Rotary cutting inst rajat /certified fixed orthodontic courses by Indian dental academy

Seminar onSeminar onROTARY CUTTING ROTARY CUTTING INSTRUMENTSINSTRUMENTS

INDIAN DENTAL ACADEMY

Leader in continuing dental education www.indiandentalacademy.com

www.indiandentalacademy.com

INDEXINDEX1. Definitions1. Definitions2. Introduction2. Introduction3. Dental Hand pieces3. Dental Hand pieces4. Improved Cutting Instruments4. Improved Cutting Instruments5. An era of increased speeds and various associated techniques5. An era of increased speeds and various associated techniques6. Care and maintenance of Rotary equipment 6. Care and maintenance of Rotary equipment 7. Water air cooling7. Water air cooling8. 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) Classification9. 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 instrumentation10. Effects of high speed cutting10. Effects of high speed cutting11. Advantages of high speed cutting11. Advantages of high speed cutting12. Disadvantages of high speed cutting12. Disadvantages of high speed cutting13. Abrasion and Polishing Agents13. Abrasion and Polishing Agents14. Review of literature 14. Review of literature 15. Summary15. Summary16. References16. References


The term “Rotary” is applied to tooth The term “Rotary” is applied to tooth cutting instrumentscutting instruments

That turn on axis to perform work, these That turn on axis to perform work, these are the units actually responsible for the are the units actually responsible for the removal of tooth structure, and may be removal of tooth structure, and may be one of two types:one of two types:

Burs; which are cutting tools, and, Stones, Burs; which are cutting tools, and, Stones, which are abrading tools.which are abrading tools.

SPEEDSPEED: Speed is the rate of change of : Speed is the rate of change of position with time (MOSBY’s Dictionary)position with time (MOSBY’s Dictionary)

SpeedSpeed is the magnitude of velocity without is the magnitude of velocity without regard to direction. (Stedman’s regard to direction. (Stedman’s Dictionary)Dictionary) www.indiandentalacademy.com

Classification of SpeedClassification of SpeedAccording 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 CharbenauConventional 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 MARZOUKUltra 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.Ultra or super speed- Above 1, 00,000 rpm.Ultra or super speed- Above 1, 00,000 rpm.


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 instruments that have bladed cutting heads. This includes instruments intended for such purposes or includes instruments intended for such purposes or finishing metal restorations and surgical removal of finishing metal restorations and surgical removal of bone as well as those primarily intended for tooth bone as well as those primarily intended for tooth preparation.preparation.

IntroductionIntroduction

Before considering the tooth preparation, Before considering the tooth preparation, Prosthodontist must be aware of the instruments at Prosthodontist must be aware of the instruments at his disposal so that the most suitable one can be his disposal so that the most suitable one can be used.used.

Teeth are vital organs; therefore they must be treated Teeth are vital organs; therefore they must be treated with consideration. The objectives of the treatment with consideration. The objectives of the treatment given to the patient are to provide oral function, given to the patient are to provide oral function, esthetics, health by restoring teeth and the adjacent esthetics, health by restoring teeth and the adjacent structures. Frequently, the efforts of restorations may structures. Frequently, the efforts of restorations may themselves transform a comfortable tooth into one themselves transform a comfortable tooth into one that is sensitive or pathologicthat is sensitive or pathologic


Dental Hand piecesDental Hand pieces

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

FOOT ENGINEFOOT ENGINE The old spinning wheel and sewing machine probably The old spinning wheel and sewing machine probably

inspired the development of a dental foot engine as a inspired the development of a dental foot engine as a source of power around 1871. Rotation of a cutting source of power around 1871. Rotation of a cutting instrument was made possible by a long belt running over instrument was made possible by a long belt running over a series of pulleys to the back of a straight hand piece. a series of pulleys to the back of a straight hand piece. When the angle hand piece was needed, it could be When the angle hand piece was needed, it could be attached to the shaft of the straight hand piece.attached to the shaft of the straight hand piece.

ELECTRIC ENGINEELECTRIC ENGINE One of the most significant advances in the early history of One of the most significant advances in the early history of

hand piece adoption was the adoption of the electric motor hand piece adoption was the adoption of the electric motor as a power source in 1874.It was incorporated into a as a power source in 1874.It was incorporated into a dental unit in 1914. Hand piece equipment and operating dental unit in 1914. Hand piece equipment and operating speeds and maximum of 5000 revolutions per minute speeds and maximum of 5000 revolutions per minute remained virtually unchanged until 1946.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 is Rotary power from an electric engine is transferred to the straight hand piece by transferred to the straight hand piece by a belt that runs over a series of pulleys a belt that runs over a series of pulleys and a three piece extension cord arm. A and a three piece extension cord arm. A variable rheostat sits on the floor and is variable rheostat sits on the floor and is operated by the foot to control the speed operated by the foot to control the speed of the hand piece. Rotary cutting of the hand piece. Rotary cutting instruments are inserted into a chucking instruments are inserted into a chucking mechanism at the front of the hand piece. mechanism at the front of the hand piece. The electric engine is seldom used as a The electric engine is seldom used as a source of power in a modern dental source of power in a modern dental operatory but is often used in dental operatory but is often used in dental laboratories where low speed and high laboratories where low speed and high torque are desirable.torque are desirable.www.indiandentalacademy.com

IMPROVED CUTTING INSTRUMENTSIMPROVED CUTTING INSTRUMENTS Progress in dental cutting procedures was delayed by a Progress in dental cutting procedures was delayed by a

lack of instruments that could effectively remove hard lack of instruments that could effectively remove hard tooth structures. The steel burs that were used at that tooth structures. The steel burs that were used at that time could not cut enamel effectively even with the time could not cut enamel effectively even with the application of great force. Silicon carbide points, application of great force. Silicon carbide points, sometimes called carborundum stones, were not hard sometimes called carborundum stones, were not hard enough and lost their shape rapidly. Diamond cutting enough and lost their shape rapidly. Diamond cutting instruments were developed in Germany around 1935, but instruments were developed in Germany around 1935, but with the outbreak of World War II and the accompanying with the outbreak of World War II and the accompanying scarcity of labor and materials, very few of these scarcity of labor and materials, very few of these instruments were produced for the duration of the war. It instruments were produced for the duration of the war. It was during this period, when large numbers of men had to was during this period, when large numbers of men had to be treated in a limited amount of time that the need of be treated in a limited amount of time that the need of better and more effective cutting instruments and better and more effective cutting instruments and procedures was dramatized.procedures was dramatized.

In a 10 year period, which started in the latter part of In a 10 year period, which started in the latter part of 1946, cutting techniques were revolutionized. Diamond 1946, cutting techniques were revolutionized. Diamond instruments were produced commercially and were joined instruments were produced commercially and were joined a year later by tungsten carbide burs. For the first time in a year later by tungsten carbide burs. For the first time in dental history, instruments became available that could dental history, instruments became available that could effectively remove hard tooth structure.effectively remove hard tooth structure.


INCREASED SPEEDSINCREASED SPEEDS It was immediately evident that diamond and It was immediately evident that diamond and

carbide instruments performed best at the highest carbide instruments performed best at the highest speeds available and that increased speeds were speeds available and that increased speeds were available for more effective cutting.available for more effective cutting.

Obtaining speeds of 10,000 to 15,000 rpm was a Obtaining speeds of 10,000 to 15,000 rpm was a relatively simple matter. The small pulley on the relatively simple matter. The small pulley on the motor drive shaft was replaced with a larger one, motor drive shaft was replaced with a larger one, while the pulley at the hand piece was reduced in while the pulley at the hand piece was reduced in size. Motor resistors were disconnected so that size. Motor resistors were disconnected so that armature could receive the full line current and armature could receive the full line current and revolve at maximum speeds. In 1949, it was revolve at maximum speeds. In 1949, it was reported that speeds of 60,000 rpm and above were reported that speeds of 60,000 rpm and above were more effective for cutting tooth structure and were more effective for cutting tooth structure and were also above the human threshold of vibration also above the human threshold of vibration perception.perception.

Equipment manufactures continued to make Equipment manufactures continued to make improvements in conventional rotary hand pieces, improvements in conventional rotary hand pieces, but heat, vibration and wear were major problems, but heat, vibration and wear were major problems, especially in the gear mechanism of angle hand especially in the gear mechanism of angle hand pieces. In the mean time two non-rotary industrial pieces. In the mean time two non-rotary industrial cutting methods, air abrasive technique and cutting methods, air abrasive technique and ultrasonics were applied in dentistry.ultrasonics were applied in dentistry.


AIRBRASIVE TECHNIQUEAIRBRASIVE TECHNIQUE

The air abrasive technique was made The air abrasive technique was made available to the dental profession in 1951. available to the dental profession in 1951. The principal involves the use of powered The principal involves the use of powered abrasive particles (aluminum oxide) and abrasive particles (aluminum oxide) and kinetic energy (mass in motion). Hard kinetic energy (mass in motion). Hard tooth structures can be reduced without tooth structures can be reduced without perceptible vibration, pressure or heat by a perceptible vibration, pressure or heat by a stream of abrasive particles traveling at a stream of abrasive particles traveling at a high velocity. This technique received high velocity. This technique received widespread interest.widespread interest.

AdvantagesAdvantages Patient acceptance was excellent.Patient acceptance was excellent. No significant pulp reaction was reported.No significant pulp reaction was reported.www.indiandentalacademy.com

The air abrasive technique never became The air abrasive technique never became popular with the dental profession.popular with the dental profession.

DisadvantagesDisadvantages Use was limited to areas of good vision Use was limited to areas of good vision

because there was no sense of touch b/n the because there was no sense of touch b/n the hand-piece and the tooth to act as a guide hand-piece and the tooth to act as a guide while cutting.while cutting.

Precise angles and margins were difficult to Precise angles and margins were difficult to obtain and the operator had to return to hand obtain and the operator had to return to hand or rotary instruments for finishing procedures.or rotary instruments for finishing procedures.

Surface of an ordinary mirror was rendered Surface of an ordinary mirror was rendered useless in a short period by rebounding useless in a short period by rebounding abrasive particles.abrasive particles.

Spent dust was not effectively removed by a Spent dust was not effectively removed by a large noisy suction apparatus.large noisy suction apparatus.

