Burs in dentisty ashish

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 Straight Hand piece Shank : simple cylindrical held in straight hand piece by a metal chuck that closes to the shank diameter 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. Friction grip angle hand-piece : The shank is simple cylinder and even smaller in dimension .

7. Classification of Burs

8. According to the Shank Design: Straight hand piece shank Latch type angle hand piece shank Friction grip angle hand-piece

9. According to Material Of Manufacturing Stainless Steel Tungsten Carbide Stainless Steel Bur Tungsten Carbide

10. According to shape of the Bur Head Round Straight inverted cone Tapered fissure Pear shaped

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

12. ACCORDING TO THE HAND PIECE THEY ARE DESIGNED FOR Contrangle bur Straight hand piece bur

13. 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.

14. 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 :

15. Bur Blade : These are uniformly spaced projections on Bur head which terminate in cutting edge. It has two surfaces : Blade Face / Rake Face 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

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

17. 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

18. 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 : It tend to clog the cut debris in flute space 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.

19. 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 : - Reduced use of crosscut burs Extended Head Length rounding of sharp tip angle

20. 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

21. Factors influencing the cutting of the burs: Factors that affects cutting of burs are following: RAKE ANGLE CONCENTRICITY CLEARANCE ANGLE RUN-OUT NUMBER OF TEETH OR BLADE & ITS DISTRIBUTION

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

23. 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

24. 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.

25. 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 .

26. 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.

27. 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 ,

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

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