Rotary cutting instruments / dental courses

Seminar onSeminar on
ROTARY CUTTINGROTARY CUTTING
INSTRUMENTSINSTRUMENTS
INDIAN DENTAL ACADEMYINDIAN DENTAL ACADEMY
Leader in continuing Dental EducationLeader in continuing Dental Education
www.indiandentalacademy.com

INDEXINDEX
1. Definitions1. Definitions
2. Introduction2. Introduction
3. Dental Hand pieces3. Dental Hand pieces
4. Improved Cutting Instruments4. Improved Cutting Instruments
5. An era of increased speeds and various associated techniques5. An era of increased speeds and various associated techniques
6. Care and maintenance of Rotary equipment6. Care and maintenance of Rotary equipment
7. Water air cooling7. Water air cooling
8. Dental cutting burs8. Dental cutting burs
(a) Composition and manufacture(a) Composition and manufacture
(b) General design of dental burs(b) General design of dental burs
© Parts of a bur© Parts of a bur
(d) Classification(d) Classification
9. Diamond Abrasive Instruments9. Diamond Abrasive Instruments
(a) Color coding(a) Color coding
(b) Manufacturing(b) Manufacturing
© Classification© Classification
(d) Diamond/bur dual instrumentation(d) Diamond/bur dual instrumentation
10. Effects of high speed cutting10. Effects of high speed cutting
11. Advantages of high speed cutting11. Advantages of high speed cutting
12. Disadvantages of high speed cutting12. Disadvantages of high speed cutting
13. Abrasion and Polishing Agents13. Abrasion and Polishing Agents
14. Review of literature14. Review of literature
15. Summary15. Summary
16. References16. References

The term “Rotary” is applied to tooth cuttingThe term “Rotary” is applied to tooth cutting
instrumentsinstruments
That turn on axis to perform work, these are theThat turn on axis to perform work, these are the
units actually responsible for the removal ofunits actually responsible for the removal of
tooth structure, and may be one of two types:tooth structure, and may be one of two types:
Burs; which are cutting tools, and, Stones, whichBurs; which are cutting tools, and, Stones, which
are abrading tools.are abrading tools.
SPEEDSPEED: Speed is the rate of change of position: Speed is the rate of change of position
with time (MOSBY’s Dictionary)with time (MOSBY’s Dictionary)
SpeedSpeed is the magnitude of velocity without regardis the magnitude of velocity without regard
to direction. (Stedman’s Dictionary)to direction. (Stedman’s Dictionary)www.indiandentalacademy.com

Classification of SpeedClassification of Speed
According to SturdevantAccording to Sturdevant
Low Speed-Below 12,000 rpm.Low Speed-Below 12,000 rpm.
Medium or Intermediate speed- 12,000 to 2lakh rpm.Medium or Intermediate speed- 12,000 to 2lakh rpm.
High or ultra high speed- Above 2lakh rpm.High or ultra high speed- Above 2lakh rpm.
According to CharbenauAccording to Charbenau
Conventional or low speed below 10,000 rpm.Conventional or low speed below 10,000 rpm.
1.1. Increased or high speed- 10,000 to 1, 50,000 rpm.Increased or high speed- 10,000 to 1, 50,000 rpm.
2.2. Ultra speed- Above 1, 50,000 rpm.Ultra speed- Above 1, 50,000 rpm.
According to MARZOUKAccording to MARZOUK
Ultra low speed- 300 to 3000 rpm.Ultra low speed- 300 to 3000 rpm.
Low speed- 3,000 to 6,000 rpm.Low speed- 3,000 to 6,000 rpm.
Medium high speed- 20,000 to 45,000 rpm.Medium high speed- 20,000 to 45,000 rpm.
High speed- 45,000 to 1, 00,000 rpm.High speed- 45,000 to 1, 00,000 rpm.
Ultra high speed- Above 1, 00,000 rpm.Ultra high speed- Above 1, 00,000 rpm.
According to Clearence L. Sock well (DCNA-1971)According to Clearence L. Sock well (DCNA-1971)
Low or conventional speed- Below 6,000 rpm.Low or conventional speed- Below 6,000 rpm.
High or intermediate speed- 6,000 to 1, 00,000 rpm.High or intermediate speed- 6,000 to 1, 00,000 rpm.www.indiandentalacademy.com

Dental BurDental Bur- The term bur is applied to all rotary cutting- The term bur is applied to all rotary cutting
instruments that have bladed cutting heads. This includesinstruments that have bladed cutting heads. This includes
instruments intended for such purposes or finishing metalinstruments intended for such purposes or finishing metal
restorations and surgical removal of bone as well as thoserestorations and surgical removal of bone as well as those
primarily intended for tooth preparation.primarily intended for tooth preparation.
IntroductionIntroduction
Before considering the tooth preparation, Prosthodontist mustBefore considering the tooth preparation, Prosthodontist must
be aware of the instruments at his disposal so that the mostbe aware of the instruments at his disposal so that the most
suitable one can be used.suitable one can be used.
Teeth are vital organs; therefore they must be treated withTeeth are vital organs; therefore they must be treated with
consideration. The objectives of the treatment given to theconsideration. The objectives of the treatment given to the
patient are to provide oral function, esthetics, health bypatient are to provide oral function, esthetics, health by
restoring teeth and the adjacent structures. Frequently, therestoring teeth and the adjacent structures. Frequently, the
efforts of restorations may themselves transform aefforts of restorations may themselves transform a
comfortable tooth into one that is sensitive or pathologiccomfortable tooth into one that is sensitive or pathologicwww.indiandentalacademy.com

Dental Hand piecesDental Hand pieces
By the middle of 17th century hand instrumentsBy the middle of 17th century hand instruments
were supplemented with steel burs of variouswere supplemented with steel burs of various
shapes and sizes. These were rotated withshapes and sizes. These were rotated with
thumb and finger because many areas of thethumb and finger because many areas of the
teeth could not be reached with this design; theteeth could not be reached with this design; the
angle hand piece and short shanked bur wereangle hand piece and short shanked bur were
developed. From this beginning, two basicdeveloped. From this beginning, two basic
designs of hand pieces and cutting instruments,designs of hand pieces and cutting instruments,
straight and angle have become standardstraight and angle have become standard
equipment in the dental office.equipment in the dental office.

FOOT ENGINEFOOT ENGINE
The old spinning wheel and sewing machine probably inspired theThe old spinning wheel and sewing machine probably inspired the
development of a dental foot engine as a source of power arounddevelopment of a dental foot engine as a source of power around
1871. Rotation of a cutting instrument was made possible by a long1871. Rotation of a cutting instrument was made possible by a long
belt running over a series of pulleys to the back of a straight handbelt running over a series of pulleys to the back of a straight hand
piece. When the angle hand piece was needed, it could be attached topiece. When the angle hand piece was needed, it could be attached to
the shaft of the straight hand piece.the shaft of the straight hand piece.
ELECTRIC ENGINEELECTRIC ENGINE
One of the most significant advances in the early history of handOne of the most significant advances in the early history of hand
piece adoption was the adoption of the electric motor as a powerpiece adoption was the adoption of the electric motor as a power
source in 1874.It was incorporated into a dental unit in 1914. Handsource in 1874.It was incorporated into a dental unit in 1914. Hand
piece equipment and operating speeds and maximum of 5000piece equipment and operating speeds and maximum of 5000
revolutions per minute remained virtually unchanged until 1946.revolutions per minute remained virtually unchanged until 1946.
Based on use, there are 3 hand piece designs-Based on use, there are 3 hand piece designs-
 StraightStraight
 AngleAngle
 ProphylaxisProphylaxis
These standardized shapes have continued over the years.These standardized shapes have continued over the years.www.indiandentalacademy.com

Rotary power from an electric engine isRotary power from an electric engine is
transferred to the straight hand piece by a belttransferred to the straight hand piece by a belt
that runs over a series of pulleys and a threethat runs over a series of pulleys and a three
piece extension cord arm. A variable rheostatpiece extension cord arm. A variable rheostat
sits on the floor and is operated by the foot tosits on the floor and is operated by the foot to
control the speed of the hand piece. Rotarycontrol the speed of the hand piece. Rotary
cutting instruments are inserted into a chuckingcutting instruments are inserted into a chucking
mechanism at the front of the hand piece. Themechanism at the front of the hand piece. The
electric engine is seldom used as a source ofelectric engine is seldom used as a source of
power in a modern dental operatory but is oftenpower in a modern dental operatory but is often
used in dental laboratories where low speed andused in dental laboratories where low speed and
high torque are desirable.high torque are desirable.www.indiandentalacademy.com

IMPROVED CUTTING INSTRUMENTSIMPROVED CUTTING INSTRUMENTS
Progress in dental cutting procedures was delayed by a lack ofProgress in dental cutting procedures was delayed by a lack of
instruments that could effectively remove hard tooth structures. Theinstruments that could effectively remove hard tooth structures. The
steel burs that were used at that time could not cut enamel effectivelysteel burs that were used at that time could not cut enamel effectively
even with the application of great force. Silicon carbide points,even with the application of great force. Silicon carbide points,
sometimes called carborundum stones, were not hard enough and lostsometimes called carborundum stones, were not hard enough and lost
their shape rapidly. Diamond cutting instruments were developed intheir shape rapidly. Diamond cutting instruments were developed in
Germany around 1935, but with the outbreak of World War II andGermany around 1935, but with the outbreak of World War II and
the accompanying scarcity of labor and materials, very few of thesethe accompanying scarcity of labor and materials, very few of these
instruments were produced for the duration of the war. It was duringinstruments were produced for the duration of the war. It was during
this period, when large numbers of men had to be treated in a limitedthis period, when large numbers of men had to be treated in a limited
amount of time that the need of better and more effective cuttingamount of time that the need of better and more effective cutting
instruments and procedures was dramatized.instruments and procedures was dramatized.
In a 10 year period, which started in the latter part of 1946, cuttingIn a 10 year period, which started in the latter part of 1946, cutting
techniques were revolutionized. Diamond instruments were producedtechniques were revolutionized. Diamond instruments were produced
commercially and were joined a year later by tungsten carbide burs.commercially and were joined a year later by tungsten carbide burs.
For the first time in dental history, instruments became available thatFor the first time in dental history, instruments became available that
could effectively remove hard tooth structure.could effectively remove hard tooth structure.