Possibility of lung damage by inhalation of the Possibility of lung damage by inhalation of the abrasive particles was investigated but not abrasive particles was investigated but not found to be a major health hazard.found to be a major health hazard.


UltrasonicsUltrasonicsAnother non-rotary (instrument) industrial cutting Another non-rotary (instrument) industrial cutting method known as ultrasonics was adapted for dental use method known as ultrasonics was adapted for dental use around 1952. Hard tooth structure can be removed by around 1952. Hard tooth structure can be removed by vibrating a slurry of abrasive particles (aluminum oxide) vibrating a slurry of abrasive particles (aluminum oxide) against the surface to be reduced with various sizes and against the surface to be reduced with various sizes and shapes of preformed instrument tips. Principle involves shapes of preformed instrument tips. Principle involves the conversion of alternating current into high the conversion of alternating current into high frequency mechanical vibrations in a phenomenon of frequency mechanical vibrations in a phenomenon of magnetostriction. The movements of the working tip, magnetostriction. The movements of the working tip, back and forth approximately 29, 000 times per second back and forth approximately 29, 000 times per second with a thrust of 0.0016” can not be detected by the with a thrust of 0.0016” can not be detected by the operator or the patient.operator or the patient.

AdvantagesAdvantages1. 1. Precise smooth cuts of predetermined shapes and Precise smooth cuts of predetermined shapes and

sizes can be made without the annoyance factor sizes can be made 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 Tactile control of the instrument is somewhat

improved over the air abrasive technique.improved over the air abrasive technique.www.indiandentalacademy.com

DisadvantagesDisadvantages Use of preshaped working point is Use of preshaped working point is

limiting because anatomy and carious limiting because anatomy and carious areas of areas of

individual teeth vary greatly.individual teeth vary greatly. Interchanging the points was a relatively Interchanging the points was a relatively

time consuming process.time consuming process. Cutting rate was slow especially in a Cutting rate was slow especially in a

lateral direction.lateral direction. Visibility was obscured because of the Visibility was obscured because of the

accumulation of slurry.accumulation of slurry. Caries and resilient filing materials such Caries and resilient filing materials such

as gold could not be removed effectively.as gold could not be removed effectively. Maintenance problems resulted from Maintenance problems resulted from

complicated mechanism of operation.complicated mechanism of operation.www.indiandentalacademy.com

BELT DRIVEN BELT DRIVEN HANDPIECESHANDPIECES A belt driven angle hand piece called the page A belt driven angle hand piece called the page

chayres became available in 1955. It was the chayres became available in 1955. It was the first angle hand piece to operate successfully at first angle hand piece to operate successfully at speeds of 1, 00, 000 rpm and was attached to a speeds of 1, 00, 000 rpm and was attached to a conventional dental unit with an electric motor conventional dental unit with an electric motor as a source of power. It was a very popular angle as a source of power. It was a very popular angle hand piece and several versions of this design hand piece and several versions of this design were marketed commercially.were marketed commercially.

AdvantagesAdvantages Free of maintenance problems.Free of maintenance problems.

Disadvantages Disadvantages Many moving parts.Many moving parts. Objectionable high pitched noise during Objectionable high pitched noise during

operation.operation. www.indiandentalacademy.com

WATER TURBINE WATER TURBINE HANDPIECESHANDPIECES A major break through in the development of rotary A major break through in the development of rotary

equipment for increased speeds came with the equipment for increased speeds came with the elimination of the gear and the belt driven sections of elimination of the gear and the belt driven sections of the angle hand piece. In 1933 a hydraulic driven turbine the angle hand piece. In 1933 a hydraulic driven turbine angle hand piece was reported to operate satisfactorily angle hand piece was reported to operate satisfactorily at 60, 000 rpm and was marketed 2 years later. The at 60, 000 rpm and was marketed 2 years later. The Turbo-Jet was designed as a compact mobile unit that Turbo-Jet was designed as a compact mobile unit that required no outside plumbing or air connections. Only a required no outside plumbing or air connections. Only a source of electricity was needed to operate the unit. source of electricity was needed to operate the unit.

Improved models had both straight and angle hand Improved models had both straight and angle hand pieces that could operate at speeds up to 1, 00,000 rpm.pieces that could operate at speeds up to 1, 00,000 rpm.

ADVANTAGEADVANTAGE 1. 1. Rotary instruments had a threshold shank to Rotary instruments had a threshold shank to

ensure concentricity when attached to shaft of the ensure concentricity when attached to shaft of the turbine.turbine.

DISADVANTAGEDISADVANTAGE1. 1. Changing the instruments was time consuming and Changing the instruments was time consuming and

carbide burs did not perform well with water turbine carbide burs did not perform well with water turbine hand piece.hand piece.


AIR TURBINE HAND AIR TURBINE HAND PIECESPIECES In the later part of 1956 the first clinically successful air In the later part of 1956 the first clinically successful air

driven turbine hand pieces became available with free driven turbine hand pieces became available with free running speeds of approximately 3,00,000 rpm.running speeds of approximately 3,00,000 rpm.

Early models were attached to a conventional dental unit Early models were attached to a conventional dental unit and consisted of a hand piece, control box, foot control, and consisted of a hand piece, control box, foot control, various connector hoses and a source of compressed air. various connector hoses and a source of compressed air. When the foot control was activated, compressed air flowed When the foot control was activated, compressed air flowed to the control box and was carried by a flexible hose to the to the control box and was carried by a flexible hose to the back of the hand piece. From there the air was directed to back of the hand piece. From there the air was directed to the head of the hand piece through a metal tube and was the head of the hand piece through a metal tube and was blown against the blades of a small turbine to produce blown against the blades of a small turbine to produce rotation. Some of the spent air was expelled at the head of rotation. Some of the spent air was expelled at the head of the hand piece, while the greater part was exhausted at the the hand piece, while the greater part was exhausted at the back of the hand piece or returned to the control box. back of the hand piece or returned to the control box. Cutting instruments were inserted into the shaft of the Cutting instruments were inserted into the shaft of the turbine and held by friction grip.turbine and held by friction grip.

Although most air turbine angle hand pieces have free Although most air turbine angle hand pieces have free running speeds of approximately 3, 00, 000 rpm, it should running speeds of approximately 3, 00, 000 rpm, it should be noted that this speed drops to approximately 1, 60, 000 be noted that this speed drops to approximately 1, 60, 000 rpm with a lateral work load of two ounces.rpm with a lateral work load of two ounces.


The reason for this is that air turbines have low torque and The reason for this is that air turbines have low torque and will stall at lateral work loads of approximately 4 to 6 ounces. will stall at lateral work loads of approximately 4 to 6 ounces. This is an excellent safety feature, since excessive pressure This is an excellent safety feature, since excessive pressure can not be applied easily to the cutting instrument.can not be applied easily to the cutting instrument.

The application of the turbine principle to the straight hand The application of the turbine principle to the straight hand piece eliminated the necessity of having an electric engine as piece eliminated the necessity of having an electric engine as part of a standard dental unit. This greatly simplified the part of a standard dental unit. This greatly simplified the design and construction of present day dental units. The design and construction of present day dental units. The design of the straight hand piece turbine provided the design of the straight hand piece turbine provided the desirable high torque for low speed operation.desirable high torque for low speed operation.

Air bearings have been used instead of ball bearings to Air bearings have been used instead of ball bearings to support the turbine shaft in some air turbine angle hand support the turbine shaft in some air turbine angle hand pieces. By having the turbine suspended in air and rotated by pieces. By having the turbine suspended in air and rotated by air, practically all friction is eliminated and speeds may be air, practically all friction is eliminated and speeds may be increased to over 8, 00, 000rpm. It is not worthy that hand increased to over 8, 00, 000rpm. It is not worthy that hand pieces using this design operated only at full speed and at this pieces using this design operated only at full speed and at this speed the dentist was handicapped by virtually no sense of speed the dentist was handicapped by virtually no sense of touch. touch.

Thus desirable control was reduced, and over cutting often Thus desirable control was reduced, and over cutting often resulted. The hand piece was very quiet in operation. High resulted. The hand piece was very quiet in operation. High costs, maintenance problems and the lack of variable speed costs, maintenance problems and the lack of variable speed kept this design from becoming widely used.kept this design from becoming widely used.

Air driven hand pieces have been and continue to be the most Air driven hand pieces have been and continue to be the most popular type of hand piece equipment because of the over all popular type of hand piece equipment because of the over all simplicity of design, ease of control, versatility and patient simplicity of design, ease of control, versatility and patient acceptance.acceptance.


CARE AND MAINTENANCE OF CARE AND MAINTENANCE OF ROTARY EQUIPMENTROTARY EQUIPMENT

Rotary cutting or polishing instruments should Rotary cutting or polishing instruments should never be left in the hand piece between never be left in the hand piece between patients or over night. Some of these patients or over night. Some of these instruments have steel shanks that may corrode instruments have steel shanks that may corrode in the metal chucking system of the hand piece. in the metal chucking system of the hand piece. When cutting instruments become worn, dull, When cutting instruments become worn, dull, bent or broken, they should be discarded. Such bent or broken, they should be discarded. Such instruments do not operate efficiently and instruments do not operate efficiently and cause added trauma to the tissue. cause added trauma to the tissue.

Dental hand pieces are expensive and must Dental hand pieces are expensive and must receive the utmost care to ensure peak receive the utmost care to ensure peak performance, to prolong their life and to reduce performance, to prolong their life and to reduce overhead costs.overhead costs. www.indiandentalacademy.com

WATER AIR COOLING:WATER AIR COOLING: With high speed instrumentation, the problem of over With high speed instrumentation, the problem of over

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


The use of water spray does not in itself guarantee that the The use of water spray does not in itself guarantee that the pulp will be protected from damage. A low quantity of water, pulp will be protected from damage. A low quantity of water, poorly directed, will result in a weak spray that can permit poorly directed, will result in a weak spray that can permit localized dentinal scorching. A small orifice that produces a localized dentinal scorching. A small orifice that produces a higher water velocity is more likely to allow penetration of higher water velocity is more likely to allow penetration of the air vortex around the instrument tip.the air vortex around the instrument tip.

