a very rare presentation on Speed and its effect in operative dentistry

2. SPEEDS
in operative dentistry
Guided By:
Dr. Sandeep Metgud
Dr. Deepali Agarwal
Presented By :
Dr.Ashish Chhajlani

3. CONTENTS
Introduction and Definition
Evolution of rotary cutting in dentistry
Classification of speed
Influence of speed on tooth
Uses , Advantages and Disadvantages
of Low ,Medium , High Speed
Bibliography

4. INTRODUCTION
•The term SPEED in dentistry has greater importance in all the treatment
procedures.
•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 .”
•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 .”

6. CLASSIFICATION
OF SPEED

7. 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 200,00 rpm

8. 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

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

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

11. HANDPIECES AS PER
SPEED
LOW SPEED
1:1 ratio contra-angle 1:4 ratio speed-increasing
handpiece
7:1 ratio speed-reducing
handpiece
straight handpiece
AIROTOR
250000-500000rpm
ACCORDING TO KIDD

12. 1:1 ratio contra-angle
handpiece
1:4 ratio speed-increasing
handpiece
7:1 ratio
speed-reducing
handpiece
A straight
handpiece
BURS USED Latch-grip friction-grip Latch-grip straight burs or
latch-grip
IDENTIFIED
BY
a blue-coloured band on
the shank of the
handpiece and a blue dot
on the head.
red band green bands A 1:1 ratio handpiece is
identified with a blue
band and
reducing speed is
identified with a green
band.
SPEED
RANGE
400–40 000 rev/minute. 16000–160000
rev/min
550–5500 rev/min
USES Caries removal finishing cavity
preparations and also
finishing
restorations.
drilling pin holes To trim temporary
restorations . Usually
used outside the
mouth

13. 1:1 ratio contra-angle
handpiece
1:4 ratio speed-increasing
7:1 ratio speed-reducing
handpiece
handpiece
straight handpiece

14. 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.

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.
•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.

16. Pressure:
•Speed is inversely proportional to the Pressure.
•Cutting at:
Low speed ranges ~ 2-5 pounds
Higher speed ranges ~ 1 pound
Ultra High speed rangees ~ 1-4 0unce

17. SPEED & RATE OF CUTTTING:
•At a given load, the rate of cutting increases with the rotational speed
but not in direct proportional.
•The rate of cutting is more at speeds above 30,000 rpm than that
below this speed.
•However at speed more than 1,50,000 rpm rate of cutting is nearly
same as at still higher speeds.
•There is also a minimum rotational speed for a given load below
which the tool will not cut.
•The greater the load , the lower this minimum rotation speed will be.

18. HEAT PRODUCTION:
Heat is directly proportional to:
RPM
Pressure
Area of tooth in contact with the tool.
•Dry cutting with air-cooling only is reported to contribute to
increasing temperatures that negatively affect the pulp and
cause cracking of the Enamel and Dentin.

19. 130 F
PERMANENT DAMAGE
TO PULP
113 F
INFLAMMATORY
RESPONSE OF PULP
PULPITIS
PULPAL
NECROSIS
EFFECT ON PULP :

20. Smear Layer:
•Tooth preparation with rotary instruments generates cutting debris, some of
which is compacted unavoidably into a layer on the cut surface. That layer of
material is called a smear layer and is typical of any cut surface.
•The smear layer fills the orifices of dentin tubules forming smear plugs &
decreases dentin permeability by 86%.
•Composition = Hydroxyapatite & altered denatured collagen.
•Is approximately 1 to 3 microns thick.
•It covers the surface & prevents the inward penetration of micro leakage
contaminants & outflow of dentinal fluid.

22. LOW SPEED :
USES
•For cleaning teeth
•Occasional caries excavation
•Finishing and polishing procedures.
ADVANTAGES
•Better tactile sensation
•Less chance for overheating cut surfaces

23. DISADVATNAGES
•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

24. Medium speed
USES:
•Cavity preparation
•Placing retentive grooves and bevels
•For areas of limited visibility
ADVANTAGES:
•Positive tactile sense
•Controlled cutting of tooth structure

25. DISADVANTAGES:
•Slower cavity preparation which increases operators fatigue &
patients discomfort
•Increased heat production.

26. HIGH SPEED:
Uses
•For tooth preparation
•Removing old restorations.
Advantages
(1) Cutting instruments remove tooth structure faster with less pressure,
vibration & heat generation
(2) Number of rotary cutting instruments needed is reduced because smaller
sizes are more universal in application
(3) Greater ease of operation for operator
(4) Instruments last longer
(5) Patients are generally less apprehensive because annoying vibrations and
operating time are decreased

27. Disadvantages:
•Rise in temperature
•Less tactile sense so overcutting possible
•Air –water spray can impair visibility
•More chances of iatrogenic errors

28. BIBLIOGRAPHY
•Sturdevant’s Art And Science Of Operative Dentistry
•Operative Dentistry-modern Theory And Practice- Marzouk
•Pickards Manual Of Operative Dentistry
•Textbook Of Operative Dentistry:vimal K. Sikri
•Charbenues Operative Dentistry
•Atraumatic Tooth Preparation:Thomas D. Larson, Minnesota Dental
Association
•Endodontics:Fifth edition-John i. Ingle

29. “SPEED IS CALCULATED AS MILE PER HOUR
….
BUT LIFE IS CALCULATED AS SMILE PER
HOUR ….
SO INCREASE YOUR SMILE AND GET EXTRA
MILAGE IN LIFE…”