INCREASED SPEEDSINCREASED SPEEDS
It was immediately evident that diamond and carbide instrumentsIt was immediately evident that diamond and carbide instruments
performed best at the highest speeds available and that increasedperformed best at the highest speeds available and that increased
speeds were available for more effective cutting.speeds were available for more effective cutting.
Obtaining speeds of 10,000 to 15,000 rpm was a relatively simpleObtaining speeds of 10,000 to 15,000 rpm was a relatively simple
matter. The small pulley on the motor drive shaft was replacedmatter. The small pulley on the motor drive shaft was replaced
with a larger one, while the pulley at the hand piece was reduced inwith a larger one, while the pulley at the hand piece was reduced in
size. Motor resistors were disconnected so that armature couldsize. Motor resistors were disconnected so that armature could
receive the full line current and revolve at maximum speeds. Inreceive the full line current and revolve at maximum speeds. In
1949, it was reported that speeds of 60,000 rpm and above were1949, it was reported that speeds of 60,000 rpm and above were
more effective for cutting tooth structure and were also above themore effective for cutting tooth structure and were also above the
human threshold of vibration perception.human threshold of vibration perception.
Equipment manufactures continued to make improvements inEquipment manufactures continued to make improvements in
conventional rotary hand pieces, but heat, vibration and wear wereconventional rotary hand pieces, but heat, vibration and wear were
major problems, especially in the gear mechanism of angle handmajor problems, especially in the gear mechanism of angle hand
pieces. In the mean time two non-rotary industrial cuttingpieces. In the mean time two non-rotary industrial cutting
methods, air abrasive technique and ultrasonics were applied inmethods, air abrasive technique and ultrasonics were applied in
dentistry.dentistry. www.indiandentalacademy.com

AIRBRASIVE TECHNIQUEAIRBRASIVE TECHNIQUE
The air abrasive technique was made available to theThe air abrasive technique was made available to the
dental profession in 1951. The principal involves thedental profession in 1951. The principal involves the
use of powered abrasive particles (aluminum oxide)use of powered abrasive particles (aluminum oxide)
and kinetic energy (mass in motion). Hard toothand kinetic energy (mass in motion). Hard tooth
structures can be reduced without perceptiblestructures can be reduced without perceptible
vibration, pressure or heat by a stream of abrasivevibration, pressure or heat by a stream of abrasive
particles traveling at a high velocity. This techniqueparticles traveling at a high velocity. This technique
received widespread interest.received widespread interest.
AdvantagesAdvantages
 Patient acceptance was excellent.Patient acceptance was excellent.
 No significant pulp reaction was reported.No significant pulp reaction was reported.

The air abrasive technique never became popularThe air abrasive technique never became popular
with the dental profession.with the dental profession.
DisadvantagesDisadvantages
 Use was limited to areas of good vision because there wasUse was limited to areas of good vision because there was
no sense of touch b/n the hand-piece and the tooth to actno sense of touch b/n the hand-piece and the tooth to act
as a guide while cutting.as a guide while cutting.
 Precise angles and margins were difficult to obtain and thePrecise angles and margins were difficult to obtain and the
operator had to return to hand or rotary instruments foroperator had to return to hand or rotary instruments for
finishing procedures.finishing procedures.
 Surface of an ordinary mirror was rendered useless in aSurface of an ordinary mirror was rendered useless in a
short period by rebounding abrasive particles.short period by rebounding abrasive particles.
 Spent dust was not effectively removed by a large noisySpent dust was not effectively removed by a large noisy
suction apparatus.suction apparatus.
 Possibility of lung damage by inhalation of the abrasivePossibility of lung damage by inhalation of the abrasive
particles was investigated but not found to be a major healthparticles was investigated but not found to be a major health
hazard.hazard. www.indiandentalacademy.com

UltrasonicsUltrasonics
Another non-rotary (instrument) industrial cutting method knownAnother non-rotary (instrument) industrial cutting method known
as ultrasonics was adapted for dental use around 1952. Hard toothas ultrasonics was adapted for dental use around 1952. Hard tooth
structure can be removed by vibrating a slurry of abrasive particlesstructure can be removed by vibrating a slurry of abrasive particles
(aluminum oxide) against the surface to be reduced with various(aluminum oxide) against the surface to be reduced with various
sizes and shapes of preformed instrument tips. Principle involvessizes and shapes of preformed instrument tips. Principle involves
the conversion of alternating current into high frequencythe conversion of alternating current into high frequency
mechanical vibrations in a phenomenon of magnetostriction. Themechanical vibrations in a phenomenon of magnetostriction. The
movements of the working tip, back and forth approximately 29,movements of the working tip, back and forth approximately 29,
000 times per second with a thrust of 0.0016” can not be detected000 times per second with a thrust of 0.0016” can not be detected
by the operator or the patient.by the operator or the patient.
1.1. Precise smooth cuts of predetermined shapes and sizes can bePrecise smooth cuts of predetermined shapes and sizes can be
made without the annoyance factormade without the annoyance factor
of heat, vibration, noise or pressure.of heat, vibration, noise or pressure.
2.2. Patient acceptance was excellent.Patient acceptance was excellent.
3.3. Tactile control of the instrument is somewhat improved over theTactile control of the instrument is somewhat improved over thewww.indiandentalacademy.com

 Use of preshaped working point is limiting becauseUse of preshaped working point is limiting because
anatomy and carious areas ofanatomy and carious areas of
 individual teeth vary greatly.individual teeth vary greatly.
 Interchanging the points was a relatively timeInterchanging the points was a relatively time
consuming process.consuming process.
 Cutting rate was slow especially in a lateral direction.Cutting rate was slow especially in a lateral direction.
 Visibility was obscured because of the accumulationVisibility was obscured because of the accumulation
of slurry.of slurry.
 Caries and resilient filing materials such as goldCaries and resilient filing materials such as gold
could not be removed effectively.could not be removed effectively.
 Maintenance problems resulted from complicatedMaintenance problems resulted from complicated
mechanism of operation.mechanism of operation.

BELT DRIVEN HANDPIECESBELT DRIVEN HANDPIECES
A belt driven angle hand piece called the page chayresA belt driven angle hand piece called the page chayres
became available in 1955. It was the first angle hand piece tobecame available in 1955. It was the first angle hand piece to
operate successfully at speeds of 1, 00, 000 rpm and wasoperate successfully at speeds of 1, 00, 000 rpm and was
attached to a conventional dental unit with an electric motorattached to a conventional dental unit with an electric motor
as a source of power. It was a very popular angle hand pieceas a source of power. It was a very popular angle hand piece
and several versions of this design were marketedand several versions of this design were marketed
commercially.commercially.
 Free of maintenance problems.Free of maintenance problems.
 Many moving parts.Many moving parts.
 Objectionable high pitched noise during operation.Objectionable high pitched noise during operation.

WATER TURBINE HANDPIECESWATER TURBINE HANDPIECES
A major break through in the development of rotary equipmentA major break through in the development of rotary equipment
for increased speeds came with the elimination of the gear andfor increased speeds came with the elimination of the gear and
the belt driven sections of the angle hand piece. In 1933 athe belt driven sections of the angle hand piece. In 1933 a
hydraulic driven turbine angle hand piece was reported tohydraulic driven turbine angle hand piece was reported to
operate satisfactorily at 60, 000 rpm and was marketed 2 yearsoperate satisfactorily at 60, 000 rpm and was marketed 2 years
later. The Turbo-Jet was designed as a compact mobile unit thatlater. The Turbo-Jet was designed as a compact mobile unit that
required no outside plumbing or air connections. Only a sourcerequired no outside plumbing or air connections. Only a source
of electricity was needed to operate the unit.of electricity was needed to operate the unit.
Improved models had both straight and angle hand piecesImproved models had both straight and angle hand pieces
that could operate at speeds up to 1, 00,000 rpm.that could operate at speeds up to 1, 00,000 rpm.
ADVANTAGEADVANTAGE
1.1. Rotary instruments had a threshold shank to ensureRotary instruments had a threshold shank to ensure
concentricity when attached to shaft of the turbine.concentricity when attached to shaft of the turbine.
DISADVANTAGEDISADVANTAGE
1.1. Changing the instruments was time consuming and carbide bursChanging the instruments was time consuming and carbide burs
did not perform well with water turbine hand piece.did not perform well with water turbine hand piece.

AIR TURBINE HAND PIECESAIR TURBINE HAND PIECES
In the later part of 1956 the first clinically successful air driven turbineIn the later part of 1956 the first clinically successful air driven turbine
hand pieces became available with free running speeds of approximatelyhand pieces became available with free running speeds of approximately
3,00,000 rpm.3,00,000 rpm.
Early models were attached to a conventional dental unit and consistedEarly models were attached to a conventional dental unit and consisted
of a hand piece, control box, foot control, various connector hoses and aof a hand piece, control box, foot control, various connector hoses and a
source of compressed air. When the foot control was activated,source of compressed air. When the foot control was activated,
compressed air flowed to the control box and was carried by a flexiblecompressed air flowed to the control box and was carried by a flexible
hose to the back of the hand piece. From there the air was directed tohose to the back of the hand piece. From there the air was directed to
the head of the hand piece through a metal tube and was blown againstthe head of the hand piece through a metal tube and was blown against
the blades of a small turbine to produce rotation. Some of the spent airthe blades of a small turbine to produce rotation. Some of the spent air
was expelled at the head of the hand piece, while the greater part waswas expelled at the head of the hand piece, while the greater part was
exhausted at the back of the hand piece or returned to the control box.exhausted at the back of the hand piece or returned to the control box.
Cutting instruments were inserted into the shaft of the turbine and heldCutting instruments were inserted into the shaft of the turbine and held
by friction grip.by friction grip.
Although most air turbine angle hand pieces have free running speeds ofAlthough most air turbine angle hand pieces have free running speeds of
approximately 3, 00, 000 rpm, it should be noted that this speed drops toapproximately 3, 00, 000 rpm, it should be noted that this speed drops to
approximately 1, 60, 000 rpm with a lateral work load of two ounces.approximately 1, 60, 000 rpm with a lateral work load of two ounces.