A water spray also increases the efficiency of high speed A water spray also increases the efficiency of high speed rotary instruments by cutting the cutting edges washed rotary instruments by cutting the cutting edges washed clean of debris. Eames et al. found that a greater flow of clean of debris. Eames et al. found that a greater flow of water coolant is required to prevent clogging when water coolant is required to prevent clogging when diamonds are used under increased pressure. Diamond diamonds are used under increased pressure. Diamond stones used under high pressure (150 gm) became more stones used under high pressure (150 gm) became more effective as the water flow rate increased from 3 to 21 effective as the water flow rate increased from 3 to 21 ml/min. If light pressure was used (50 gm), there was still an ml/min. If light pressure was used (50 gm), there was still an increase in effectiveness, but it leveled off after the flow rate increase in effectiveness, but it leveled off after the flow rate reached 7 ml/min.reached 7 ml/min.

The spray enhances visibility in many instances by flushing The spray enhances visibility in many instances by flushing away blood and debris. Even indirect vision can be utilized away blood and debris. Even indirect vision can be utilized while cutting wet, if the mirror is first coated with a film of while cutting wet, if the mirror is first coated with a film of detergent. This allows the water to form a smooth detergent. This allows the water to form a smooth transparent film on the surface of the mirror with only a transparent film on the surface of the mirror with only a moderate decrease in visibility. moderate decrease in visibility. www.indiandentalacademy.com

DENTAL CUTTING BURSDENTAL CUTTING BURS 1. 1. Composition and manufactureComposition and manufacture: Dental Burs can : Dental Burs can

be classified by their composition into two types:be classified by their composition into two types: (a). (a). Steel bursSteel burs: Steel burs are cut from blank steel : Steel burs are cut from blank steel

stock by means of a rotary cutter that cuts stock by means of a rotary cutter that cuts parallel to the long axis of the bur. The bur is then parallel to the long axis of the bur. The bur is then hardened and tempered until its Vicker’s hardened and tempered until its Vicker’s hardness number is approximately 800.hardness number is approximately 800.

(b).(b).Tungsten carbide bursTungsten carbide burs: Tungsten carbide burs : Tungsten carbide burs are best for making precise preparation features are best for making precise preparation features and smooth surfaces in enamel or dentin. A and smooth surfaces in enamel or dentin. A logical application of their planning capability is logical application of their planning capability is the production of smooth finish lines. Carbide the production of smooth finish lines. Carbide burs can also be used to cut through metal, while burs can also be used to cut through metal, while both carbide burs and diamonds can be used to both carbide burs and diamonds can be used to cut sound dentin.cut sound dentin.


The metal in the head of the carbide bur is formed by The metal in the head of the carbide bur is formed by sinteringsintering, or , or pressure molding, tungsten carbide powder and cobalt powder pressure molding, tungsten carbide powder and cobalt powder under heat and vacuum. The tungsten carbide is cut into small under heat and vacuum. The tungsten carbide is cut into small cylinders and then attached to steel rods by soldering or welding cylinders and then attached to steel rods by soldering or welding to form blanks. The tungsten carbide head is machined with large to form blanks. The tungsten carbide head is machined with large diamond disks to create the specific head for the type of bur being diamond disks to create the specific head for the type of bur being formed. The attachment of the carbide bur is quite secure, and formed. The attachment of the carbide bur is quite secure, and loss of the carbide portion of the bur is rare. Only when the loss of the carbide portion of the bur is rare. Only when the process has been completed is the shank of the instrument process has been completed is the shank of the instrument shortened, notched, or diminished in diameter to make a straight shortened, notched, or diminished in diameter to make a straight hand piece, latch, or friction grip bur.hand piece, latch, or friction grip bur.

Most burs intended primarily for cutting are made with six and Most burs intended primarily for cutting are made with six and occasionally eight blades. Those burs made for finishing usually occasionally eight blades. Those burs made for finishing usually have 12 blades, but they can have 20, or even as many as 40.have 12 blades, but they can have 20, or even as many as 40.

Several carbide burs of specific shapes are included in the Several carbide burs of specific shapes are included in the standard armamentarium. These include at least 2 tapered standard armamentarium. These include at least 2 tapered fissured burs, long and standard length, an end cutting bur and a fissured burs, long and standard length, an end cutting bur and a friction grip no. 4 round bur. For removal of deep caries a low friction grip no. 4 round bur. For removal of deep caries a low speed hand piece no. 6 round bur is used so that sound dentin can speed hand piece no. 6 round bur is used so that sound dentin can be distinguished from softer carious dentin by its greater 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 Tapered fissure burs have a number of uses in preparing teeth for cast metal and porcelain restorations. In addition to the placement cast metal and porcelain restorations. In addition to the placement of grooves, box forms, and isthmuses, they are especially useful for of grooves, box forms, and isthmuses, they are especially useful for planning vertical axial surfaces. There are a number of tapered planning vertical axial surfaces. There are a number of tapered finishing burs whose greater length and diameter make them finishing burs whose greater length and diameter make them suited better for this task, the commonly used sizes are shown in suited better for this task, the commonly used sizes are shown in the figure below:the figure below:



2. 2. General design of General design of Dental BursDental Burs: :

The dental bur is a The dental bur is a small milling small milling (cutting) instrument. (cutting) instrument. A common design is A common design is displayed in the displayed in the figure underneath:figure underneath:


Bur toothBur tooth: :

This terminates in the cutting This terminates in the cutting edge, or blade. It has two edge, or blade. It has two surfaces, the tooth face, which surfaces, the tooth face, which is the side of the tooth on the is the side of the tooth on the leading edge; and the back or leading edge; and the back or flank of the tooth, which is the flank of the tooth, which is the side of the tooth on the trailing side of the tooth on the trailing edge.edge.


Rake angleRake angle: The rake angle is the angle that the face : The rake angle is the angle that the face of the bur tooth makes with the radial line from of the bur tooth makes with the radial line from the centre of the bur to the blade. This angle can the centre of the bur to the blade. This angle can be negative if the face is beyond or leading the be negative if the face is beyond or leading the radial line (referring to the direction of rotation). radial line (referring to the direction of rotation). It can be 0 if the radial line and the tooth face It can be 0 if the radial line and the tooth face coincide with each other (radial rake angle). The coincide with each other (radial rake angle). The angle can also be positive if the radial line leads angle can also be positive if the radial line leads the face, so that the rake angle is on the inside of the face, so that the rake angle is on the inside of the radial line. The more positive the rake angle the radial line. The more positive the rake angle the more acute the edge of the blade, and more the more acute the edge of the blade, and more effective the cutting action. A positive rake angle, effective the cutting action. A positive rake angle, unfortunately, also has a weaker edge. Therefore, unfortunately, also has a weaker edge. Therefore, the blades are usually made with either negative the blades are usually made with either negative or neutral (radial) rake angles, and wider bases. or neutral (radial) rake angles, and wider bases. These are slightly less efficient for cutting, but These are slightly less efficient for cutting, but because of their greater bulk they are less likely 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 : The angle between the back of the tooth and the work. If a land is back of the tooth and the work. If a land is present on the bur, the clearance angle is present on the bur, the clearance angle is divided into: primary clearance which is the divided into: primary clearance which is the angle the land will make with work, and angle the land will make with work, and secondary clearance, which is the angle secondary clearance, which is the angle between the back of the bur tooth and work. between the back of the bur tooth and work. When the back surface of the tooth is curved, When the back surface of the tooth is curved, the clearance is called radial clearance. the clearance is called radial clearance. There is an optimum clearance angle for There is an optimum clearance angle for each diameter of bur, and the larger the each diameter of bur, and the larger the diameter, the smaller the clearance angle diameter, the smaller the clearance angle that is required. The smaller the clearance that is required. The smaller the clearance angle, the stronger the cutting blade. angle, the stronger the cutting blade. However, if the angle becomes too small, the However, if the angle becomes too small, the back of the blade may rub against the cut back of the blade may rub against the cut surface, generating heat and decreasing surface, generating heat and decreasing efficiency.efficiency.



Tooth angleTooth angle: This is measured between the : This is measured between the face and back. If a land is present, it is face and back. If a land is present, it is measured between the face and land.measured between the face and land.

Flute or chip spaceFlute or chip space: The space between : The space between successive teeth, which are the grooves successive teeth, which are the grooves between the blades the amount of spiral, or between the blades the amount of spiral, or helical angle, of the blades affects the helical angle, of the blades affects the cutting characteristics of the bur. A greater cutting characteristics of the bur. A greater helical angle produces a smoother surface helical angle produces a smoother surface on the preparation, and reduces the on the preparation, and reduces the “chatter,” or vibration of the bur on the “chatter,” or vibration of the bur on the tooth surface. This also reduces chipping of tooth surface. This also reduces chipping of the tungsten carbide during use on a tooth, the tungsten carbide during use on a tooth, and it prevents debris from clogging the and it prevents debris from clogging the flutes between the blades.flutes between the blades.

The number of teeth in dental cutting burs The number of teeth in dental cutting burs is usually 6-8.is usually 6-8.


Every bur will have Every bur will have three partsthree parts: The head: The head –The portion carrying –The portion carrying the cutting blades.the cutting blades.

The shankThe shank-The -The portion connecting portion connecting the head to the the head to the attachment part, and attachment part, and the the

Shaft Shaft or the or the attachment part- The attachment part- The portion which will be portion which will be engaged within the engaged within the hand piece.hand piece.


CLASSIFICATIONCLASSIFICATION1. 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 type2. 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 bur3. They can also be classified as right and left. The most 3. They can also be classified as right and left. The most

common ones are the right, which cut when they revolve common ones are the right, which cut when they revolve clockwise.clockwise.

