SPEEDS

in operative dentistry

Guided By:Dr. Sandeep MetgudDr. Deepali Agarwal

Presented By :Dr.Ashish Chhajlani

CONTENTS

Introduction and DefinitionEvolution of rotary cutting in dentistryClassification of speedInfluence of speed on toothUses , Advantages and Disadvantages

of Low ,Medium , High Speed Bibliography

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.”

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 200,00 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

ACCORDING TO MARZOUK:

Ultra -Low speed- 300 to 3,000 rpmLow speed-3,000 to 6,000 rpmMedium High speed- 20,000 to 45,000 rpmHigh speed- 45,000 to 100,000 rpmUltra high speed- 100,000 rpm and more

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

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

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 orlatch-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 andreducing 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 finishingrestorations.

drilling pin holes To trim temporaryrestorations . Usually used outside the mouth

1:1 ratio contra-angle handpiece

1:4 ratio speed-increasing handpiece

7:1 ratio speed-reducing handpiece

straight handpiece

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.

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.

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

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.

HEAT PRODUCTION:Heat is directly proportional to:RPMPressureArea 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.

130 F

PERMANENT DAMAGE TO PULP

113 F

INFLAMMATORY RESPONSE OF PULP

PULPITISPULPAL

NECROSIS

EFFECT ON PULP :

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.

USES

•For cleaning teeth•Occasional caries excavation•Finishing and polishing procedures.

ADVANTAGES

•Better tactile sensation•Less chance for overheating cut surfaces

LOW SPEED :

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

Medium speed

USES:

•Cavity preparation•Placing retentive grooves and bevels•For areas of limited visibility

ADVANTAGES:

•Positive tactile sense•Controlled cutting of tooth structure

DISADVANTAGES:

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

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

Disadvantages:

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

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

“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…”