The reason for this is that air turbines have low torque and will stall atThe reason for this is that air turbines have low torque and will stall at
lateral work loads of approximately 4 to 6 ounces. This is an excellentlateral work loads of approximately 4 to 6 ounces. This is an excellent
safety feature, since excessive pressure can not be applied easily to thesafety feature, since excessive pressure can not be applied easily to the
cutting instrument.cutting instrument.
The application of the turbine principle to the straight hand pieceThe application of the turbine principle to the straight hand piece
eliminated the necessity of having an electric engine as part of a standardeliminated the necessity of having an electric engine as part of a standard
dental unit. This greatly simplified the design and construction ofdental unit. This greatly simplified the design and construction of
present day dental units. The design of the straight hand piece turbinepresent day dental units. The design of the straight hand piece turbine
provided the desirable high torque for low speed operation.provided the desirable high torque for low speed operation.
Air bearings have been used instead of ball bearings to support theAir bearings have been used instead of ball bearings to support the
turbine shaft in some air turbine angle hand pieces. By having theturbine shaft in some air turbine angle hand pieces. By having the
turbine suspended in air and rotated by air, practically all friction isturbine suspended in air and rotated by air, practically all friction is
eliminated and speeds may be increased to over 8, 00, 000rpm. It is noteliminated and speeds may be increased to over 8, 00, 000rpm. It is not
worthy that hand pieces using this design operated only at full speed andworthy that hand pieces using this design operated only at full speed and
at this speed the dentist was handicapped by virtually no sense of touch.at this speed the dentist was handicapped by virtually no sense of touch.
Thus desirable control was reduced, and over cutting often resulted. TheThus desirable control was reduced, and over cutting often resulted. The
hand piece was very quiet in operation. High costs, maintenancehand piece was very quiet in operation. High costs, maintenance
problems and the lack of variable speed kept this design from becomingproblems and the lack of variable speed kept this design from becoming
widely used.widely used.
Air driven hand pieces have been and continue to be the most popularAir driven hand pieces have been and continue to be the most popular
type of hand piece equipment because of the over all simplicity oftype of hand piece equipment because of the over all simplicity of
design, ease of control, versatility and patient acceptance.design, ease of control, versatility and patient acceptance.www.indiandentalacademy.com

CARE AND MAINTENANCE OFCARE AND MAINTENANCE OF
ROTARY EQUIPMENTROTARY EQUIPMENT
Rotary cutting or polishing instruments should neverRotary cutting or polishing instruments should never
be left in the hand piece between patients or overbe left in the hand piece between patients or over
night. Some of these instruments have steel shanksnight. Some of these instruments have steel shanks
that may corrode in the metal chucking system of thethat may corrode in the metal chucking system of the
hand piece. When cutting instruments become worn,hand piece. When cutting instruments become worn,
dull, bent or broken, they should be discarded. Suchdull, bent or broken, they should be discarded. Such
instruments do not operate efficiently and cause addedinstruments do not operate efficiently and cause added
trauma to the tissue.trauma to the tissue.
Dental hand pieces are expensive and must receiveDental hand pieces are expensive and must receive
the utmost care to ensure peak performance, tothe utmost care to ensure peak performance, to
prolong their life and to reduce overhead costs.prolong their life and to reduce overhead costs.www.indiandentalacademy.com

WATER AIR COOLING:WATER AIR COOLING:
With high speed instrumentation, the problem of over heating theWith high speed instrumentation, the problem of over heating the
tooth during preparation is critical. Cutting dry at high speeds willtooth during preparation is critical. Cutting dry at high speeds will
produce nearly three times as much dentinal burning as cutting with aproduce nearly three times as much dentinal burning as cutting with a
water spray, and thermal changes can result in pulpal inflammation orwater spray, and thermal changes can result in pulpal inflammation or
necrosis.Brown et al calculated the temperature of dentin at a distancenecrosis.Brown et al calculated the temperature of dentin at a distance
of 0.5mm from a high speed bur cutting dry to be 245 degrees F. Inof 0.5mm from a high speed bur cutting dry to be 245 degrees F. In
light of this, Zach’s contention that a temperature rise of only 20light of this, Zach’s contention that a temperature rise of only 20
degrees F will lead to pulpal death in 60% of teeth is most seriousdegrees F will lead to pulpal death in 60% of teeth is most serious
indeed. Even in non vital teeth, dry cutting at high speeds should beindeed. Even in non vital teeth, dry cutting at high speeds should be
avoided, since the thermal stresses will cause micro fractures inavoided, since the thermal stresses will cause micro fractures in
enamel. This could contribute to marginal factor of the restoration atenamel. This could contribute to marginal factor of the restoration at
some future time. The use of air alone as a coolant is harmful to thesome future time. The use of air alone as a coolant is harmful to the
pulp and is therefore not an acceptable substitute for a water airpulp and is therefore not an acceptable substitute for a water air
spray. Prolonged dehydration of freshly cut dentin will increase pulpalspray. Prolonged dehydration of freshly cut dentin will increase pulpal
damage producing odontoblastic displacement. To minimize pulpaldamage producing odontoblastic displacement. To minimize pulpal
trauma, a water spray should always be used when cutting a toothtrauma, a water spray should always be used when cutting a tooth
preparation at high speeds.preparation at high speeds.www.indiandentalacademy.com

The use of water spray does not in itself guarantee that the pulp will beThe use of water spray does not in itself guarantee that the pulp will be
protected from damage. A low quantity of water, poorly directed, willprotected from damage. A low quantity of water, poorly directed, will
result in a weak spray that can permit localized dentinal scorching. Aresult in a weak spray that can permit localized dentinal scorching. A
small orifice that produces a higher water velocity is more likely tosmall orifice that produces a higher water velocity is more likely to
allow penetration of the air vortex around the instrument tip.allow penetration of the air vortex around the instrument tip.
A water spray also increases the efficiency of high speed rotaryA water spray also increases the efficiency of high speed rotary
instruments by cutting the cutting edges washed clean of debris.instruments by cutting the cutting edges washed clean of debris.
Eames et al. found that a greater flow of water coolant is required toEames et al. found that a greater flow of water coolant is required to
prevent clogging when diamonds are used under increased pressure.prevent clogging when diamonds are used under increased pressure.
Diamond stones used under high pressure (150 gm) became moreDiamond stones used under high pressure (150 gm) became more
effective as the water flow rate increased from 3 to 21 ml/min. Ifeffective as the water flow rate increased from 3 to 21 ml/min. If
light pressure was used (50 gm), there was still an increase inlight pressure was used (50 gm), there was still an increase in
effectiveness, but it leveled off after the flow rate reached 7 ml/min.effectiveness, but it leveled off after the flow rate reached 7 ml/min.
The spray enhances visibility in many instances by flushing awayThe spray enhances visibility in many instances by flushing away
blood and debris. Even indirect vision can be utilized while cuttingblood and debris. Even indirect vision can be utilized while cutting
wet, if the mirror is first coated with a film of detergent. This allowswet, if the mirror is first coated with a film of detergent. This allows
the water to form a smooth transparent film on the surface of thethe water to form a smooth transparent film on the surface of the
mirror with only a moderate decrease in visibility.mirror with only a moderate decrease in visibility.

DENTAL CUTTING BURSDENTAL CUTTING BURS
1.1. Composition and manufactureComposition and manufacture: Dental Burs can be: Dental Burs can be
classified by their composition into two types:classified by their composition into two types:
(a).(a). Steel bursSteel burs: Steel burs are cut from blank steel stock by: Steel burs are cut from blank steel stock by
means of a rotary cutter that cuts parallel to the long axismeans of a rotary cutter that cuts parallel to the long axis
of the bur. The bur is then hardened and tempered untilof the bur. The bur is then hardened and tempered until
its Vicker’s hardness number is approximately 800.its Vicker’s hardness number is approximately 800.
(b).(b).Tungsten carbide bursTungsten carbide burs: Tungsten carbide burs are best: Tungsten carbide burs are best
for making precise preparation features and smoothfor making precise preparation features and smooth
surfaces in enamel or dentin. A logical application of theirsurfaces in enamel or dentin. A logical application of their
planning capability is the production of smooth finishplanning capability is the production of smooth finish
lines. Carbide burs can also be used to cut through metal,lines. Carbide burs can also be used to cut through metal,
while both carbide burs and diamonds can be used to cutwhile both carbide burs and diamonds can be used to cut
sound dentin.sound dentin.

The metal in the head of the carbide bur is formed byThe metal in the head of the carbide bur is formed by sinteringsintering, or pressure, or pressure
molding, tungsten carbide powder and cobalt powder under heat and vacuum.molding, tungsten carbide powder and cobalt powder under heat and vacuum.
The tungsten carbide is cut into small cylinders and then attached to steel rodsThe tungsten carbide is cut into small cylinders and then attached to steel rods
by soldering or welding to form blanks. The tungsten carbide head is machinedby soldering or welding to form blanks. The tungsten carbide head is machined
with large diamond disks to create the specific head for the type of bur beingwith large diamond disks to create the specific head for the type of bur being
formed. The attachment of the carbide bur is quite secure, and loss of theformed. The attachment of the carbide bur is quite secure, and loss of the
carbide portion of the bur is rare. Only when the process has been completed iscarbide portion of the bur is rare. Only when the process has been completed is
the shank of the instrument shortened, notched, or diminished in diameter tothe shank of the instrument shortened, notched, or diminished in diameter to
make a straight hand piece, latch, or friction grip bur.make a straight hand piece, latch, or friction grip bur.
Most burs intended primarily for cutting are made with six and occasionallyMost burs intended primarily for cutting are made with six and occasionally
eight blades. Those burs made for finishing usually have 12 blades, but they caneight blades. Those burs made for finishing usually have 12 blades, but they can
have 20, or even as many as 40.have 20, or even as many as 40.
Several carbide burs of specific shapes are included in the standardSeveral carbide burs of specific shapes are included in the standard
armamentarium. These include at least 2 tapered fissured burs, long andarmamentarium. These include at least 2 tapered fissured burs, long and
standard length, an end cutting bur and a friction grip no. 4 round bur. Forstandard length, an end cutting bur and a friction grip no. 4 round bur. For
removal of deep caries a low speed hand piece no. 6 round bur is used so thatremoval of deep caries a low speed hand piece no. 6 round bur is used so that
sound dentin can be distinguished from softer carious dentin by its greatersound dentin can be distinguished from softer carious dentin by its greater
resistance to cutting.resistance to cutting.
Tapered fissure burs have a number of uses in preparing teeth for cast metalTapered fissure burs have a number of uses in preparing teeth for cast metal
and porcelain restorations. In addition to the placement of grooves, box forms,and porcelain restorations. In addition to the placement of grooves, box forms,
and isthmuses, they are especially useful for planning vertical axial surfaces.and isthmuses, they are especially useful for planning vertical axial surfaces.
There are a number of tapered finishing burs whose greater length andThere are a number of tapered finishing burs whose greater length and
diameter make them suited better for this task, the commonly used sizes arediameter make them suited better for this task, the commonly used sizes are
shown in the figure below:shown in the figure below: www.indiandentalacademy.com

2.2. General design of Dental BursGeneral design of Dental Burs::
The dental bur is a smallThe dental bur is a small
milling (cutting)milling (cutting)
instrument. A commoninstrument. A common
design is displayed in thedesign is displayed in the
figure underneath:figure underneath:

Bur toothBur tooth::
This terminates in the cutting edge, orThis terminates in the cutting edge, or
blade. It has two surfaces, the tooth face,blade. It has two surfaces, the tooth face,
which is the side of the tooth on thewhich is the side of the tooth on the
leading edge; and the back or flank of theleading edge; and the back or flank of the
tooth, which is the side of the tooth ontooth, which is the side of the tooth on
the trailing edge.the trailing edge.