4. According to the length of the head:4. According to the length of the head:-Long-Long-Short-Short-Regular-Regular5. According to the function:5. According to the function:-Cutting burs-Cutting burs-Finishing and polishing burs-Finishing and polishing burswww.indiandentalacademy.com

DIAMOND ABRASIVE DIAMOND ABRASIVE INSTRUMENTSINSTRUMENTS The second major category of rotary dental cutting The second major category of rotary dental cutting

instruments involve abrasives rather then blade instruments involve abrasives rather then blade cutting. Abrasive instruments are generally cutting. Abrasive instruments are generally grouped as diamond or other instruments. grouped as diamond or other instruments. Diamond instruments for dental use were 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 These diamond instruments are nothing but small angular particles of diamond held in a matrix of angular particles of diamond held in a matrix of softer material. The diamond employed is softer material. The diamond employed is industrial diamonds either natural or synthetic that industrial diamonds either natural or synthetic that have been crushed to powder and then carefully 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 Diamond particle size is commonly categorized as coarse (125 to 150um) medium (88 to 125 um) fine coarse (125 to 150um) medium (88 to 125 um) fine (60 to 74um) and very fine (38 to 44 um).(60 to 74um) and very fine (38 to 44 um).www.indiandentalacademy.com

Color coding is done Color coding is done depending on the particle size depending on the particle size

i.e.,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 The particle size used by four major U.S. dental firms is major U.S. dental firms is compared by both U.S. Mesh- compared by both U.S. Mesh- Standard and equivalent metric Standard and equivalent metric size. size.



Manufacturing of Diamond Manufacturing of Diamond AbrasiveAbrasive Abrasive particles are held together by means of a Abrasive particles are held together by means of a

“binder” (base) of variable nature. A ceramic binder “binder” (base) of variable nature. A ceramic binder is used in many cases particularly for binding is used in many cases particularly for binding diamond chips. Also, an electroplating process diamond chips. Also, an electroplating process providing a metallic binder may be used. For soft providing a metallic binder may be used. For soft grade stone, rubber or shellac may be used. Sintered grade stone, rubber or shellac may be used. Sintered types are strongest because abrasive particles are types are strongest because abrasive particles are fused together.fused together.

The type of binder is intimately related to the life of The type of binder is intimately related to the life of the tool in use with most abrasives, the binder is the tool in use with most abrasives, the binder is impregnated through out with abrasive particles of impregnated through out with abrasive particles of certain grade so that as a particle is wrenched from certain grade so that as a particle is wrenched from the binder during use; another will take its place as the binder during use; another will take its place as binder wears. Eames et al. found that they cut tooth 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 the They are deposited in one to three layers on the surface of the instrument. The best diamond surface of the instrument. The best diamond stones have abrasive particles evenly spaced stones have abrasive particles evenly spaced over the surface of the instrument. There also over the surface of the instrument. There also should be intimate contact between the chips should be intimate contact between the chips and the binding material.and the binding material.

While there are many shapes and sizes of While there are many shapes and sizes of diamonds to be used for special applications and diamonds to be used for special applications and to suit the taste of every operator, there are a to suit the taste of every operator, there are a few diamond stones which should be included in few diamond stones which should be included in a basic set of instruments: the round-end a basic set of instruments: the round-end tapered, flat-end tapered, long-needle, short-tapered, flat-end tapered, long-needle, short-needle, and small round-edge wheel diamonds. needle, and small round-edge wheel diamonds. Two other diamonds also commonly used, the Two other diamonds also commonly used, the torpedo and flame, are frequently paired with torpedo and flame, are frequently paired with carbide burs of matching shapes. Figures and carbide burs of matching shapes. Figures and dimensions for these instruments are shown dimensions for these instruments are shown below:below: www.indiandentalacademy.com


According to their shapes According to their shapes and sizes they can be and sizes they can be

classified as:classified as: ((a)Flat ended a)Flat ended

tapered diamond tapered diamond cylindercylinder: It is used : It is used for bulk axial and for bulk axial and occlusal reduction and occlusal reduction and shoulder preparation shoulder preparation on PJC and PFM tooth on PJC and PFM tooth preparations. End preparations. End cutting burs are also cutting burs are also used to develop and used to develop and lower shoulder lower shoulder preparation. They are preparation. They are kept perpendicular to kept perpendicular to the plane being the plane being reduced.reduced.


(b) (b) Straight cylinder Straight cylinder diamond with a diamond with a tapered pointtapered point: A : A suitable instrument suitable instrument for chamfer placement for chamfer placement is a Tinker diamond; a is a Tinker diamond; a straight cylinder with straight cylinder with a tapered point. This a tapered point. This tapered point creates tapered point creates a chamfer with a chamfer with greater control then greater control then the round-end tapered the round-end tapered diamond. It is usually diamond. It is usually indicated for molars.indicated for molars.


c)Twelve fluted c)Twelve fluted carbide bur:carbide bur: It It is a smooth is a smooth cutting cutting instrument and instrument and gives a highly gives a highly finished surface finished surface to a preparation. to a preparation. The greater the The greater the number of blades number of blades on a bur, the on a bur, the smoother the cut.smoother the cut.


((d)Round-ended d)Round-ended tapered diamond tapered diamond cylinders:cylinders: They are They are available in various available in various sizes. They are used for sizes. They are used for axial and occlusal axial and occlusal reduction and reduction and developing chamfer developing chamfer margins. Less than half margins. Less than half the diameter of the tip the diameter of the tip is used for chamfer is used for chamfer margins. Cutting to a margins. Cutting to a depth greater then one-depth greater then one-half the diameter of the half the diameter of the tip produces a shoulder.tip produces a shoulder.


((e)Round diamonds:e)Round diamonds: They facilitate They facilitate establishing depth establishing depth grooves before grooves before reduction. They vary in reduction. They vary in size and are measured size and are measured to determine the cut to determine the cut depth. They are also depth. They are also used to establish rest used to establish rest seats and reduce seats and reduce lingual surfaces of lingual surfaces of anterior teeth. They anterior teeth. They are numbered from ¼, are numbered from ¼, ½, 1, 2 to 10.½, 1, 2 to 10.


((f)Round f)Round diamond wheels diamond wheels (donut):(donut): They They are gross are gross reduction reduction instruments and instruments and also used in also used in anterior teeth anterior teeth lingual lingual reductions. They reductions. They are numbered as are numbered as 14 and 15.14 and 15.


(g)Oblong (g)Oblong diamonds diamonds (football):(football): Variously shaped Variously shaped football diamonds football diamonds are available for are available for lingual reduction lingual reduction of anterior teeth. of anterior teeth. They are available They are available in sizes that in sizes that uniformly reduce uniformly reduce the foosae.the foosae.


((h)Thin tapered h)Thin tapered diamond cones diamond cones (needle):(needle): Thin Thin tapered cones are tapered cones are used for proximal used for proximal slices to isolate slices to isolate teeth from adjacent teeth from adjacent teeth. They tend to teeth. They tend to lose their sharpness lose their sharpness sooner than coarse sooner than coarse diamonds and are diamonds and are replaced replaced frequently.frequently.


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


((j)Cross cut fissure j)Cross cut fissure burs:burs: They come in They come in varying sizes and are varying sizes and are numbered from numbered from 555,556 to 560, both 555,556 to 560, both tapered and tapered and cylindrical. The cylindrical. The tapered burs are tapered burs are used for groove used for groove placement in three placement in three quarter crowns, quarter crowns, flutes, and for seating flutes, and for seating grooves in complete grooves in complete gold crowns.gold crowns.


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


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


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


((n) Mounted green n) Mounted green and white stones and white stones (low speed):(low speed): Various Various mounted green and mounted green and white stones exist for white stones exist for straight and straight and contraangle hand contraangle hand pieces. They are not pieces. They are not for high speeds. They for high speeds. They can be altered by can be altered by grinding against a grinding against a coarse/heatless stone. coarse/heatless stone. White stones have a White stones have a finer texture than finer texture than green stones and are green stones and are preferable.preferable.


(o) Sand paper (o) Sand paper discs:discs: Sand paper Sand paper discs of various discs of various grits are excellent grits are excellent in finishing in finishing marginal areas of marginal areas of castings while castings while maintaining maintaining contours. They contours. They may also be used may also be used in finishing tooth in finishing tooth preparations.preparations.


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


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


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


((s) Robinson brushes s) Robinson brushes (laboratory):(laboratory): Robinson brushes Robinson brushes (stiff, medium, soft) (stiff, medium, soft) are used with pumice are used with pumice or tripoli. Slow speed or tripoli. Slow speed with pressure with pressure produces greater produces greater cutting potential; cutting potential; high speed with light high speed with light pressure produces a pressure produces a high-lustre finish.high-lustre finish.


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


Diamond/bur dual Diamond/bur dual instrumentation: instrumentation: Diamonds remove tooth structure more efficiently Diamonds remove tooth structure more efficiently

than do burs, but they leave undesirably rough than do burs, but they leave undesirably rough surfaces and irregular cavosurface finish lines. surfaces and irregular cavosurface finish lines. Tungsten carbide burs produce smooth finish lines Tungsten carbide burs produce smooth finish lines and precise internal features, but they cut more and precise internal features, but they cut more slowly. Therefore, to take advantage of the best slowly. Therefore, to take advantage of the best features of both types of instrument, diamonds should features of both types of instrument, diamonds should be used for the bulk reduction and carbide burs for be used for the bulk reduction and carbide burs for finishing the preparation and placing internal finishing the preparation and placing internal features such as grooves, box forms, isthmuses, etc.features such as grooves, box forms, isthmuses, etc.

The technique of choice in this situation utilizes The technique of choice in this situation utilizes diamonds and carbide burs of matching size and diamonds and carbide burs of matching size and configuration as described by configuration as described by Lustig.Lustig. These These instruments are manufactured by making both the instruments are manufactured by making both the diamond and bur from a common blank configuration. diamond and bur from a common blank configuration. This assumes that the shape of the instrument and This assumes that the shape of the instrument and the resultant contour of the tooth will match exactly the resultant contour of the tooth will match exactly when the diamond and carbide finishing bur are used when the diamond and carbide finishing bur are used for each step of the preparation.for each step of the preparation.www.indiandentalacademy.com


EFFECTS OF HIGH SPEED EFFECTS OF HIGH SPEED CUTTINGCUTTING ENAMEL:ENAMEL:

Enamel is composed of 92% mineral and 8% of Enamel is composed of 92% mineral and 8% of organic material and water. It is recognized as the organic material and water. It is recognized as the hardest human tissue. The basic structure of enamel hardest human tissue. The basic structure of enamel is mushroom shaped enamel rod, which begins at the is mushroom shaped enamel rod, which begins at the dentinoenamel junction and ends at enamel surface. dentinoenamel junction and ends at enamel surface. Usually enamel originates at right angles to the dentin Usually enamel originates at right angles to the dentin surface and follows a spiral pattern towards the surface and follows a spiral pattern towards the surface ending at near right angles to the surface.surface ending at near right angles to the surface.

