disease
• Precautions -adequate water spray,
suction
eyeware,
facemasks
proper ventilation
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45. ADVANCED TECHNOLOGIES
Air abrasive Technology
• Alternative to rotary instrument cutting.
• High pressure stream of 2530µm
• ‘Air polishing’- controlled delivery of air, water and
Sodium bicarbonate slurry
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46. 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
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47. GRIPPED DIAMOND STRIPS
Diamond-coated stainless steel metal strips
Features: used for smoothing, contouring, finishing and
trimming proximal, incisal and interproximal areas
Two color-coded working areas with different grit sizes
handles help to pull through tight contact area
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48. CVD diamond-coated burs
Advantages such as-
▪ less noise
▪ less pain for the patient,
▪ precise cutting,
▪ conservative cavity preparation,
▪ longer lifetime,
▪ less injury to the dental structures,
▪ no cutting of soft tissues
▪ easier access of the carious lesion
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49. Finishing and Polishing system
▪ Designed to finish and polish all types of resin
restoratives by incorporating a superior abrasive into a
special resin.
▪ System uses a one-piece disc and mandrel - with no
metal . no possibility of discolouring the restoration
▪ It completes intermediate and final finishing without the
need to change discs.
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50. Perforated Diamond Strips
 Designed for complete control during interproximal
reduction, shaping, and contouring.
 The design assists in debris removal, provides improved
visibility, control, and flexibility;
 Made of stainless steel to resist breaking and stretching.
 They are color coded for grit identification: blue for
medium, red for fine and yellow for super-fine
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51. Single-gel diamond polishing system
▪ It can polish the surface of all restorative materials:
composite, glass ionomer, compomer, amalgam,
precious metal and enamel.
▪ Even porcelain achieves a lustrous surface in less time
due to the optimal concentration of micron-sized
diamond particles.
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52. CONCLUSION
A lot of materials are avilable commercially to perform
finishing and polishing .Discretion on the part of the
dentist is necessary to select the right material for the
technique.
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53. REFERENCES
• Anusavice, Phillips Science of Dental Materials, 11th edition,
Elsevier publications.
• Craig . Powers and Wataha, Dental Materials, Properties and
manipulation, 8th edition, Elsevier publications.
• Contemporary fixed prosthodontics. 2nd Edition, Stephen F.
Rosensteil.
• Sturdevant’sArt and Science of Operative Dentistry, 5th edition,
Elsevier publications.
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