What is Dental bur ?

Bur is defined as a rotary cutting instrument with cutting heads of various shapes and two or more sharp edged blades, used as a rotary grinder.

Historical facts about dental burs 

• The earliest burs were hand made 
• First machine made burs introduced in 1891
• Early burs were made of steel
• William and Schroeder first made diamond dental bur in 1897, modern diamond bur was introduced in 1932 by WH Drendel 
• Carbide burs was introduced in 1947 

Materials Used for Bur -  Stainless steel burs, Tungsten carbide burs etc 

Anatomy of a Bur – Comprises of shank, neck and head 

• Shank - Fits into the handpiece: length, crosssection and the end shape can be different  
• Neck -  Transmit the rotational and translational forces to head. It has taper form, and the taper can influence the visibility, the access and the strength 
• Head - Makes the preparation. The shape and the material of the head depends on the work (enamel, dentin, or carious dentin) 

General Design of Dental Bur –  

• Rake Angle - It is angle between the rake face and the radial line 
• Positive rake angle: When rake face trails the radial line 
• Negative rake angle: When rake face is ahead of radial line 
• Zero rake angle: When rake face and radial line coincide each other 

Important terms related to dental burs

• Concentricity - It is a direct measurement of symmetry of the bur head 
• Run out - It measures the maximum displacement of bur head from its center of rotation 
• Clearance angle - Clearance angle reduces the friction between cutting edge and the work 
• Prevents the bur from digging excessively into the tooth structure 
• Linear Surface Speed - Faster the speed of cutting instrument, faster is the abrasive action and more efficient is the tooth cutting instrument

Classification of Dental Burs 

According to their mode of attachment to the handpiece 

• • Latch type 
  • Friction grip type 

According to their composition 

• • Stainless steel burs 
  • Tungsten carbide burs 
  • Combination of both 

According to their motion 

• • Right bur 
  • Left bur 

According to the Length of their head 

• • Long 
  • Short 
  • Regular 

According to their Use 

• • Cutting burs 
  • Finishing burs 
  • Polishing burs 

According to their Shapes 

• • Round bur 
  • Inverted cone 
  • Pear-shaped 
  • Wheel shaped 
  • Tapering fissure 
  • Straight fissure 
  • End cutting bur 

Additional points on dental burs:

• A bur with a more obtuse angle produces a negative rake angle, increasing the longevity and strength of the bur.
• Burs with more acute angles produce positive rake angles, so cutting is quicker, but the bur will become blunt sooner.
• Crosscuts or additional cuts across the blades increase cutting efficacy. Crosscut burs are faster due to less debris build-up.

 Article by Dr. Siri P. B.