Eccentric burs that do not run true in the high-speed Eccentric burs that do not run true in the high-speed hand piece can produce crazing of the enamel. hand piece can produce crazing of the enamel. Crazing can also be brought about by internal Crazing can also be brought about by internal stresses, such as might be induced by thermal stresses, such as might be induced by thermal changes or a retentive pin i.e., angled outward and 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. Dentin is composed of 65% inorganic material.

The remaining 35% is organic matter and water, The remaining 35% is organic matter and water, which allows it to be cut more readily than enamel which allows it to be cut more readily than enamel with a dental bur. Dentin is organized in the form with a dental bur. Dentin is organized in the form of tubules that are supported by calcified network of tubules that are supported by calcified network of collagen fibers. The tubules contain the living of collagen fibers. The tubules contain the living extensions of the odontoblasts whose cell bodies extensions of the odontoblasts whose cell bodies are in the periphery of the pulp.are in the periphery of the pulp.

Crown preparations involve the exposure of Crown preparations involve the exposure of dentinal tubules, cutting of odontoblast processes. dentinal tubules, cutting of odontoblast processes. Generation of heat, desiccation and pressure. The Generation of heat, desiccation and pressure. The deeper the dentin is cut, more severly deeper the dentin is cut, more severly odontoblasts may be damaged. If the water odontoblasts may be damaged. If the water coolant does not reach the interface between the coolant does not reach the interface between the cutting instrument and the tooth surface in the cutting instrument and the tooth surface in the crown preparation a surface “dentin burn” lesion crown preparation a surface “dentin burn” lesion will occur. The odontoblast destruction will be will occur. The odontoblast destruction will be extensive.extensive.


PULPPULP The pulp of a tooth is unique among other body tissues or The pulp of a tooth is unique among other body tissues or

organs. It is very small, but it is able to fulfill sensory and organs. It is very small, but it is able to fulfill sensory and nutritional functions for a tooth. It also forms additional nutritional functions for a tooth. It also forms additional dentin and form provides a defense against infection. The dentin and form provides a defense against infection. The pulp responds very quickly to external stimuli and the pulp responds very quickly to external stimuli and the response depends on the severity of the stimuli.response depends on the severity of the stimuli.

The degree of pulp reaction is proptionately increased in The degree of pulp reaction is proptionately increased in direct relation to the depth and particularly the direct relation to the depth and particularly the extensiveness of crown preparation.extensiveness of crown preparation.

If the odontoblasts are injured primarily by desiccation, If the odontoblasts are injured primarily by desiccation, the disintegration products of these cells will act as an the disintegration products of these cells will act as an irritant and cause an inflammatory response in the pulp in irritant and cause an inflammatory response in the pulp in that area where cut dentinal tubules terminate. When that area where cut dentinal tubules terminate. When there is dentin burn odontoblast destruction will be there is dentin burn odontoblast destruction will be extensive.extensive.

Photo and Schenin (1958) showed if pulp temperature Photo and Schenin (1958) showed if pulp temperature was raised above 46 degree C irreversible changes such was raised above 46 degree C irreversible changes such as stasis and thrombosis could occur in the pulp. Drying as stasis and thrombosis could occur in the pulp. Drying the tooth with a constant air blowing also cause the tooth with a constant air blowing also cause irreversible pulp damage, even if the cavity is prepared irreversible pulp damage, even if the cavity is prepared under sufficient water coolant. Therefore the preparation under sufficient water coolant. Therefore the preparation should be dried with careful blasts of air at short duration should be dried with careful blasts of air at short duration and with sterile cotton after preparation.and with sterile cotton after preparation.


Advantages of high speed Advantages of high speed cuttingcutting

1. Increased cutting efficiency.1. Increased cutting efficiency.

2. Faster tooth removal, hence less pressure, less 2. Faster tooth removal, hence less pressure, less vibration and less heat generation.vibration and 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 5. Patients less apprehensive because less vibration, less noise and less operation time.vibration, less noise and less operation time.

6. Reduced tension and fatigue for both operator 6. Reduced tension and fatigue for both operator and the patient due to reduced operation time.and the patient 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 8. As a whole, it is possible to manage more patients in less time.patients in less time.www.indiandentalacademy.com

Disadvantages of high Disadvantages of high speed cuttingspeed 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. Mechanical injury to soft tissues due to coarse speed.

This can be avoided by This can be avoided by Using rubber dams.Using rubber dams.

Taking care while removing hand piece.Taking care while removing hand piece. Over reduction of tooth Over reduction of tooth

This can be avoided by properly following the steps This can be avoided by properly following the steps during preparation and experience.during preparation and experience.

Eye damage Eye damage Due to flying tooth restorative material particles. This Due to flying tooth restorative material particles. This

can be avoided by protective eyewear for dentist, patient can be avoided by protective eyewear for dentist, patient and assistant.and assistant.

NoiseNoise Hi pitched noise from air turbine can cause hearing Hi pitched noise from air turbine can cause hearing

damage.damage. Cross contaminationCross contamination

Use of face masks for the protection from air borne Use of face masks for the protection from air borne infections like tuberculosis etc reduces the risk.infections like tuberculosis etc reduces the risk.


ABRASION AND POLISHING ABRASION AND POLISHING AGENTSAGENTS

The finishing and polishing of restorative The finishing and polishing of restorative dental materials are important steps in dental materials are important steps in the fabrication of clinically successful the fabrication of clinically successful restorations. The techniques employed for restorations. The techniques employed for these procedures are meant not only for these procedures are meant not only for removal of excess material but also to removal of excess material but also to smoothen rough surfaces.smoothen rough surfaces.

The finishing of dental restorations prior The finishing of dental restorations prior to their placement in the oral cavity has to their placement in the oral cavity has therefore three benefits:therefore three 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 DESIRABLE CHARACTERISTICS OF AN ABRASIVEOF AN ABRASIVE

It should be irregular in shape so that it presents It should be irregular in shape so that it presents a sharp edge. (Jagged particles are more a sharp edge. (Jagged particles are more effective. Round sand particles and cubicle effective. Round sand particles and cubicle particles of sand paper are poor abrasives).particles of sand paper are poor abrasives).

It should be harder than the work it abrades. If It should be harder than the work it abrades. If it cannot indent the surface to be abraded then it cannot indent the surface to be abraded then it cannot cut it and therefore wears out.it cannot cut it and therefore wears out.

Abrasive should posses a high impact strength Abrasive should posses a high impact strength or body strength. Abrasive point should always or body strength. Abrasive point should always fracture than dull out so that always, a sharp fracture than dull out so that always, a sharp point or edge is available. The cuts also help in point or edge is available. The cuts also help in shredding debris accumulated from work for eg, 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 Abrasive should posses attrition resistance so that it does not wear.that it does not wear.www.indiandentalacademy.com

DESIGN OF ABRASIVE DESIGN OF ABRASIVE INSTRUMENTSINSTRUMENTS

The abrasives employed could be The abrasives employed could be one of the three types,one of the three types,

Abrasive Grits.Abrasive Grits. Bonded Abrasives.Bonded Abrasives. Coated Abrasive Disks and Coated Abrasive Disks and

Strips.Strips.


A. Abrasive GritsA. Abrasive Grits Abrasive grits are derived from Abrasive grits are derived from

(abrasive) materials that have been (abrasive) materials that have been crushed and passed through series crushed and passed through series of mesh screens to obtain different of mesh screens to obtain different particle size ranges. The grits are particle size ranges. The grits are classified as COARSE, MEDIUM classified as COARSE, MEDIUM COARSE, MEDIUM FINE and COARSE, MEDIUM FINE and SUPER FINE according to the SUPER FINE according to the particle size ranges.particle size ranges.


B. Bonded AbrasivesB. Bonded Abrasives These consist of abrasive particles incorporated These consist of abrasive particles incorporated

through a binder to form grinding tools.through a binder to form grinding tools. The abrasive particles are bonded by 4 general The abrasive particles are bonded by 4 general

methods: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 Sintered abrasives are the strongest variety since the abrasive particles are fused together.variety since the abrasive particles are fused together.

Vitreous bonded-Vitreous bonded- Are mixed with a glassy or ceramic Are mixed with a glassy or ceramic matrix material, cold pressed to the instrument shape matrix material, cold pressed to the instrument shape and fired to fuse with the binder.and fired to fuse with the binder.

Resin bonded-Resin bonded- are cold or hot pressed and then are cold or hot pressed and then heated to cure the resin.heated to cure the resin.

Rubber bonded-Rubber bonded- made in a manner that is similar to made in a manner that is similar to resin bonded.resin bonded.


C. Coated Abrasive Disks C. Coated Abrasive Disks and Stripsand Strips These abrasives are supplied as disks These abrasives are supplied as disks

and finishing strips. They are fabricated and finishing strips. They are fabricated by securing abrasive particles to a by securing abrasive particles to a flexible backing material (heavy weight flexible backing material (heavy weight paper or Mylar).paper or Mylar).

The disks are available in different The disks are available in different diameters with thin and very thin diameters with thin and very thin backings. Moisture – resistant backings backings. Moisture – resistant backings are advantageous, as the abrasive are advantageous, as the abrasive stiffness is not reduced by water stiffness is not reduced by water degradation.degradation.


ABRASIVE ACTIONABRASIVE ACTION The mode of action of the abrasives The mode of action of the abrasives

is similar to that of the dental burs, is similar to that of the dental burs, that is, it is meraly a cutting action. that is, it is meraly a cutting action. Each fine abrasive particle thus Each fine abrasive particle thus presents as a sharp edge, which cuts presents as a sharp edge, which cuts through the surface similar to a through the surface similar to a pointed chisel. During this cutting pointed chisel. During this cutting process, the shaving thus formed is process, the shaving thus formed is powdered and usually clogs the powdered and usually clogs the abrasive which thus makes periodic abrasive which thus makes periodic cleaning of the abrasive necessary.cleaning of the abrasive necessary.www.indiandentalacademy.com

FACTORS AFFECTING RATE OF FACTORS AFFECTING RATE OF ABRASIONABRASION

Rate of abrasion of a given material by a Rate of abrasion of a given material by a given abrasive is determined primarily by given abrasive is determined primarily by three factors: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. Pressure of the work against the abrasive. When work is pressed against the abrasive, When work is pressed against the abrasive, scratches are deeper and abrasion is more scratches are deeper and abrasion is more rapid – so greater chances of the abrasives rapid – so greater chances of the abrasives to fracture.to fracture.