Rake angleRake angle: The rake angle is the angle that the face of the bur: The rake angle is the angle that the face of the bur
tooth makes with the radial line from the centre of the burtooth makes with the radial line from the centre of the bur
to the blade. This angle can be negative if the face is beyondto the blade. This angle can be negative if the face is beyond
or leading the radial line (referring to the direction ofor leading the radial line (referring to the direction of
rotation). It can be 0 if the radial line and the tooth facerotation). It can be 0 if the radial line and the tooth face
coincide with each other (radial rake angle). The angle cancoincide with each other (radial rake angle). The angle can
also be positive if the radial line leads the face, so that thealso be positive if the radial line leads the face, so that the
rake angle is on the inside of the radial line. The morerake angle is on the inside of the radial line. The more
positive the rake angle the more acute the edge of the blade,positive the rake angle the more acute the edge of the blade,
and more effective the cutting action. A positive rake angle,and more effective the cutting action. A positive rake angle,
unfortunately, also has a weaker edge. Therefore, the bladesunfortunately, also has a weaker edge. Therefore, the blades
are usually made with either negative or neutral (radial) rakeare usually made with either negative or neutral (radial) rake
angles, and wider bases. These are slightly less efficient forangles, and wider bases. These are slightly less efficient for
cutting, but because of their greater bulk they are less likelycutting, but because of their greater bulk they are less likely
to chip.to chip.

Land: The plane surface immediately
following the cutting edge.

 Clearance angleClearance angle: The angle between the back of the: The angle between the back of the
tooth and the work. If a land is present on the bur,tooth and the work. If a land is present on the bur,
the clearance angle is divided into: primary clearancethe clearance angle is divided into: primary clearance
which is the angle the land will make with work, andwhich is the angle the land will make with work, and
secondary clearance, which is the angle between thesecondary clearance, which is the angle between the
back of the bur tooth and work. When the backback of the bur tooth and work. When the back
surface of the tooth is curved, the clearance is calledsurface of the tooth is curved, the clearance is called
radial clearance. There is an optimum clearanceradial clearance. There is an optimum clearance
angle for each diameter of bur, and the larger theangle for each diameter of bur, and the larger the
diameter, the smaller the clearance angle that isdiameter, the smaller the clearance angle that is
required. The smaller the clearance angle, therequired. The smaller the clearance angle, the
stronger the cutting blade. However, if the anglestronger the cutting blade. However, if the angle
becomes too small, the back of the blade may rubbecomes too small, the back of the blade may rub
against the cut surface, generating heat andagainst the cut surface, generating heat and
decreasing efficiency.decreasing efficiency.www.indiandentalacademy.com

 Tooth angleTooth angle: This is measured between the face and: This is measured between the face and
back. If a land is present, it is measured between theback. If a land is present, it is measured between the
face and land.face and land.
 Flute or chip spaceFlute or chip space: The space between successive: The space between successive
teeth, which are the grooves between the blades theteeth, which are the grooves between the blades the
amount of spiral, or helical angle, of the bladesamount of spiral, or helical angle, of the blades
affects the cutting characteristics of the bur. Aaffects the cutting characteristics of the bur. A
greater helical angle produces a smoother surface ongreater helical angle produces a smoother surface on
the preparation, and reduces the “chatter,” orthe preparation, and reduces the “chatter,” or
vibration of the bur on the tooth surface. This alsovibration of the bur on the tooth surface. This also
reduces chipping of the tungsten carbide during usereduces chipping of the tungsten carbide during use
on a tooth, and it prevents debris from clogging theon a tooth, and it prevents debris from clogging the
flutes between the blades.flutes between the blades.
 The number of teeth in dental cutting burs is usuallyThe number of teeth in dental cutting burs is usually
6-8.6-8. www.indiandentalacademy.com

 Every bur will have threeEvery bur will have three
partsparts: The head: The head –The–The
portion carrying the cuttingportion carrying the cutting
blades.blades.
 The shankThe shank-The portion-The portion
connecting the head to theconnecting the head to the
attachment part, and theattachment part, and the
 ShaftShaft or the attachmentor the attachment
part- The portion which willpart- The portion which will
be engaged within the handbe engaged within the hand
piece.piece.

CLASSIFICATIONCLASSIFICATION
1. According to their mode of attachment to the hand piece:1. According to their mode of attachment to the hand piece:
-Latch type-Latch type
-Friction grip type-Friction grip type
2. According to the hand piece they are designed for:2. According to the hand piece they are designed for:
-Contrangle bur-Contrangle bur
-Straight hand piece bur-Straight hand piece bur
3. They can also be classified as right and left. The most common ones3. They can also be classified as right and left. The most common ones
are the right, which cut when they revolve clockwise.are the right, which cut when they revolve clockwise.
4. According to the length of the head:4. According to the length of the head:
-Long-Long
-Short-Short
-Regular-Regular
5. According to the function:5. According to the function:
-Cutting burs-Cutting burs
-Finishing and polishing burs-Finishing and polishing burs

DIAMOND ABRASIVE INSTRUMENTSDIAMOND ABRASIVE INSTRUMENTS
 The second major category of rotary dental cuttingThe second major category of rotary dental cutting
instruments involve abrasives rather then blade cutting.instruments involve abrasives rather then blade cutting.
Abrasive instruments are generally grouped as diamond orAbrasive instruments are generally grouped as diamond or
other instruments. Diamond instruments for dental use wereother instruments. Diamond instruments for dental use were
introduced in the United States in 1942.introduced in the United States in 1942.
 These diamond instruments are nothing but small angularThese diamond instruments are nothing but small angular
particles of diamond held in a matrix of softer material. Theparticles of diamond held in a matrix of softer material. The
diamond employed is industrial diamonds either natural ordiamond employed is industrial diamonds either natural or
synthetic that have been crushed to powder and then carefullysynthetic that have been crushed to powder and then carefully
graded for size and quality.graded for size and quality.
 Diamond particle size is commonly categorized as coarse (125Diamond particle size is commonly categorized as coarse (125
to 150um) medium (88 to 125 um) fine (60 to 74um) and veryto 150um) medium (88 to 125 um) fine (60 to 74um) and very
fine (38 to 44 um).fine (38 to 44 um).

Color coding is done depending on theColor coding is done depending on the
particle size i.e.,particle size i.e.,
 Coarse- Green (125 – 150 um )Coarse- Green (125 – 150 um )
 Medium-Blue (125 – 88 um )Medium-Blue (125 – 88 um )
 Fine- Red (60 – 74 um )Fine- Red (60 – 74 um )
 Very fine- Yellow ( 38 – 44 um )Very fine- Yellow ( 38 – 44 um )
The particle size used by four major U.S.The particle size used by four major U.S.
dental firms is compared by both U.S. Mesh-dental firms is compared by both U.S. Mesh-
Standard and equivalent metric size.Standard and equivalent metric size.

Manufacturing of Diamond AbrasiveManufacturing of Diamond Abrasive
 Abrasive particles are held together by means of a “binder”Abrasive particles are held together by means of a “binder”
(base) of variable nature. A ceramic binder is used in many(base) of variable nature. A ceramic binder is used in many
cases particularly for binding diamond chips. Also, ancases particularly for binding diamond chips. Also, an
electroplating process providing a metallic binder may beelectroplating process providing a metallic binder may be
used. For soft grade stone, rubber or shellac may be used.used. For soft grade stone, rubber or shellac may be used.
Sintered types are strongest because abrasive particles areSintered types are strongest because abrasive particles are
fused together.fused together.
 The type of binder is intimately related to the life of the tool inThe type of binder is intimately related to the life of the tool in
use with most abrasives, the binder is impregnated throughuse with most abrasives, the binder is impregnated through
out with abrasive particles of certain grade so that as a particleout with abrasive particles of certain grade so that as a particle
is wrenched from the binder during use; another will take itsis wrenched from the binder during use; another will take its
place as binder wears. Eames et al. found that they cut toothplace as binder wears. Eames et al. found that they cut tooth
structure two to three times as quickly as burs.structure two to three times as quickly as burs.www.indiandentalacademy.com

 They are deposited in one to three layers on theThey are deposited in one to three layers on the
surface of the instrument. The best diamond stonessurface of the instrument. The best diamond stones
have abrasive particles evenly spaced over the surfacehave abrasive particles evenly spaced over the surface
of the instrument. There also should be intimateof the instrument. There also should be intimate
contact between the chips and the binding material.contact between the chips and the binding material.
 While there are many shapes and sizes of diamonds toWhile there are many shapes and sizes of diamonds to
be used for special applications and to suit the taste ofbe used for special applications and to suit the taste of
every operator, there are a few diamond stones whichevery operator, there are a few diamond stones which
should be included in a basic set of instruments: theshould be included in a basic set of instruments: the
round-end tapered, flat-end tapered, long-needle,round-end tapered, flat-end tapered, long-needle,
short-needle, and small round-edge wheel diamonds.short-needle, and small round-edge wheel diamonds.
Two other diamonds also commonly used, theTwo other diamonds also commonly used, the
torpedo and flame, are frequently paired with carbidetorpedo and flame, are frequently paired with carbide
burs of matching shapes. Figures and dimensions forburs of matching shapes. Figures and dimensions for
these instruments are shown below:these instruments are shown below:www.indiandentalacademy.com

According to their shapes and sizesAccording to their shapes and sizes
they can be classified as:they can be classified as:
((a)Flat ended tapereda)Flat ended tapered
diamond cylinderdiamond cylinder: It is: It is
used for bulk axial andused for bulk axial and
occlusal reduction andocclusal reduction and
shoulder preparation onshoulder preparation on
PJC and PFM toothPJC and PFM tooth
preparations. End cuttingpreparations. End cutting
burs are also used toburs are also used to
develop and lowerdevelop and lower
shoulder preparation.shoulder preparation.
They are keptThey are kept
perpendicular to the planeperpendicular to the plane
being reduced.being reduced.

