all About Burs in dentistry

1. DENTAL BURS
Guided By:
Dr Sandeep Metgud
Dr Deepali Aggerwal
Presented by:
Dr Ashish chhajlani

2. Content
Introduction and Definition
History
Parts of the Dental Bur
Classification of Dental Bur
Design Of Dental Bur
Significance Of Bur Design
Modification in Bur Design
Cutting Mechanism of Dental Bur
Factor Influencing Dental Bur

3. DEFINITION:
“The term Bur is applied to all
rotary cutting instrument that
have bladed cutting heads.”
Strudevants 5th edition
or
A bur is revolving cutting
instrument which has a cutting
blades on head.

4. History
Early around 1728 Hand rotated drills were used
First machine made burs introduced in1891 made up
of steel.
In 1940s Diamond abrasive points were introduced
In 1947 carbide burs were introduced

5. Parts of dental bur
The dental bur has 3 basic parts :
Shank
Neck
Head

6. Shank design : 3 types of designs are commonly seen
1. Straight Hand piece Shank : simple cylindrical held in
straight hand piece by a metal chuck that closes to the
shank diameter
2. Latch type angle hand piece shank : it is also in cylindrical in
shape but the posterior portion of the bur shank is flattened
on one side.
3. Friction grip angle hand-piece : The shank is simple cylinder
and even smaller in dimension .

8. Classification of
Burs

9. According to the Shank Design:
1. Straight hand piece shank
2. Latch type angle hand piece shank
3. Friction grip angle hand-piece

10. According to Material Of Manufacturing
1. Stainless Steel
2. Tungsten Carbide
Stainless Steel Bur Tungsten Carbide

11. According to shape of the Bur Head
1. Round
2. Straight
3. inverted cone
4. Tapered fissure
5. Pear shaped

13. ACCORDING TO THE DIRECTION OF ROTATION
Clockwise (right)- most common
Anticlockwise (left)

14. ACCORDING TO THE HAND PIECE THEY ARE
DESIGNED FOR
1. Contrangle bur
2. Straight hand piece bur

15. According to the Size of the bur head :
The original numbering system groped burs by 9 shapes and
11 sizes
The 1/2 and 1/4 designations were added later when small
instruments were included in the system.

17. Design of Dental Bur
Dental Burs have blades which are usually in even
numbers.
cavity preparation burs have 6 , 8 , 10 blades
The following features we normally seen in the Dental bur :

18. Bur Blade : These are uniformly spaced projections on Bur
head which terminate in cutting edge.
It has two surfaces :
1. Blade Face / Rake Face
2. Blade back / Clearance face
Flute / Chip Spaces: These are the depressed areas in
between the bur blades.
Radial Line : This is the line connecting the centre of the bur
and blades

20. Rake Angle : This is the angle between the rake face and the radial line
. This may be
Negative
Positive
Zero

21. Land: This represents the plane surface immediately
following the cutting edge
Clearance angle: This is angle between the clearance face
and the work that is tooth.
Blade Angle : this is the angle between the rake face and
clearance face or the rake face of the land
Radial Clearance : If the clearance face is curved it is
known as radial clearance

22. Significance of Bur
Design
The rake angle is most important design feature of a bur
blade.
A positive angle increases the cutting efficiency but having
following drawbacks :
1. It tend to clog the cut debris in flute space
2. it reduces the life of bur.
A negative rake angle reduces the fracture of cutting edge
thus increases the life of bur .
Neck Design is also important feature in Bur.

23. Modification in Bur design
With the development of high speed ranges a new cycle of
modification of bur occurred
The three major trends in bur design : -
1. Reduced use of crosscut burs
2. Extended Head Length
3. rounding of sharp tip angle

24. Cutting Mechanism of Dental Burs
For Effective cutting tooth structure the dental bur should be
used at high speed .
Adequate pressure must be applied .
Two types of fracture mechanism Brittle and Ductile fracture
occurs in tooth structure

25. Factors influencing the cutting of the burs:
Factors that affects cutting of burs are following:
1. RAKE ANGLE
2. CONCENTRICITY
3. CLEARANCE ANGLE
4. RUN-OUT
5. NUMBER OF TEETH OR BLADE & ITS DISTRIBUTION

26. RAKE ANGLE
Order of cutting efficiency :
Positive rake angle > radial rake angle > Negative rake angle.

27. Concentricity
Concentricity is a direct measurement of the symmetry of the
bur head itself.
it measures how closely a single circle can be passed
through the tips of all the blades of bur

28. CLEARANCE ANGLE:
It provides clearance between the work & the cutting edge to
prevent the tooth back from rubbing on the work.
Large clearance angle may result in less rapid dulling of the
bur.

29. Run Out
Run Out is a procedure measuring the accuracy with which
all blade tips pass through a single point when the instrument
is rotated.
It measures concentricity as well as accuracy of the centre of
rotation passes through the centre of the head .

30. NUMBER OF TEETH OR BLADE & ITS DISTRIBUTION
As the number of blades decreases, the magnitude of forces at
each blade increases & the thickness of the chip removed by
each flute correspondingly increases.
Fewer number of bur teeth has increased space between bur
teeth & thus decreases the clogging tendency.

31. Sterlization of Burs
Some common sterilisation technique used for Burs :
Dry Heat : Temperature at 320 F for 30 min
Chemiclave : Aldehyde vapours at 270 F and 20 lb of
pressure
Autoclave : 2 % soduim nitrate solution is used ,

32. BIBLIOGRAPHY
•Sturdevant’s Art And Science Of Operative Dentistry
•Charbenues Operative Dentistry
•Pickards manual of conservative dentistry

33. Life is full of Twists and
Twirls…
keep Your Attitude Sharpened
with Positive Mentality
Thank You