Speed at which the abrasive particles travels Speed at which the abrasive particles travels across the work. Greater the speed, greater across the work. Greater the speed, greater would be the rate of abrasion.would be the rate of abrasion.www.indiandentalacademy.com

FACTORS INFLUENCING FACTORS INFLUENCING EFFICIENCY OF THE EFFICIENCY OF THE

ABRASIVESABRASIVES These factors are as follows:These factors are as follows: The hardness of the abrasive particle (diamond is The hardness of the abrasive particle (diamond is

hardest; pumice and garnet etc. are relatively mild).hardest; pumice and garnet etc. are relatively mild). The shape of the abrasive particle (particles with The shape of the abrasive particle (particles with

sharp edge are more effective).sharp edge are more effective). Particle size of the abrasive (longer particle size will Particle size of the abrasive (longer particle size will

cut deeper grooves).cut deeper grooves). Mechanical properties of the abrasive (If the Mechanical properties of the abrasive (If the

material breaks, it should form a new cutting edge. material breaks, it should form a new cutting edge. Therefore brittleness can be an advantage). Therefore brittleness can be an advantage).

Rate of movement of the abrasive particles (slower Rate of movement of the abrasive particles (slower abrasion – deeper scratches).abrasion – deeper scratches).

Pressure applied to the abrasive (too much pressure Pressure applied to the abrasive (too much pressure can fracture the abrasive instrument and increase can fracture the abrasive instrument and increase heat of friction that has evolved).heat of friction that has evolved).

Properties of material that is being abraded. (a Properties of material that is being abraded. (a brittle material can be rapidly abraded whereas brittle material can be rapidly abraded whereas ductile / malleable metal like pure gold will flow ductile / malleable metal like pure gold will flow instead of being removed by the abrasive).instead of being removed by the abrasive).


TYPES OS ABRASIVESTYPES OS ABRASIVES According to Craig : The According to Craig : The

abrasives used can be abrasives used can be classified and grouped as 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 These are hard, coarse abrasives used

initially to develop desired contours and initially to develop desired contours and remove off gross irregularities.remove off gross irregularities.

Polishing AbrasivesPolishing Abrasives These have a smaller particle size and These have a smaller particle size and

are less hard than abrasives used for are less hard than abrasives used for finishing. They are used for smoothening finishing. They are used for smoothening surfaces that are typically roughened by surfaces that are typically roughened by finishing abrasives.finishing abrasives.

Cleaning AbrasivesCleaning Abrasives These are soft abrasives with small These are soft abrasives with small

particle size and are intended to remove particle size and are intended to remove softer materials that adhere to enamel or softer materials that adhere to enamel or a restoration.a restoration.


2. Skinner has grouped the 2. Skinner has grouped the abrasives employed in abrasives employed in dentistry as follows:dentistry as follows:

A. Natural Abrasives.A. Natural Abrasives.

B. Manufactured B. Manufactured Abrasives. Abrasives.


Under Natural Abrasives we have:Under Natural Abrasives we have:1. Arkansas stone1. Arkansas stone- Semi translucent, light gray, siliceous - Semi translucent, light gray, siliceous

sedimentary rock, mined in Arkansas.sedimentary rock, mined in Arkansas.- It contains microcrystalline quartz.- It contains microcrystalline quartz.- Small pieces of this mineral is attached to - Small pieces of this mineral is attached to

metal shanks and trued to various shapes metal shanks and trued to various shapes for fine grinding of tooth enamel and metal for fine grinding of tooth enamel and metal alloys.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 - Used as mild abrasive paste to polish teeth

enamel, gold foil, amalgam and plastic enamel, gold foil, amalgam and plastic materials.materials.


3. Corundum3. Corundum

- Is largely replaced by alpha Aluminum oxide - Is largely replaced by alpha Aluminum oxide due to its superior physical properties. due to its superior physical properties. However corundum is primarily used for However corundum is primarily used for grinding metal alloys and is available as a grinding metal alloys and is available as a bonded abrasive.bonded abrasive.

4. Diamond 4. Diamond is a transparent colorless mineral is a transparent colorless mineral composed of carbon called super abrasive composed of carbon called super abrasive because of its ability to abrade any other because of its ability to abrade any other known substance. It is used on ceramic and known substance. It is used on ceramic and resin based composite materials.resin based composite 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 - This abrasive is grayish black corundum that is prepared in a fine grain form.prepared in 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 the term garnet includes several minerals which possess similar physical properties minerals which possess similar physical properties like Silicates of Al, Co, Fe, Mg and Mn.like Silicates of Al, Co, Fe, Mg and Mn.

- Garnet is dark red, extremely hard and when - Garnet is dark red, extremely hard and when fractured during abrasive abrasive activity forms fractured during abrasive abrasive activity forms sharp chisel shaped plates – therefore making sharp chisel shaped plates – therefore making Garnet an effective abrasive.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 - Used in grinding metal alloys and plastic materials.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 - Flour of pumice is an extremely fine grinded

volcanic rock derivative from Italy. volcanic rock derivative from Italy. - Used in polishing teeth enamel, gold foil, dental - Used in polishing teeth enamel, gold foil, dental

amalgam and acrylic resins.amalgam and acrylic resins.8. Quartz8. Quartz – the particles are pulverized to form – the particles are pulverized to form

sharp angular particles which are useful in sharp angular particles which are useful in making coated disks.making coated disks.

- Used to finish metal alloys and may be used to - Used to finish metal alloys and may be used to grind dental enamel.grind dental enamel.

9. Sand9. Sand- Is a mixture of small mineral particles - Is a mixture of small mineral particles

predominantly silica.predominantly silica.- Particles have rounded to angular shape.- Particles have rounded to angular shape.- Used to remove refractory investment material - Used to remove refractory investment material

from base metal castings.from base metal castings.- It is coated on paper disks for grinding of metal - It is coated on paper disks for grinding of metal

alloys and plastic materials.alloys and plastic materials.www.indiandentalacademy.com

10. Tripoli10. Tripoli

- Derived from a light weight, siliceous - Derived from a light weight, siliceous sedimentary rock.sedimentary 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 - Used for finishing metal alloys and some plastic materials.plastic materials.

11. Zirconium silicate11. Zirconium silicate

- - Off white mineral, ground to various sizes Off white mineral, ground to various sizes used to make coated disks and strips.used to make coated disks and strips.

- Also used as a component of dental - Also used as a component of dental prophylaxis pastes.prophylaxis pastes.


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 This is the first of the synthetic abrasive to be developed.developed.

- Two types were manufactured 1. Green form and 2. - Two types were manufactured 1. Green form and 2. Blue form. Both are having similar physical Blue form. Both are having similar physical properties.properties.

- However, the green variety is preferred because - However, the green variety is preferred because substrates are more visible against the green color.substrates are more visible against the green color.

- The cutting efficiency of silicon carbide abrasives is - The cutting efficiency of silicon carbide abrasives is higher as the particles are sharp and break to form higher as the particles are sharp and break to form new sharp particles.new sharp particles.

- Supplied as air abrasive in coated disks and vitreous - Supplied as air abrasive in coated disks and vitreous and rubber bonded instruments.and rubber bonded instruments.

- Used in cutting metal alloys, ceramics and plastic - Used in cutting metal alloys, ceramics and plastic materials.materials. www.indiandentalacademy.com

2. Aluminium Oxide2. Aluminium Oxide

- This is the second synthetic abrasive to be - This is the second synthetic abrasive to be manufactured.manufactured.

- This form of alumina is much harder than its - This form of alumina is much harder than its natural counterpart (CORUNDUM) because of its natural counterpart (CORUNDUM) because of its purity.purity.

- The forms usually prepared are:- The forms usually prepared are:

a. White stones – made of sintered aluminium oxide a. White stones – made of sintered aluminium oxide are used for contouring of enamel and finishing are used for contouring of enamel and finishing metal and ceramic materials.metal and ceramic materials.

b. Variations of aluminium oxide include those with b. Variations of aluminium oxide include those with chromium compound additions, these obtained in chromium compound additions, these obtained in pink and ruby colours are obtained as vitreous pink and ruby colours are obtained as vitreous bonded non-contaminating mounted stones – used bonded non-contaminating mounted stones – used for preparation of metal ceramic alloys to receive for preparation of metal ceramic alloys to receive porcelain.porcelain.


3. Synthetic Diamond – developed in 3. Synthetic Diamond – developed in 19551955..

- Synthetic or manufactured for of - Synthetic or manufactured for of diamond is produced at 5 times the diamond is produced at 5 times the level of the natural diamond abrasive.level of the natural diamond abrasive.

- This synthetic diamond is used for the - This synthetic diamond is used for the manufacture of diamond saws, wheels manufacture of diamond saws, wheels and burs and also diamond locks and burs and also diamond locks employed for truing of bonded employed for truing of bonded abrasives.abrasives.

- Synthetic diamond abrasives are used - Synthetic diamond abrasives are used primarily on tooth structure, ceramic primarily on tooth structure, ceramic materials and resin based components.materials and resin based components.


4. Rouge4. Rouge

- - Principle component is iron oxide blended Principle component is iron oxide blended with various binders.with various binders.

- Used to polish high noble metal alloys.- Used to polish high noble metal alloys.

- May be impregnated in paper or fabric - May be impregnated in paper or fabric known as CROCUS CLOTH.known as 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 - May be employed in an abrasive paste form along with water, alcohol or glycerin.along with water, alcohol or glycerin.

- Used as a polishing agent for teeth and - Used as a polishing agent for teeth and metallic restorations.metallic restorations.


