Speeds in Dentistry

1. Speeds In Dentistry
Dr. Deepesh
Mehta
Batch 2018-
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2. Content
• Introduction and Definition
• History
• Evolution of rotary cutting in dentistry
• Classification of speed
• Classification of Handpiece
• Uses, Advantages and Disadvantages of Low, Medium and High
Speed
• Dental Burs
• Recent advances in rotary cutting instruments
• Conclusion
• References
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3. Introduction
• The term Speed in dentistry has greater importance in all the
treatment procedures.
Definition
According to Sturdevant: “Speed is defined as the number of
revolution per minute (RPM) or the number of times a rotating
instrument, such as a bur, will make a full turn during a
minute.”
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4. According to Marzouk: “Speed not only refers to revolutions per
minute but also to surface feet per unit time of contact that the
tool has with the work to be cut.”
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5. History
• 1728: Pierre Fauchard mentioned the use of bow
drill to complete the root canal procedures.
• 1778: Release of near mechanical drill, which was
powered by simple hand-crank attached to a gear.
First dental tool to remove bits of teeth without
gouging or chipping them away by hand.
• 1864: British dentist George F. Green invents a
pneumatic dental drill
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6. • 1875: Green patent the first electric dental drill.
• 1914: Electric dental drills reach speeds up to
3,000 RPM.
• 1949: Air turbine handpiece was patented by John
Patrick Walsh in New Zealand.
• 1957: Bordon Airotor air turbine handpiece is
commercially manufactured and distributed in the
U.S. by DENTSPLY.
• 1973: StarDental introduced the first highspeed
handpiece with integrated fibre-optic illumination.
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7. Evolution of Rotary Cutting Equipments in Dentistry
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8. Classification of Speed:
According to Sturdevant:
• Low or slow speed - below 12,000 rpm
• Medium or intermediate speed - 12,000 to 200,000 rpm
• High or ultra speeds - above 200,000 rpm
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9. According to Marzouk:
• Ultra-Low speed- 300 to 3,000 rpm
• Low speed-3,000 to 6,000 rpm
• Medium High speed- 20,000 to 45,000 rpm
• High speed- 45,000 to 100,000 rpm
• Ultra-high speed- 100,000 rpm and more
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10. According to Vimal Sikri:
• Conventional or Low speed - below 6,000 rpm
• Intermediate or High speed - 6,000 to 100,000 rpm
• Ultra or Super speeds - above 100,000 rpm
According to Charbeneau:
• Conventional or Low speed - below 10,000 rpm
• Increased or high speed - 10,000 to 150,000 rpm
• Ultra speeds - above 150,00 rpm
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11. Classification of Handpiece
• 1:1 ratio contra-angle handpiece
• 1:4 ratio speed-increasing handpiece
• 7:1 ratio speed-reducing handpiece
• Straight handpiece
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12. According to the type of power mechanism:
• Belt driven
• Gear driven
• Direct motor driven
• Water driven
• Air driven
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13. Torque:
• Torque is the turning movement of the instrument.
• Torque is the ability of hand piece to withstand lateral pressure
on the revolving tool without decreasing the speed or its
cutting efficiency.
• The speed is inversely proportional to the torque.
• It is more efficient to cut hard materials such as enamel,
porcelain, and metal at high speeds with lower torque & softer
carious dentine at lower speeds with higher torque.
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14. Importance:
• Influence the incidence of instrument locking, deformation,
and separation.
• Instrument used with high torque is very active.
• Low torque would reduce the cutting efficiency of instrument.
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15. Tactile sense:
• An important characteristic of cutting systems is the ‘feel’
which the operator senses through the hand piece.
• At high speed there is very little ‘feel’ and the cutting must be
controlled visually which is difficult because of the water
spray.
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16. • At lower speeds ‘feel’ is useful in controlling the cutting
process, particularly close to the pulp.
• This is the principle reason why low-speed sharp burs should
be used for removing carious dentine.
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17. Pressure:
Pressure is a resultant effect of two factors under the control of
the dentist.
1. Force (F): The gripping of the handpiece and its positioning
and application to the tooth.
2. Area (A): The amount of surface area of the cutting tool in
contact with the tooth surface during a cutting operation.
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18. Pressure relates as follows:
P=F/A
• Speed is inversely proportional to the Pressure.
Cutting at:
• Low speed requires 2-5 pounds
• Higher speed requires 1 pound
• Ultra High speed requires 1-4 ounces.
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19. Vibration:
• Vibration annoys the patient, causes fatigue to the operator,
results in excessive wear of instruments and leads to
destructive reactions in the tools and supporting tissues.
• Ideal requirements of a good cutting instruments are:
▫ Greater speed
▫ Smaller cutting tool
▫ Less force
▫ Effective lubrication
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20. Heat Production:
Heat is directly proportional to:
1. RPM
2. Pressure
3. Area of tooth in contact with the tool
Therefore, if any of these factors is increased, heat production is
increased.
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21. • Heat production will cause pulps of teeth to be permanently
damaged if a temperature of 130̊ F is reached, heat must be carefully
controlled.
• Even a temperature of 113̊ F within the pulp can produce
inflammatory responses that could result in pulpitis and eventual
pulp necrosis.
• It has been shown that when the area of the cutting tool is reduced,
but the speed of rotation is increased, it is an absolute necessity that
coolants be employed to eliminate pulpal damage.
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22. Low Speed (below 12,000 rpm)
Uses:
• For cleaning teeth
• Occasional caries excavation
• Finishing and polishing procedures
Advantages:
• Better tactile sensation
• Less chance for overheating cut surfaces
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23. Disadvantage:
• Ineffective.
• Time consuming.
