1. Rotary instruments

2. Rotary instruments
Operating Speed ranges and uses:
Regular, low or conventional speed: (2.000 to rpm).
Higher or intermediate speed ( to rpm).
Ultra or super speed (above rpm) is accomplished with the air turbine.

3. Bur 2. Stone. Rotary instruments Cutting Points:
The smallest unit and the one actually removing tooth structures, may be one of two:
Bur Stone.

4. Bur parts: Rotary instruments Shank:
The shank is secured to the hand piece for the purpose of driving the bur.

5. The Shaft connects the head of the bur with the shank. Head:
Rotary instruments
 Shaft:
The Shaft connects the head of the bur with the shank.
Head:
This part of the bur does the cutting by the means of the small blades located on the metal.
shaft

6. Rotary instruments
Burs are classified according to their shanks into:
The friction-grip bur is used for the ultra- speed air turbine.
The latch type: are used for regular and medium-speed instruments.

7. Rotary instruments
Round bur
Gainig access.
Excavation of caries.

8. Inverted cone bur Rotary instruments Extension of cavity outline form
Flattening of pulpal floor

9. Fissure Bur Rotary instruments
May be used instead of the inverted cone bur in making extension of cavity walls to obtain outline form.
Finishing of cavity walls and margins to form sweeping curves.

10. Tapered Fissure Bur Rotary instruments
1. Tapered a few degrees in order to place wall inclinations for the cast gold inlay.
2. The burs are selected to produce grooves for retention of the proximal amalgam and inlay restorations.

11. Finishing bur Rotary instruments
The blades are shorter and closer together than in other burs.
They are used for finishing and polishing of metallic restorations.

12. Bur Design Design of dental bur:
The bur head may be divided into 6 or 8 blades (also called teeth, flutes).
Each flute or blade has a leading side “Face”, and a trailing side “Back” with an angle in between, called the “flute Angle” or blade angle.
Clearance angle

13. Bur Design Clearance Angle:
It is the angle between the back of the blade and the “work”
It acts to decrease the friction between the back of bur blade and the work or tooth tissues during cutting, and therefore, decrease heat generation.
Clearance angle

14. Bur Design
Clearance or Chip Space:.
The space between each two successive blades
A space where the chips formed during the cutting procedures collect and get eliminated.
Too small, the formed chips will remain in-between the bur blades, causing its clogging generation of more heat and loss of effectiveness.
Clearance angle

15. Bur Design

16. Bur Design
Rake Angle:
An angle created between the face of the blade with the radius of the bur .
The rake angle may be positive, Zero (radial), and negative, depending on whether the radial line is ahead, over-lying. Or tailing the face of the blade respectively.

17. Bur Design where the radial line is ahead to the face of the blade.
A positive rake angle enables the blade to cut more effectively.
making the rake angle more positive can only be attained by thinning out the blade.
This will cause the blade to become weak and to turn and lose its effectiveness quite more rapidly.
Radius

18. Bur Design
Zero Rake Angle: where the radial line is over-lying the face of the blade.
A positive rake angle enables the blade to cut more effectively than a zero one.

19. Bur Design
Radius
Negative rake angle: where the radial line is tailing the face of the blade.
A positive rake angle enables the blade to cut more effectively than a negative one.

21. Cutting efficiency Cutting efficiency:
It is the ability of the instrument to remove a maximum amount of tooth tissues with a minimum of effort and time involved.
Factors influencing the cutting efficiency of burs:
Bur design.
Composition of the bur.
Tissues to be cut.

22. Cutting efficiency 1. Bur design: The number of blades.
The more positive the rake angle the more effective is the bur in cutting.