(b)(b) Straight cylinderStraight cylinder
diamond with a tapereddiamond with a tapered
pointpoint: A suitable: A suitable
instrument for chamferinstrument for chamfer
placement is a Tinkerplacement is a Tinker
diamond; a straight cylinderdiamond; a straight cylinder
with a tapered point. Thiswith a tapered point. This
tapered point creates atapered point creates a
chamfer with greaterchamfer with greater
control then the round-endcontrol then the round-end
tapered diamond. It istapered diamond. It is
usually indicated forusually indicated for
molars.molars.

c)Twelve flutedc)Twelve fluted
carbide bur:carbide bur: It is aIt is a
smooth cuttingsmooth cutting
instrument and givesinstrument and gives
a highly finisheda highly finished
surface to asurface to a
preparation. Thepreparation. The
greater the number ofgreater the number of
blades on a bur, theblades on a bur, the
smoother the cut.smoother the cut.

((d)Round-ended taperedd)Round-ended tapered
diamond cylinders:diamond cylinders: TheyThey
are available in variousare available in various
sizes. They are used forsizes. They are used for
axial and occlusal reductionaxial and occlusal reduction
and developing chamferand developing chamfer
margins. Less than half themargins. Less than half the
diameter of the tip is useddiameter of the tip is used
for chamfer margins.for chamfer margins.
Cutting to a depth greaterCutting to a depth greater
then one-half the diameterthen one-half the diameter
of the tip produces aof the tip produces a
shoulder.shoulder.

((e)Round diamonds:e)Round diamonds:
They facilitateThey facilitate
establishing depthestablishing depth
grooves beforegrooves before
reduction. They vary inreduction. They vary in
size and are measured tosize and are measured to
determine the cut depth.determine the cut depth.
They are also used toThey are also used to
establish rest seats andestablish rest seats and
reduce lingual surfacesreduce lingual surfaces
of anterior teeth. Theyof anterior teeth. They
are numbered from ¼,are numbered from ¼,
½, 1, 2 to 10.½, 1, 2 to 10. www.indiandentalacademy.com

((f)Round diamondf)Round diamond
wheels (donut):wheels (donut):
They are grossThey are gross
reductionreduction
instruments andinstruments and
also used inalso used in
anterior teethanterior teeth
lingual reductions.lingual reductions.
They are numberedThey are numbered
as 14 and 15.as 14 and 15.

(g)Oblong(g)Oblong
diamondsdiamonds
(football):(football):
Variously shapedVariously shaped
football diamondsfootball diamonds
are available forare available for
lingual reduction oflingual reduction of
anterior teeth. Theyanterior teeth. They
are available inare available in
sizes that uniformlysizes that uniformly
reduce the foosae.reduce the foosae.

((h)Thin taperedh)Thin tapered
diamond conesdiamond cones
(needle):(needle): Thin taperedThin tapered
cones are used forcones are used for
proximal slices to isolateproximal slices to isolate
teeth from adjacentteeth from adjacent
teeth. They tend to loseteeth. They tend to lose
their sharpness soonertheir sharpness sooner
than coarse diamondsthan coarse diamonds
and are replacedand are replaced
frequently.frequently.

((i)Tapered oblongi)Tapered oblong
diamond (flame):diamond (flame):
Small flame-shapedSmall flame-shaped
diamonds are used indiamonds are used in
bevel placement.bevel placement.
There are many multiThere are many multi
fluted flame-shapedfluted flame-shaped
carbides that havecarbides that have
identical functions.identical functions.

((j)Cross cut fissurej)Cross cut fissure
burs:burs: They come inThey come in
varying sizes and arevarying sizes and are
numbered fromnumbered from
555,556 to 560, both555,556 to 560, both
tapered and cylindrical.tapered and cylindrical.
The tapered burs areThe tapered burs are
used for grooveused for groove
placement in threeplacement in three
quarter crowns, flutes,quarter crowns, flutes,
and for seating groovesand for seating grooves
in complete goldin complete gold
crowns.crowns. www.indiandentalacademy.com

((k)Plain fissure burs:k)Plain fissure burs:
They cut smoothlyThey cut smoothly
and come in a varietyand come in a variety
of sizes, both taperedof sizes, both tapered
and cylindrical. Theyand cylindrical. They
may also be used formay also be used for
groove placementgroove placement
and finishing ofand finishing of
preparationspreparations..

((l)Large carborunduml)Large carborundum
disc (laboratory):disc (laboratory):
Mounted stones, discs,Mounted stones, discs,
and wheels are all usedand wheels are all used
in finishing cast gold,in finishing cast gold,
porcelains, acrylics, andporcelains, acrylics, and
tooth structure. Large,tooth structure. Large,
thin carborundum discsthin carborundum discs
quickly section a spruequickly section a sprue
from a casting. Similarfrom a casting. Similar
diamond discs can bediamond discs can be
used to shape bulkused to shape bulk
porcelain.porcelain.

((m)Heatless stonem)Heatless stone
(laboratory):(laboratory):
Large heatlessLarge heatless
stones will removestones will remove
the remnant of thethe remnant of the
sprue attached tosprue attached to
the casting.the casting.

((n) Mounted green andn) Mounted green and
white stones (lowwhite stones (low
speed):speed): VariousVarious
mounted green and whitemounted green and white
stones exist for straightstones exist for straight
and contraangle handand contraangle hand
pieces. They are not forpieces. They are not for
high speeds. They can behigh speeds. They can be
altered by grindingaltered by grinding
against a coarse/heatlessagainst a coarse/heatless
stone. White stones havestone. White stones have
a finer texture than greena finer texture than green
stones and are preferable.stones and are preferable.

(o) Sand paper discs:(o) Sand paper discs:
Sand paper discs ofSand paper discs of
various grits arevarious grits are
excellent in finishingexcellent in finishing
marginal areas ofmarginal areas of
castings whilecastings while
maintainingmaintaining
contours. They maycontours. They may
also be used inalso be used in
finishing toothfinishing tooth
preparations.preparations.

(p) Small pin discs:(p) Small pin discs:
Small-pin sand paperSmall-pin sand paper
discs are fine fordiscs are fine for
accessible margins inaccessible margins in
the mouth andthe mouth and
finishing axial walls infinishing axial walls in
inlay preparations.inlay preparations.

((q) Chamois wheelsq) Chamois wheels
(laboratory):(laboratory):
Chamois wheel areChamois wheel are
used only with dentalused only with dental
rouge and give arouge and give a
luster to the casting.luster to the casting.

(r) Rubber burlew discs(r) Rubber burlew discs
(laboratory):(laboratory): RubberRubber
burlew discs used afterburlew discs used after
the fine sandpaper stagethe fine sandpaper stage
of finishing provide aof finishing provide a
smooth surface to thesmooth surface to the
casting. Smaller sulcicasting. Smaller sulci
discs exist for smallerdiscs exist for smaller
ridge and groove areasridge and groove areas
but are rarely usedbut are rarely used
intraorallyintraorally..

((s) Robinson brushess) Robinson brushes
(laboratory):(laboratory): RobinsonRobinson
brushes (stiff, medium,brushes (stiff, medium,
soft) are used withsoft) are used with
pumice or tripoli. Slowpumice or tripoli. Slow
speed with pressurespeed with pressure
produces greater cuttingproduces greater cutting
potential; high speedpotential; high speed
with light pressurewith light pressure
produces a high-lustreproduces a high-lustre
finish.finish.

((t) End cutting burs:t) End cutting burs: They areThey are
cylindrical in shape with just the endcylindrical in shape with just the end
carrying blades. They are very efficientcarrying blades. They are very efficient
in extending preparations apicallyin extending preparations apically
without axial reduction. They arewithout axial reduction. They are
numbered from 900 to 904.numbered from 900 to 904.

Diamond/bur dual instrumentation:Diamond/bur dual instrumentation:
 Diamonds remove tooth structure more efficiently than doDiamonds remove tooth structure more efficiently than do
burs, but they leave undesirably rough surfaces and irregularburs, but they leave undesirably rough surfaces and irregular
cavosurface finish lines. Tungsten carbide burs producecavosurface finish lines. Tungsten carbide burs produce
smooth finish lines and precise internal features, but they cutsmooth finish lines and precise internal features, but they cut
more slowly. Therefore, to take advantage of the best featuresmore slowly. Therefore, to take advantage of the best features
of both types of instrument, diamonds should be used for theof both types of instrument, diamonds should be used for the
bulk reduction and carbide burs for finishing the preparationbulk reduction and carbide burs for finishing the preparation
and placing internal features such as grooves, box forms,and placing internal features such as grooves, box forms,
isthmuses, etc.isthmuses, etc.
 The technique of choice in this situation utilizes diamonds andThe technique of choice in this situation utilizes diamonds and
carbide burs of matching size and configuration as describedcarbide burs of matching size and configuration as described
byby Lustig.Lustig. These instruments are manufactured by makingThese instruments are manufactured by making
both the diamond and bur from a common blankboth the diamond and bur from a common blank
configuration. This assumes that the shape of the instrumentconfiguration. This assumes that the shape of the instrument
and the resultant contour of the tooth will match exactly whenand the resultant contour of the tooth will match exactly when
the diamond and carbide finishing bur are used for each stepthe diamond and carbide finishing bur are used for each step
of the preparation.of the preparation. www.indiandentalacademy.com

EFFECTS OF HIGH SPEED CUTTINGEFFECTS OF HIGH SPEED CUTTING
ENAMEL:ENAMEL:
Enamel is composed of 92% mineral and 8% of organicEnamel is composed of 92% mineral and 8% of organic
material and water. It is recognized as the hardest humanmaterial and water. It is recognized as the hardest human
tissue. The basic structure of enamel is mushroom shapedtissue. The basic structure of enamel is mushroom shaped
enamel rod, which begins at the dentinoenamel junction andenamel rod, which begins at the dentinoenamel junction and
ends at enamel surface. Usually enamel originates at rightends at enamel surface. Usually enamel originates at right
angles to the dentin surface and follows a spiral patternangles to the dentin surface and follows a spiral pattern
towards the surface ending at near right angles to the surface.towards the surface ending at near right angles to the surface.
Eccentric burs that do not run true in the high-speed handEccentric burs that do not run true in the high-speed hand
piece can produce crazing of the enamel. Crazing can also bepiece can produce crazing of the enamel. Crazing can also be
brought about by internal stresses, such as might be inducedbrought about by internal stresses, such as might be induced
by thermal changes or a retentive pin i.e., angled outward andby thermal changes or a retentive pin i.e., angled outward and
that has been forced into enamel.that has been forced into enamel.

