A dental bur is a type of burr (cutter) used in a handpiece. The burs are usually made of tungsten carbide or diamond. The three parts to a bur are the head, the neck, and the shank.
The heads of some burs (such as tungsten carbide burs) contain the blades which remove material. These blades may be positioned at different angles in order to change the property of the bur. More obtuse angles will produce a negative rake angle which increases the strength and longevity of the bur. More acute angles will produce a positive rake angle which has a sharper blade, but which dulls more quickly. The heads of other commonly used burs are covered in a fine grit which has a similar cutting function to blades (e.g. high speed diamond burs).
There are various shapes of burs that include round, inverted cone, straight fissure, tapered fissure, and pear-shaped burs. Additional cuts across the blades of burs were added to increase cutting efficiency, but their benefit has been minimized with the advent of high-speed handpieces. These extra cuts are called crosscuts.
Due to the wide array of different burs, numbering systems to categorize burs are used and include a US numbering system and a numbering system used by theInternational Organisation for Standardisation (ISO).