3. Contents :-
Introduction
Definition
Purpose of finishing and polishing
Classification of finishing and polishing devices
Design of abrasive instrument
Types of the abrasives
Finishing and polishing of the cast metal framework
Fitting the framework
Biological hazards of finishing and polishing
Review of literature
Summary and conclusion
References
4. introduction
Finishing, polishing of dental restorations are
important aspects of clinical restorative procedures
that enhance both aesthetics and longetivity of
restored teeth.
Residual surface roughness, associated with improper
finishing and polishing of dental restorations ,can
result in number of clinical difficulties.
The problems include excessive plaque accumulation
,gingival irritation, increased surface staining, poor or
suboptimal aesthetics of the restored teeth.
5. Finishing and polishing refers to gross contouring of the
restoration to obtain the desired anatomy,
and the reduction and smoothing of the roughness and
scratches created by finishing instruments.
A number of methods and tools for finishing and
polishing restorations are available to clinicians
including: fluted carbide bur; diamond burs; stones;
coated abrasive discs and strips; polishing pastes; and
soft or hard rubber type cups, points, and wheels
impregnated with various abrasives grits.
6. Proper finishing of restorations is desirable not only for
esthetic considerations but also for oral health.
The primary goal of finishing is to obtain a restoration
which has good contour, occlusion, healthy embrasure
forms, and smoothness. Tight margins should blend
esthetically into the toothâs natural contours.
The polish should be smooth enough to be tolerated
well by gingival tissue.
It has been proven that rough surfaced restorations can
create clinical problems such as plaque retention,
gingival irritation, staining, higher wear rates, and
recurrent caries.
7. Definition :-
ď Finishing â Process of removing surface defects or scratches
created during the contouring process through the use of
cutting or grinding instruments or both.
ď Cutting â process of removing material from the substrate
by use of a bladed bur or a abrasive embedded in a binding
matrix on a bur or disk.
ď Grinding â Process of removing material from a substrate by
abrasion with relatively coarse particles.
ď Polishing â Process of providing luster or gloss on a material
surface.
8. Abrasion
âA 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
surfaceâ.
Abrasivity: property of one material to abrade another material
by means of frictional heat
Polishing agents: any material used to impart luster to a surface
9. Purpose of finishing and polishing
Provides 3 benefits of dental care-
Oral health
Oral function
Esthetics
10. Oral health
A well contoured and polished restorations
promotes oral health by resisting the
accumulation of food debris and pathogenic
bacteria.
This is accomplished through reduction in total
surface area and reduced roughness of the
restoration
Smoother surfaces have less retention areas and
are easier to maintain in a hygenic state.
11. ORAL FUNCTION
A highly polished restoration show a very less tarnish
and corrosion
Oral function is enhanced with a well polished
restoration because food glides more freely over occlusal
and embrasure surfaces during mastication, and
minimizes the wear rates.
Rough surfaces will develop high contact stress that can
cause the loss of functional and stabilizing contacts
between teeth.
12. Finishing and polishing improves the
strength of the restoration especially in
the areas that are under tension.
13. AESTHETICS
Finishing and polishing gives lusture to visible surface
of a restoration thus increases the optical property of
materials.
A high mirror like polish is preferred in highly visible
areas such as the labial surfaces of the maxillary
anterior teeth.
These surfaces are not subject to high contact
stresses and they are easily accessible for cleaning.
Important anatomic features and textures may be
added to these area without affecting oral health or
function
15. According to Hardness
a) Hard abrasive - Diamond, Silicon carbide.
b) Medium abrasive - Pumice, Silicates,
Zirconates.
c) Soft (Polishing) abrasive - calcites
16. According to use
a) Finishing abrasive.
b) Polishing abrasive.
c) Cleansing abrasive.
17. Design of abrasive instrument
Abrasive grits â Abrasive grits are derived from materials that
have been crushed and passed through a series of mesh
screens to obtain different particle size ranges.
Dental abrasive grits are classified as â
Coarse
medium coarse
medium
fine
super fine
19. Bonded abrasives
These consists of abrasive particles incorporated through a
binder to form grinding tools such as points,wheels,separating
discs and abrasive strips.
The abrasives are bonded by four methods:
1. Sintering.
2. Vitreous bonding.
3. Resinous bonding.
4. Rubber bonding
20. Sintered abrasives are strongest of abrasives where the
particles are fused together
Vitreous abrasives mixed with a glass or ceramic matrix
material, cold pressed or hot pressed in instrument
shape and fired to fuse the binder
Resin bonded cold pressed or hot pressed and then
heated to cure the resin
Rubber bonded are cured same as the resin bonded
21. Ideal binder holds the abrasive particles in the tool
sufficiently long enough to cut, grind, or polish the
substrate
Bonded abrasives should be trued and dressed before its
use.
Truing is a procedure through which abrasive instrument
is run against harder abrasive block until it runs out.
it indicates the efficiency of instruments, before clinical
use.