DENTINDENTIN
Dentin is composed of 65% inorganic material. The remainingDentin is composed of 65% inorganic material. The remaining
35% is organic matter and water, which allows it to be cut35% is organic matter and water, which allows it to be cut
more readily than enamel with a dental bur. Dentin ismore readily than enamel with a dental bur. Dentin is
organized in the form of tubules that are supported byorganized in the form of tubules that are supported by
calcified network of collagen fibers. The tubules contain thecalcified network of collagen fibers. The tubules contain the
living extensions of the odontoblasts whose cell bodies are inliving extensions of the odontoblasts whose cell bodies are in
the periphery of the pulp.the periphery of the pulp.
Crown preparations involve the exposure of dentinal tubules,Crown preparations involve the exposure of dentinal tubules,
cutting of odontoblast processes. Generation of heat,cutting of odontoblast processes. Generation of heat,
desiccation and pressure. The deeper the dentin is cut, moredesiccation and pressure. The deeper the dentin is cut, more
severly odontoblasts may be damaged. If the water coolantseverly odontoblasts may be damaged. If the water coolant
does not reach the interface between the cutting instrumentdoes not reach the interface between the cutting instrument
and the tooth surface in the crown preparation a surfaceand the tooth surface in the crown preparation a surface
“dentin burn” lesion will occur. The odontoblast destruction“dentin burn” lesion will occur. The odontoblast destruction
will be extensive.will be extensive.

PULPPULP
The pulp of a tooth is unique among other body tissues or organs. It isThe pulp of a tooth is unique among other body tissues or organs. It is
very small, but it is able to fulfill sensory and nutritional functions forvery small, but it is able to fulfill sensory and nutritional functions for
a tooth. It also forms additional dentin and form provides a defensea tooth. It also forms additional dentin and form provides a defense
against infection. The pulp responds very quickly to external stimuliagainst infection. The pulp responds very quickly to external stimuli
and the response depends on the severity of the stimuli.and the response depends on the severity of the stimuli.
The degree of pulp reaction is proptionately increased in directThe degree of pulp reaction is proptionately increased in direct
relation to the depth and particularly the extensiveness of crownrelation to the depth and particularly the extensiveness of crown
preparation.preparation.
If the odontoblasts are injured primarily by desiccation, theIf the odontoblasts are injured primarily by desiccation, the
disintegration products of these cells will act as an irritant and causedisintegration products of these cells will act as an irritant and cause
an inflammatory response in the pulp in that area where cut dentinalan inflammatory response in the pulp in that area where cut dentinal
tubules terminate. When there is dentin burn odontoblast destructiontubules terminate. When there is dentin burn odontoblast destruction
will be extensive.will be extensive.
Photo and Schenin (1958) showed if pulp temperature was raisedPhoto and Schenin (1958) showed if pulp temperature was raised
above 46 degree C irreversible changes such as stasis and thrombosisabove 46 degree C irreversible changes such as stasis and thrombosis
could occur in the pulp. Drying the tooth with a constant air blowingcould occur in the pulp. Drying the tooth with a constant air blowing
also cause irreversible pulp damage, even if the cavity is preparedalso cause irreversible pulp damage, even if the cavity is prepared
under sufficient water coolant. Therefore the preparation should beunder sufficient water coolant. Therefore the preparation should be
dried with careful blasts of air at short duration and with steriledried with careful blasts of air at short duration and with sterile
cotton after preparation.cotton after preparation. www.indiandentalacademy.com

Advantages of high speed cuttingAdvantages of high speed cutting
1. Increased cutting efficiency.1. Increased cutting efficiency.
2. Faster tooth removal, hence less pressure, less vibration and2. Faster tooth removal, hence less pressure, less vibration and
less heat generation.less heat generation.
3. Operator has better control and less fatigue.3. Operator has better control and less fatigue.
4. Great ease of operation.4. Great ease of operation.
5. Patients less apprehensive because less vibration, less noise5. Patients less apprehensive because less vibration, less noise
and less operation time.and less operation time.
6. Reduced tension and fatigue for both operator and the patient6. Reduced tension and fatigue for both operator and the patient
due to reduced operation time.due to reduced operation time.
7. Greater ease of operation.7. Greater ease of operation.
8. As a whole, it is possible to manage more patients in less time.8. As a whole, it is possible to manage more patients in less time.

Disadvantages of high speed cuttingDisadvantages of high speed cutting

Desiccation of dentinal tubules.Desiccation of dentinal tubules.
 Impaired visibility due to water spray.Impaired visibility due to water spray.
 Mechanical injury to soft tissues due to coarse speed. This can beMechanical injury to soft tissues due to coarse speed. This can be
avoided byavoided by
Using rubber dams.Using rubber dams.
Taking care while removing hand piece.Taking care while removing hand piece.
 Over reduction of toothOver reduction of tooth
This can be avoided by properly following the steps duringThis can be avoided by properly following the steps during
preparation and experience.preparation and experience.
 Eye damageEye damage
Due to flying tooth restorative material particles. This can be avoidedDue to flying tooth restorative material particles. This can be avoided
by protective eyewear for dentist, patient and assistant.by protective eyewear for dentist, patient and assistant.
 NoiseNoise
Hi pitched noise from air turbine can cause hearing damage.Hi pitched noise from air turbine can cause hearing damage.
 Cross contaminationCross contamination
Use of face masks for the protection from air borne infections likeUse of face masks for the protection from air borne infections like
tuberculosis etc reduces the risk.tuberculosis etc reduces the risk.www.indiandentalacademy.com

ABRASION AND POLISHING AGENTSABRASION AND POLISHING AGENTS
 The finishing and polishing of restorative dentalThe finishing and polishing of restorative dental
materials are important steps in the fabrication ofmaterials are important steps in the fabrication of
clinically successful restorations. The techniquesclinically successful restorations. The techniques
employed for these procedures are meant not onlyemployed for these procedures are meant not only
for removal of excess material but also to smoothenfor removal of excess material but also to smoothen
rough surfaces.rough surfaces.
 The finishing of dental restorations prior to theirThe finishing of dental restorations prior to their
placement in the oral cavity has therefore threeplacement in the oral cavity has therefore three
benefits:benefits:
 To promote oral hygiene.To promote oral hygiene.
 Enhance oral function.Enhance oral function.
 To improve esthetics.To improve esthetics.www.indiandentalacademy.com

DESIRABLE CHARACTERISTICS OF ANDESIRABLE CHARACTERISTICS OF AN
ABRASIVEABRASIVE
 It should be irregular in shape so that it presents a sharpIt should be irregular in shape so that it presents a sharp
edge. (Jagged particles are more effective. Round sandedge. (Jagged particles are more effective. Round sand
particles and cubicle particles of sand paper are poorparticles and cubicle particles of sand paper are poor
abrasives).abrasives).
 It should be harder than the work it abrades. If it cannotIt should be harder than the work it abrades. If it cannot
indent the surface to be abraded then it cannot cut it andindent the surface to be abraded then it cannot cut it and
therefore wears out.therefore wears out.
 Abrasive should posses a high impact strength or bodyAbrasive should posses a high impact strength or body
strength. Abrasive point should always fracture than dull outstrength. Abrasive point should always fracture than dull out
so that always, a sharp point or edge is available. The cutsso that always, a sharp point or edge is available. The cuts
also help in shredding debris accumulated from work for eg,also help in shredding debris accumulated from work for eg,
a grinding wheel against a metal.a grinding wheel against a metal.
 Abrasive should posses attrition resistance so that it doesAbrasive should posses attrition resistance so that it does
not wear.not wear. www.indiandentalacademy.com

DESIGN OF ABRASIVEDESIGN OF ABRASIVE
INSTRUMENTSINSTRUMENTS
The abrasives employed could be one of theThe abrasives employed could be one of the
three types,three types,
 Abrasive Grits.Abrasive Grits.
 Bonded Abrasives.Bonded Abrasives.
 Coated Abrasive Disks and Strips.Coated Abrasive Disks and Strips.

A. Abrasive GritsA. Abrasive Grits
Abrasive grits are derived from (abrasive)Abrasive grits are derived from (abrasive)
materials that have been crushed and passedmaterials that have been crushed and passed
through series of mesh screens to obtainthrough series of mesh screens to obtain
different particle size ranges. The grits aredifferent particle size ranges. The grits are
classified as COARSE, MEDIUM COARSE,classified as COARSE, MEDIUM COARSE,
MEDIUM FINE and SUPER FINE accordingMEDIUM FINE and SUPER FINE according
to the particle size ranges.to the particle size ranges.

B. Bonded AbrasivesB. Bonded Abrasives
 These consist of abrasive particles incorporated through a binder toThese consist of abrasive particles incorporated through a binder to
form grinding tools.form grinding tools.
 The abrasive particles are bonded by 4 general methods:The abrasive particles are bonded by 4 general methods:
 Sintering.Sintering.
 Vitreous bonding (Glass/Ceramic)Vitreous bonding (Glass/Ceramic)
 Resin bonding (usually phenolic resin).Resin bonding (usually phenolic resin).
 Rubber bonding (usually silicon rubber).Rubber bonding (usually silicon rubber).
 Sintering-Sintering- Sintered abrasives are the strongest variety since theSintered abrasives are the strongest variety since the
abrasive particles are fused together.abrasive particles are fused together.
 Vitreous bonded-Vitreous bonded- Are mixed with a glassy or ceramic matrixAre mixed with a glassy or ceramic matrix
material, cold pressed to the instrument shape and fired to fusematerial, cold pressed to the instrument shape and fired to fuse
with the binder.with the binder.
 Resin bonded-Resin bonded- are cold or hot pressed and then heated to cure theare cold or hot pressed and then heated to cure the
resin.resin.
 Rubber bonded-Rubber bonded- made in a manner that is similar to resin bonded.made in a manner that is similar to resin bonded.www.indiandentalacademy.com

C. Coated Abrasive Disks and StripsC. Coated Abrasive Disks and Strips
 These abrasives are supplied as disks andThese abrasives are supplied as disks and
finishing strips. They are fabricated by securingfinishing strips. They are fabricated by securing
abrasive particles to a flexible backing materialabrasive particles to a flexible backing material
(heavy weight paper or Mylar).(heavy weight paper or Mylar).
 The disks are available in different diametersThe disks are available in different diameters
with thin and very thin backings. Moisture –with thin and very thin backings. Moisture –
resistant backings are advantageous, as theresistant backings are advantageous, as the
abrasive stiffness is not reduced by waterabrasive stiffness is not reduced by water
degradation.degradation.