REVIEW OF LITERATUREREVIEW OF LITERATURE1. In 1952, 1. In 1952, Lawrence H. ClaymanLawrence H. Clayman described the described the

modern techniques for the full crown and plastic modern techniques for the full crown and plastic faced gold veneer crown preparations using faced gold veneer crown preparations using diamond instruments. The introduction of diamond diamond instruments. The introduction of diamond cutting instruments into dentistry has been a great cutting instruments into dentistry has been a great aid for crown and bridge prosthesis. Diamond aid for crown and bridge prosthesis. Diamond instruments have enabled us to prepare teeth instruments have enabled us to prepare teeth faster and have also reduced trauma incident to faster and have also reduced trauma incident to operative dentistry procedures by cutting more operative dentistry procedures by cutting more efficiently, more quickly, and with less friction and efficiently, more quickly, and with less friction and resulting heat.resulting heat.

For maximum cutting efficiency, diamond For maximum cutting efficiency, diamond instruments should be used at high speed with instruments should be used at high speed with light pressure and should be well lubricated by a light pressure and should be well lubricated by a continuous stream of water.continuous stream of water.


2. In 1953, 2. In 1953, Edwin S. Smyd Edwin S. Smyd mentions the mentions the importance of diamond tools in dentistry; importance of diamond tools in dentistry; diamond tools are distinct from burs or diamond tools are distinct from burs or cutting tools in that they work by a scoring cutting tools in that they work by a scoring action, that is, each diamond particle action, that is, each diamond particle scrapes off the surface of the object it is scrapes off the surface of the object it is abrading to the depth of the diamond abrading to the depth of the diamond protruding from the tool. Light pressure protruding from the tool. Light pressure minimizes frictional heat. Experimental minimizes frictional heat. Experimental studies in Germany indicates that diamond studies in Germany indicates that diamond tools are best used wet or dry in a moist tools are best used wet or dry in a moist loose slurry of the abraded material- both loose slurry of the abraded material- both too much water and dryness should be too much water and dryness should be avoided.avoided.

Diamond tools are not selective in their Diamond tools are not selective in their grinding action. They will grind enamel, grinding action. They will grind enamel, dentin and cementum at equal rate.dentin and cementum at equal rate.


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

4. In 1958, 4. In 1958, Allison G. James, Allison G. James, discussed the subject of discussed the subject of high speeds and concluded that unless steps are high speeds and concluded that unless steps are taken to bring adequate instruction to the vast taken to bring adequate instruction to the vast majority of dentists who are influenced to use high majority of dentists who are influenced to use high speed rotary instruments, it may be anticipated that speed rotary instruments, it may be anticipated that an era of slovenly tooth preparations will plague an era of slovenly tooth preparations will plague dentistry for some time to come.dentistry for some time to come.

5. In 1959, 5. In 1959, Edmund V. Street, Edmund V. Street, did a critical did a critical evaluation of ultrasonics in dentistry and concluded evaluation of ultrasonics in dentistry and concluded that pulps of vital permanent teeth appear to be that pulps of vital permanent teeth appear to be unaffected, but operations on children’s teeth unaffected, but operations on children’s teeth should not be attempted until future research should not be attempted until future research indicates no ill effects. The ultrasonic method of indicates no ill effects. The ultrasonic method of cutting instruments carious or sound enamel, cutting instruments carious or sound enamel, carious or sound dentin and certain types of carious or sound dentin and certain types of restorative materials does not approach the restorative materials does not approach the effectiveness that can be demonstrated with the effectiveness that can be demonstrated with the ultra high speed rotational instruments. ultra high speed rotational instruments.


6. In 1960, 6. In 1960, Alexander Leff, Alexander Leff, did an evaluation of high did an evaluation of high speed in full coverage preparations. From a speed in full coverage preparations. From a practical point of view, high speed can be defined as practical point of view, high speed can be defined as rotational speeds starting at 1, 00,000 rpm. This is rotational speeds starting at 1, 00,000 rpm. This is the beginning range of speed at which tools can be the beginning range of speed at which tools can be used efficiently with light pressure.used efficiently with light pressure.

7. In 1965, 7. In 1965, Schuchard and Watkins, Schuchard and Watkins, compared the compared the efficiency of rotary cutting instruments. efficiency of rotary cutting instruments.

a. Any of the high or low torque rotary cutting a. Any of the high or low torque rotary cutting equipment will operate efficiently in its useful equipment will operate efficiently in its useful range, if properly used. range, if properly used.

b. The various low torque ultrahigh speed contra b. The various low torque ultrahigh speed contra angle instruments are comparable, and are most angle instruments are comparable, and are most efficient at the higher operating air pressures.efficient at the higher operating air pressures.

c. Simplicity of design and size of equipment are c. Simplicity of design and size of equipment are significant in evaluation.significant in evaluation.

d. High torque air driven straight hand pieces are not d. High torque air driven straight hand pieces are not as efficient as comparable electric driven as efficient as comparable electric driven equipment.equipment.


8. In 1970, 8. In 1970, Charles Watkins, Charles Watkins, elaborated on the elaborated on the cutting effectiveness of rotary instruments in a cutting effectiveness of rotary instruments in a turbine hand piece and concluded that in enamel, turbine hand piece and concluded that in enamel, diamond cutting instruments compare favorably diamond cutting instruments compare favorably with TC burs. The carbide burs remove dentin more with TC burs. The carbide burs remove dentin more rapidly than do the diamond points. The ‘lubricating’ rapidly than do the diamond points. The ‘lubricating’ effect of water to enhance the cutting effectiveness effect of water to enhance the cutting effectiveness of diamonds in not documented in this study.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 did a study on the effect of air powder abrasive instrument on effect of air powder abrasive instrument on porcelain. The effects of an air powder abrasive porcelain. The effects of an air powder abrasive instrument on porcelain were evaluated. Sample instrument on porcelain were evaluated. Sample disks made from two commercial porcelains and disks made from two commercial porcelains and three porcelain strains were treated for 80 seconds three porcelain strains were treated for 80 seconds with this instrument.with this instrument.

It was recommended that the air powder abrasive It was recommended that the air powder abrasive instrument be used cautiously or not at all on instrument be used cautiously or not at all on porcelain restorations, especially those with staining porcelain restorations, especially those with staining and / or specific characterizations.and / or specific characterizations.www.indiandentalacademy.com

10. In 1988, 10. In 1988, Price and Sutow, Price and Sutow, conducted a conducted a micrographic and profilometric evaluation of micrographic and profilometric evaluation of the finish produced by diamond and TC the finish produced by diamond and TC finishing burs on enamel and dentin and finishing burs on enamel and dentin and concluded that-concluded that-

a. Minimal marginal chipping combined with a. Minimal marginal chipping combined with low surface roughness suggests that a low surface roughness suggests that a superfine superfine

diamond is indicated for producing clinically diamond is indicated for producing clinically acceptable margins on all surfaces of the acceptable margins on all surfaces of the teeth.teeth.

b. Where the rotation of the bur was away from b. Where the rotation of the bur was away from the margin, multifluted tungsten carbide burs the margin, multifluted tungsten carbide burs

frequently produced chipping of the enamel frequently produced chipping of the enamel margin.margin.


11. In 1988, 11. In 1988, Prattern and Johnson,Prattern and Johnson, did an did an evaluation of finishing instruments for an evaluation of finishing instruments for an anterior and a posterior composite. The same anterior and a posterior composite. The same finishing instruments and techniques revealed finishing instruments and techniques revealed no significant differences in the surface no significant differences in the surface roughness of the anterior and posterior roughness of the anterior and posterior composites. The smoothest surface was composites. The smoothest surface was achieved with Mylar strips; the smoothest achieved with Mylar strips; the smoothest instrumented surface was achieved with a series instrumented surface was achieved with a series of abrasive disks, but a fine diamond bur with of abrasive disks, but a fine diamond bur with 25 um particles produced the roughest surface. 25 um particles produced the roughest surface. However an X-fine diamond with 15 um However an X-fine diamond with 15 um particles produced a surface smoothness particles produced a surface smoothness superior to that produced with a white stone superior to that produced with a white stone and similar to the smoothness produced with a and similar to the smoothness produced with a carbide bur and rubber point. Diamond finishing carbide bur and rubber point. Diamond finishing with slow speed produced a somewhat smooth with slow speed produced a somewhat smooth finish than with high speed.finish than with high speed.www.indiandentalacademy.com

12. In 1988, 12. In 1988, Jeffrey Norlandes and Dennis Jeffrey Norlandes and Dennis wies and Warren Stoffer, wies and Warren Stoffer, studied the taperstudied the taper of clinical preparations for fixed of clinical preparations for fixed prosthodontics and concluded that-prosthodontics and concluded that-

a. The ideal convergence angle of 4-10 degrees a. The ideal convergence angle of 4-10 degrees is seldom achieved in clinical practice.is seldom achieved in clinical practice.

b. Mean convergence angles for mandibular b. Mean convergence angles for mandibular preparations were greater than mean preparations were greater than mean maxillary convergence angles.maxillary convergence angles.

c. No significant differences were found c. No significant differences were found between the mean convergence angles of between the mean convergence angles of crowns and FPD retainers.crowns and FPD retainers.

d. Auxiliary retention should be used in the d. Auxiliary retention should be used in the molar region because these preparations molar region because these preparations were found to have large convergence angles.were found to have large convergence angles.


13. In 1990,13. In 1990, Robert W. Schutt, Robert W. Schutt, did a procedure did a procedure to sterilize dental burs with dry heat.to sterilize dental burs with dry heat.

a. After dental treatment, debride the bur and a. After dental treatment, debride the bur and wipe dry with gauze. Both short and long wipe dry with gauze. Both short and long shank burs can be used.shank burs can be used.

b. Place the burs in screw-cap 13 x 100 mm b. Place the burs in screw-cap 13 x 100 mm glass test tubes with a maximum of 10 burs per glass test tubes with a maximum of 10 burs per tube.tube.

c. Place the tubes in wire racks and insert in a c. Place the tubes in wire racks and insert in a dry heat even at a monitored temperature of dry heat even at a monitored temperature of 170 degree C for a minimum period of 60 170 degree C for a minimum period of 60 minutes.minutes.

d. After the sterilization period, remove the wire d. After the sterilization period, remove the wire racks and allow the tubes to cool. The glass racks and allow the tubes to cool. The glass tubes containing the sterile burs may be stored tubes containing the sterile burs may be stored and indefinitely and will maintain the sterility and indefinitely and will maintain the sterility of the burs.of the burs.