24. Abrasive strips
Bonded with either plastic or metal backing.
used to smooth and polish the proximal surfaces of all
direct and indirect bonded restorations
Metal strips are usually limited when tight inter proximal
contacts are seen especially in ceramic restorations
Plastic strips primarily used for composites,compomers,
hybridonomers and resin cements
25. Coated abrasives
Coated abrasives are fabricated by securing abrasive particles to
a flexible backing materials with a adhesive material.
Non bonded abrasives
They are applied with synthetic foam,rubber felt or chamois cloth.
26. LOOSE ABARSIVES
Loose abrasives are polishing pastes contain a fine particle size
distribution of either aluminum oxide or diamond particles
dispersed in water soluble vehicle, such as glycerin,
Aluminum oxide particles pastes are designed for final polishing
of composite resin materials
Particles size ranging from 0.3um to 1um
Diamond polishing pastes contain loose abrasive diamond
particles in size range less than 10um.
Effective particles size distributions of diamonds polishing pastes
size range0.3um to and 1um.
27. Indicated for final polishing of adjusted porcelain and
ceramic materials.
Binders for diamond abrasives are manufactured
specially to resist abrasive particles loss
diamond is his hardest particle and bonded to metal
wheels and been blanks with special heat resistant resins
such as polyamides.
Super coarse and fine grades are then plated with nickel
28. Nickel plating provides improved properties and acts
as a heat absorber.
Titanium coatings are given to extend the longitivity.
Finishing diamonds for composites contain particles
40um or less in diameter.
Diamond burs should be used with copious amounts
of water spray and rotational speed less than 50.000
rpm.
31. 1. Arkansas Stone :
Semi-translucent , light grey , siliceous sedimentary rock
emended in Arkansas
Contains mico-crystalline quartz .
Small pieces are attached to metal shanks and trued to various
shapes for fine grinding of tooth enamel and metal alloys.
32. 2. Chalk :
mineral form of calcite
contains calcium carbonate
used as a mild abrasive paste to polish enamel, gold fillings
3.Corundum :
Largely replaced by alpha aluminium oxide due to its superior
physical properties .
Available as bonded abrasive and is used primarily to grind
metals.
33. 4.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 â bonded abrasive , diamond abrasive pastes ,
abrasive strips .
34. 5. 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.
6. Garnet :
Includes several minerals , which posses similar physical properties
and crystalline form like silicates of Al,Co,Mg, Mn. Usually coated
on paper or cloth with a binder. Cuts both metal and porcelain.
35. 7. 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.
8. Quartz :
The particles are pulverized to form sharp angular particles , which
are useful in making coated discs . Used to finish metal alloys.
36. 9. Sand :
-Itâs a mixture of small mineral particles predominantly
composed of silica.
-Sand blasting
-Coated abrasives
37. 10. Tripoli :
Itâs a siliceous rock
Mild abrasive and polishing agent
Used for polishing metal alloys.
11. 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 .
38. 13.Kieselguhr :
It is composed of siliceous remains of minute aquatic plants know
as diatoms .
It is an excellent mild abrasive and polishing agent .
12. Cuttle :
A fine , relatively soft polishing agent made from calcified internal
shell of cuttle fish .
It is used on paper discs for polishing of metal margins .
39. Manufactured abrasives
Silicon carbide :
First of the synthetic abrasives to be developed .
It is the basic material of carborundum
Supplied as an abrasive in coated discs, vitreous bonded and
rubber bonded instrument.
40. Rouge:
It is a fine red powder composed of iron oxide.
Its blended in cake form.
Excellent polishing agent for gold and noble metal alloys.
Aluminium oxide:
Its widely used in dentistry to make bonded abrasives,coated
abrasives and air propelled grit abrasives.
Sintered aluminium oxide is used to make white stones which are
used for finishing metal alloys.
41. Material f/ p Chem.
Comp
Forms available uses
Pumice Polishing Silica Grit form, Rubber
bonded abrasive
Acrylic, tooth
enamel, gold
foil, amalgam
Quartz Finishing Silica Coated Abrasive
disks
Metal alloys
Sand Finishing Silica Sand paper &
powder form for
sand blasting
Metal alloys,
Acrylic resin
Tripoli Polishing Silica Bar form Metal alloys
Zirconium
Silicate
Polishing Silica Coated abrasive
disks, strips
Metal margins,
tooth enamel
Cuttle Polishing Silica (white
Calcereous
powder)
Coated abrasive Metal margins,
Amalgam
restorations
Kieslghur Polishing Silica Coated abrasive Amalgam
restorations
Tin Oxide Polishing Tin Oxide Paste Form High noble
metal alloys
42. Material f/ p Chem. Comp Forms available uses
Arkansas stone Finishing Microcrystall
ine quartz
Attached to metal
shanks
Fine grinding of
tooth enamel
Chalk Polishing Calcium
carbonate
Paste form tooth enamel,
gold foil,
amalgam.
Corundum Grinding. Alpha
aluminium
oxide
bonded abrasive Grinding metal
alloys
Diamond Finishing and
polishing
Mineral of
carbon
Bonded abrasive,
rotary instruments
, abrasive strips
and polishing
pastes
Finishing and
polishing of
porcelain and
ceramics
Emery Finishing Grayish
black
corundum
Coated abrasive
disks
Finishing metal
alloys and acrylic
resin
Silicon Carbide Cutting Silica Coated discs Metal
Aluminium Oxide Finishing &
polishing
Al203 Bonded abrasive Composites &
Porcelain
Rouge Polishing Iron oxide Cake Form High noble alloys
44. SHAPE AND HARDNESS OF A PARTICLE
SIZE OF PARTICLE
SUBSTRATE PROPERTY.