• Requires relatively heavy force application at the operating site.
• Produces vibrations causing patient discomfort.
• Slower cavity preparation which increases operators fatigue &
patients discomfort.
• Burs have a tendency to roll out of the tooth preparation.
• Carbide bur blades break easily at low speeds-Brittle blades.
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24. Medium Speed (12,000-200,000)
Uses:
• Cavity preparation
• Placing retentive grooves and bevels
• For areas of limited visibility
Advantages:
• Positive tactile sense
• Controlled cutting of tooth structure
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25. Disadvantages:
• Slower cavity preparation which increases operators fatigue &
patients discomfort.
• Increased heat production.
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26. High Speed (above 200,000)
Uses:
• For tooth preparation
Advantages:
• Cutting instruments remove tooth structure faster with
less pressure, vibration & heat generation.
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27. • Number of rotary cutting instruments needed is reduced
because smaller sizes are more universal in application.
• Greater ease of operation for operator.
• Instruments last longer
• Patients are generally less apprehensive because annoying
vibrations and operating time are decreased.
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28. Disadvantages:
• Rise in temperature
• Less tactile sense so overcutting possible
• Air-water spray can impair visibility
• More chances of iatrogenic errors
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29. Dental burs:
The term bur is applied to all rotary cutting instruments that have
bladed cutting head.
Shapes are-
• Round bur
• Inverted cone
• Pear shaped
• Straight fissure
• Tapered fissure
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30. Modification of bur design:
▫ Reduced use of crosscuts
▫ Extended head length
▫ Rounding of sharp tip angles
Bur blade design:
• The actual cutting action of a bur takes place in a very small
region at the edge of the blade.
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31. Each blade has
2 sides:
• Rake face
• Clearance face
3 important angles:
• Rake angle
• Clearance angle
• Edge angle
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32. Ultrasonics:
• Richman in 1957 first suggested the use of ultrasonic in endodontics
during apical surgery.
• Bertrand in 1976 suggested using ultrasonic during retropreparation.
• Cunningham & martin developed the first full-fledged endo
ultrasonic scaler.
• Definition:(According to E. M. KIDD) These are devices by which
the hard tooth structure can be removed by vibrating slurry of
abrasive particles against the surface to be reduced with various
sizes and shapes of preformed instrument tips.
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33. Principle:
• It involves the conversion of an alternating current into a high
frequency mechanical vibration via a phenomenon of
magnetostriction.
Advantages:
• Patient acceptance: excellent
• Control of instrument improved.
• Improved visibility
• Decreased risk of perforation
• Increased conservation of tooth structure
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34. Disadvantages:
• Use of preshaped working point is limited because of the
anatomy and carious areas of individual teeth vary greatly.
• Cutting rate was slow especially in lateral direction.
• Caries and old fillings of gold cannot be removed effectively.
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35. Uses:
• Access modification
• Orifice opening and relocating and straightening
• Locating small narrow canals
• Passive instrumentation to cleaning the canal along with an irrigant
• Apical root resection during apicectomy
• Preparation of apical seat for retrograde filling
• During obturation
• Removal of broken instruments
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36. Sonic instrumentation :
• The sonic instruments exhibit different behaviour when inside
and outside the root canal.
• The side to side motion has virtually disappeared and there is a
small vertical movement.
• This is highly effective in removing obstructions.
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37. Recent Advances in Rotary Instruments:
• Fibreoptic handpiece
• Fissurectomy burs
• Smart prep burs
• CVD (chemical vapour deposition) diamond burs
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38. Fibreoptic handpiece:
• These handpieces have built in fibreoptic which helps in
delivering high beam of light from the handpiece head to the
operating site.
• Their advantage is better visibility of the operating site.
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39. Fissurectomy burs:
• Specifically designed burs for pit and fissure lesions.
• Help in ultraconservative dental treatment.
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40. Smart prep burs:
• Specially designed to remove only the decayed tooth and not
the healthy tooth.
• Made up of polymer and are also referred to as ‘plymer bur’.
• Used with low-speed handpiece and have single use.
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41. Advantages:
• Used for deep carious lesions.
• Reduces the chances of pulpal exposure.
• Tooth structure removal is minimal.
Disadvantages:
• Technique sensitive and expensive.
• If the bur contacts the sound tooth, there are chances of
damage of bur.
• Tendency of leaving large amount of unexcavated caries.
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42. CVD (chemical vapour deposition) diamond burs:
• Introduced in 1996 to eliminate the drawbacks of the diamond
burs.
• Manufactured by depositing diamond film by chemical vapour
on a molybdenum substrate.
• For tooth reduction, only slight contact with such burs is
sufficient.
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43. Advantages:
• Minimal damage to the soft tissues.
• Effective tooth cutting.
• Improved access and visibility.
• Greater durability.
• Better cooling.
Disadvantages:
• Technique sensitive
• Costly
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44. Conclusion:
• The crucial factor for rotary speeds is the surface speed of the
instrument, the velocity at which the edges of cutting
instrument passes across the surface being cut.
• This is proportional to both the rotational speed and the
diameter of instrument with larger instrument having higher
surface speeds at any given rate of rotation.
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45. References:
• Sturdevant’s Art and Science of Dentistry (5th edition)
• Operative Dentistry-Modern Theory And Practice: Marzouk
• Pickard’s Manual of Operative Dentistry (8th edition)
• Concise Conservative Dentistry & Endodontics: Gupta, Hegde
• Textbook of Operative Dentistry: Vimal K Sikri
• Charbeneau’s Operative Dentistry
• Prashanth Kumar et al; Handpieces in Dentistry; Journal of Dental
Sciences and Research; 5(1); 1-9.
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46. Thank You..!
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