ABRASIVE ACTIONABRASIVE ACTION
The mode of action of the abrasives is similar toThe mode of action of the abrasives is similar to
that of the dental burs, that is, it is meraly athat of the dental burs, that is, it is meraly a
cutting action. Each fine abrasive particle thuscutting action. Each fine abrasive particle thus
presents as a sharp edge, which cuts through thepresents as a sharp edge, which cuts through the
surface similar to a pointed chisel. During thissurface similar to a pointed chisel. During this
cutting process, the shaving thus formed iscutting process, the shaving thus formed is
powdered and usually clogs the abrasive whichpowdered and usually clogs the abrasive which
thus makes periodic cleaning of the abrasivethus makes periodic cleaning of the abrasive
necessary.necessary.

FACTORS AFFECTING RATE OFFACTORS AFFECTING RATE OF
ABRASIONABRASION
Rate of abrasion of a given material by a givenRate of abrasion of a given material by a given
abrasive is determined primarily by three factors:abrasive is determined primarily by three factors:
 Size of the abrasive particle – larger the size –Size of the abrasive particle – larger the size –
greater the abrasion.greater the abrasion.
 Pressure of the work against the abrasive. WhenPressure of the work against the abrasive. When
work is pressed against the abrasive, scratches arework is pressed against the abrasive, scratches are
deeper and abrasion is more rapid – so greaterdeeper and abrasion is more rapid – so greater
chances of the abrasives to fracture.chances of the abrasives to fracture.
 Speed at which the abrasive particles travels acrossSpeed at which the abrasive particles travels across
the work. Greater the speed, greater would be thethe work. Greater the speed, greater would be the
rate of abrasion.rate of abrasion.www.indiandentalacademy.com

FACTORS INFLUENCINGFACTORS INFLUENCING
EFFICIENCY OF THE ABRASIVESEFFICIENCY OF THE ABRASIVES
These factors are as follows:These factors are as follows:
 The hardness of the abrasive particle (diamond is hardest; pumice andThe hardness of the abrasive particle (diamond is hardest; pumice and
garnet etc. are relatively mild).garnet etc. are relatively mild).
 The shape of the abrasive particle (particles with sharp edge are moreThe shape of the abrasive particle (particles with sharp edge are more
effective).effective).
 Particle size of the abrasive (longer particle size will cut deeperParticle size of the abrasive (longer particle size will cut deeper
grooves).grooves).
 Mechanical properties of the abrasive (If the material breaks, it shouldMechanical properties of the abrasive (If the material breaks, it should
form a new cutting edge. Therefore brittleness can be an advantage).form a new cutting edge. Therefore brittleness can be an advantage).
 Rate of movement of the abrasive particles (slower abrasion – deeperRate of movement of the abrasive particles (slower abrasion – deeper
scratches).scratches).
 Pressure applied to the abrasive (too much pressure can fracture thePressure applied to the abrasive (too much pressure can fracture the
abrasive instrument and increase heat of friction that has evolved).abrasive instrument and increase heat of friction that has evolved).
 Properties of material that is being abraded. (a brittle material can beProperties of material that is being abraded. (a brittle material can be
rapidly abraded whereas ductile / malleable metal like pure gold willrapidly abraded whereas ductile / malleable metal like pure gold will
flow instead of being removed by the abrasive).flow instead of being removed by the abrasive).

TYPES OS ABRASIVESTYPES OS ABRASIVES
According to Craig : The abrasivesAccording to Craig : The abrasives
used can be classified and grouped asused can be classified and grouped as
 Finishing Abrasives.Finishing Abrasives.
 Polishing Abrasives.Polishing Abrasives.
 Cleaning abrasives.Cleaning abrasives.

Finishing AbrasivesFinishing Abrasives
 These are hard, coarse abrasives used initially toThese are hard, coarse abrasives used initially to
develop desired contours and remove off grossdevelop desired contours and remove off gross
irregularities.irregularities.
Polishing AbrasivesPolishing Abrasives
 These have a smaller particle size and are less hardThese have a smaller particle size and are less hard
than abrasives used for finishing. They are used forthan abrasives used for finishing. They are used for
smoothening surfaces that are typically roughenedsmoothening surfaces that are typically roughened
by finishing abrasives.by finishing abrasives.
Cleaning AbrasivesCleaning Abrasives
 These are soft abrasives with small particle size andThese are soft abrasives with small particle size and
are intended to remove softer materials that adhereare intended to remove softer materials that adhere
to enamel or a restoration.to enamel or a restoration.

2. Skinner has grouped the abrasives2. Skinner has grouped the abrasives
employed in dentistry as follows:employed in dentistry as follows:
A. Natural Abrasives.A. Natural Abrasives.
B. Manufactured Abrasives.B. Manufactured Abrasives.

Under Natural Abrasives we have:Under Natural Abrasives we have:
1. Arkansas stone1. Arkansas stone
- Semi translucent, light gray, siliceous sedimentary rock,- Semi translucent, light gray, siliceous sedimentary rock,
mined in Arkansas.mined in Arkansas.
- It contains microcrystalline quartz.- It contains microcrystalline quartz.
- Small pieces of this mineral is attached to metal shanks- Small pieces of this mineral is attached to metal shanks
and trued to various shapes for fine grinding of toothand trued to various shapes for fine grinding of tooth
enamel and metal alloys.enamel and metal alloys.
2. Chalk2. Chalk
- Mineral form of calcite.- Mineral form of calcite.
- Contains calcium carbonate.- Contains calcium carbonate.
- Used as mild abrasive paste to polish teeth enamel,- Used as mild abrasive paste to polish teeth enamel,
gold foil, amalgam and plastic materials.gold foil, amalgam and plastic materials.www.indiandentalacademy.com

3. Corundum3. Corundum
- Is largely replaced by alpha Aluminum oxide due to its- Is largely replaced by alpha Aluminum oxide due to its
superior physical properties. However corundum issuperior physical properties. However corundum is
primarily used for grinding metal alloys and isprimarily used for grinding metal alloys and is
available as a bonded abrasive.available as a bonded abrasive.
4. Diamond4. Diamond is a transparent colorless mineralis a transparent colorless mineral
composed of carbon called super abrasive becausecomposed of carbon called super abrasive because
of its ability to abrade any other known substance. Itof its ability to abrade any other known substance. It
is used on ceramic and resin based compositeis used on ceramic and resin based composite
materials.materials.
Supplied as:Supplied as:
Bonded abrasive rotary instrument.Bonded abrasive rotary instrument.
Flexible metal backed abrasive strips.Flexible metal backed abrasive strips.
Diamond polishing pastes.Diamond polishing pastes.www.indiandentalacademy.com

5. Emery5. Emery
- This abrasive is grayish black corundum that is prepared in- This abrasive is grayish black corundum that is prepared in
a fine grain form.a fine grain form.
- Supplied predominantly as coated abrasive disks.- Supplied predominantly as coated abrasive disks.
- Used for finishing metal alloys or plastic materials.- Used for finishing metal alloys or plastic materials.
6. Garnet –6. Garnet – the term garnet includes several minerals whichthe term garnet includes several minerals which
possess similar physical properties like Silicates of Al, Co,possess similar physical properties like Silicates of Al, Co,
Fe, Mg and Mn.Fe, Mg and Mn.
- Garnet is dark red, extremely hard and when fractured- Garnet is dark red, extremely hard and when fractured
during abrasive abrasive activity forms sharp chisel shapedduring abrasive abrasive activity forms sharp chisel shaped
plates – therefore making Garnet an effective abrasive.plates – therefore making Garnet an effective abrasive.
- Garnet is available on coated disks and Arbor box.- Garnet is available on coated disks and Arbor box.
- Used in grinding metal alloys and plastic materials.- Used in grinding metal alloys and plastic materials.www.indiandentalacademy.com

7. Pumice7. Pumice
- Is produced from volcanic activity.- Is produced from volcanic activity.
- Flour of pumice is an extremely fine grinded volcanic rock- Flour of pumice is an extremely fine grinded volcanic rock
derivative from Italy.derivative from Italy.
- Used in polishing teeth enamel, gold foil, dental amalgam and- Used in polishing teeth enamel, gold foil, dental amalgam and
acrylic resins.acrylic resins.
8. Quartz8. Quartz – the particles are pulverized to form sharp angular– the particles are pulverized to form sharp angular
particles which are useful in making coated disks.particles which are useful in making coated disks.
- Used to finish metal alloys and may be used to grind dental- Used to finish metal alloys and may be used to grind dental
enamel.enamel.
9. Sand9. Sand
- Is a mixture of small mineral particles predominantly silica.- Is a mixture of small mineral particles predominantly silica.
- Particles have rounded to angular shape.- Particles have rounded to angular shape.
- Used to remove refractory investment material from base metal- Used to remove refractory investment material from base metal
castings.castings.
- It is coated on paper disks for grinding of metal alloys and- It is coated on paper disks for grinding of metal alloys and
plastic materials.plastic materials. www.indiandentalacademy.com

10. Tripoli10. Tripoli
- Derived from a light weight, siliceous sedimentary- Derived from a light weight, siliceous sedimentary
rock.rock.
- Could be white, gray, pink, red or yellow.- Could be white, gray, pink, red or yellow.
- Gray and red are most frequently used.- Gray and red are most frequently used.
- Used for finishing metal alloys and some plastic- Used for finishing metal alloys and some plastic
materials.materials.
11. Zirconium silicate11. Zirconium silicate
-- Off white mineral, ground to various sizes used toOff white mineral, ground to various sizes used to
make coated disks and strips.make coated disks and strips.
- Also used as a component of dental prophylaxis- Also used as a component of dental prophylaxis
pastes.pastes. www.indiandentalacademy.com

Under Manufactured Abrasives we have:Under Manufactured Abrasives we have:
1. Silicon Carbide1. Silicon Carbide
-- This is the first of the synthetic abrasive to be developed.This is the first of the synthetic abrasive to be developed.
- Two types were manufactured 1. Green form and 2. Blue- Two types were manufactured 1. Green form and 2. Blue
form. Both are having similar physical properties.form. Both are having similar physical properties.
- However, the green variety is preferred because substrates- However, the green variety is preferred because substrates
are more visible against the green color.are more visible against the green color.
- The cutting efficiency of silicon carbide abrasives is higher- The cutting efficiency of silicon carbide abrasives is higher
as the particles are sharp and break to form new sharpas the particles are sharp and break to form new sharp
particles.particles.
- Supplied as air abrasive in coated disks and vitreous and- Supplied as air abrasive in coated disks and vitreous and
rubber bonded instruments.rubber bonded instruments.
- Used in cutting metal alloys, ceramics and plastic materials.- Used in cutting metal alloys, ceramics and plastic materials.www.indiandentalacademy.com

2. Aluminium Oxide2. Aluminium Oxide
- This is the second synthetic abrasive to be manufactured.- This is the second synthetic abrasive to be manufactured.
- This form of alumina is much harder than its natural- This form of alumina is much harder than its natural
counterpart (CORUNDUM) because of its purity.counterpart (CORUNDUM) because of its purity.
- The forms usually prepared are:- The forms usually prepared are:
a. White stones – made of sintered aluminium oxide area. White stones – made of sintered aluminium oxide are
used for contouring of enamel and finishing metal andused for contouring of enamel and finishing metal and
ceramic materials.ceramic materials.
b. Variations of aluminium oxide include those withb. Variations of aluminium oxide include those with
chromium compound additions, these obtained in pinkchromium compound additions, these obtained in pink
and ruby colours are obtained as vitreous bonded non-and ruby colours are obtained as vitreous bonded non-
contaminating mounted stones – used for preparation ofcontaminating mounted stones – used for preparation of
metal ceramic alloys to receive porcelain.metal ceramic alloys to receive porcelain.