SPEED
PRESSURE
HEAT PRODUCTION
Factors affecting the efficiency of abrasives
45. 1. SHAPE AND HARDNESS OF A PARTICLE:
Abrasive must be harder than the material which it abrades.
Abrasive must be strong and should show no permanent
deformation under load.
In other words the elastic limit should be equal to its maximum
strength.
Hardness is a surface measurement of the resistance of one
material to plastic deformation by another material.
Shape also plays an important role. Sharp edges will abrasive more
than the dull particle and particle with acute angle will cut more
than a particle with obtuse angle.
46. 2. SIZE OF PARTICLE:
Large abrasive particles present inside the cutting edge and will cut
large and deep grooves.
Fine abrasive will remove small shavings.
Therefore coarse abrasive instruments followed by finer one before
the surface is polished.
Taking a large and deep cut, the coarse abrasive is subjected to
large force resisting its progress across material.
Therefore such an abrasive is moved slowly over a surface,
frequently fracture of grain of abrasive would be expected in this
case if it is moved fastly.
48. SPEED
Slower the speed more deep are the scratches and more
force is required to dislodge the abrasive from the
binder.
Faster the speed, the action become vice-versa.
But since more particles will be followed in rapid
succession, the total amount of material removed will
remain approximately same
Therefore for the given abrasive particle size the high
rotation speed does not alter the amount of material
removed, but reduces the amount of wear of abrasive.
49. Finishing and polishing of cast metal framework
It should be completed in a systematic sequence.
Principles in finishing the casting â
⢠High speed
⢠Excessive pressure should be avoided
⢠Definite sequence of finishing
⢠Clean polishing wheel should be used
50. ďś Quenching
ďś Sandblasting
- Its used to clean the alloy surface
- To achieve both microretentive topography and increased surface
area
67. Biological hazards -
Dispersion of solid particles are generated and
released into the breathing space of laboratories and
dental clinics whenever finishing operations are
performed.
These airborne particles may contain tooth structure,
dental materials, and micro organisms. Such aerosols
have been identified as potential sources of infectious
and chronic diseases of the eyes and lungs.
Silicosis (Grinderâs disease) is a major aerosol hazard
in dentistry because
68. number silica based is used in the processing and
finishing of dental restorations. About 75% of
airborne particles are potentially contaminated with
the infectious micro organisms.
Aerosols can remain airborne for more than 24 hr
before settling and are therefore capable of cross
contaminating other areas of the treatment facility.
69. Aerosols produced during finishing procedures may
be controlled in three ways-
1.They may be controlled at the source through the use of
adequate infection control procedures, water spray and high
volume suction.
2.Personal projection such as safety glasses and disposable face
masks can protect the eyes and respiratory tract from aerosols.
3.The entire family should have an adequate ventilation system
that efficiently removes any residual particulates from the air.
70. Review of literature
A.Kevser Aydin (1991) evaluated the finishing and polishing
techniques on surface roughness of chromium-cobalt castings
and concluded that the best surface finish was obtained when
sand blasting,
hard stone,
medium abrasive disk,
sand blasting,
electro polishing,
hard rubber point,
hard felt disk,with pumice slurry,
and soft brush with polishing paste were used progressively.
71. Dr. Ponnanna A.A. (1999) under the able guidance of Dr. N.P.Patil
evaluated 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
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.
72. 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.
73. Dr Srinivas reddy (2002) under the able guidance of Dr. N.P.Patil
conducted a study to evaluate the effects of different finishing and
polishing agents on the surface roughness of the cast pure titanium.
A total of 60 specimens were cast in commercially pure titanium.They
were divided into three groups of 20 specimens each.
74. Group A was finished with tungsten carbide and polished with
black, brown and green rubber points.
Group Bwith gold finishing and polishing kit.
Group C with specific titanium kit.
Surface roughness was measured with a pertherometer
instrument.
It was concluded that surface roughness was less on a cast
titanium specimens which were finished and polished from
cutters designed specifically for titanium
75. Conclusion
A detailed and proper knowledge of finishing
and polishing agents is necessary for a dental
practitioner and the dental technician for the
particular prosthesis. So it should not affect
the proper funtioning of the patients oral
function,oral hygiene and it should be
esthetcally acceptable to the patient.
76. References -
Anusavice K.J. âPhillips Science Of Dental Materialsâ 11th edition,
Philadelphia,W.B. Saunders
Craig R.G. âDental Materials, properties and manipulationâ. 8th edition
Jeffries S.R. âThe art and science of abrasive and finishing and
polisjhing in restorative dentistryâ. DCNA,1998;42(4): 613-628.
Kern M.,Thompson V.P. âEffect of sandblasting and silicoating
procedures on pure titaniumâ. J.Dent.,1994;22:300-305