14. In 1991, 14. In 1991, Kevin M. Gureckis et al, Kevin M. Gureckis et al, conducted a conducted a study on the cutting effectiveness of diamond study on the cutting effectiveness of diamond instruments subjected to cyclic sterilization methods instruments subjected to cyclic sterilization methods and concluded that-and concluded that-

a. The cutting effectiveness of rotary dental diamond a. The cutting effectiveness of rotary dental diamond instruments was not influenced by the sterilization instruments was not influenced by the sterilization method.method.

b. There are considerable differences in the cutting b. There are considerable differences in the cutting efficiency of new individual diamond instruments.efficiency of new individual diamond instruments.

15. In 1999, a study was done which investigated a 15. In 1999, a study was done which investigated a new diamond rotary instrument made of a new diamond rotary instrument made of a continuous diamond film obtained by chemical vapor continuous diamond film obtained by chemical vapor deposition (CVD). This bur characterized by a pure deposition (CVD). This bur characterized by a pure diamond cutting surface without metallic binder diamond cutting surface without metallic binder between crystals was compared with a conventional between crystals was compared with a conventional diamond bur and they came down to a conclusion diamond bur and they came down to a conclusion that the new CVD bur not only proves to be more that the new CVD bur not only proves to be more efficient in its cutting ability and longevity, but also efficient in its cutting ability and longevity, but also excludes the risk of metal contamination.excludes the risk of metal contamination.www.indiandentalacademy.com

16. In 2001, 16. In 2001, Katoh Y and Sunico M, Katoh Y and Sunico M, did a did a study on the newly developed diamond study on the newly developed diamond points and said that the rapid decrease in points and said that the rapid decrease in size of dental restorations has increased size of dental restorations has increased the demand for the smallest rotary cutting the demand for the smallest rotary cutting instrument possible. The width of cavities instrument possible. The width of cavities prepared with two experimental diamond prepared with two experimental diamond points and the smallest commercial points and the smallest commercial diamond point were compared and diamond point were compared and significant differences found. SEM significant differences found. SEM observation of the head surfaces of the observation of the head surfaces of the three diamond points revealed that the three diamond points revealed that the experimental points had comparable experimental points had comparable cutting characteristics with the cutting characteristics with the commercial diamond point.commercial diamond point.


17. In 2002, 17. In 2002, Bruno Neves Cavalcanti, Bruno Neves Cavalcanti, Choyu Otani and Sigmourmello Rode, Choyu Otani and Sigmourmello Rode, did a study and evaluated the efficiency of did a study and evaluated the efficiency of 3 different water flows for 2 different tooth 3 different water flows for 2 different tooth preparation techniques to determine which preparation techniques to determine which one is safe for use. Cavity and tooth one is safe for use. Cavity and tooth preparations generate heat because the preparations generate heat because the use of rotary cutting instruments on dental use of rotary cutting instruments on dental tissues creates friction. Dental pulps tissues creates friction. Dental pulps cannot survive temperature increases cannot survive temperature increases greater than 5.5 degree C. The results of greater than 5.5 degree C. The results of this study confirms that thenecessity of this study confirms that thenecessity of using a low-load technique and water using a low-load technique and water coolants during cavity and tooth coolants during cavity and tooth preparation procedures. preparation procedures.


SUMMARY AND SUMMARY AND CONCLUSIONCONCLUSION

Tooth preparations for cast Tooth preparations for cast restorations have been influenced at restorations have been influenced at least in part, by the technology of least in part, by the technology of instrumentation. This is seen in the instrumentation. This is seen in the development of hand pieces and development of hand pieces and power sources as well as in the power sources as well as in the evolution of abrasives and cutting evolution of abrasives and cutting instruments. This seminar considers instruments. This seminar considers all the aspects of instrumentation in all the aspects of instrumentation in fixed prosthodontics and is based on fixed prosthodontics and is based on the current available literature. the current available literature. www.indiandentalacademy.com

REFRENCESREFRENCES M A Marzouk- M A Marzouk- Operative Dentistry, Operative Dentistry,

modern theory and practice.modern theory and practice. Herbert T Shillingburg-Herbert T Shillingburg- Fundamentals of Fundamentals of

fixed prosthodontics- third edition.fixed prosthodontics- third edition. Tylman’s-Tylman’s- Theory and practice of fixed Theory and practice of fixed

prosthodontics-eight edition.prosthodontics-eight edition. Stephen F Rosenstiel-Stephen F Rosenstiel- Contemporary Contemporary

fixed prosthodontics.fixed prosthodontics. Gerald T Charbeneau- Gerald T Charbeneau- Principles and Principles and

practice of operative dentistry.practice of operative dentistry. Sturdewant’s- Sturdewant’s- Art and science of operative Art and science of operative

dentistry- fourth edition.dentistry- fourth edition.www.indiandentalacademy.com

Bruno Neves Cavalcanti, Choyu otani, Bruno Neves Cavalcanti, Choyu otani, Sigmar mello rode- Sigmar mello rode- High speed cavity High speed cavity cutting preparation techniques with different cutting preparation techniques with different water flows.JPD 87(2) 158-161, FEB 2002.water flows.JPD 87(2) 158-161, FEB 2002.

Katoh Y, Sunico M- Katoh Y, Sunico M- Newly developed Newly developed diamond points for conservative operative diamond points for conservative operative procedures.Oper Dent 2001 Jan 26(1)76-80.procedures.Oper Dent 2001 Jan 26(1)76-80.

Dental diamond burs made with a new Dental diamond burs made with a new technology.JPD 1999 July, 82(1), 73-79.technology.JPD 1999 July, 82(1), 73-79.

Kevin Guruckes-Kevin Guruckes- Cutting effectiveness of Cutting effectiveness of diamond instruments subjected cyclic diamond instruments subjected cyclic sterilization. JPD 1991, 56 300-306.sterilization. JPD 1991, 56 300-306.

Robert Schutt- Robert Schutt- Sterilization of dental burs Sterilization of dental burs with dry heat. JPD 1990,42 22-26.with dry heat. JPD 1990,42 22-26.

Pratten and Johnson- Pratten and Johnson- Evaluation of Evaluation of finishing instrumentsfinishing instruments for an anterior and a for an anterior and a posterior composite.JPD 1988, 38, 362-365.posterior composite.JPD 1988, 38, 362-365.www.indiandentalacademy.com

Price and Sutow-Price and Sutow- Micrographic and profilometric Micrographic and profilometric evaluation of the finish produced by diamond and evaluation of the finish produced by diamond and tungsten carbide finishing burs on enamel and tungsten carbide finishing burs on enamel and dentin. JPD 1988; Vol39,30-35.dentin. JPD 1988; Vol39,30-35.

Robert Colley-Robert Colley- Effect of air powder abrasive Effect of air powder abrasive instrument on porcelain.JPD1988,vol39,88-92.instrument on porcelain.JPD1988,vol39,88-92.

Jeffrey Norchlander & Dennis Wies & Warren Jeffrey Norchlander & Dennis Wies & Warren Cloffer- Cloffer- Tips of clinical preparation for fixed Tips of clinical preparation for fixed prosthodontia.JPD 1988;Vol38,42-46.prosthodontia.JPD 1988;Vol38,42-46.

Charles Watkins-Charles Watkins- Cutting effectiveness of rotary Cutting effectiveness of rotary instruments in a turbine hand piece. JPD 1970; Vol instruments in a turbine hand piece. JPD 1970; Vol 19; 88-105.19; 88-105.

Schuchard & WatkinsSchuchard & Watkins- Comparison of cutting - Comparison of cutting efficiency of tungsten carbide burs and diamond efficiency of tungsten carbide burs and diamond points at ultra high rotational speeds. JPD 1967; Vol points at ultra high rotational speeds. JPD 1967; Vol 20; 362-366.20; 362-366.

Schuchard & Watkins- Schuchard & Watkins- Comparison of efficiency of Comparison of efficiency of rotary cutting instruments. JP 1965; Vol 18; 25-28.rotary cutting instruments. JP 1965; Vol 18; 25-28.www.indiandentalacademy.com

Alexander Leff-Alexander Leff- Evaluation of high speed Evaluation of high speed in full coverage preparations. JPD 1960; Vol in full coverage preparations. JPD 1960; Vol 10; 220-224.10; 220-224.

Allison G.Allison G. James-James- High speeds. JPD 1958; High speeds. JPD 1958; Vol 8; 168-172.Vol 8; 168-172.

Rex Ingraham-Rex Ingraham- Evaluation of recent Evaluation of recent progress in the field of increased speeds progress in the field of increased speeds and modern instrument design. JPD 1957; and modern instrument design. JPD 1957; Vol 7; 112-118.Vol 7; 112-118.

Edwin Smyd-Edwin Smyd- Importance of diamond tools Importance of diamond tools in dentistry. JPD 1953; Vol 3; 361-364.in dentistry. JPD 1953; Vol 3; 361-364.

Lawrence Claywan-Lawrence Claywan- Modern techniques Modern techniques for full crown and plastic faced gold veneer for full crown and plastic faced gold veneer crown preparations using diamond crown preparations using diamond instruments. JPD 1952; Vol 2; 272-276.instruments. JPD 1952; Vol 2; 272-276.www.indiandentalacademy.com

Griscome-Griscome- History of dentistry- History of dentistry-Weinburg.Weinburg.

Robert Arthur-Robert Arthur- History of History of dentistry-dentistry-WeinburgWeinburg

Archigenes- Archigenes- History of dentistryHistory of dentistry--Weinburg; Weinburg; ‘Instrumentation’.‘Instrumentation’.

Dendel & Zweiling- Dendel & Zweiling- History of History of dentistrydentistry-Weinburg; -Weinburg; ‘Instrumentation’.‘Instrumentation’.

Brown et al- Brown et al- Operative dentistry Operative dentistry byby Sturdevant; Sturdevant; Cutting Cutting instruments.instruments.


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Rotary cutting inst rajat /certified fixed orthodontic courses by Indian dental academy