3. Synthetic Diamond – developed in 19553. Synthetic Diamond – developed in 1955..
- Synthetic or manufactured for of diamond is- Synthetic or manufactured for of diamond is
produced at 5 times the level of the naturalproduced at 5 times the level of the natural
diamond abrasive.diamond abrasive.
- This synthetic diamond is used for the- This synthetic diamond is used for the
manufacture of diamond saws, wheels and bursmanufacture of diamond saws, wheels and burs
and also diamond locks employed for truing ofand also diamond locks employed for truing of
bonded abrasives.bonded abrasives.
- Synthetic diamond abrasives are used primarily- Synthetic diamond abrasives are used primarily
on tooth structure, ceramic materials and resinon tooth structure, ceramic materials and resin
based components.based components.

4. Rouge4. Rouge
-- Principle component is iron oxide blended withPrinciple component is iron oxide blended with
various binders.various binders.
- Used to polish high noble metal alloys.- Used to polish high noble metal alloys.
- May be impregnated in paper or fabric known as- May be impregnated in paper or fabric known as
CROCUS CLOTH.CROCUS CLOTH.
5. Tin Oxide5. Tin Oxide
- Is composed of very fine abrasive particles.- Is composed of very fine abrasive particles.
- May be employed in an abrasive paste form along with- May be employed in an abrasive paste form along with
water, alcohol or glycerin.water, alcohol or glycerin.
- Used as a polishing agent for teeth and metallic- Used as a polishing agent for teeth and metallic
restorations.restorations. www.indiandentalacademy.com

REVIEW OF LITERATUREREVIEW OF LITERATURE
1. In 1952,1. In 1952, Lawrence H. ClaymanLawrence H. Clayman described the moderndescribed the modern
techniques for the full crown and plastic faced goldtechniques for the full crown and plastic faced gold
veneer crown preparations using diamond instruments.veneer crown preparations using diamond instruments.
The introduction of diamond cutting instruments intoThe introduction of diamond cutting instruments into
dentistry has been a great aid for crown and bridgedentistry has been a great aid for crown and bridge
prosthesis. Diamond instruments have enabled us toprosthesis. Diamond instruments have enabled us to
prepare teeth faster and have also reduced trauma incidentprepare teeth faster and have also reduced trauma incident
to operative dentistry procedures by cutting moreto operative dentistry procedures by cutting more
efficiently, more quickly, and with less friction andefficiently, more quickly, and with less friction and
resulting heat.resulting heat.
For maximum cutting efficiency, diamond instrumentsFor maximum cutting efficiency, diamond instruments
should be used at high speed with light pressure andshould be used at high speed with light pressure and
should be well lubricated by a continuous stream of water.

2. In 1953,2. In 1953, Edwin S. SmydEdwin S. Smyd mentions the importancementions the importance
of diamond tools in dentistry; diamond tools areof diamond tools in dentistry; diamond tools are
distinct from burs or cutting tools in that they workdistinct from burs or cutting tools in that they work
by a scoring action, that is, each diamond particleby a scoring action, that is, each diamond particle
scrapes off the surface of the object it is abrading toscrapes off the surface of the object it is abrading to
the depth of the diamond protruding from the tool.the depth of the diamond protruding from the tool.
Light pressure minimizes frictional heat.Light pressure minimizes frictional heat.
Experimental studies in Germany indicates thatExperimental studies in Germany indicates that
diamond tools are best used wet or dry in a moistdiamond tools are best used wet or dry in a moist
loose slurry of the abraded material- both too muchloose slurry of the abraded material- both too much
water and dryness should be avoided.water and dryness should be avoided.
Diamond tools are not selective in their grindingDiamond tools are not selective in their grinding
action. They will grind enamel, dentin andaction. They will grind enamel, dentin and
cementum at equal rate.cementum at equal rate.

3. In 1957,3. In 1957, Rex Ingraham,Rex Ingraham, did an evaluation of recentdid an evaluation of recent
progress in the field of increased speeds and modernprogress in the field of increased speeds and modern
instrument design. Increased speeds for the rotaryinstrument design. Increased speeds for the rotary
instruments is one of the newest fields in dentalinstruments is one of the newest fields in dental
science and one involving the most rapid and dramaticscience and one involving the most rapid and dramatic
changes in the history of the profession. The ultrachanges in the history of the profession. The ultra
high speeds (above the threshold of vibrationhigh speeds (above the threshold of vibration
perception) produce a favorable response. Operatingperception) produce a favorable response. Operating
at about 10,000 rpm and above requires only a lightat about 10,000 rpm and above requires only a light
‘feather like’ touch which reduces digital fatigue for‘feather like’ touch which reduces digital fatigue for
the operator. However, it becomes necessary tothe operator. However, it becomes necessary to
operate with much more exactness and a keen visualoperate with much more exactness and a keen visual
sense must be employed to safeguard against over-sense must be employed to safeguard against over-
cutting and inadvertent damage to adjacent toothcutting and inadvertent damage to adjacent tooth
surfaces.surfaces. www.indiandentalacademy.com

4. In 1958,4. In 1958, Allison G. James,Allison G. James, discussed the subject of highdiscussed the subject of high
speeds and concluded that unless steps are taken to bringspeeds and concluded that unless steps are taken to bring
adequate instruction to the vast majority of dentists who areadequate instruction to the vast majority of dentists who are
influenced to use high speed rotary instruments, it may beinfluenced to use high speed rotary instruments, it may be
anticipated that an era of slovenly tooth preparations willanticipated that an era of slovenly tooth preparations will
plague dentistry for some time to come.plague dentistry for some time to come.
5. In 1959,5. In 1959, Edmund V. Street,Edmund V. Street, did a critical evaluation ofdid a critical evaluation of
ultrasonics in dentistry and concluded that pulps of vitalultrasonics in dentistry and concluded that pulps of vital
permanent teeth appear to be unaffected, but operations onpermanent teeth appear to be unaffected, but operations on
children’s teeth should not be attempted until futurechildren’s teeth should not be attempted until future
research indicates no ill effects. The ultrasonic method ofresearch indicates no ill effects. The ultrasonic method of
cutting instruments carious or sound enamel, carious orcutting instruments carious or sound enamel, carious or
sound dentin and certain types of restorative materials doessound dentin and certain types of restorative materials does
not approach the effectiveness that can be demonstratednot approach the effectiveness that can be demonstrated
with the ultra high speed rotational instruments.with the ultra high speed rotational instruments.www.indiandentalacademy.com

6. In 1960,6. In 1960, Alexander Leff,Alexander Leff, did an evaluation of high speed indid an evaluation of high speed in
full coverage preparations. From a practical point of view,full coverage preparations. From a practical point of view,
high speed can be defined as rotational speeds starting at 1,high speed can be defined as rotational speeds starting at 1,
00,000 rpm. This is the beginning range of speed at which00,000 rpm. This is the beginning range of speed at which
tools can be used efficiently with light pressure.tools can be used efficiently with light pressure.
7. In 1965,7. In 1965, Schuchard and Watkins,Schuchard and Watkins, compared the efficiencycompared the efficiency
of rotary cutting instruments.of rotary cutting instruments.
a. Any of the high or low torque rotary cutting equipment willa. Any of the high or low torque rotary cutting equipment will
operate efficiently in its useful range, if properly used.operate efficiently in its useful range, if properly used.
b. The various low torque ultrahigh speed contra angleb. The various low torque ultrahigh speed contra angle
instruments are comparable, and are most efficient at theinstruments are comparable, and are most efficient at the
higher operating air pressures.higher operating air pressures.
c. Simplicity of design and size of equipment are significant inc. Simplicity of design and size of equipment are significant in
evaluation.evaluation.
d. High torque air driven straight hand pieces are not as efficientd. High torque air driven straight hand pieces are not as efficient
as comparable electric driven equipment.as comparable electric driven equipment.www.indiandentalacademy.com

8. In 1970,8. In 1970, Charles Watkins,Charles Watkins, elaborated on the cuttingelaborated on the cutting
effectiveness of rotary instruments in a turbine hand piece andeffectiveness of rotary instruments in a turbine hand piece and
concluded that in enamel, diamond cutting instrumentsconcluded that in enamel, diamond cutting instruments
compare favorably with TC burs. The carbide burs removecompare favorably with TC burs. The carbide burs remove
dentin more rapidly than do the diamond points. Thedentin more rapidly than do the diamond points. The
‘lubricating’ effect of water to enhance the cutting‘lubricating’ effect of water to enhance the cutting
effectiveness of diamonds in not documented in this study.effectiveness of diamonds in not documented in this study.
9. In 1988,9. In 1988, Robert Cooley et al,Robert Cooley et al, did a study on the effect of airdid a study on the effect of air
powder abrasive instrument on porcelain. The effects of an airpowder abrasive instrument on porcelain. The effects of an air
powder abrasive instrument on porcelain were evaluated.powder abrasive instrument on porcelain were evaluated.
Sample disks made from two commercial porcelains and threeSample disks made from two commercial porcelains and three
porcelain strains were treated for 80 seconds with thisporcelain strains were treated for 80 seconds with this
instrument.instrument.
It was recommended that the air powder abrasive instrumentIt was recommended that the air powder abrasive instrument
be used cautiously or not at all on porcelain restorations,be used cautiously or not at all on porcelain restorations,
especially those with staining and / or specificespecially those with staining and / or specific
characterizations.characterizations. www.indiandentalacademy.com

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